The centrality of the photon concept in modern physics is strongly evident in wide spheres of photonics and nanophotonics. Despite the resilience and persistence of earlier classical representations, there are numerous optical features and phenomena that only truly photon-based descriptions of theory can properly address. It is crucial to cast theory in terms of observables, and in this respect the quantum theory of light engages most directly and pragmatically with experiment. No other theory adequately reconciles the discreteness in energy of optical quanta, with their characteristic quantum mechanical delocalization in space. Examples of the distinctiveness of a photonic representation are to be found in nonclassical optical correlations; intensity fluctuations and phase; polarization, spin, and information content; measures of optical chirality; near-field interactions; and plasmonics. Increasingly, links between these fundamental properties and features are proving significant in the context of nanoscale interactions. Yet, even as new technologies are being built on the framework of modern photonics, a number of difficult questions surrounding the nature of the photon still remain. Both in its flourishing applications and in matters of fundamental entity, the photon is still a subject very much at the heart of current research.

We have synthesized SiO_x nanodots (NDs) on a TiO₂ dielectric using a glancing angle deposition technique. The SiO_x NDs were 11 to 22 nm in diameter, which was confirmed by atomic force microscopy image. A green light emission (550 nm) was observed from SiO_x NDs when excited with a xenon lamp of wavelength 322 nm. The emission was redshifted (∼6  nm) when the excitation was changed to 325 nm. The SiO_x NDs-based detector showed a very low leakage current of ∼9  nA (−0.05  V) and responded to the green light at 550 nm.

Since the surface-structure-related state dominates the photoluminescence (PL) emissions of cubic silicon carbide (3C-SiC) nanocrystals (NCs) with a diameter lower than 3.0 nm, the PL lines of 3C-SiC NCs in deionized water with different pH values, methanol, ethanol, chloroform, and toluene are characterized at the excitation of 300 to 360 nm. The position and intensity of the PL peaks provide experimental evidence that the surface of 3C-SiC is hydrophilic and hydroxyl bonding on the surface decreases the energy gap of the NCs. The PL emission wavelength of 3C-SiC NCs can be adjusted by adjusting the pH value of the solvent. The polar 3C-SiC NCs prefer to precipitate in chloroform and toluene.

We induced forced and auto-oscillations in one-dimensional photonic crystals (1-D-PCs) with localized defects when light impinges transversally to the defect layer. The photonic structure used consists of a microcavity-like structure formed of two 1-D-PCs made of free-standing porous silicon, separated by a variable air gap (the defect) and the working wavelength is 633 nm. The force generation was made evident by driving a laser light by means of a chopper; the light hit the photonic structure and induced a vibration and the vibration was characterized by using a very sensitive vibrometer. For example, we measured peak displacements and velocities ranging from 2 to 167  μm and 0.4 to 2.1  mm/s with a power light level from 2.6 to 13 mW. In comparison, recent evidence showed that giant resonant light forces could induce average velocity values of 0.45  mm/s in microspheres embedded in water with a 43-mW light power.

An optical modality to sense a fluid by exploiting Dyakonov–Tamm (DT) waves was devised. In the modality, the fluid is present on both sides of the guiding interface. Theoretical analysis indicated that the angular location of the reflectance dip in a practically implementable configuration will shift if the refractive index of the fluid changes. Furthermore, the detection sensitivity will decrease as the refractive index of the fluid increases over a wide range, and should be comparable to that for sensing modalities that exploit surface-plasmon-polariton (SPP) waves. Higher sensitivities are available with DT waves than with SPP waves, and the DT-wave-based sensor should be simpler to fabricate than the SPP-wave-based sensor. Multiple DT waves are excitable at the same frequency, leading to multiple channels for more reliable sensing as well as for sensing multiple analytes simultaneously.

In photonic crystals (PCs) waveguides, the speed of light can be significantly reduced due to the weak coupling between adjacent high-quality-factor nanocavity resonators. However, little research focuses on the length between two cavities associated with slow light characteristics. A waveguide based on a PC within a square array with adjustable rods spreading regularly at the edge and center of the cavity is proposed. Slow light properties in this new structure are studied by using the plane wave expansion method. Through a series of experiments, we find the most suitable coupling length to compromise various parameters of slow light, which is just the half-period of that in a conventional structure. Furthermore, the numerical results reveal that the group velocity is below 3.532×10⁻³  c in the new model. The corresponding normalized delay-bandwidth product can reach as high as 0.3068 since the group velocity dispersion is at the range of (−5 to 5)×10⁶. All of above signify that the very small size and ultraslow light, as well as outstanding dispersion performance, are realized and there are some advanced features, such as low loss and high integration, in this half-periodic structure.

We introduce and theoretically describe internally twisted optical metamaterials, in which the metamolecules can have an arbitrary, but common, orientation in the unit cells. The molecules, and consequently the material, are not chiral, but they are allowed to be noncentrosymmetric. While such internally twisted crystalline structures are difficult to find in natural materials, metamaterials of this type can be designed and fabricated at will. Here, we present a theoretical method that enables a detailed analysis of such metamaterials. The method establishes a connection between the optical properties of a metamaterial and the plane-wave optical response of a single two-dimensional array of metamolecules. In the theory, the effective wave parameters, such as the refractive index and wave impedance, are retrieved. Using the model, we show that these parameters can dramatically depend on the wave propagation direction and metamolecular orientation, which can be used, along with optical anisotropy, to efficiently adjust and control the plane-wave content of optical beams.

Herein, we apply a plasmonic near-field scanning nanoscope using a resonant ridge aperture to measure the thickness of a metal thin film. We determine an appropriate design for the resonant ridge aperture to obtain a high dynamic range and sensitivity for the measurement. As a proof of concept, we measure the thickness of gold thin films with thicknesses ranging between 5 and 30 nm. We demonstrate that the experimental and calculated results are in good agreement with one another. Also, we find that any observed errors are caused by uncertainties in the material properties of the metal and by tolerances in the fabrication of the ridge aperture. By comparing these thickness measurements with those taken with atomic force microscopy, we are able to obtain an uncertainty of ∼5% for our thickness measurements. Regarding the spatial resolution, theoretical analysis indicates that the thickness of a metal thin film should be detectable below 40 nm.

The optical force of an evanescent field is useful for trapping individual proteins and molecules. We theoretically investigate the optical pressure exerted on an attached and well-spread cell on a waveguide in the vicinity of an evanescent field. To do this, the cell is modeled as a three-planar-layer (membrane-cytoplasm-membrane). These layers and a gap of water are used as a stratified cover medium for the waveguide. Then, the mode equation of a slab waveguide with a simple and semi-infinite cover medium is modified and solved graphically. The effects of the cell cytoplasm and membrane thicknesses and their refractive indices and the sample-waveguide separation distance on the optical pressure are numerically studied. The results show that the optical pressure increases when the cytoplasm thickness increases, but decreases when the cell membrane thickness is increased. Furthermore, the optical pressure does not significantly change when the sample film thickness increases to more than 0.2 of a wavelength. The optical pressure decreases when the waveguide-sample distance for a specific mode is increased, but can be attractive or repulsive depending on both the cytoplasm refractive index and the mode number.

Stochastic threshold devices using a trap-filling transition (TFT) coupled with molecular dynamics in poly(3-alkylthiophene)s were fabricated as potential key devices for noise-driven bioinspired sensors and information processors. This article deals with variable-temperature direct current conductivity and alternating current impedance measurements for vertical-type device elements of Au/regioregular poly(3-decylthiophene) ((RR−P3DT) (thickness:  100  nm)/Au, which show multiple conducting states and quasi-stochastic transitions between these states. Noise measurements indicate the ω⁻²-type (if V<V_TFT=10  V) and ω⁻¹-type (if V<VTFT) power spectral densities, where V and V_TFT are an applied voltage and the voltage for TFT, respectively. The noise generation is due to the TFT associated with twist dynamics of π-conjugated polymers near the order-disorder phase transition (ODT). At 298 K, the quasi-stochastic behavior is more noticeable for RR-P3DT than poly(3-hexylthiophene). The quasi-stochastic property is employed to a stochastic one-directional signal transmitting device using optical-electric conversion. The dynamics of ODT for powder samples were also investigated by differential scanning calorimetry measurements and high-resolution solid-state ¹³C nuclear magnetic resonance spectroscopy, and the correlation of the molecular structure and dynamics with electric properties was discussed.

The discrete dipole approximation method is used to investigate the optical extinction spectra and the electric field enhancement of Ag conical helix (CH) nanostructures. Based on an expected similarity between the radio frequency response of the antenna with the infrared and the visible response of the nanoantenna, the Ag CH nanostructures were designed as a broadband nanoantenna. It is shown that with engineering the structure parameters of the CH nanostructure the plasmonic response of the nanostructure can be designed for a desirable application. In addition, the change of the substrate material for the nanohelix growth is shown to have infinitesimal effect on the resonance peaks of the conical nanohelix. However, varying the surrounding medium can lead to considerable red-shifting of the plasmonic resonance peaks (up to 230 nm). Calculations of the near field around the helical nanoantenna show that the smaller and the larger sides of the CH are related to the plasmonic resonance peaks at low and high wavelengths, respectively. The calculation result for the extinction spectrum has also been compared with similar experimental data for a 2-pitch Ag conical nanohelix and a relatively good agreement between the numerical calculation and the experiment has been obtained.

A plasmonic lens composed of a dielectric-filled nanoslits structure on an aluminum film is proposed and experimentally demonstrated. The slits’ structure is designed with equal distance, length, and width, but filled with variant thickness SiO₂ dielectric for specific phase retardations. A dual focused ion beam instrument is employed to mill the slits and deposit SiO₂ into the slits. The phase modulation by SiO₂-filled slits is illustrated by a double slits interference experiment. The light focusing behavior of the fabricated plasmonic lens is experimentally characterized by a scanning near-field optical microscope. Experimental results show good agreement with the simulations.

We propose a hybrid hyperlens–superlens structure to achieve demagnifying nanolithography. It consists of a core of planar superlens and a shell of cylinder hyperlens. In the nanolithography process, the shell of the cylinder hyperlens could demagnify the mask patterns to the interior cylinder interface, and then the core of the planar superlens transmits the demagnified patterns to the planar output photoresist layer. The performance of this hybrid hyperlens–superlens structure is analyzed for different periods and spacing of mask and demagnification factors. The numerical simulation results agree well with the theory. It is demonstrated that the hybrid structure could be used as a superresolution device for plane demagnifying nanolithography.

We investigated the influence of free-standing GaN (FS-GaN) substrates on the performance of ultraviolet light-emitting-diodes (UV-LEDs) grown on top by atmospheric pressure metal-organic chemical vapor deposition. High-resolution double-crystal x-ray diffraction (HRDCXD) analysis demonstrated high-order satellite peaks and clear fringes between them for UV-LEDs grown on the FS-GaN substrate, from which the interface roughness was estimated. In addition, the full width at half maximum of the HRDCXD rocking curve in the (0002) and the (101¯2) reflections were reduced to below 90 arc sec. The Raman results indicated that the GaN-based epilayer of strain free was grown. Additionally, the effect of the FS-GaN substrate on the crystal quality of the UV-LEDs was examined in detail by transmission electron microscopy (TEM). The TEM characterizations revealed no defects and V-pits were found in the scanned area. Based on the results mentioned above, the light output power of UV-LEDs on the FS-GaN substrate can be enhanced drastically by 80% and 90% at 20 and 100 mA, respectively. Furthermore, an ultralow efficiency degradation of about 3% can be obtained for the UV-LEDs on the FS-GaN substrate at a high injection current. The use of an FS-GaN substrate is suggested to be effective for improving the emission efficiency and droop of UV-LEDs grown thereon.

The planar interface of an isotropic homogeneous metal and an ambichiral dielectric material can guide surface-plasmon-polariton (SPP) waves. The planar interface of an isotropic, homogeneous dielectric material and an ambichiral dielectric material can guide Dyakonov–Tamm waves. In either instance, we found that, as the ambichiral partnering material evolves into a finely chiral material, the solutions of the dispersion equation for surface-wave propagation evince convergence. The convergence is faster for Dyakonov–Tamm waves than for SPP waves.

We have detected the surface-enhanced Raman scattering (SERS) signals of toluene and 1,2-dichlorobenzene (ODCB) vapors at parts per million concentrations using 1-propanethiol-linked Ag nanoparticles and a fiber optics–coupled Raman spectrograph. Calibration curves were constructed for each detector by plotting Raman band intensity ratios of toluene and ODCB with respect to that of 1-propanethiol as a function of vapor concentration. The detectors showed effective vapor sensing ranges of 0.6 to 600 and 10 to 600 ppm for toluene and ODCB, respectively, following vapor adsorption to the SERS hot spots. We provide evidence for the facility of the SERS detection system for instantaneously discriminating and quantifying respective vapors from a composite vapor.

Comparing predicted and measured spectra from isolated and ordered nanoparticles (NPs) indicates that ordering NPs into lattices can blueshift the localized surface plasmon resonant (LSPR) spectral feature and increase its wavelength sensitivity to local changes in refractive index. This occurs at lattice constants at or above the resonant wavelength. Numerical analysis indicates its results from effects of diffractive modes on LSPR features that are distinct from Fano resonances, which arise separately due to coupling between diffractive modes and localized plasmons. Refractive index sensitivity of the aggregate LSPR peak from NPs in a square lattice (314  nm RIU ⁻¹ ) was 5.8-fold higher than a comparable peak from random NPs (54  nm RIU ⁻¹ ). Measured sensitivities of Fano resonance features in two ordered samples were 127% and 312%, respectively, of the highest LSPR sensitivity from a random assembly of NPs.

Metamaterial perfect absorber (MPA) promises many applications due to its capability of complete suppression of transmission or/and reflection. The complete dissipation of the incident electromagnetic energy by the absorptive meta-atoms makes it a unique candidate in many photonic and optoelectronic devices. An ultrathin metamaterial absorber that consists of a periodic nanostrip metal on top of a planar dielectric slab backed by a conducting metal plate is presented. The spectral absorptivity of MPA is investigated by the finite difference time domain method from visible to near-infrared. The various geometrical and material parameters of MPA are optimized for maximum absorption.

EuMnO₃ nanocrystals (Φ _av ∼5  nm ) synthesized using sol-gel thermolysis exhibit significant difference in magnetic structure in comparison to their bulk-counterpart (Φ _av ∼3  μm ). Opto- and magneto-impedance techniques are successful local probes to bring out the difference between the bulk, nano-manganites with the latter manifesting in multiplicity of spin-defect ensembles attributed to pronounced difference between surface and core states. Electron paramagnetic resonance spectra also confirm the variety of spin-defect ensembles arising from pronounced surface states. Upon optical perturbation, there is significant drop in resistivity (approximately four orders) at room temperature observed for the bulk EuMnO₃ , an otherwise insulating system, which suggests an interesting scope for possible application.

Results of theoretical and experimental investigations of local fields in prepercolation ultrathin nanostructured silver films are presented. Numerical calculations based on the film structure obtained by atomic force microscopy imaging indicate that a substantial amplification of the initial exciting field is possible. The effect is experimentally confirmed by luminescence and Raman measurements.

A photonic crystal (PhC) waveguide platform based on ring-shaped holes in a silicon-on-insulator substrate is proposed in order to realize a refractive index sensor with an improved sensitivity. The three-dimensional finite-difference time domain method is used to analyze the proposed design. The sensitivity is estimated by measuring the shift in the upper band-edge of the output transmission spectrum. Sensitivity analysis of a conventionally designed PhC waveguide, followed by modification of the structure, has been carried out for improving the sensitivity by introducing a row of holes that forms the line defect. Further improvement in sensitivity is obtained by replacing the defect row of holes by ring-shaped holes, which shows a significantly high sensitivity along with considerable output signal strength. The optimized design shows a wavelength shift of 210 nm for a change in ambient refractive index from air (RI=1 ) to xylene (RI=1.5 ), corresponding to an average sensitivity of 420  nm/RIU .

A bilayer hybrid nanoimprinting (NI) method was developed for fabricating embedded metal nanopatterns with greater processability and improved reliability for enhanced photoluminescence (PL) in optoelectronic devices. Bilayer hybrid NI consists of the following: (a) spin-coating ultraviolet (UV) and thermally curable NI resists in sequence, (b) high-pressure thermal NI and UV exposure while maintaining the stamp in a pressed position, and (c) silver (Ag) deposition and lift-off using a thermal NI resist on the upper surface to create embedded Ag nanoarrays. Reference samples with no Ag nanopatterns and with protruding Ag dot-shaped nanopatterns were also fabricated for comparison. The transmittance and PL of all samples were measured. All samples containing Ag nanopatterns exhibited improved PL compared with reference samples with no Ag. For all pattern sizes, the samples with the embedded Ag nanoarrays exhibited the highest PL; the relative PL enhancements compared with samples with Ag dot-shaped nanoarrays were 32.2%, 36.1%, and 62.7% for pattern sizes of 150, 200, and 265 nm, respectively.

The deformed potential structure of CdSe/ZnS core/shell quantum dots (QDs) was analyzed by calculating precise state energies and state functions. Exactly how an external electric field affects the photoluminescence was also studied. Additionally, the tilt potential structure induced by the external electric field, commonly referred to as the quantum-confined Stark effect, was calculated to account for the observed blue and red shifts. Experimental results indicated that the deformation also includes a bend, which is attributed to the shape of a QD. Calculations of the localization of electrons of the foregoing phenomena closely correspond to the experimental data.

Wire-grid polarizers (WGPs) are currently limited by their wafer-scale manufacturing methods to sizes of approximately 12 to 18 in. For large-size displays, a new method for the production of large-area WGPs is required. Large-area WGPs were simulated using the finite-difference-time-domain method, and a scaleable method for their production based on a block copolymer (BCP)-nanostructured template was implemented. The nanostructured template is globally aligned through the use of a cylinder-forming liquid crystal (LC) diblock copolymer, which is first aligned on a rubbed polyimide substrate. A surface-relief template is produced using the differential dry etch rates of the cylinder-forming component and LC polymer matrix component of the BCP. The template is metalized to produce a WGP. Polarizers of arbitrary size with polarization efficiency up to 0.6 have been made in close agreement with calculated values for idealized structures. The choice of the cylinder-forming polymer is critical to the degree of alignment of the template, and the thermal stability of the LC polymer matrix is critical to the stability of the template during etching.

In the present work, the effect of incorporation of graphene on the poly(3-hexylthiophene) (P3HT):CuInS ₂ quantum dot (CIS QD)-based solar cell has been studied. For this purpose, the concentration of graphene is varied from 0 to 0.01% w/w in P3HT–CIS (1:0.5) film. It is found that graphene does not deteriorate the absorption of the composite film. It assists in dissociating the photogenerated excitons (both in P3HT and QDs) owing to its two-dimensional structure and high electron affinity as is evident by photoluminescence (PL) quenching. At 0.01% w/w concentration of graphene about ∼95% of PL is quenched. The electrical characteristics show that the incorporation of graphene enhances the efficiency of the device by establishing interconnected conducting pathways in the volume of polymer matrix. The maximum efficiency is observed to be 1.5% at 0.005% w/w content of graphene. However, at higher concentration, i.e., 0.01% w/w, the device starts deteriorating.

Intense infrared-to-visible upconversion (UC) emission in Tm ³+ /Yb ³+ -codoped sodium niobate (NaNbO ₃ ) nanocrystals under resonant excitation at 976 nm is presented. The results showed that by increasing the pump power/intensity, a strong reduction is observed at the 800/480  nm emitted intensity ratio, characterizing what can be denominated as laser pump power-induced color tunability or luminescent switching. The physical origin is discussed with a focus on tailoring of luminescent switchers to operate at a large pump power range and, indeed, it is intrinsically associated with the competition of the two- and three-photon UC processes and with highly efficient UC emissions in the investigated material. The effect of Yb ³+ -ion concentration along with the theoretical aspects on luminescence switching has been investigated. The results obtained here could be useful in the field of sensors and networks for optical processing and optical communications.

Interference of surface plasmon (SP) waves plays a key role in light transmission through a subwavelength aperture surrounded by groove structures. In order to characterize interference of the hole and groove-generated SP waves, their phase information was carefully investigated using finite difference time domain simulations. In a structure with only one groove, constructive interference of the generated SP waves will enhance transmitted light by a factor of 5.4 compared with that of a single hole. Increasing the groove number to 3 in the design, which supports constructive interference of SP waves, will enhance the transmission coefficient to 10.5 times that for the single-hole transmission coefficient.

III-nitride-based nanowires are a promising platform for solid-state lighting. III-nitride nanowires that act as natural waveguides to enhance directed extraction have previously been shown to be free of extended defects even on foreign substrates, such as silicon. While the efficiency of nanowire-based light-emitting diodes (LEDs) has been investigated, there has yet to be a comparison of heterostructures based on nanowires grown in different crystallographic directions. We compared the directed external quantum efficiency (EQE) of III-nitride LEDs on silicon based on axial and radial nanowire heterostructures, considering m- and c -directional nanowires. The directed extraction efficiency was calculated using photonic simulations, and the internal quantum efficiency (IQE) was estimated using the A-B-C model. We found that m -directional axial heterostructures have the highest directed extraction efficiency, due to the strong polarization anisotropy of III-nitrides, and display similar IQE as c -directional axial heterostructures. By combining IQE and directed extraction, a range of directed expected EQEs reveal that m-directional axial heterostructures have EQEs up to three times that of c -directional axial heterostructures, providing guidelines for the design of future nanowire-based LEDs.

Single- and multiple-quantum well (QW) nanophotonic devices, such as detectors and solar cells, are often fabricated by the concatenation of low-dimensional heterojunctions of different semiconductors. Quantum effects dominate the well structure, with dimensions of the order of several nanometers. At this width regime, even small variations in the fundamental material properties, such as band gap, dielectric constant, lattice constant, and effective mass of the materials, may give rise to errors in determining the fundamental design parameters. This, in turn, can significantly affect the device performance. In cadmium-sulfide/cadmium-telluride (CdS/CdTe) material system, the failure to include the mismatch of electronic effective masses can lead to <30% shift from the real position of the eigenstate energy levels, and <40% shift from the real position of quasi-Fermi levels E _Fn and E _Fp . In addition, depending on the width of the QW active layer, the absorption coefficient value can lead to <12% shift from its real value. These results prompt the need for accurate estimation of such errors in the precise analysis and design of CdS/CdTe heterojunction-based nanophotonic devices.

The fitting of metal optical properties is a topic that has applications in advanced simulations of spectroscopy, plasmonics, and optical engineering. In particular, the finite difference time domain method (FDTD) requires an analytical model of dispersion that verifies specific conditions to produce a full spectrum in a single run. Combination of Drude and Lorentz models, and Drude and critical points models, are known to be efficient, but the number of parameters to be adjusted for fitting data can prevent accurate results from simulated annealing or Nelder-Mead. The complex number relative permittivities of Au, Ag, Al, Cr, and Ti from either Palik or Johnson and Christy experimental data in the visible domain of wavelengths are successfully fitted by using the result of the particle swarm optimization method with FDTD constraint, as a starting point for the Nelder-Mead method. The results are well positioned compared to those that can be found in the literature. The results can be used directly for numerical simulations in the visible domain. The method can be applied to other materials, such as dielectrics, and to other domain of wavelengths.

We carried out a multiparameter fabrication study designed to reduce the line edge roughness (LER) of electron beam (e-beam) patterned hydrogen silsesquioxane resist for the purpose of producing low-loss silicon strip waveguides. Reduced mask roughness was achieved for 50°C pre-exposure baking, 5000  μC/cm ² dose with a beam spot size more than twice as large as the electron beam step size, development in 25% tetramethylammonium hydroxide and postdevelopment baking with rapid thermal annealing in an O ₂ ambient at 1000°C. The LER caused by pattern fracturing and stage stitches was reduced with multipass writing and per-pass linear and rotational offsets. Si strip waveguides patterned with the optimized mask have root-mean-square sidewall roughness of 2.1 nm with a correlation length of 94 nm, as measured by three-dimensional atomic force microscopy. Measured optical propagation losses of these waveguides across the telecommunications C-band were 2.5 and 2.8  dB/cm for the transverse magnetic and transverse electric modes, respectively. These reduced loss waveguides enable the fabrication of advanced planar lightwave circuit topologies.

We employed noncontact terahertz time-domain spectroscopy to investigate and compare the electrical/optical properties of nonaligned single-walled carbon nanotube and nonaligned multiwalled carbon nanotube thin films. Using Drude–Lorentz model together with the Maxwell Garnett effective medium theory, we determined the electrical conductivities from the extracted data of differential complex terahertz analysis in the frequency range of 0.1 to 2 THz. The results demonstrate that the conductivity of isotropic single-walled carbon nanotube thin film is almost two times larger compared to isotropic multiwalled carbon nanotube thin film due to the increased number of surface defects and the availability of mobile carriers. By using Drude–Lorentz model, the broadening optical density and conductivity can be studied at higher frequencies.

Over the past decade, scientists have learned how to manipulate the interaction of radiation with structured materials to an unprecedented level. For decades, our world was limited to materials with primarily positive permittivities and permeabilities, with a few exceptions such as plasmas, for example, whose permittivities can be negative. The research in metamaterials coupled with the rapid advancements in micro- and nanofabrication technologies has removed this limitation and has opened the door to almost arbitrary material properties with some extraordinary consequences across the electromagnetic spectrum, ranging from radio frequencies to optical frequencies. These developments have been strongly complemented by the developments in periodic dielectric photonic crystals where band-gap effects lead to mind-blowing dispersion characteristics and consequent effects. Almost simultaneously, the optics of metals has been brought to center-stage where the plasmonic excitations enable the electromagnetic radiation to interact resonantly with the structured material at very small sub-wavelength scales. These interactions prove to be the key to manipulating the optical near-field, and surprising effects such as sub-wavelength scale imaging by so-called super-lenses made of negative refractive index or plasmonic materials have been discovered.

Graphene’s unique electronic structure due to its two-dimensional nature results in numerous advantageous properties, such as highly tunable chemical potential and the ability to support highly confined surface plasmons with exceptionally long lifetimes. In the context of optical absorbers, we theoretically calculate, using both analytical and numerical techniques, that the coupling of a continuous monolayer of perforated graphene to simple optical cavities results in greatly enhanced absorption in the mid-infrared regime due to graphene surface plasmons, with tunability of the resonance peak by more than its full width at half maximum. We identified and studied two distinct cases: quarter wavelength Fabry–Perot cavities which result in near-unity absorption, and deeply subwavelength cavities which enhance the universal graphene absorption approximately fourfold. The structural simplicity and large spectral tunability of the proposed designs render them applicable to infrared modulators, sensors, and bolometers.

Periodic arrays of subwavelength holes in plasmonic thin films can provide for large broadband transmission in the near-infrared spectrum. The optical transmission properties of these thin films with respect to the film thickness, size, and shape of the holes and the period of the arrays was systematically investigated using finite difference time domain computations. Structured gold and silver films of 20-nm thickness can provide for up to 90% transmittance at near-infrared wavelength, thereby rendering them suitable as transparent conducting electrodes for near-infrared emitters or sensors and photovoltaic applications.

The supercontinuum (SC) generated by pumping in anomalous dispersion is sensitive to the input pulse fluctuations and pump laser’s shot noises and does not possess a single-pulse waveform, so the incident pulse becomes a noise-like train of spikes. A simple method of creating pulsed lasers with either pulse-maintaining ultrabroad SC or specially shaped pulse waveforms can be implemented using all-normal-dispersion microstructured optical fibers (ANDi-MOFs). An ANDi-MOF with a simple topology and dispersion profile maximum at 800 nm was designed using the effective index method. Its properties and suitability were characterized via numerical simulation of femtosecond parabolic pulse formation and generation of an octave-spanning pulse-maintaining SC using a generalized propagation equation. The designed ANDi-MOF is suitable for resolving both problems and allows some detuning of the pulse’s wavelength around 800 nm. However, a better choice for SC generation is pumping at or near the wavelength where the third-order dispersion becomes zero. This configuration benefits from the absence of pulse break-up under large pulse energies, which appears otherwise. The fiber can provide a low-cost method for developing supercontinuum sources and a solution to the problems of parabolic waveform formation to meet the needs of optical signal processing and pulse amplification and compression.

Polarization selectors, especially, those involving quantum dots (QDs) in photonic crystals (PCs) are interesting as they offer scalability for planar architectures. Three-dimensional finite difference time domain simulations were used to design PC structures suitable for polarization-selective transmission of QD emission into different regions as well as polarization beam splitters with different splitting ratios. Different waveguide out couplers were also designed for these coupled waveguide PC structures. As the transmitted intensity is the net result of superposition of all scattered beams, QD position defines the coupling efficiency to different paths. A detailed study showed that the transmission efficiency has intermediate maxima when the QD is shifted in either x- or z-directions.

Many varieties of layered inorganic-organic (IO) perovskite of type (R-NH3 )2 MX4 (where R: organic moiety, M: divalent metal, and X: halogen) were successfully fabricated and characterized. X-ray diffraction data suggest that these inorganic and organic structures are alternatively stacked up along c -axis, where inorganic mono layers are of extended corner-shared MX6 octahedra and organic spacers are the bi-layers of organic entities. These layered perovskites show unusual room-temperature exciton absorption and photoluminescence due to the quantum and dielectric confinement-induced enhancement in the exciton binding energies. A wide spectral range of optical exciton tunability (350 to 600 nm) was observed experimentally from systematic compositional variation in (i) divalent metal ions (M=Pb2+ , Sn2+ , Hg2+), (ii) halides (X=I − and Br − ), and (iii) organic moieties (R). Specific photoluminescence features are due to the structure of the extended MX 2− 4 network and the eventual electronic band structure. The compositionally dependent photoluminescence of these IO hybrids could be useful in various photonic and optoelectronic devices.

Enhanced third-harmonic generation in a one-dimensional photonic crystal doped with third-order nonlinear medium was numerically investigated using the multiple-scale method and the split-step Fourier transform. The optimal fundamental frequency for third-harmonic wave generation was determined from the transmission spectrum. The third-harmonic pulse intensities grow, depending on the structure thickness and the fundamental-frequency detuning parameter, which determines the band-edge phase matching condition. Furthermore, the total energy output of third-harmonic pulses, depending on the fundamental-frequency pulse width, may be more than 1000 times the energy produced by a phase-matched bulk medium. A narrow pulse with bandwidth less than the band-edge transmission peak enables high conversion efficiency. The maximum conversion efficiency of the forward component may be 12 to 13 orders of magnitude greater than that of the backward component.

A periodic lattice wavefield with multiple nondiffracting negative defect sites at the desired locations is very useful in photonic crystal device fabrication and other applications. Such a nondiffracting wavefield was realized by coherently superposing periodic lattice wavefields with Bessel wavefields at each of the defect sites. The experimental verification was done by making use of a phase only spatial light modulator (SLM) in a basic 4f Fourier filtering geometry where the image to be displayed on the SLM was calculated by making use of phase engineering. Photonic crystals with very small periods are possible to be fabricated as the method is wavelength independent and completely scalable.

We investigated optical properties of nanostructured metal-dielectric multilayered lattices under the conditions of epsilon-near-zero (ENZ), a concept derived from the effective-medium approach (EMA). We theoretically found that the periodic array of metallic nanolayers may exhibit either superlensing driven by broadband canalization from point emitters or single-polarization double refraction, and conventional positive as well as negative, even at subwavelength regimes. For the latter case, we formulated a modified EMA, and subsequently a generalized refraction law, that describes both refractive behaviors concurrently. The modal coupling of plasmonic lattice resonances, and nonlocality induced by partial screening across the nanolayer length, are responsible for these distinct effects. Numerical simulations show that deep-subwavelength lensing along the optical axis of Ag-GaAs metamaterial is clearly enhanced at optical wavelengths. On the other hand, transverse-magnetic-polarized radiation that is obliquely incident on the ENZ periodic nanostructures with the same materials in the infrared (around 1.55  μm ) undergoes double refraction neighboring 50/50 beamsplitting.

Fabrication of metal-dielectric nanostructures with subwavelength precision is necessary for plasmon-mediated novel applications. Electron beam lithography (EBL) offers such precision, but for shapes other than circles, squares, and lines, process optimization is required. The EBL and dry etching processes are optimized for subwavelength precision in large area arrays of air groove patterns in gold film in two different length scales. We fabricated one structure for optical frequencies with an asymmetric, nonstandard element having a minimum feature size of about 50 nm and another for terahertz wavelength region with a large aspect ratio of about 975.

Compound plasmonic resonances arise due to the interaction between discrete and continuous metallic nanostructures. Such combined nanostructures provide a versatility and tunability beyond that of most other metallic nanostructures. In order to observe such resonances and their tunability, multiple nanostructure arrays composed of periodic metallic gratings of varying width and an underlying metallic film should be studied. Large-area compound plasmonic structures composed of various Au grating arrays with sub-100 nm features spaced nanometers above an Au film were fabricated using extreme ultraviolet interference lithography. Reflection spectra, via both numerical simulations and experimental measurements over a wide range of incidence angles and excitation wavelengths, show the existence of not only the usual propagating and localized plasmon resonances, but also compound plasmonic resonances. These resonances exhibit not only propagative features, but also a spectral evolution with varying grating width. Additionally, a reduction of the width of the grating elements results in coupling with the localized dipolar resonance of the grating elements and thus plasmon hybridization. This newly acquired perspective on the various interactions present in such a plasmonic system will aid in an increased understanding of the mechanisms at play when designing plasmonic structures composed of both discrete and continuous elements.

We investigated the optical characteristics and polarization insensitivity of an epsilon-near-zero metamaterial structure comprising aluminum-doped zinc oxide nanoparticles (NPs) hosted by a medium of ligands. By the use of an equivalent circuit model for the pairs of NPs, or dimers, and also of fullwave simulations, we studied the response of this self-assembled metamaterial for near-infrared applications. Considering the coupling of localized surface plasmons, we demonstrated the dominance of a certain dimer configuration and then applied this result to the whole medium as a simplifying approximation for a random structure. The consequent results showed a polarization insensitivity and also a general redshift in the plasmon resonance of the structure.

Surface-enhanced Raman scattering (SERS) has emerged as a powerful tool to probe molecules at nanoscale. By utilizing plasmon polaritons on metallic nanowires, remote-excitation SERS can be achieved. Enhancement and modulation of remote-SERS intensity are vital for nano-optical spectroscopy. Counter-propagating plasmons have been excited in a plasmonic nanowire-nanoparticle (NW-NP) system and further utilized to perform remote-excitation SERS. By using the polarization of counter-propagating fields, remote-SERS intensity from NW-NP hot-spot junction was enhanced and modulated. Such capabilities of counter-propagating plasmons to control optical fields and SERS intensity at NW-NP junction can have implications in nanowire photonics and nano-optical spectroscopy.

In the ever onward march of nanotechnology, thin films with engineered structures at nanometer length scales continue to play central roles. Advances in theoretical and numerical methods together with the establishment of ingenious fabrication and characterization techniques have led to the development of nanostructured thin films with controlled compositions and dimensions, highly specific properties, and several functionalities. This development of increasingly sophisticated nanostructured thin films continues unabated. Clear evidence of the vitality of this field is on display each year at the Nanostructured Thin Films conference, which is a constituent of the SPIE Optics + Photonics annual meeting.

The propagation of a surface plasmon polariton (SPP) wave can be guided by the interface of a metal and a columnar thin film (CTF). Theory predicts that the angle of incidence on the prism/metal interface in the Turbadar–Kretschmann–Raether prism-coupled configuration required to excite the SPP wave shifts upon infiltration of the CTF by a fluid. Otherwise identical CTFs of different thicknesses were partnered with dense thin films of aluminum in optical experiments. The angle of incidence for exciting the SPP wave was found to shift to a higher value each time the CTF was infiltrated by a fluid of refractive index of increasing value. Experimental data indicated that the sensor offers a state-of-research sensitivity, thereby proving that a CTF can be a useful platform for SPP-wave-based optical sensing.

A periodic layer of resonant scatterers was considered in the dipolar approximation. The field diffracted by the layer has an asymptotic expression in terms of an impedance operator, which leads to a description of the layer by means of effective properties. Surface Bloch modes appear as a collective effect due to the resonances of the scatterers.

Structural colors are optical phenomena of physical origin, where microscale and nanoscale structures determine the reflected spectrum of light. Artificial structural colors have been realized within recent years. However, multilayer structures require substantial fabrication. Instead we considered one-layer surface textures of silicon. We explored four patterns of square structures in a square lattice with periods of 500, 400, 300, and 200 nm. The reflectivity and daylight-colors were measured and compared with simulations based on rigorously coupled-wave analysis with excellent agreement. Based on the 200-nm periodic pattern, it was found that angle-independent specular colors up to 60 deg of incidence may be provided. The underlying mechanisms include (1) the suppression of diffraction and (2) a strong coupling of light to localized surface states. The strong coupling yields absorption anomalies in the visual spectrum, causing robust colors to be defined for a large angular interval. The result is a manifestation of a uniformly defined color, similar to pigment-based colors. These mechanisms hold potential for color engineering and can be used to explain and predict the structural-color appearance of silicon-based textures for a wide range of structural parameters.

Limitations of current sensors include large dimensions, sometimes limited sensitivity and inherent single-parameter measurement capability. Surface-enhanced Raman spectroscopy can be utilized for environment and pharmaceutical applications with the intensity of the Raman scattering enhanced by a factor of 10⁶. By fabricating and characterizing an integrated optical waveguide beneath a nanostructured precious metal coated surface a new surface-enhanced Raman spectroscopy sensing arrangement can be achieved. Nanostructured sensors can provide both multiparameter and high-resolution sensing. Using the slab waveguide core to interrogate the nanostructures at the base allows for the emission to reach discrete sensing areas effectively and should provide ideal parameters for maximum Raman interactions. Thin slab waveguide films of silicon oxynitride were etched and gold coated to create localized nanostructured sensing areas of various pitch, diameter, and shape. These were interrogated using a Ti:Sapphire laser tuned to 785-nm end coupled into the slab waveguide. The nanostructured sensors vertically projected a Raman signal, which was used to actively detect a thin layer of benzyl mercaptan attached to the sensors.

In the past decade, plasmonic resonators have emerged and exploited field compression to create ultrasmall mode volume devices and to enhance light–matter interactions. We devised a ring resonator on a metal substrate separated by a low-permittivity dielectric, which supports hybrid plasmonic modes with a highly localized electromagnetic field. The finite difference time domain method was used to calculate the properties of the ring resonator. By changing the cavity’s geometry and low-permittivity dielectric’s height, a high-quality factor along with ultracompact mode confinement was achieved, leading to Purcell factor as high as 2.7×10 4 . The hybrid plasmonic ring resonator exhibits a trade-off between the high-quality factor and the ultrasmall mode volume at subwavelength scale in the visible spectrum.

We investigated the optical characteristics and microstructures of wave plates composed of Ta₂O₅(100−x)+TiO₂(x) and prepared by the so-called serial bideposition technique. While a single-layer film prepared by conventional oblique deposition technique has a tilted columnar structure (i.e., tilted optical axis), a serial bideposition film has a narrow, long columnar structure; this ensures that the optical axis of the film is along the quasinormal to the substrate, thus reducing haze. The influence of using additives with Ta₂O₅ was investigated as well. It was found that additive TiO₂ improves optical transmittance at shorter wavelengths. For verifying the advantage of this type of wave plates, quarter wave plates with optimized TiO₂ content were fabricated and their optical performance and reliability were evaluated against those of organic-type wave plates. The results show that the inorganic wave plate prepared by serial bideposition is advantageous for applications where high-transmittance and high-temperature durability are essential.

We considered luminescent TiO ₂ films whose surface was imprinted with a two-dimensional (2-D) square shaped photonic crystal with different pattern depths (from 20 to 61 nm). The aim of this work is to develop a straightforward method to characterize the PhC efficiency on light extraction. Transmission spectra of the patterned areas as obtained using a routine spectrometer exhibit peaks evidencing the coupling by the photonic crystal structure of free-space light with guided modes within the film, in good agreement with 2-D rigorous-coupled wave analysis (RCWA) simulations. As expected, the deeper the pattern depth, the stronger the coupling between the guided light and the photonic crystal. RCWA simulations allow evaluating quantitatively the extraction length, characteristic of the efficiency of light extraction, from the transmission spectra, in good agreement with direct measurements.

Voigt wave propagation (VWP) was considered in a porous biaxial dielectric material that was infiltrated with a material of refractive index n _a . The infiltrated material was regarded as a homogenized composite material in the long wavelength regime, and its constitutive parameters were estimated using the extended Bruggeman homogenization formalism. In our numerical studies, the directions that support VWP were found to vary by as much as 300 deg per RIU as the refractive index n a was varied. The sensitivities achieved were acutely dependent upon the refractive index n a and the degrees of anisotropy and dissipation of the porous biaxial material. The orientations, shapes, and sizes of the particles that constitute the infiltrating material and the porous biaxial material exerted only a secondary influence on the maximum sensitivities achieved. Also, for the parameter ranges considered, the degree of porosity of the biaxial material had little effect on the maximum sensitivities achieved. These numerical findings bode well for the possible harnessing of VWP for optical sensing applications.

Three aluminum (Al)/silicon dioxide (SiO ₂ )/aluminum (Al) nanosandwich films (SWFs) of various heights were fabricated using glancing angle deposition. An SWF comprises a 45-nm thick SiO ₂ layer sandwiched between two Al nanopillars. The thicknesses of both top and bottom nanopillars were varied from 187.5 to 217.5 nm. The equivalent constitutive and related parameters of each SWF were obtained from the reflection coefficients and transmission coefficients that were measured using a walk-off interferometer. Both the equivalent permittivity and the equivalent permeability of each SWF turned out to be negative real. Exactly how the height of the Al nanopillars of the double negative SWF affects its low reflectance through destructive interference is also examined using the wave tracing method. Moreover, the localized reversed magnetic field in the SiO ₂ layer of each SWF was simulated by finite-difference time-domain method to qualitatively interpret the negative real permeability.

We theoretically explain and experimentally demonstrate light trapping in thin-film solar cells through guided-mode resonance (GMR) effects. Resonant field enhancement and propagation path elongation lead to enhanced solar absorption. We fabricate nanopatterned solar cells containing embedded 300-nm period, one-dimensional gratings. The grating pattern is fabricated on a glass substrate using laser interference lithography followed by a transparent conducting oxide coating as a top contact. A ∼320-nm thick p-i-n hydrogenated amorphous silicon solar cell is deposited over the patterned substrate followed by bottom contact deposition. We measure optical and electrical properties of the resonant solar cells. Compared to a planar reference solar cell, around 35% integrated absorption enhancement is observed over the 450 to 750-nm wavelength range. This light-management method results in enhanced short-circuit current density of 14.8  mA/cm ² , which is a ∼40% improvement over planar solar cells. Our experimental demonstration proves the potential of simple and well-designed GMR features in thin-film solar cells.

Thermionic vacuum arc (TVA) method is currently developing, in particular, to work easily with heavy fusible material for the advantage presented by control of directing energy for the elements forming a plasma. The category of heavy fusible material can recall C and W (high-melting point materials), and are difficult to obtain or to control by other means. Carbon is now used in many areas of special mechanical, thermal, and electrical properties. We refer in particular to high-temperature applications where unwanted effects may occur due to oxidation. Changed properties may lead to improper functioning of the item or device. For example, increasing the coefficient of friction may induce additional heat on moving items. One solution is to protect the item in question by coating with proper materials. Silicon carbide (SiC) was chosen mainly due to compatibility with coated carbon substrate. Recently, SiC has been used as conductive transparent window for optical devices, particularly in thin film solar cells. Using the TVA method, SiC coatings were obtained as thin films (multilayer structures), finishing with a thermal treatment up to 1000°C. Structural properties and oxidation behavior of the multilayer films were investigated, and the measurements showed that the third layer acts as a stopping layer for oxygen. Also, the friction coefficient of the protected films is lower relative to unprotected carbon films.

Wave propagation in optical mediums greatly depends on the materials of which the guides are composed. Among the other forms of optical mediums, liquid crystals are both inhomogeneous and optically anisotropic in nature, and exhibit strong electro-optic behavior, which allows alternation in their optical properties under the influence of external electrical fields. These features make optical fibers containing liquid crystals greatly useful for fabricating many optical devices for practical applications. As such, the analytical investigation of wave propagation through liquid crystal optical fibers, particularly a three-layer fiber with radially anisotropic liquid crystal material in the outermost clad section, remains interesting. The power confinement in the liquid crystal section of such fibers can be enhanced for these to be efficiently used in optical coupling and/or sensing applications. Furthermore, a control over the dispersion characteristics, and, hence, the confinement of power, in such fibers may be imposed by making the guide even more complex in the form of introducing a conducting sheath helix structure at the core-inner clad interface.

The relative permittivity dyadic of a dielectric structurally chiral material (SCM) varies helicoidally along a fixed direction; in consequence, the SCM exhibits the circular Bragg phenomenon, which is the circular-polarization-selective reflection of light. The introduction of hyperbolicity in an SCM—by making either one or two but not all three eigenvalues of the relative permittivity dyadic acquire negative real parts—does not eliminate the circular Bragg phenomenon, but significantly alters the regime for its exhibition. Significantly wider circular-polarization-sensitive stopbands may be exhibited by hyperbolic SCMs in comparison to nonhyperbolic SCMs. Physical vapor deposition techniques appear to be suitable to fabricate hyperbolic SCMs.

Pulsed laser deposition is an energetic deposition technique in which thin films are deposited when a laser pulse at 248-nm wavelength strikes a target and material is subsequently deposited onto a substrate with ideally the same stoichiometry. By synchronizing a high-speed mirror system with the pulsing of the laser, and using two separate targets, thin films having tunable stoichiometry have been deposited. Depositions were performed in a high vacuum environment to obtain as much kinetic energy as possible during growth. Typically, some 150 pulses at 300 mJ/pulse were required to deposit 1 nm. Island growth must occur on a per pulse basis since over 100 pulses are required to deposit a 1 nm film thickness. Films were deposited to ∼100-nm thickness, and in situ ellipsometry data were modeled to calculate thickness, n and k. X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and atomic force microscopy (AFM) were all performed on each of the films. XPS demonstrated change in film composition with change in laser pulse ratio; ellipsometry displayed thickness from the model generated as well as the optical properties from 370 to 1690 nm. AFM thickness measurements were in agreement with independently modeled ellipsometry thickness values.

This PDF file contains the editorial “Special Section Guest Editorial: Nanophotonic Materials and Devices” for JNP Vol. 8 Issue 01

A method for the correction of positioning error in Talbot lithography is proposed and investigated both experimentally and theoretically. The enhancement of the features in this method is achieved by the temporally noncoherent illumination, which leads to the overlap between Talbot images of different frequencies. This results in an improvement in the depth of focus and, thus, less sensitive patterns to the positioning error. A spectral-domain analysis for the estimation of the positioning error is employed for the verification and finding of a criterion for selecting appropriate light sources.

A photonics crystal (PhC) waveguide that operates in the slow-light regime is reported in this paper. A second line of circular air holes from the PhC waveguide in a triangular lattice is replaced by a line of elliptical air holes. Based on a three-dimensional plane wave expansion, the lateral shift of elliptical air holes is conducted to enhance the slow-light characteristics. A group index of 166 and a delay-bandwidth product of 0.1812 are derived from an optimized PhC using elliptical air holes with a lateral shift of 160 nm according to the simulation results. A Mach–Zehnder interferometer (MZI) is integrated with the above-mentioned PhC waveguide with a 17  μm length in one of its arms. The measured transmission spectrum of the fabricated MZI embedded with a PhC waveguide shows slow-light interference patterns.

Al-doped ZnO (AZO) films were deposited on glass and polycarbonate (PC) at room temperature by using pulsed Nd:YAG laser at 355 nm. AZO thin films were obtained for both substrates at laser fluences from 2 to 5  J/cm² in O₂ partial pressure of 2.1 Pa. The effects of laser fluence on the structural, electrical, and optical properties of the films were investigated. The films with lowest resistivity and highest transmittance have been obtained at 2  J/cm². The resistivities were 2.29×10⁻³  Ω cm for AZO on glass and 1.49×10⁻³  Ω cm for AZO on PC. With increasing laser fluence, the deposited films have lower crystallinity, higher resistivity, and smaller optical bandgap.

We have realized and characterized an optically pumped hybrid photonic crystal (PhC) L3 nanocavity made of an organic material as a gain medium and a Si₃N₄ two-dimensional PhC. The organic gain medium consists of a guest-host system with tris(8-hydroxyquinolinato) aluminum (Alq3) as the hosting matrix doped with 4-(dicyanomethylene)-2–t-butyl-6(1,1,7,7–tetramethyljulolidyl–9-enyl)-4H-pyran (DCJTB) as a guest. A laser emission at 662 nm with a threshold of 9.3  μJ/cm² is experimentally observed. The impact of the organic layer thickness on the laser threshold is studied.

A negative Goos–Hänchen (GH) shift of light beam reflecting from planar microphotonic structures consisting of two parallel dielectric subwavelength diffraction gratings is predicted. The phenomenon occurs because the energy flow of the mode guided in the subwavelength structure is predominantly directed in the opposite direction to the energy flow of the incident beam. The numerical calculations show that the negative GH shift can reach approximately six times that of the wavelength in realistic structures, so that the phenomenon can be experimentally observed. In addition to the negative lateral shift, the focusing of the beam in reflection from the grating is also observed as a secondary effect.

We explore, theoretically and experimentally, the spatial (angular) filtering of two-dimensional light beams by longitudinally chirped axisymmetric photonic microstructures. The structures comprise a set of planes of concentric rings with the separation between the plates smoothly varying along the propagation direction. Axisymmetric structures were recorded in a bulk of glass, in which the refractive index has been modulated using tightly focused femtosecond laser pulses. We show that the spatial filtering recently shown in nonchirped axisymmetric structures can be substantially improved by the chirp: the angular range of filtering was increased approximately two times. The numerical study reveals that the filtering efficiency can be strongly increased using the longer and larger index contrast axisymmetric photonic structures.

The photocatalytic water splitting using Cu_xO film on metallic structures under visible light illumination is investigated. A plasmonic enhanced layer is applied for high efficient light harvest and to form a heterojunction to prolong the lifetime of the photogenerated electron-hole pairs. Although Cu_xO is a potential photocatalyst with high efficiency, it suffers from serious photocorrosion. The photocorrosion mechanism of p-type Cu_xO has been investigated using x-ray photoelectron spectroscopy. Through analyzing the composition of Cu_xO during a photocatalytic water splitting reaction, it is found that the photocorrosion of Cu₂O on Pt is caused by the reduction of Cu₂O to Cu, while the photocorrosion of Cu₂O on Au is caused by the oxidation of Cu₂O to CuO.

We present the design and the characterization of a polycrystalline silicon (Si)-based photonic crystal (PhC)-suspended membrane, working in the mid-infrared wavelengths. In order to facilitate transmission measurement, the PhC membrane is released by removing the underneath Si substrateWe present the design and the characterization of a polycrystalline silicon (Si)-based photonic crystal (PhC)-suspended membrane, working in the mid-infrared wavelengths. In order to facilitate transmission measurement, the PhC membrane is released by removing the underneath Si substrate. Around 97% reflection and 3% transmission at 3.58-μm wavelength are measured at room temperature. Characterization is also done at 450°C and it reveals that the peak reflection of the PhC membrane shifts by 75 nm to higher wavelengths. This corresponds to a linear wavelength shift of 0.174  nm/°C and the thermo-optic coefficient is calculated to be +1.70×10⁻⁴  K⁻¹. By altering the dimension of the PhC air holes, it is also shown that such a thermo-optic effect is compensated.

The polarization-dependent optical properties of InGaN/GaN multiquantum wells blue light-emitting diode with one-dimensional (1-D) plasmonic nanoparticles grating are investigated using an angle-resolved photoluminescence spectrometer. The light extraction efficiencies of the 1-D GaN grating coated with an Au layer and 1-D GaN grating coated with an Au nanoparticle monolayer are measured. It is shown that the light extraction efficiency of plasmonic nanoparticle grating coated with an Au nanoparticle monolayer is 1.4-fold higher than that of a 1-D GaN grating coated with Au film because the surface plasmon losses are conquered. In addition, the experimental dispersion of the surface plasmon (SP)-assisted light enhancement shows a good agreement with the dispersion of SP at the Au/GaN interface.

Plasmonic materials, especially silver, are widely used to increase efficiency of solar cells due to their ability to localize the light in nanoscale. This tight confinement increases the absorption of a thin film solar cell. However, these materials are expensive and increase the cost/watt of the solar cell. Thus, finding an abundant and cheap material with a comparable plasmonic effect can dramatically reduce solar cell cost by enabling the use of ultrathin active layers. In this work, we investigate TiN as an alternative cheap and abundant plasmonic material. TiN is also more CMOS compatible. Several TiN plasmonic solar cell configurations are studied and analyzed. These studies show that the TiN plasmonic solar cell has a comparable performance for back side plasmonic configuration.

Nonreciprocal transmission is achieved through an optical prism coupling system composed of magneto-optical (MO) media. The transmission properties of the system are studied through the developed transfer matrix method for magnetic materials. The unusual result is that a tunable nonreciprocal resonance tunneling occurs if two MO cavities have reversal magnetization. The results are verified through an electromagnetic field simulation based on the finite element solver.

This paper is devoted to the 90th anniversary of the 1924 publication of the seminal paper by Bose titled “Planck’s law and the hypothesis on light quanta” (Zeitschrift für Physik26, 178–181). The paper has been the cornerstone quantum statistical physics. Remarkably, the very starting idea is the discreteness of phase space expressed in the form of the density of states. Bose considered equilibrium electromagnetic radiation as gas of photons and, therefore, introduced the photon density of states notion into the physics though without using directly the term “density of states.” Today, engineering photon density of states to modify light-matter interaction in nanostructures including both spontaneous emission and spontaneous scattering of photons constitutes the solid part of nanophotonics.

This paper [J. Nanophoton. 8(1), 083097 (2014)] was published on 6 January 2014. Thanks to a question by Yoann Brûlé from the Fresnel institute (Marseille, France), we found that the values of γL and γD were swapped in tables in Ref. 1. The problem comes from a bug in the automatic extraction of data from optimization method. Fortunately the curves in Ref. 1 are correct. This erratum gives a more readily available formulation of fitting for all considered metals and the corresponding criteria.

An author’s affiliation in this article [J. Nanophoton.. 7, (1 ), 073077 (2013)] was changed. The affiliations appear correctly above. All online versions of the article were corrected on 23 May 2014.

This article [J. Nanophoton.. 8, (1 ), 083095 ( Feb 13 , 2014)] was originally published with two figures out of order. Figure 7 appeared above the caption for Fig. 6, and Fig. 6 appeared over the caption for Fig. 7. All online versions of the article were corrected on 28 February 2014.

This article [J. Nanophoton.. 8, (1 ), 083890 ( Feb 5 , 2014)] mistakenly appeared in the Special Section on Metamaterials and Photonic Nanostructures. It was republished in the Special Section on Nanostructured Thin Films VI with a corrected CID on 10 February 2014. The updated citation is shown below: