This PDF file contains the front matter associated with SPIE Proceedings Volume 8564 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

Strong optical confinement to the low-index slot, such as Er_xY_2-xSiO₅, is expected for guided TM mode. The confinement effect leads to modification of the optical mode density, resulting in the enhancement of radiative transition. We have fabricated slab Si-slot waveguides with Er₂SiO₅ slot layers in order to demonstrate the dependence of radiative emission on the guided waveguide modes. The PL fine structure particular to Er₂SiO₅ crystal has been observed through the waveguide structure. We confirmed the enhancement of the TM mode edge emission, and the intensity was about two times higher than that of TE mode.

Erbium silicates and Yttrium and Ytterbium co-doped Er silicates have been fabricated in sol-gel and sputtering methods. Two orders of magnitude photoluminescence intensity enhancement was observed by Yttrium and Ytterbium co-doping Er silicates compared with that of pure Er silicate. Three kinds of waveguide structure, the strip-loaded, slot and hybrid ErYb/Y silicates waveguides have been obtained, and the optical amplification was observed in these waveguide structures. 1.53μm electroluminescence in ErYb silicates was also realized using hot carriers’ impact excitations of Er ions.

In this paper, we propose a new design of all-normal and ultra-flat dispersion As₂Se₃-based chalcogenide photonic crystal fibers (PCF). The generation of supercontinuum (SC) in the designed fibers is investigated, which has flat and smooth profile, covers a broad range extending from 2 to 8 μm. The significance of this work is that it provides a new type of mid-infrared SC source with flat shape, broadband and high coherence properties by pumping the As₂Se₃-based PCF. Thus many applications can be performed such as fiber lasers, pulse compression and multi-wavelength optical sources in the mid-infrared region.

We develop a low-temperature theory of the resonant Raman scattering from a semiconductor quantum dot, whose electronic subsystem is resonant with the confined longitudinal-optical (LO) phonon modes. Our theory employs a generalized model for the quantum dot's energy spectrum renormalization, which is induced by the polar electron-phonon interaction. The model takes into account the degeneration of electronic states and allows for arbitrary LO-phonon modes to be involved in the vibrational resonance. We solve the generalized master equation for the reduced density matrix, in order to derive an analytical expression for the differential cross section of the resonant Raman scattering from a single quantum dot.

The photophysical properties of a novel series dendrimer phthalocyanine-SWNTs nanoconjugates in which the dendrimer phthalocyanine was tetra-[3,5-di-(4-carboxylic benzyloxy)benzyloxy] zinc(Ⅱ) phthalocyanine covalently linked with SWNTs using ethylenediamine or hexamethylenediamine as space linkers were investigated in detailed by the fluorescent spectra and time-resolved spectroscopy. The photoindued intramolecular electron was transferred from phthalocyanine (donor) to carbon nanotubes (acceptor). Novel functionalized constituents in this work are fundamentally important due to the synergy effects of carbon nanotubes and dendritic zinc phthalocyanine, which may find potential applications in the drug delivery, biological labels and many other related fields.

The base current (I_B) plays a key role in the transistor since its discovery (16 December 1947, Bardeen and Brattain). It separates the low impedance input (emitter) from the high impedance output (collector), thus yielding a “transfer resistor.” Recently, III-V semiconductor material has been fabricated as a heterojunction bipolar transistor (HBT) which can operate as a high speed device. The HBT can be modified and operated as a three-port light-emitting device (an electrical input, electrical output, and a third port optical output) by incorporating one or more quantum wells in the base region, thus becoming a heterojunction bipolar light-emitting transistor (LET). In the present work, we have designed different sizes of emitter diameter D_E and base diameter D_B of InGaP/GaAs LETs in aperture layout design. Through different layout designs, the LETs exhibit different electrical current gain (β= I_C/I_B) and optical light output due to different carrier recombination processes in the transistor base region. By reducing the lateral emitter size from 18 to 13 μm, β increases due to the higher injection current densities and better confinement of the radiative recombination in the base region. Moreover, β increases when reducing the base diameter from 27 to 22 μm with fixed emitter diameter. The effective carrier recombination lifetime, τ_rec, can be estimated from dc analysis and rf measurement (small-signal modulation).We have obtained multi-GHz spontaneous light modulation of LETs, and the device performance is closely related to different layout designs with different device parasitics.

In this paper, we first review and compare the two main techniques allowing to purify and extract selectively semiconducting single-walled carbon nanotubes (s-SWNT)). These purification steps are essential to obtain an optical-quality material. Such material is then suitable for optical applications and photonic devices. We present two major advances in carbon nanotubes optics and photonics: on one hand, the demonstration of optical gain in s-swnt by two independent methods, with modal gain as high as 160 ±10 cm^-1 at 1.3 μm and on the other hand, the integration of SWNT in silicon-on-insulator (SOI) platform as a potential material for integrated photonic devices. Overall coupling efficiency could be estimated up to 10^-1.

We review our recent efforts of optical modulators and routers for photonic networks-on-chip. Through the optimization of the doping concentration and profile as well as the coplanar waveguide electrodes, we demonstrate a 2-mm-long carrier-depletion optical modulator which can work at a speed of 40 Gb/s under a differential voltage of 0.36 V with no reverse bias. We demonstrate a spatially non-blocking five-port optical router based on thermo-optically tuned microring resonators. The optical router has a footprint of 440×660 μm², a 3-dB bandwidth of 0.31 nm (38 GHz), an extinction ratio of 21 dB for through port, and an extinction ratio of 16 dB for drop port at 1551 nm. 12.5 Gbps high-speed data transmission experiments verify the good routing functionality of the optical router.

In this work we present results from high performance silicon optical modulators produced within the two largest silicon photonics projects in Europe; UK Silicon Photonics (UKSP) and HELIOS. Two conventional MZI based optical modulators featuring novel self-aligned fabrication processes are presented. The first is based in 400nm overlayer SOI and demonstrates 40Gbit/s modulation with the same extinction ratio for both TE and TM polarisations, which relaxes coupling requirements to the device. The second design is based in 220nm SOI and demonstrates 40Gbits/s modulation with a 10dB extinction ratio as well modulation at 50Gbit/s for the first time. A ring resonator based optical modulator, featuring FIB error correction is presented. 40Gbit/s, 32fJ/bit operation is also shown from this device which has a 6um radius. Further to this slow light enhancement of the modulation effect is demonstrated through the use of both convention photonic crystal structures and corrugated waveguides. Fabricated conventional photonic crystal modulators have shown an enhancement factor of 8 over the fast light case. The corrugated waveguide device shows modulation efficiency down to 0.45V.cm compared to 2.2V.cm in the fast light case. 40Gbit/s modulation is demonstrated with a 3dB modulation depth from this device. Novel photonic crystal based cavity modulators are also demonstrated which offer the potential for low fibre to fibre loss. In this case preliminary modulation results at 1Gbit/s are demonstrated. Ge/SiGe Stark effect devices operating at 1300nm are presented. Finally an integrated transmitter featuring a III-V source and MZI modulator operating at 10Gbit/s is presented.

Optical properties of a azo-dye attached on the surface of the monodisperse silica photonic crystal have been investigated. The azo-chromophore was covalently attached to a 3-isocyanatopropyl triethoxysilane (ICPTES) having isocynate functional group by a urethane bond formation reaction. The resulting disperse red/ICPTES (DRICP) was attached on the surface of the silica photonic crystal by hydrolysis and condensation reactions. The FTIR spectrum of the resulting product DRICP/silica sphere (DRICPSS) shows no characteristic isocynate absorption peak at 2270 cm^-1 and shows a new absorption peat at 1700 cm^-1 corresponding the C=O stretching vibration. This result indicates the complete reaction between –N=C=O and –OH. The DRICPSS has weak brownish color when it is dried. The color of the DRICPSS changed to intense red when it is wetted in methanol, ethanol and 2-propanol. The near infrared absorption maximum at 788 nm shifted to 718 nm for the ICPDRSS after wetting in methanol. This system can be applicable to a sensitive alcohol sensor.

One-dimensional PhC mirrors are constructed in a single-mode silica slab waveguide with a row of elliptical holes. The photonic band gap (PBG) of the PhC structure is attained by fast eigen-mode calculations. Being aware that component radiated waves of the PhC mirror are generated at interfaces between different waveguide sections, when propagating guided waves impinge on these interfaces, we point out that the total radiation loss of the PhC mirror is consequence of interferometric interplays of component radiated waves. We visualize this radiation generation process with intuitive pictures. We also estimate total radiation losses of PhC mirrors by using an analytical model. For uniform PhC mirrors, our model explains the oscillations of the total radiation loss with the increase of the period number. The calculated results agree well with the numerical simulations in terms of the oscillation period, the damping speed, the initial phase, and the relative intensity. For non-uniform PhC mirrors, our model finds that the progressively tapered transition from the feeding waveguide to the PhC mirror does not yield the lowest radiation loss. This finding is against to the well known “impedance-matching” picture. The matching of our model with the simulated results certifies the interferometric nature of the radiation generation process in a PhC mirror especially when a low-index waveguide is considered.

We report experimental measurements of slow light in Comb Photonic Crystal Waveguides (CPCW). The tailoring of the slot into a comb allows performing dispersion engineering in order to achieve slow light regime, and efficient tapers allow a high coupling efficiency. We also investigate the losses with cut-back measurements and show that losses are comparable with those of a standard W1 Photonic Crystal Waveguide, whereas the nonlinear effective area is strongly reduced. This type of waveguide offers opportunities to realize compact devices with an ultra-high light confinement for achieving optical nonlinearities with a low index material.

The dispersive properties of planar photonic crystals (PhCs) have been envisaged for years. In particular, the superprism effect has been considered to obtain a strong influence of input beam conditions (e.g. wavelength or input angle) on the light group velocity direction, enabling the design and fabrication of on-chip infra-red spectrometers and integrated optical demultiplexers. We extend here the properties of PhCs to the study of graded photonic crystals (GPhCs) made of a two-dimensional chirp of lattice parameters and show that GPhCs enable solving several drawbacks of dispersive PhCs like the beam divergence issues or the need of long preconditioning regions to precompensate beam diffraction effects. The proposed approach is applied to a square lattice air-hole PhC with a gradual filling factor that was fabricated using ebeam lithography and ICP etching techniques. A nearly-constant 0.25μm/nm spatial dispersion is demonstrated for a 60μm square GPhC structure in the 1470-1600nm spectral range without noticeable spatial or spectral spreading. Moreover, contrary to PhC superprism structures, a linear dispersion is obtained in the considered wavelength range.

Two kinds of full-filled photonic crystal fibers (PCFs) with different air hole size were investigated by experiments. All the air holes were filled with liquid crystal (LC). The full-filled part was heated to different temperatures to research the transmission character. In different temperature conditions, below or over 65°C, the two kinds full-filled LC-PCFs had their own performance. Mode coupling analysis and LC phase theory were used to explain their different performance. By researching their output light spots and transmission spectra, we demonstrated that LC-PCFs could be applied in optical switching, filter, attenuator or other optical devices.

We report a four-channel on-chip true-time-delay (TTD) module based on a photonic crystal waveguide (PCW) array. By minimizing the coupling loss with a photonic crystal taper (PC taper), the delay lines with 1–3mm long PCWs can operate up to a group index ng~23 without significant loss. The large group velocity dispersion enables continuous and wavelength-tunable time delays. Measurements show a highly linear phase-frequency relation, highest time delay up to 216.7 ps, and large tuning ranges of 58.28 ps, 115.74 ps, and 194.16 ps for 1–3mm delay lines, respectively. The chip-scale TTD module can provide ±44.38° steering for an X-band phased array antenna (PAA), but occupies only 0.18 mm² area.

Porous anodic alumina (PAA), with highly ordered microstructures, has attracted much attention due to some unique physical and optical characteristics. In recent years, PAA is also used to obtain different colors by methods such as growing nanowires, tuning pore depth, or sputtering metal on PAA surface. In this paper, we report a simple and precisely controllable method to tune color by changing the pore diameter of PAA. In order to obtain PPA with different pore diameter, we first prepare the PPA membrane by two step anodization of high purity aluminium foil in acidic solutions and then immerse the fabricated PPA membrane into phosphoric acid to enlarge pore diameter. The different pore diameters of PAA are controlled by immersed time in phosphoric acid. After sputtering metal on surface of PAA, the brilliant color can be seen on the surface of PAA. Different colors of PAA film with metal-coated are obtained using this method and colorful patterns are successfully fabricated. The physical model of the PAA is constructed and the mechanism of tuning color is analyzed. It is concluded that the color can be tuned by changing pore diameter of the PAA membrane. This method will be of potential use in decoration, color displays and anti-counterfeiting technology.

In the past decades, Si has been the most important material for electronics. By exploiting this mature semiconductor fabrication technique, it is also highly desired to use Si for applications in other areas. Here we report the use of Si micro-structures for optical-communications and Si nano-structures for energy applications. Sub-micron Si waveguides is fabricated on Si substrates rather than SOI (silicon on insulator) substrate using laser reformation technique. This method helps solve the incompatible problem for the integration of optics and electronics on a single Si chip. The typical thickness of the oxide layer on the CMOS transistor layer is below 100nm which, however, creates excessive optical loss due to the light coupling into Si substrate. Besides, fabricating Si photonics on Si wafer is much cheaper than that on SOI wafer. The method is using high-power pulse laser to melt high-aspect ratio Si ridges. This creates a structure with wider upper portion and narrower lower portion, which can be further oxidized and forming waveguides. For energy applications, Si nanostructures are fabricated using the metal-assisted chemical etching (MacEtch) technique. Si nanostructures could greatly reduce the surface reflection to enhance light harvest. In addition, Si nanowires are further combined with organic materials to form hetero-junction solar cells using low-cost solution process. Furthermore, the Si nanostructures and MacEtch process are refined to form completely single-crystal Si thin film. Thus the material cost of Si solar cells can be potentially reduced to only 1/10 of current ones.

Chalcogenide glasses, namely the amorphous compounds containing sulfur, selenium, and/or tellurium, have emerged as a promising material candidate for integrated photonics given their wide infrared transparency window, low processing temperature, almost infinite capacity for composition alloying, as well as high linear and nonlinear indices. Here we present the fabrication and characterization of chalcogenide glass based photonic devices integrated on silicon as well as on flexible polymer substrates for sensing, optical interconnect and nonlinear optics applications.

Fano resonances, sometimes behaving like electromagnetic induced transparency (EIT)-like resonances in whisperinggallery- mode (WGM) microcavities are attracting much attention due to the important applications in high-sensitivity biosensing, optical switch, and slow light. In this paper, Fano resonances in several WGM systems are reported, including in a single WGM photonic microcavity and in coupled WGM microcavities. Specifically, in a single WGM microcavity system, Fano or EIT-like resonances in both polydimethylsiloxane (PDMS) coated silica microtoroid and bare silica microtoroid are experimentally investigated. In coupled microcavity system, we report a theoretical study of EIT-like resonance in an array of microcavities indirectly coupled through a parallel waveguides system. Finally, we experimentally investigate the Fano resonance in two microcavities indirectly coupled via a single fiber taper.

We theoretically investigate electromagnetic responses of a bilayered metamaterial in the optical frequency range. The metamaterial consists of two stacked split ring resonators with a twist angle spatially separated by a dielectric layer. The simulated results show that the bilayered metamaterial exhibits multiple transmission windows based on mutually coupling between two twisted resonators at normal incidence and the manifested transmission properties can be controlled efficiently by adjusting structural parameters of a unit cell. The coupling in metamaterials offers an effective way to manipulate the electromagnetic properties of metamaterial-based devices.

A compact 1.6×10μm² germanium pin waveguide photodetector was demonstrated on a Silicon-on-Insulator substrate. The dark current of the photodetector was measured to be 0.66μA at -1V bias voltage, which is much lower than recently reported. The photodetector exhibited a 3-dB bandwidth of 20GHz at the wavelength of 1.55μm. A clear open eye diagram at 10Gb/s was also obtained.

Silicon photonic biosensors based on cascaded resonators employing the Vernier effect are shown to be capable of greatly increasing the sensitivity. Two implementation schemes are presented, one using two cascaded ring resonators with a broadband light source, and the other by cascading a Fabry-Perot laser with a silicon ring resonator. Simple intensity interrogation schemes are developed to advance the planar waveguide sensor technology towards low-cost practical applications.

The fiber-to-the-home (FTTH) systems are growing fast these days, where two different wavelengths are used for upstream and downstream traffic, typically 1310nm and 1490nm. The duplexers are the key elements to separate these wavelengths into different path in central offices (CO) and optical network unit (ONU) in passive optical network (PON). Multimode interference (MMI) has some benefits to be a duplexer including large fabrication tolerance, low-temperature dependence, and low-polarization dependence, but its size is too large to integrate in conventional case. Based on the silicon photonics platform, ultra-short silicon MMI duplexer was demonstrated to separate the 1310nm and 1490nm lights. By studying the theory of self-image phenomena in MMI, the first order images are adopted in order to keep the device short. A cascaded MMI structure was investigated to implement the wavelength splitting, where both the light of 1310nm and 1490nm was input from the same port, and the 1490nm light was coupling cross the first MMI and output at the cross-port in the device while the 1310nm light was coupling through the first and second MMI and output at the bar-port in the device. The experiment was carried on with the SOI wafer of 340nm top silicon. The cascaded MMI was investigated to fold the length of the duplexer as short as 117μm with the extinct ratio over 10dB.

A new modal analysis based on the simplified mode method and multi-beam interference theory is proposed. Multiple reflection of propagating modes at grating interfaces is considered by introducing equivalent Fresnel coefficients into the diffraction process analysis. Then the proposed modal analysis is applied to design a rectangular-groove fused-silica grating as a three-port beam splitter. The diffraction efficiency expressions are derived in this paper, which are analogous to the results of multi-beam interference of a plane-parallel plate. Dependence of diffraction efficiencies of the transmission 0th and 1st diffractive orders on the groove depth is obtained with optimized grating period and duty cycle. Compared with the simplified mode method, the results based on the proposed modal analysis can match much better with those from rigorous coupled-wave analysis (RCWA), which proves the validity of the new modal analysis method. Moreover, the analysis results give an intuitionistic proof that the ideal 100% diffraction efficiencies of the transmission diffractive orders can’t be realized and the transmission 0th order can’t be cancelled in low-contrast grating. As the effective refractive indices of diffractive orders are introduced into the diffraction process analysis, this modal analysis is all valid under the usual incidence cases of normal incidence, Littrow mounting, and second Bragg angle incidence. More importantly, the proposed modal analysis provides a more accurate physical image of grating diffraction process, which should be a useful analysis tool for high-density grating.

A modal method is concerned with the modes excited, propagating, and coupled out into diffraction orders of a grating. Compared with the well-known rigorous-coupled-wave algorithm (RCWA), the modal method is less recognized. While the RCWA is a pure-numerical method, the modal method reveals a clear physical picture of the modes inside the grating. When a grating has a large period, it usually has too-many modes that are excited and propagating, and its analysis would be too complex. When a grating has a subwavelength period or a close-to-wavelength period, a few modes will be excited and propagating. When a few modes are concerned in the analysis, we have a simplified modal method. We have developed a simplified modal method to explain diffraction due to a deep-etched fused silica grating. Here the “deep-etched” means that the grating has a high ratio of deep-etched depth to the groove width. When a deep-etched fused silica grating has a subwavelength period, there are a few (one to two) lower modes that are propagating modes, and higher-order modes are evanescent. We have developed an average effective-index concept to describe a triangular deep-etched grating, and obtained simple analytical equations to describe a three-port beam-splitting grating. These analytical equations are impossible to obtain with the pure-numerical RCWA. This simplified modal method should be a useful tool for designing a variety of subwavelength deep-etched fused silica gratings for practical applications.

Diffraction grating is a high-resolution dispersion optical element. It has been widely used as the key component in optical spectroscopy, telecommunication multiplexing and laser systems, etc. Recently there is a growing demand for large-sized diffraction gratings in spectrometers industry, laser fusion facility, and its fabrication method is also a hot topic now. To fabricate large sized gratings, we have developed a grating imaging scanning lithography system. In this technology, the phase grating with jagged edge is used to generate diffractive beams and the spatial filter is used to select ±1 order diffractive beams. Then two-beam interference on the substrate forms the grating fringes. At the same time, a 4f-system is used to form an identical image with clear boundary in the interference area. A high precision twodimensional mobile station, which enables the accurate positioning and move of the substrate, is utilized for complementary cyclical scanning, thus the image stitching errors are effectively eliminated. With this technology, we have fabricated a grating with period of 20μm and size of 100mm×100mm. In this paper the grating imaging scanning lithography procedure is described step by step. The principles and the experimental results are also explained in detail. With the characteristics of a simple structure, high energy utilization and stability, this new lithography technology should be an efficient way to fabricate large sized grating in the future.

A polarization-independent bandwidth-tunable filter with a large tuning range using binary blazed grating based on silicon on insulator (SOI) is proposed and designed. This grating filter can show different spectral bandwidths under different angles of incidence. When the angles of incidence ranges from 42° to 48°, the grating functions as an ultranarrow filter, and its minimal full width at half-maximum (FWHM) is about 0.6nm. More importantly, its resonant wavelength shifts linearly with respect to changes in the angle of incidence, with a slope of 4.5nm/°regardless of the polarization states. When the angle of incidence is changed to 10°it turns into a broadband filter, which has a reflectivity of over 99% in the wavelength range of 1510nm~1600nm for both polarization states.

An eigenvalue analysis of plasmonic waveguides built in a general layered medium is introduced by combining the Multiple Multipole Program (MMP) with modified layered media Green's functions (LMGF). The new method, first, provides the possible locations of the eigenvalues on a given complex plane (called search functions in the MMP analysis), which provides a very useful information when locating the eigenvalues not only by MMP but also by other numerical methods. Special eigenvalue search and tracing routines are then used to determine the exact locations of the eigenvalues around the possible locations provided by the search functions. The details of the MMP and the modification on LMGF is introduced, together with various numerical examples demonstrating the efficiency of the method.

To promote the miniaturization and integration of devices, various optical components based on hybrid plasmonic waveguides have been proposed such as microring resonators and Y-splitter. However, their footprints are strongly limited by the radiation loss of the bends. Here, we propose and analyze a novel hybrid plasmonic waveguide (NHPW) which can be used to realize sharp bend with little radiation loss. Based on NHPW, ultracompact racetrack resonators are realized. A racetrack resonator with an outer radius of 0.5μm and straight waveguide of 0.1μm is constructed, which has an extinction ration of 12.56dB and a significantly large free space range of 265nm.

Silicon-on-insulator (SOI) nanowire provides a very promising way to realize the future large-scale nano-photonic integrated circuits because of the CMOS compatibility and the ability for ultrasharp bending. The giant birefringence of SOI nanowires makes on-chip polarization handling become very important and useful for many applications, like polarization-transparent silicon photonics, coherent optical communications, and on-chip quantum photonics. In this paper, our recent work on on-chip polarization handling is reviewed and summarized, including polarization-beam splitters, polarization rotators, as well as polarization splitter rotators.

In particular, the surface plasmon polariton (SPP) is attractive to enhance the spontaneous emission (SE) from active materials due to the larger density of state (DOS) and smaller mode volume comparing with optical wave, namely Purcell effect. Usually, the Purcell factor (PF) is calculated from the reduced form of Fermi’s golden rule, where only the DOS and mode volume of photon (or SPP mode) are involved. Obviously, the PFs calculated with reduced form exclude the influence of active material and only evaluate the effect of cavity or SPP waveguide. However, for a practical emitter, the linewidth could not always be ignored. For example, the ensemble emission linewidth of mass Si- quantum dots (QD) is about 220meV~400meV (90~160nm), which are much wider than the linewidth of the SPP DOS In this work, the PF of SPP mode on Au-Si₃N₄ grating is calculated with full integration formula of Fermi’s golden rule by taking account of the spontaneous emission linewidth from single Si-QD. The calculated PF is about 1.7~1.4 within the emission range of †hω₀ =1.9~1.6eV. Comparing with the PF value of 266.9~30.1, which is calculated without including the emission linewidth of Si-QD, it could be easily concluded that the impact of rather wide emission linewidth is fatal for applying plasmonic enhancement. To obtain some useful guidelines, we also discuss the necessary linewidth for effective plasmonic enhancement on Si-QDs. It is found that if the emission linewidth could be decreased to several tens of μeV, plasmonic enhancement would be helpful.

A designed multilayered metamaterial cavity formed by the metallo-dielectric multilayer structure (MDMS) and a nano Aluminum layer coated substrate is exploited to achieve the sub-20 nm patterns feature sizes at the wavelength of 248 nm with p-polarization. The filtering and SPP cavity resonance coupling provided by this MDMS cavity regime enable the SPP interference patterns with high uniformity and intensity output in the photoresist (PR) layer. Furthermore, compared with the conventional grating metal waveguide structure, this lithography system demonstrates the better stability of patterns period against the cavity thickness variation. The enhancement and the longitudinal extension of SPP localized field offered by the proposed cavity scheme will provide a potential way to obtain the lithography patterns with improved depth, contrast and perpendicularity.

Fabrication and characterization of straight dielectric loaded surface plasmon polaritons (DLSPP) waveguides doped with gain medium of methyl orange in their dielectric layer are investigated in this paper. The DLSPP waveguides are fabricated by using direct-laser writing. DLSPP waveguides with different widths and lengths are demonstrated. The DLSPP modes propagating in the waveguide is excited with a He-Ne laser at 632.8nm and pumped with a diode pumped solid state (DPSS) laser at a wave length of 532nm. A leakage radiation microscopy (LRM) is used to characterize the DLSPP modes. A propagation length without pump laser beam of 14.2um is obtained, corresponds to a propagation loss of 259cm^-1. We also get the optical gain as a function of the pumped irradiance. And an optical gain of 145cm^-1 (a loss compensation of ~56%) is observed.

As the desire growing of the thin film absorption structure for various sub-wavelength applications such as photo detector, thin-film thermal emitters, thermo photovoltaic cells, and multi-color filters, we proposed a type of subwavelength multi-branch dimers which exhibit several tunable dipole-dipole-like plasmonic resonances and integrated it into metal-insulator-metal structure as the top layer. The structures are studied through numerical calculation by finite element method. When normal incident is considered, the novel structure shows three absorption peaks in the considered wavelength range. One peak has near-perfect absorption and the other two also show excellent absorption.. When different angle oblique incident is considered, the absorption only has slight change, which is useful to an ultrathin absorber structure. In addition, we find that the thickness of the dielectric layer can tune the absorption rates for each absorption peak. In general, the multi-branch dimers can easily tune its absorption rates and spectrum via the change of their geometric parameters such as branch lengths, branch angles, and dielectric layer thickness.

Novel antireflective surfaces with silica particles arranged regularly and tightly are proposed and fabricated by self assemble silica nanoparticle through electrostatic attraction between charged colloidal particles and charged polyelectrolyte multilayer. Due to regularly arrangement of the particles, the nanoparticle coatings, as homogeneous porous layers with uniform distribution, show high-quality and uniform antireflective capability in each region on the substrate. It has been sufficiently demonstrated in our experiments. Furthermore, the relations among the antireflective capability, average size of nanoparticles, and incident angle of the irradiated light are calculated by finite-difference time-domain method. It is demonstrated that the nanostructure coatings with particles of 100 nm size possess the excellently suitable performance for reflection/transmission with respect to visible-light region. From the results, the fabricated anti-reflective nanostructures have great potential to improve the efficiency of optoelectronic devices such as a photo-detector and solar cells.

Effects of grating marks parameters on alignment precision and scope are investigated in this paper. In the lithography alignment method based on moiré fringe, gratings are especially used as alignment marks. However, the rational design of grating marks for this approach to realize high-precision alignment is of great importance. In order to improve the feasibility of the alignment method, effects of several physical parameters of grating marks on alignment precision are analyzed by numerical calculation. The results imply that qualities of grating marks, such as size of period and ratio between two gratings, have an important impact on alignment precision and scope.

Controlling the propagation of light by using a square lattice photonic crystal (PC) is investigated. Beam bending is accomplished by gradually varying the orientation of dielectric rods. The beam redirection relies on gradual modification of PC structural parameters which make the group velocity location dependent. A Y-shaped beam splitter is then designed by means of a composite structure consisting of two graded PCs. The splitting ability of the beam splitter is further discussed. We demonstrate that one input beam can be split into two output beams. The equal and unequal energy splitting are obtained.

We propose a method to bend a self-collimated beam propagating in a photonic crystal (PhC). The PhC is made of elliptically dielectric rods. We investigate the effect of orientation angle of elliptical rods on the light propagation. The propagation of light is analyzed by the use of finite-difference time-domain technique. A modulated PhC is then designed by gradually varying the orientation of ellipse. We demonstrate that the gradually variation of orientation angle results in smooth change in the propagation direction. The capability of bending light by gradually modulated PhC structure suggests a new direction for the realization of PhC light circuits.

In this work, preparation of zinc nanostructured thin films using the pulsed laser deposition (PLD) technique has been described. Optical absorption spectera of the thin films have been obtained by Spectrophotometry. Morphology and mean size of nanoparticles in the prepared nanostructured thin films were obtained by Atomic Force Microscopy. Nonlinear optical properties of the films have been investigated using the well-known Z-scan technique. Our measurements indicate positive signs for both nonlinear optical absorption coefficients and refraction indices of the nanostructured zinc thin films. The used method for measuring the optical limiting properties of the thin films and its results are also represented.

Minimizing surface reflection loss is critical when designing high efficiency solar cells. In recent years, biomimetic antireflection nanostructures (such as moth-eye structures), with their extraordinary broadband and omnidirectional antireflection properties, have caught much attention. Single side biomimetic antireflection (AR) coatings show good performance in suppressing broadband reflection between air and glass interface. However, reflection from the interface between absorption layer and transparent window layer still remains. In this study, we proposed a double-side gradient-index nanostructure, and examined its reflection spectrum in comparison with different biomimetic nanostructures using a finite-difference time-domain (FDTD) simulation and effective medium theory (EMT). In order to minimize surface reflection, all abrupt interfaces were replaced by gradientindex biomimetic nanostructures, including air/glass interface and absorber/glass interface. Monolayer of silica spheres serve as double-side gradient-index nanostructures, partially immersed into photoabsorbing material. Spheres with diameter smaller than incoming light wavelength show excellent antireflection properties. From simulation results, in normal incidence, average reflection rate of optimized AR coating structure was lower to around 5% compared to originally above 25% within visible spectrum region (350nm – 850nm). Details of how to apply such biomimetic nanostructures in thin film solar cells were also discussed.

We report on transmission enhancement and suppression in rectangular aperture arrays at terahertz range. Experiments and simulations reveal that transmission maxima and minima of metal film perforated with rectangular apertures arrays are caused by the shape resonance and the interference between surface waves respectively. To further investigate the relative contributions of shape resonance and interference between SPPs, we have examined the density of electrons whose distribution property is identified to the normal component of E-filed which clearly shows that transmission resonance stems from excitation of shape resonance at the edge of the hole. This resonance dominated by cutoff function is responsible for resonance peak at transmitted spectrum. The interference of SPPs originated at surface further enhances the resonances and gives a set of minima in the transmittance spectrum. This study contributes a better understanding of fundamental physics behind the extraordinary transmission of aperture arrays at THz range and provides a simple method for the design of THz devices.

In this paper, in order to improve the photocatalytic application of TiO₂, the low-density material such as Ps and TiCl₄ is proposed to be the raw carrier, and the nana-structured TiO₂ composite is obtained by combining the sol-gel technology and layer-by-layer self-assembly methods; The pure rutile nano-structured TiO₂ whose diameter is about 0.25mm are prepared under different conditions at low temperature. By being calcined under 450 ℃ the hollow sphere TiO₂ is prepared and its composition, size, structure analysis and characterization are studied by using X ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermal gravimetric analysis (DSC-TG) respectively.

The technique of atomic layer deposition (ALD) has been introduced to fabricate PbS-doped silica fibers, whose absorption peaks are discovered to be shifted from 1230 nm to 920 nm when the number of ALD deposition cycles varies from 80 to 30 during optical fiber preform fabrication. This is explained by suggesting that the PbS doped in fiber are under the 3D quantum confinement, i.e., quantum dots (QDs). An effective-mass approximat ion of the PbS QDs ’ sizes is then made to show the shift of absorption peaks can be attributed to the change of size distribution of these dots.

An ultrathin metasurface which is constructed with planar arrays of V-shaped nanoantennas is presented to realize the focusing of cross-polarized light. Based on the particular resonance properties of the V-shaped antennas, we can design the amplitude, phase, and polarization state of the scattered light, and then choose the proper antennas to satisfy the optical phase discontinuities calculated from the equal optical length principle. Numerical simulation of an illustrative metasurface is performed through finite element method (FEM) and shows agreement with the pre-design. In addition, broadband light focusing is also discussed in this article. This lens may find potential applications in integrate optics, controllable focusing, wave plates, and optical interconnection devices.

We propose As₂S₃ slot waveguides, which have four zero-dispersion wavelengths and exhibit a flattened and low dispersion over a 1800-nm bandwidth from near-IR to mid-IR wavelength range. The dispersive wave generation is investigated based on this kind of dispersive profile by launching femtosecond pulses into As₂S₃ waveguides. Detailed simulations under realistic conditions show that considerable amount of dispersive wave emission occur in As₂S₃ waveguide and therefore can be desirable for optical communication and on-chip signal processing, such as frequency metrology, optical coherence tomography and microscopy.

The structures and optical properties of (PbS)_n cluster in silica optical fiber material are investigated. The microstructures models of (PbS)_n (n=1-4) and PbS-(SiO2)_n (n=1-6) have been built and calculated by Gaussian-03 software using density functional theory with the B3LYP level. The gap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) is also calculated for microstructures. Compared with the (PbS)_n clusters and (SiO2)_n clusters, The HOMO-LUMO gaps of (PbS)_n clusters combined with (SiO2)n clusters make a big difference. The geometry structures of (PbS)_n-(SiO2)₄ (n=2-4) clusters are calculated by using the singles configuration interaction (CIS) method. The calculation results show that the excitation energies of (PbS)_n-(SiO2)₄ clusters changed as the sizes or the structures are changed. The PbS-doped silica optical fiber is fabricated, and the optical properties are measured to compare with the theoretical results.

We develop a theory of secondary emission from a single quantum dot, when the lowest-energy states of its electron–hole pairs are involved in the photoluminescence process. For the sake of definiteness, our model allows for two states contributing to the luminescence. We analyze the dependency of secondary emission intensity on the energy gap between the states, while considering that the gap is determined by the quantum dot’s size. An analytical expression for the time-dependent signal of thermalized luminescence is obtained using an analytical solution to the kinetic Pauli equation. This expression yields the signal of stationary luminescence as the spectral width of the excitation pulse tends to zero.

We study size dependence of kinetic and spectral properties of near-infrared luminescence from PbS quantum dots in colloidal solution. Luminescence lifetimes are found to lie between 250 ns for the largest quantum dots and 2:5 μs for the smallest ones, while the Stoke's shift is found to increase from 4-5 to 300 meV. These results are explained by the presence of the long-living in-gap state, with the size-dependent energy. Analytical modeling shows that the relaxation from this state is dominant in small quantum dots and negligible in large ones. Biexponential luminescence decay with the size-dependent recombination rates is predicted for quantum dots of all sizes.

Coherent random fiber laser is obtained by end pumping a hollow optical fiber (HOF) filled with a dispersive solution of polyhedral oligomeric silsesquioxanes (POSS) nanoparticles and laser dye pyrromethene 597 (PM597) in carbon disulfide (CS₂). However, coherent random laser can not been observed for the same solution in the quartz cuvette. We suggest that the coherent feedback is caused by the cooperative effect of light scattering and waveguide effect. We will deep research the effect in the near future.

We theoretically investigate utilizing the enhanced plasmonic fields in metallic nanostructures. Numerical techniques are employed to optimize nanoantennas to attain the enhanced plasmonic fields up to 270. In the volume of 15 × 15 × 30 nm³ in nanoantenna, the intensity could be enhanced to 1014 W/cm² for high harmonic generation (HHG). Optimal conditions for the production of MHz isolated attosecond pulse of 140 attosecond via HHG have been identified. These findings open up the possibility for the development of a compact source of ultrashort XUV pulses with MHz repetition rates. our simulations indicate a potential route towards the temporal shaping of the plasmonic near-field and in turn the generation of single attosecond pulses. Such XUV sources, which may operate at MHz repetition rate, could find applications in high-precision spectroscopy and for spatio-time-resolved measurements of collective electron dynamics on nanostructured surfaces. Moreover, the asymmetric cross nanoantennas is proposed to control the polarizations and select the wavelengths via varying the ratio of nanoantennas and generate the XUV pulse in both polarized direction.

In the paper, we have proposed a structure with only one photonic crystal (PC) micro-cavity side-coupled to a PC one-way waveguide to generate strong on-resonance optical delay. According to the coupled mode theory (CMT), the resonator system can maintain a 100% transmission spectrum throughout the complete resonant bandwidth, which is also demonstrated by the numerical results calculated by the finite element method (FEM). As a temporal Gaussian pulse is launched, the simulation results show that the device introduces a strong pulse delay while maintaining total transmission efficiency within the resonant bandwidth, and the resonator structure may be of great significance for making delay lines in optical buffer applications.

A comparative study of semi-insulating GaAs substrate, p-Al_xGa_1-x As/ semi-insulating GaAs and p-GaAs/p-Al_xGa_1-xAs/ semi-insulating GaAs structure has been done using the surface photovoltage (SPV) spectroscopy in metal–insulator–semiconductor (MIS) configuration. Which space charge region (SCR) dominated contribution to SPV in a certain wavelength range was determined. The SPV signals were calculated in a similar way as the open circuit voltage of an illuminated photodiode. One-dimensional continuity equations was adopted for determine the distribution of excess minority carrier. The ideality factor of MIS configuration was investigated in air ambient. The contributions for SPV signal of different layers were discussed in detail. At last the minority carrier diffusion length of different layers and surface or interface recombination velocity were simulated.

We propose a novel optical modulator based on poly-on-silicon slot-loaded waveguide to fit the CMOS process and it demonstrated a large loss reduction from 54.2dB/cm to 22.9dB/cm numerically compared with strip-loaded waveguide structure.

We demonstrate the fabrication of two-dimensional (2D) metallic photonic crystals (MPCs) based on colloidal gold nanoparticles, where laser interference ablation combining subsequent high temperature annealing is employed for the construction of 2D gold nano-dot arrays in square lattices. The microscopic and spectroscopic properties of the 2-D MPCs are systematically characterized by the scanning electron microscope and the angle-resolved optical extinction spectroscopic measurements, the strong coupling between the waveguide resonance mode and the particle plasmon resonance of the MPCs imply the success of the fabrication method, which show potential applications in optoelectronic devices and sensors.

Silver (Ag) island films have been prepared by pulsed laser ablation in vacuum using a XeCl excimer laser. The effects of the number of ablation pulses, the temperature and time of post-annealing on morphology and surface plasmons properties of the prepared Ag island films were investigated by extinction spectra and scanning electron microscopy. It is found that the films deposited with the ablation pulses of 60 or less are isolated Ag nanoparticles and the mean size of the nanoparticles increases monotonically with increasing the number of ablation pulses. Further increase of the number of ablation pulses up to 240, quasi-percolated Ag films are obtained, and for 600 pulses or more, continuous films will be formed. Extinction spectra results show that localized surface plasmons (LSPs) are supported by the Ag island films, while propagating surface plasmons are supported by the continuous Ag films. The LSPs of Ag island films consist of inplane and out-of-plane modes. By changing the ablation pulse numbers and annealing conditions, the longitudinal and transverse dimensions of Ag islands could be adjusted, and then the peak positions and peak widths of in-plane and outof- plane LSPs resonance modes could be effectively controlled.

A cost-effective method, using reactive ion etch (RIE) process to etch Si with Ag nanoparticle mask for fabricating antireflection structure, is proposed. The formation of Ag nanoparticle adopts wet-chemical method to deposit Ag layer on Si substrate, and then through rapid thermal annealing of Ag at 200°C-600°Crange, Ag nanoparticle were formed on Si substrate. Effects of parameters including etching parameters and deposited factors were investigated. According to analysis result of experiment, a group of high performance antireflection structure parameters was obtained.

Gold nanoparticles are considered to be better probes than the traditional polystyrene nanobeads in nanomaterials and nanobiotechnology. Meanwhile, optical tweezers are very popular tool for manipulation and force measurement in these fields. Gold nanoparticles with different size will receive radiation forces with different scale in optical tweezers. This paper theoretically studies the trapping performance of the optical tweezers for the gold nanoparticle with different size, and finally gives the relation curves between the radiation forces and the radius of the of the particle.