Femtosecond laser inscription or writing has been recognized as a powerful technique to engineer various materials toward a number of applications. By efficient modification of refractive indices of dielectric crystals, optical waveguides with diverse configurations have been produced by femtosecond laser writing. The waveguiding properties depend not only on the parameters of the laser writing but also on the nature of the crystals. The mode profile tailoring and polarization engineering are realizable by selecting appropriate fabrication conditions. In addition, regardless of the complexity of crystal refractive index changes induced by ultrafast pulses, several three-dimensional geometries have been designed and implemented that are useful for the fabrication of laser-written photonic chips. Some intriguing devices, e.g., waveguide lasers, wavelength converters, and quantum memories, have been made, exhibiting potential for applications in various areas. Our work gives a concise review of the femtosecond laser-inscribed waveguides in dielectric crystals and focuses on the recent advances of this research area, including the fundamentals, fabrication, and selected photonic applications.
In practical applications, the linear to circular (LTC) polarization conversion of electromagnetic waves is of great significance. In this work, we designed a broadband high-efficiency reflective LTC polarization converter with temperature control in the visible range. Each periodic unit of the LTC polarization converter is composed of a gold mirror, a dielectric layer, a wide L-shaped gold plate and a narrow anti-L-shaped VO2 strip. The results show that the conversion efficiency can reach 0.9 in the visible range, and the switch of polarization converter can be controlled by VO2. The linear to circular polarization converter has potential applications in stealth technology, electromagnetic measurement.
High performance absorber is desirable for solar energy, photo detection and optical interconnects. Here an active tunable graphene metamaterials quad-band absorber is theoretically demonstrated. The designed absorber has four higher than 97% absorption peaks in terahertz and infrared range. This absorber consists of a graphene layer, a silica substrate and a metal reflective surface. Simulation demonstrates that absorbance peak can be adjusted by changing geometric parameters of the periodic array structure or the Fermi level of the graphene. Such devices may have potential application in active plasmonic sensor, Light detection, photo thermal conversion and optoelectronic devices.
The ultrashort, ultrahigh intensity pulse laser has been fully developed in past three decades. Chirped pulse amplification (CPA) system plays an important role in the generation of the ultrashort, ultrahigh intensity pulse laser. Pulse compression gratings (PCGs) are the key element of CPA system and determine the performance and lifetime of the whole system. We introduce the principle of CPA system and the performance requirements of PCGs. Then the development status of PCGs, including Au-coated grating, multilayer dielectric grating (MDG), and metal MDG, is fully reviewed. Finally, the development prospect of PCGs in the future is presented. Our study is helpful for comprehensive understanding of PCGs.
Potassium titanyl phosphate (KTiOPO4, KTP) possesses superior properties in several optical applications. A KTP crystal is irradiated by swift Kr8 + ions with high energies and low fluences. The stopping and range of ions in matter code is used to simulate the energy deposition process of swift Kr8 + ions in the irradiated crystal. The electronic and nuclear stopping power profiles of swift Kr8 + ions irradiated on the KTP crystal are simulated, and the micro-Raman spectrum of the irradiated layer at different depths is measured by a confocal micro-Raman system. The results show that the high electronic energy loss can cause lattice damage along the ion trajectory, whereas the nuclear energy loss causes damage at the end of the ion track. The optical transmission properties of the irradiated KTP crystal are researched at visible and near-infrared bands.
In this paper, we theoretically design a nanostructure combined bowtie nanoantenna with V-structured hole, which offers a way to increase the ability of the nanostructure to enhance the optical near field. This nanostructure is designed to both limit the incident light in the nanoscale and produce large near-field enhancement. In addition, we study the effect of the geometric parameters of the bowtie nanoantenna with V-structured hole on the enhancement. Such structure will be beneficial to the focusing and collimating capabilities of integrated lens antennas.
In this paper, we propose a tunable dual-band metamaterial absorber with wide-angle characteristics. The absorber is composed of a cross-shaped graphene layer and a layer of gold separated by a dielectric spacer. The simulated results show that there are two near-perfect absorption peaks in infrared band. Also, the peak wavelengths of absorber can be adjusted by changing the Fermi energy of the graphene and geometric parameters. In addition, the absorber can maintain a high absorption at a wide range of incident angles for both TE and TM waves. Such a device could be used as tunable sensors, filters, detector or other graphene-based photonic devices.
In this paper, a composite grating with nanogaps was designed to realize local field enhancement. The composite grating consists of a short and a long rod each period, which is seperated by a nanogap with two alternating metal width. And a small rectangle is dug in the middle of long rods. The simulation result shows that the local field can be greatly enhanced. This is because that the plasmonics resonance couple between each metal section occurs. And this nanostructure can be used in improving local field enhancement.
A structure consists of a rectangular ring and a rectangular strip based on metal-insulator-metal (MIM) waveguide is proposed. When the rectangular strip is added in the suitable position, the plasmonic-induced transparency (PIT) effect will occur compared with the original single rectangular ring structure. The transmittance and resonance frequency can be changed via variation length and width of the rectangular strip. The structure is simulated by finite element method (FEM).
We design a broadband polarization beam splitter (PBS) operating in the terahertz (THz) communication band 0.1THz-1.2THz. The transmittance of the TM mode is larger than 95%, in the meanwhile, the extinction ratio can even reach 49dB. Considering the unavoidable deformation in grating fabrication, we also check the performance of the PBS based on trapeziform grating. Results show that increasing the duty cycle while the slope angle diminishing can effectively increase the TM mode transmittance and the extinction ratio, which can compensate the affection induced by the geometric deformation. This design may achieve some potential applications in THz manipulation system.
Plasmonic-induced transparency (PIT) in the metal-insulator-metal plasmonic waveguide with two side-coupled rectangular ring disk structures is numerically investigated. The PIT resonance occurs as a consequence of the destructive interference between the two structures. It is found that the transmittance can be easily adjusted by changing the parameters of the structure and coupling distance between the structure and waveguide. By optimizing the parameters, the transmittance of the structure can up to 75% in our discussion. These results may have important applications for designing integrated devices such as narrow-frequency optical filters, novel sensors and high-speed switches.
A new optical sensor based on the surface plasmon resonance (SPR) is proposed and characterized. The sensor is composed by sandwiching the graphene sheets between two metal films in the Kretschmann configuration. The resonance angle and the sensitivity of proposed sensor are analyzed through the transfer matrix method. Moreover, the refractive index change of the analyte can be detected accurately by using the proposed sensor. It is observed that the sensitivity of the proposed bimetallic sensor configuration can be greatly enhanced than conventional single metal configuration by optimizing the thickness of the metals and the number of graphene layers. Finally, we believe that the proposed SPR configuration can further promote the biosensing application.
In this paper, we theoretically demonstrate a polarizing filter consisted of graphene ribbon arrays with varying width placed on the top surface of dielectric and a metal reflector rested at the bottom of the structure. It is found that proper ribbon width, which corresponds to resonant frequency of graphene plasmons, is a crucial factor that can significantly influence the absorption effect. The results of fullwave numerical simulations indicate that total absorption of more than 90% for TE polarization and approaching to 1% for TM polarization can be achieved at normal incidence in the infrared range. Therefore, this characteristic can be applied into polarizing filter by adjusting the coupling effect between the graphene ribbon arrays. Such structure will be beneficial to the manufacture of infrared nano-photonic devices for optical filtering and selective absorption.
A novel and simple multi-wavelength band-pass filter based on
metal-insular-metal (MIM) waveguide with different nanodisk cavity is proposed and
investigated numerically by Finite-Element-Method (FEM) simulations. According to
resonant theory of nanodisk, multi-wavelength band-pass filter can be achieved for
different wavelength. It also shows that the transmission characteristics of the filter and
the resonant wavelength can be easily manipulated by changing the gap between
nanodisk and straight waveguide or changing the radius of the nanodisk. This kind of
plasmonic waveguide filter may become important promising application in highly
plasmonic integrated circuits.
A nonlinear hybrid plasmonic waveguide (HPW) with a metal cap on a nonlinear material-on-insulator rib is proposed. By using a finite-difference time-domain method, its light confinement and effective nonlinearity coefficient of the Kerr effect for all-optical switches are analyzed in detail. Numerical simulations illustrate that the nonlinear HPW structure has nanoscale confinement and high effective nonlinearity coefficient at the wavelength of 1550 nm. Consequently, the HPW can be used in all-optical signal processing of integrated photonics.
The special abilities of plasmonic waveguide including tight field confinement and beyond diffraction limit within nano-scale structure have been exploited in many different fields. In order to overcome the trade-off between tight mode confinement and long propagation length, many kinds of nano-scale structures have been proposed in recent years. In this paper, a novel hybrid plasmonic waveguide consisting of the layer of metal Ag, a spherical cap with low-index dielectric layer placed above the metal Ag and a high-index dielectric layer placed above the spherical cap is proposed and analyzed theoretically. The relations between the characteristics of the bound modes, such as mode confinement, propagation lengths, and parameters of the spherical cap, the curvature and width, are numerically investigated in detail. The simulation results show that the nano-scale confinement can be realized. The simulation result shows that the performance of the proposed spherical cap hybrid plasmonic waveguide is better than the rectangle or cylindrical hybrid plasmonic waveguide. Such hybrid plasmonic waveguide has a tight mode confinement and long propagation length. This novel structure provides a promising application for high-integration density photonic components.
In order to improve integration density, it is essential to develop a nano-scale optical waveguide
which is the key element to build varies of optical components. In this paper, a novel cylindrical hybrid
plasmonic waveguide, which has an air core surrounded by a metal layer and a silicon layer, is
proposed to achieve nano-scale confinement of light at the operating wavelength of 1550nm. And there
is a low-index material nano-layer between the metal layer and the silicon layer, in which the field
enhancement provides a nano-scale confinement of the optical field. The relations between the
characteristics of the bound modes, including the effective mode indices, propagation lengths, mode
sizes, mode shapes and parameters of the plasmonic waveguide are numerically investigated in detail.
The simulation results show that the nano-scale confinement can be realized and the proposed hybrid
plasmonic waveguide has a potential application in high density photonic integration.
Keywords: Surface Plasmon, Mode confinement, Subwavelength structure
This article deals with designing broadband and high efficiency metal multi-layer dielectric grating (MMDG) used to
compress and stretch ultra-short laser pulse. The diffraction characteristics of MMDG are analyzed with the method of
rigorous coupled-wave analysis (RCWA). Taking the diffraction efficiency of the -1 order as the value of merit function,
the parameters such as groove depth, residual thickness, duty cycle are optimized to obtain broadband and high
diffraction efficiency. The optimized MMDG shows an ultra-broadband working spectrum with the average efficiency
exceeding 97% over 135nm wavelength centered at 800nm and TE polarization. The optimized MMDG should be useful
for chirped pulse amplification.
The optical property of multi-layer dielectric thin film is determined by its operation on the more or less complete
cancellation of the light reflected at the upper and lower of the multi-layer interface of the thin film. An enhanced,
numerically stable transmittance matrix approach based on rigorous coupled-wave analysis (RCWA) is applied to the
analysis of optical character for multi-layer dielectric thin film. A design of a thin film stack used in multi-lay dielectric
grating was presented by using the method of RCWA. The numerical calculation shows that RCWA is a relatively
straightforward and deterministic technique for analysis the optical property of multi-layer dielectric thin film.
The purpose of this study is dedicated to the new design of the Multi-layer dielectric grating with the best performance
giving a highly diffraction efficiency in the -1 order, by using the rigorous coupled wave Analysis (RCWA). The
formulation for the implementation of the RCWA for multi-layer dielectric gratings incorporating the developed
enhanced transmittance approach is presented. An optimized design of multi-layer dielectric grating working at 1053-nm with TE polarized light and 51.2° incident can obtain the diffraction efficiency of 99%.
Superresolution plays an important role in the super high-density optical storage systems. With the superresolution technology the storage capacity can be increased by the decrease of the Airy spot. General the optical superresoluiton is realized by inserting the conventional superresolution pupil filters in the optical system. But there lies an obvious limitation in the conventional pupil filters. It is that once the pupil filter is fabricated, the corresponding superresolution characteristics can not be changed. In order to overcome this drawback, a new set of pure phase filters for realizing the tunable transverse superresolution is presented in this paper. The filters, whose significant feature are their ability to tune and simplicity, consist of one half-wave plate between of two quarter-wave plates, and the half-wave plate is made of two zones that can rotate with respect to each other. By rotating any zone of the half-wave plate, the central lobe width of the irradiance point spread function (PSF) in the transverse direction can be tunable reduced.
Reactive magnetron sputtering can be used to prepare graded index coatings. In this paper the relationship between the refractive index of the coatings and the partial pressure of reactive gas is discussed by experiment, in which A, O2 and Si are taken as sputtering gas, reactive gas and target material separately. And we have come to such conclusions that with the increase of partial pressure of reactive gas the color of the coatings turns shoal, the transmittance minimum of the coatings increases and the refractive index of coatings decreases according to the fitting rule of cubic polynomial. From XRD analysis, it can be seen that the coatings are identified to be amorphous.
Multi-layer dielectric grating is a key element used in chirped-pulse amplification technique. It includes high reflectivity film and periodic gratings on its top. Design of HR coating and top layer film (called multi-layer dielectric grating film) to produce gratings is important to fabricate such element with perfect optical properties and high laser induced damage threshold. In this paper, needle method is employed to synthesize the HR film with non-quarter wave coatings. The top layer is constructed by Fourier modal method, which is a rigorous method to analyze gratings. The synthesized multi-layer dielectric grating film shows good optical properties and electric intensity distribution.
By introducing scattering probability and statistical distribution functions of substrate subsurface defects' radius, refractive indices and positions, extended bidirectional reflectance distribution function (BRDF) was derived on the foundation of Jones scattering matrix. A numerical calculation of the extended BRDF for p-polarization incident light has been performed by employing Monte Carlo method. The calculating results indicate that the extended BRDF depends strongly on incident angle, scattering angle and azimuth angle, and presents a specific symmetry. For real refractive index, the extended BRDF is independent of subsurface defects' positions. And the extended BRDF will provide a more precise model for the calculation and measurement of polarized light scattering resulting from subsurface defects.
Multi-layer dielectric gratings (MDG) have been more and more used in the chirped-pulse amplification (CPA) system because of its higher diffraction efficiencies and higher damage threshold, which is compared with metallic gratings. Design parameter of multi-layer dielectric and gratings are both given. Laser-induced damage threshold (LIDT) of MDG has been test by employing 1-on-1 methods. The result is 3.24J/cm2 at 1064nm and 12ns pulselength (51.2° incidence). The mechanics of damage is also discussed in several ways.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.