Photonic Crystal Optical Filter Research Articles

Evaluation of a ZrO2/ZrO2-aerogel one-dimensional photonic crystal as an optical filter for thermophotovoltaic applications

This paper computationally explores the optical response of various designs of one-dimensional photonic crystal optical filters comprised of alternating layers of dense zirconia and zirconia aerogel. COMSOL Multiphysics software is used to assess the optical characteristics of the filters. The performance of the filters within a thermophotovoltaic (TPV) system with a blackbody emitter and GaSb PV cell is investigated using two different methods including an ideal case wherein the emitter and PV cell are infinite parallel planes and the Monte Carlo ray-tracing method (MCM) with finite areas of its components. Results show that the optimized filter structure is comprised of two stacks of 5 bilayers with different peak positions stacked to form a single structure. When the optimized filter is used in the ideal TPV configuration, a spectral efficiency of 46%, a system efficiency of 33%, and a power density of 8.5 W/cm2 are achieved at the emitter temperature of 1800 K. According to the MCM code, a TPV system comprised of the optimized filter, an emitter, and a PV cell with equal areas of 2 x 2 cm and a 1 mm gap achieves a spectral efficiency of 45%, a system efficiency of 25% and a power density of 7.8 W/cm2 at the emitter temperature of 1800 K. Moreover, MCM results reveal that when the emitter temperature and gap length are 1800 K and 1 mm, respectively, a maximum system efficiency of 27% is realized at an optimal ratio of 0.75 between the PV cell area and the emitter area.

Magneto-sensitive photonic crystal optical filter with tunable response in 12–19 GHz; cross over from design to prediction of performance using machine learning

Photonic crystal structure made of Si, SiO2 and a plasma defect layer is suggested for optical filter applications. Generation of stop band and resonant modes localizations at transmittance spectrum of the structure are studied by exploring the dependences of the response on the period number of the layers and the electron density of the plasma slab. Also, the role of the magnetically induced birefringence in the anisotropic defect layer and the light incident angle on the optical features of crystal are studied. Results show that the response of the proposed structure could be tuned remarkably in practice by the selected structural as well as external parameters. Furthermore, an artificial intelligence (AI) approach is proposed to predict the final response of the suggested crystal in various input circumstances. Very significant concordance between results of the AI and transfer matrix method (TMM) approaches is observed.

Defect mode tunability based on the electro-optical characteristics of the one-dimensional graphene photonic crystals.

New (to the best of our knowledge) photonic crystal optical filters with unique optical characteristics are theoretically introduced in this research. Here, our design is composed of a defect layer inside one-dimensional photonic crystals. The main idea of our study is dependent on the tunability of the permittivity of graphene by means of the electro-optical effect. The transfer matrix method and the electro-optical effect represent the cornerstone of our methodology to investigate the numerical results of this design. The numerical results are investigated for four different configurations of the defective one-dimensional photonic crystals for the electric polarization mode. The graphene as a defect layer is deposited on two different electro-optical materials (lithium niobate and polystyrene) to obtain the four different configurations. The electro-optical properties of graphene represent the main role of our numerical results. In the infrared wavelength range from 0.7 µm to 1.6 µm, the reflectance properties of the composite structures are numerically simulated by varying several parameters such as defect layer thickness, applied electrical field, and incident angle. The numerical results show that graphene could enhance the reflectance characteristics of the defect mode in comparison with the two electro-optical materials without graphene. In the presence of graphene with lithium niobate, the intensity of the defect mode increased by 5% beside the shift in its position with 41 nm. For the case of polystyrene, the intensity of the defect mode increased from 6.5% to 68.8%, and its position is shifted with 72 nm. Such a design could be of significant interest in the sensing and measuring of electric fields, as well as for filtering purposes.

Graphene based photonic crystal optical filter: Design and exploration of the tunability

Optical characteristics of two new graphene based photonic crystals are studied in detail. A structure containing alternating layers of graphene and SiO2 slabs is considered as the ideal crystal. The dependency of the photonic band gaps (PBGs) to the dielectric layer thickness and the period number is explored at first step. Potential of the proposed crystal to be used as an optical filter is then investigated. Adding a nonlinear electro-optic polymer as a defect layer, the alterations of the optical features are inspected. Results show that the defect layer insertion causes a resonant mode inside the PBGs. However, the location of the defect layer inside the crystal is very effective on both the frequency and width of the resonant mode. Tunability of the optical features is probed by taking into account of the dependencies to the wave incident angle, graphene chemical potential and the applied external voltage to the defect layer.

Terahertz tunable photonic crystal optical filter containing graphene and nonlinear electro-optic polymer

In this paper, new photonic crystal optical filters with very unique optical characteristics are presented. The designed structures are composed of stacked SiO2 isotropic dielectric slabs separated by monolayer graphene sheets. Defect layers of nonlinear electro-optical polymer materials are also inserted to behave as the resonant areas. Results obtained by using the transfer matrix method approach clearly reflect the possibility of the wide photonic band gap generation in the absorption spectra of the proposed crystals in the terahertz frequency range. Furthermore, a very strong relation is seen between the defect layer(s) induced resonant modes and the location/number of the defect(s) inside the crystal. To widen the scope of our findings, in addition to studying the dependencies on the structural characteristics, the tunability of the optical features using the external parameters is investigated systematically. It is shown that the number and central frequencies of the resonant modes are controllable in the far-infrared range by adjusting the temperature and wave incident angle. Thus, the proposed crystals might have remarkable applications in the fabrication of multi-channel tunable filters used in optical integrated circuits.

复合缺陷光子晶体滤波器设计与数值研究

To eliminate the multimode property of the photonic crystal ring cavity filter,a composite defect photonic crystal filter structure combined point defect with ring cavity is proposed,in which the line defect is taken as the main waveguide and the load waveguide combining the point defect with the ring cavity is adopted to achieve the filtering for the certain wavelength.By changing the refractive index of the rods in the general photonic crystal structure,the refractive index of the point defect or the size of the point defect,the influences on the filtering property is analyzed.Mis regarded as m=r-point/r,the numerical simulation result shows that the filtering wavelength will remain the same the filtering characteristic when mis varied from 0to 0.6,while mis in the reasonable range from 0.6to 1.8,the single longitudinal mode filtering characteristic and its tunability can be achieved by changing the point defect radius,which can make the effective theoretical reference for the design of multi-channel filter.

Tunable anisotropic photonic crystal channel-drop filter

In this numerical study, we present a tunable photonic crystal optical filter designcomposed of anisotropic material. Various tunable optical filters which are composed ofpoint and line defects in a square lattice of dielectric rods, with selective infiltration ofsome of the rods with anisotropic material, are presented. Our numerical simulations withthe finite-difference time-domain (FDTD) technique reveal that defect states originatingfrom the anisotropic material impurities can be effectively tuned. The tunable range of20 nm of the optical channel is obtained. Moreover, we suggest a new tunabletwo-port channel-drop photonic crystal filter based on a Y-splitter and show that, bytuning the characteristics of this structure, total transmission up to 94% and 84%in each output port is achievable. Also, we come to the fact that our proposedstructure, compared to conventional photonic crystal channel-drop filters, hasthe advantages in miniaturizing wavelength-selective filters for WDM systems.

Sensing micrometer-scale deformations via stretching of a photonic crystal

This paper reports micrometer-scale strain measurements that are enabled through the observed wavelength shift in a stretched surface photonic crystal narrow bandwidth optical reflectance filter. The photonic crystal optical filter is comprised of a 550 nm period, dielectric-coated linear grating structure, which was fabricated on the surface of a thin sheet of silicone rubber. When stretched, the change in grating period induced a change in the wavelength of light coupled into the photonic crystal, which could be measured using a spectrometer. The observed wavelength change was 4.53 nm per 1% strain and was linear up to 3.75% strain. The measurement was affected by temperature fluctuations, which could be compensated. The resolution of the measurement was 78 μɛ.

Design of Narrowband Optical Filters Using Binary Number Sequence Photonic Crystals

A theory to design narrow band optical filters by using a new photonic crystal structure is presented. This new photonic crystal structure is composed of low index layers and high index layers arranged in mod. 4 up and down binary number sequence. The new structure exhibits narrow transmission peaks in the forbidden frequency gap region with high optical transmission (greater than 99.98%) at C.W.D.M. (Coarse Wavelength Division Multiplexing) center wavelengths. The proposed filters use only 8 layers. These new binary number sequence photonic crystal narrowband optical filters are much smaller in size, lower in cost and easier to fabricate as compared to narrowband photonic crystal optical filters based on defect Fractal Cantor multilayers, suggested recently by a group of researchers.

Vertically coupled photonic crystal optical filters

A novel design of optical filters, based on the vertical coupling between channel waveguides and photonic crystal microcavities, is proposed. The choice of channel waveguides can be arbitrary because of the flexibility of the device geometry, which makes it possible to utilize conventional low-loss waveguides. The separation between waveguides and microcavities, which determines filter bandwidths and drop efficiencies, can be accurately controlled by material growth (or deposition). The filters might also be switchable, e.g., by mechanical movements of microcavities. An example of a reflection-type optical filter is demonstrated in numerical experiments using the finite-difference time-domain method.

Wide-field-of-view GaAs/AlxOy one-dimensional photonic crystal filter

The design, fabrication, and characterization of a one-dimensional photonic crystal optical filter that has a relatively narrow, flat-topped passband within a wide stop band and small angular sensitivity is presented. The filter is based on a one-dimensional photonic crystal structure that has multiple defects, facilitating simultaneous minimization of the angular sensitivity and optimization of the passband's characteristics. We use epitaxially grown and selectively oxidized GaAs/AlxOy multilayers to achieve a high-index-contrast material system and incorporate the experimentally determined optical and material properties into the design of the device. A flat-topped bandpass filter with a bandwidth of 65 nm and a wide field of view of 50 degrees is experimentally characterized and compared with the design predictions.

Photonic crystal optical filter based on contra-directional waveguide coupling

Wavelength-selective operation of an optical filter (add/drop) based on a contra-directional photonic crystal waveguide coupler is demonstrated. The waveguides are defined as line defects in a two-dimensional triangular photonic crystal fabricated in an InP/GaInAsP heterostructure. The device is characterized using the end-fire method for the drop functionality. The experimental data are in good agreement with the theoretical results predicted by finite-difference time-domain simulations.