High-efficiency guided-mode resonance filter

A high-efficiency guided-mode resonance reflection filter is reported. The device consists of a surface-relief photoresist grating and an underlying HfO (2) waveguide layer deposited on a fused-silica substrate. The spectral response measured with a dye-laser beam at normal incidence exhibited a peak reflectance of 98% at a wavelength of 860 nm with sideband reflectance below ~5% extending over the wavelength range provided by the dye (800-900 nm). At normal incidence the filter linewidth was 2.2 nm. High-efficiency double-peak resonances occurred at nonnormal incidence, with the spectral locations of the maxima vayring with the incidence angle. The filter response at various angles of incidence agreed well with the theoretically calculated reflectance curves.     

Design of single-material guided-mode resonance filter

In this letter, a guided-mode resonance （GMR） filter with the same material for both the grating layer and the waveguide layer is designed, and its optical properties are investigated. The GMR filter owns almost 100% reflection at the resonance wavelength of 800 nm with the full-width at half-maximum （FWHM） of 20 nm, and its sideband reflection from 700 to 1000 nm is less than 5%. As the resonance wavelength is influenced by more than one parameter during the fabrication process, GMR filter with the same resonance wavelength can be obtained by adjusting other parameters or even one parameter to deviate from the design value.     

Colored image produced with guided-mode resonance filter array

A method to reproduce colored images with a guided-mode resonance filter (GMRF) array is presented in this Letter. Because of their excellent characteristics, monochromatic light of the three primary colors with high purity can be achieved by using GMRF structures. Moreover, the primary colors are obtained without changing other GMRF parameters except the period, which could be realized easily with laser direct writing technology. The result shows that a colored image with high resolution and verisimilitude can be reproduced.     

Design of internal Brewster guided-mode resonance filter

An internal Brewster guided-mode resonance （GMR） filter is designed. For this kind of GMR filter, the Brewster reflection occurs at the interface of grating/waveguide layers rather than at the interface of air/grating layers. At Brewster angle of 60~, the GMR filter owns almost 100% reflection at the resonance wavelength of 800 nm with the full-width at half-maximum （FWHM） of 0.2 nm. Its angle response changing with the fabrication deviation is also discussed.     

Nonpolarizing and tunable perpendicular dual-grating guided-mode resonance filter

A perpendicular dual-grating (PDG) guided-mode resonance filter was constructed by placing two identical waveguide gratings close to and their grooves perpendicular to each other. Multilayer waveguide theory was used to estimate the resonant wavelength for the TE and TM polarization incidences, and the rigorous coupled wave analysis (RCWA) was used to investigate the resonant wavelength, the lineshape and linewidth of the resonant peaks for arbitrary polarization incidences. The filter presents identical spectral characteristics for normally incident wave with arbitrary polarization. The separation of the resonant reflection peaks corresponding to the TE₀ and TM₀ split modes were realized by properly selecting the geometrical and material parameters of the grating layers and the waveguide layers. Measurement of the nano air gap between 0 and 0.4 p by determining one of the two resonant reflection peaks of the TE₀/TM₀ split modes was achieved without being interfered by the TM₀/TE₀ split modes.     

Superconducting tunable filter with constant bandwidth using coplanar waveguide resonators

In this paper we propose a two-pole varactor-tuned superconducting filter using coplanar waveguide(CPW) spiralin-spiral-out(SISO) resonators. Novel internal and external coupling structures are introduced to meet the requirements for a tunable filter with a constant absolute bandwidth. The fabricated device has a frequency tuning range of 14.4%at frequencies ranging from 274.1 MHz to 317.7 MHz, a 3-d B bandwidth of 5.14 ± 0.06 MHz, and an insertion loss of0.08 d B–0.70 d B. The simulated and measured results are in excellent agreement with each other.     

Tunable guided-mode resonance filter based on dielectric elastomer actuators

A tunable guided-mode resonant (GMR) reflection filter based on dielectric elastomer actuators (DEA) is designed. Simulating the characteristics of the filter with rigorous coupled wave analysis, it is shown that the resonant wavelength of the kind of GMR filter can be tuned from 1442.8 nm to 1644.6 nm by applying voltage on the dielectric elastomer actuators which changes the period of the grating layer of the GMR filter conveniently. Furthermore, there is an almost perfect linear relationship of resonant wavelength tuned and the period varied with negligible effect on the linewidth.     

Single-material guided-mode resonance filter for TE waves under normal incidence

<正>A guided-mode resonance(GMR) filter with the same material(Ta_2O_5) for both the grating layer and the waveguide layer is designed and fabricated.This simple structure is easy to fabricate and can avoid the defects at the grating/waveguide interface using different materials.The spectral response measured with a Lambda 900 spectrophotometer under normal incidence for TE waves exhibits a peak reflectance exceeding 80%at the wavelength of 1040 nm with a full-width half-maximum(FWHM) linewidth of 23 nm.We evaluate the deviations of the fabricated structure from the designed parameters.     

Novel high-quality Fano resonance based on metal-insulator-metal waveguide with L-shaped resonators

Developing a convenient method that can be routinely applied for ascertaining proportions of different vegetable oils employed in commercial blended edible oils remains a significant challenge. We address this issue by proposing a novel method for detecting volume fraction of different oils based on the fact that these oils are optically transparent and have slightly different indices of refraction at a given temperature and wavelength. Accordingly, we develop a highly sensitive sensor for measuring the index of refraction of oil blends based on Fano resonance spectra obtained using a metal-insulatormetal(MIM) waveguide structure comprising a gapped straight waveguide coupled with two L-shaped resonators. The index of refraction sensitivity and figure of merit of the structure are calculated based on modeling using the finite element method, and the waveguide structure is accordingly optimized by adjusting the different geometric parameters to achieve a high-quality Fano resonance spectrum. The optimized structure achieves an ultra-high refractive index sensitivity of 770 nm/RIU in terms of a refractive index unit(RIU) of 1. Moreover, a highly stable linear relationship is obtained between the refractive index of mixed edible oils and the resonance wavelength. Experimental results demonstrate that the proposed structure can detect slight changes in the volume fractions of the components in blended oils.     

Tunable intensity of the spectral reflectance of a guided-mode resonance filter with dual channels

Simulating the characteristics of a guided-mode resonance filter with rigorous coupled wave analysis, we find that, by adjusting the azimuthal angle of the grating used as a sub-layer of the guided-mode resonance filter from 0° to 90° under TE-reflectance, the intensity of the spectral reflectance of the guided-mode resonance filter monotonically increases at the wavelength of 684.6 nm, while the spectral reflectance monotonically decreases at the wavelength of 723 nm. Moreover, the spectral reflectance with TE-reflectance at 90° corresponds to the TM-reflectance at 0°. The phenomenon means that the intensity of the spectral reflectance can be easily tuned with different azimuthal angles by choosing appropriate structure parameters of the guided-mode resonance filter.     

Numerical analysis of a dual-wave band guided-mode resonance filter with embedded bilayer asymmetric metallic gratings

In this paper, a novel guided-mode resonances (GMRs) based embedded dual-wavelength filter, which had the bilayer gratings located at the two sides of dielectric substrate and arranged at asymmetric position, was investigated and studied theoretically. As compared to symmetric structures that usually provided single wavelength of transmission resonance, as one normal incidence was used for transverse magnetic polarized light, the designed asymmetric structure could generate two remarkable narrow band wavelengths of transmission resonance. The parameters to affect the resonance wavelengths and the transmission resonance Q value (Q = λ/Δλ) of two bands were the distance between the two metallic gratings, the relatively lateral positions of the upper and lower gratings, the number of structure period, the thicknesses of metallic gratings, and the thickness of dielectric film. By optimizing the designed parameters, a GMR device with two resonance wavelengths located at 1239 and 1302 nm showed relative optimal performance because they had high transmission depth (99.9% and 90%) and ultra-narrow transmission bandwidth (2.8 and 1.8 nm) at the two resonance wavelengths. The presented structure can offer a potential route towards dual-band narrow-band filters and refractive index sensors in the near infrared.     

带虚设层的抗反射结构导模共振滤波器设计与分析

提出带虚设层的抗反射导模共振滤波器结构及设计方法,该方法适用于任意角度入射带虚设层的抗反射结构导模共振滤波器设计与分析.得到带虚设层的导模共振滤波器抗反射结构所满足的关系式.指出在维持虚设层光学厚度不变的情况下,可以通过不同选材,在低反射旁带中实现等带宽不同波长的选择.此外,由于结构的抗反射特性在低角范围内具有较大的角度容差,改变入射角,可以实现滤波波长及光谱带宽在宽光谱范围内的准线性可调谐.     

偏振无关的波长间隔可调的全光纤双折射滤波器

 设计了一种新的便于调谐且波长间隔可调的全光纤双折射滤波器。该滤波器由一个偏振分束器（PBS）、2段保偏光纤（PMFs）和4个二分之一波片（HWPs）连接而成。计算并分析了它的理论结果,发现在合理调节环中4个二分之一波片的情况下,该滤波器除了可以获得有很好的滤波光谱输出之外,还具有波长间隔可调的作用。这种滤波器在设计可灵活改变波长间隔的多波长光纤激光器及光纤系统等方面具有巨大的应用前景。     

Composite right/left-handed coplanar waveguide band-pass filter using capacitively-coupled zeroth-order resonators

Design and performance of a coplanar waveguide (CPW) bandpass filter (BPF) using composite right/left-handed (CRLH) zeroth-order resonators have been studied. The unit cell of the CRLH CPW consists of a series interdigital capacitor and two shunt stub inductors embedded between two sections of CPWs. The Bloch analysis is applied based on the S parameters to derive the characteristics of the eigen modes (Bloch modes), from which the right/left-handed frequency band and the zeroth-order resonant frequency are clearly determined. Then, the susceptance slope parameter of the resonator is extracted and the admittance (J-) inverters are introduced to synthesize a capacitively coupled CPW BPF. The measured performance agrees with the simulated one. They show that the size of the filter is greatly reduced (more than 60%) when compared to a conventional structure. PACS 41.20.Jb; 84.40.Dc; 42.70.Qs; 77.84.Lf     

Characteristics of resonance absorption of microwave energy in dielectric waveguide resonators

Institute of Radio Physics and Electronics, Academy of Sciences of Ukraine. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 34, No. 9, pp. 1071–1075, September, 1991.     

Optimization of a guided-mode resonance filter by varying the thickness of the buffer layer

In this Letter, we demonstrate that by adjusting the thickness of the buffer layer, the optical responses of a guided-mode resonance filter(GMRF) can be improved for sensor applications. The GMRF is fabricated using a replica molding with a plastic substrate and a UV-curable polymer. SiO_2 buffer layers of different thicknesses are deposited before the waveguide-layer deposition. The sensitivity of the GMRFs decreases slightly with increasing SiO_2 layer thickness. By contrast, the full width at half-maximum reduces substantially with increasing SiO_2 layer thickness, resulting in the improvement of the overall figure of merit.     

Silica waveguide ring resonators with multi-turn structure

Optical waveguide ring resonator is the basic element of resonator integrated optic gyro (RIOG). In this paper, we report a novel configuration of optical waveguide ring resonator using a multi-turn structure. The characteristic of the light propagating across the crossed waveguides is analyzed using the finite difference beam propagation method. The relationship between the propagation loss and the intersection angle for arbitrary intersecting angles has been analyzed. Some crossed waveguides are fabricated in silica waveguides to verify the theoretical results. On this basis, the influences of the loop numbers and the excess loss of the crossed waveguide on the limited sensitivity of the RIOG have been analyzed. There is a critical intersection angle for certain resonator, only when the intersection angle is bigger than the critical angle, the gyro sensitivity can be improved by increasing the loop numbers. This will be helpful to how to determine the optimum length in resonator for its application in RIOG.     

Matching of quasioptical open resonators with waveguide feeders

We consider a semisymmetric open resonator (OR) included in a waveguide feeder, in which the first higher-order mode is excited. We show that a high efficiency of excitation of the mode can be achieved by appropriate choice of coupler dimensions due to the matching of structures of the exciting and operating fields. We analyze the behavior of the resonance reflection and transmission coefficients as well as the loaded Q-factor of an OR as functions of the parameters of one-dimensional E-polarized diffraction gratings located in a coupler aperture with dimensions of a few of wavelengths. Calculations are made with allowance for the resonance and excitation losses. The numerical results differ from the experimental data by no more than 13%, which allows one to construct open resonance systems with the required properties by changing the parameters of diffraction gratings in the coupler aperture. Institute of Radiophysics and Electronics, National Academy of Sciences of Ukraine, Kharkov, Ukraine Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 43, No. 4, pp. 325–334, September, 2000.     

Multidimensional angle sensing method using guided-mode resonance

Optical Review - A waveguide grating on a transparent substrate can serve as an optical notch filter owing to guided-mode resonance. The filtering wavelength is highly sensitive to an incidence...     

Integrated-optic temperature sensors based on guided-mode radiation in polymer waveguide

Optical temperature sensors consisting of low-loss polymer waveguides with a glass lower cladding are demonstrated. The refractive index of the optical polymer is precisely controlled to have a certain initial refractive index contrast with the glass substrate used for lower cladding. Depending on the initial index contrast, the operating temperature ranges of the sensors are determined. The polymer devices are fabricated by spin-coating and UV curing, which could be replaced by the cost-effective imprinting or injection molding process. The sensor exhibits a monotonic decrease of the transmission intensity corresponding to the temperature increase, which enables straightforward reading of temperature from the measured optical power.