Guided-mode Resonance Filter Research Articles

Polarization-insensitive one-dimensional guided-mode resonance filter operating at conical mounting.

We report the design and implementation of a one-dimensional guided-mode resonance filter (1D-GMRF) aiming to achieve polarization insensitivity at conical mounting. (The incident plane is aligned neither perpendicularly nor parallelly to the grating bars.) The design guideline indicates that, at conical mounting, polarization insensitivity of the 1D-GMRF can be achieved by optimizing the grating parameters to excite the fundamental TE and the fundamental TM waveguide modes simultaneously. Moreover, it is revealed that, at conical mounting, the polarization-insensitive GMR position in the angle-resolved resonance spectra is azimuthal angle ϕ-dependent. The experimental results demonstrate that polarization insensitivity of the fabricated 1D-GMRF occurs at the resonance wavelength of ∼673 nm for the conical mounting of azimuthal angle ϕ≈30° and incident angle θ≈11.2°, which agree with the simulated results.

Tunable nonpolarizing guided-mode resonance filter incorporating electrically driving liquid crystal

A tunable nonpolarizing guided-mode resonance filter (GMRF) incorporating an electrically driving polymer-dispersed liquid crystal (PDLC) cell is designed, fabricated and demonstrated. By studying the dependence of the resonance wavelength on the grating period, the two-dimensional (2D) nonpolarizing GMRF is designed using different grating periods along the x and y axes at oblique incidence. The 2D electrically driving GMRF sample is fabricated through thin-film deposition, electron beam lithography and PDLC injection. Moreover, the resonance spectra of the fabricated sample are measured by a spectrometer and themeasuredresults areconsistentwiththetheory. Thus the nonpolarizing resonance spectra can be tuned by electrically driving the refractive index of PDLC cell inrealtime.

Mounting‐insensitive nonpolarizing guided‐mode resonance filters for optical communications

AbstractMounting‐insensitive nonpolarizing guided‐mode resonance filters (GMRFs) for the optical communication wavelength O‐band and C‐band have been designed and fabricated. The rigorous coupled‐wave analysis (RCWA) is used to calculate the reflection spectra of the designed GMRFs. The grating structures of the GMRFs are patterned by interference lithography with two ultraviolet laser beams. The reflection spectra of the fabricated samples at different incident angles are measured by rotating a motorized stage. Compared with previous reported one‐dimensional nonpolarizing GMRFs, the tolerances of conical angle of the fabricated samples are remarkably improved.

Optical spectrometer based on continuously-chirped guided mode resonance filter.

In this work we introduce a tunable GMR filter based on continuously period-chirped (ΔP = 130 nm) gratings using a Ta2O5 waveguide layer with graded thickness (ΔT = 36 nm). The structure of the gradient-period grating is defined using a modified Lloyd's mirror interferometer with a convex mirror, and Ta2O5 film used for the gradient is deposited using masked e-beam evaporation. The as-realized chirped GMR filter provides sharp transmission dips at resonant wavelengths with a filter bandwidth of approximately 4.2 nm and 0.78 nm when respectively applied to TE and TM polarized light under normal incidence. Gradually sweeping the chirped GMR filter makes it possible to monotonically sweep through resonant wavelengths from 500 to 700 nm, while maintaining stable filter bandwidth and transmission intensity. The optical spectrum of the incoming light can then be loyally reconstructed accordingly. We successfully demonstrate the spectrum reconstruction of a white light emitting diode and a dual-peak laser beam using the proposed chirped GMR filter as a dispersive device.

Spectral characteristics of a guided mode resonant filter with planes of incidence.

Spectral responses of the guided mode resonant filter under different planes of incidence are comprehensively investigated in this paper. Commercially available software based on the rigorous coupled wave analysis method is used to perform the reflectance spectra. For normal incidence, there exists a pair of resonance bands, whose diffraction efficiencies can be tuned from 3.5% to 100% and 3.2% to 100% without shifting the resonant location as the plane of incidence (POI) angle ranges from 0° to 90°, whereas the resonances split into two branches as the POI angle decreases from 90° to 0° for oblique incidence. There exists a crossing point between the split bands that is proved to be polarization independent. Moreover, the physical mechanism of the above spectral characteristics is analyzed in detail by means of the wave vectors. The intensity-tunable feature under normal incidence can be used in the field of bioactive fluorescent protein dyes, displays, and signal processing. And the split characteristic under oblique incidence is applied to seek the polarization-independent wavelength, which has potential applications in the field of dense wavelength division multiplexing and laser devices.

Transmission characteristics of all-dielectric guided-mode resonance filter in the THz region

In this study we report the first on the terahertz (THz) transmission characteristics of a guided-mode resonance (GMR) filter made of all-dielectric material. Two strong transverse electric (TE) resonance modes, TE0,1 and TE1,1, and one strong transverse magnetic (TM) resonance mode, TM0,1, were detected. The measured resonances can be explained by diffraction from the grating surface of the GMR filter, and by guiding along the inside of the filter (slab waveguide). Because two identical GMR filters were employed to overcome limited grating numbers, the measured Q-factors of the TM0,1, TE1,1, and TM0,1 modes were as high as 62.9, 71.0, and 74.4 respectively. Also, we obtained polarization efficiencies of up to 96.9, 96.3, and 92.9% for the TM0,1, TM1,1, and TM0,1 modes, respectively, when the GMR filter was rotated to 90°. By increasing the incident THz beam angle, one TE resonance can be divided into two TE resonances, and the resonant frequency can be adjusted like a THz tunable resonance filter. Furthermore, when the GMR filters were inserted between Teflon plates, only the TM1,1 mode was perfectly removed. The designed GMR filter has a high Q-factor, tunable filter, good polarizer, and good modulator characteristics. These experimental results were in good agreement with simulation results.

Wide wavelength range tunable guided-mode resonance filter based on incident angle rotation

ABSTRACTA wide wavelength range tunable guided-mode resonance filter (GMRF) with high peak efficiencies, narrow linewidths, and low sidebands is experimentally demonstrated. The resonance wavelength can be tuned under TM polarized light illumination by rotating the angle of incidence. The GMRF composed of a one-dimensional grating layer and two waveguide layers on a glass substrate is designed with rigorous coupled-wave analysis. The grating structure of the GMRF is patterned by interference lithography with two ultraviolet laser beams. The reflection colours of fabricated GMRF can be shifted from blue to red by rotating the angle of incidence. The measured full width at half-maximums of the reflection peaks located at 450.6, 500.9, 551.0, 601.1, and 651.3 nm are 3.1, 3.9, 4.3, 3.8, and 4.1 nm, respectively. The corresponding sidebands of measured spectra are below 0.2. Compared with previous experimental studies on tunable structures, the narrow linewidths and low sidebands of the proposed GMRF are remarkably improved.

Non-homogeneous composite GMR structure to realize increased filtering range.

A non-homogeneous composite guided-mode resonant (GMR) filter structure is proposed that avoids the multi-mode resonance effect and increases resonant wavelength tuning range. The composite filter structure is engineered using a combination of a varied-line-spacing (VLS) grating layer with a wedge-shaped waveguide layer. The grating is fabricated by holographic interference lithography (IL), while the wedge-shaped layer is fabricated using masked ion beam etching (MIBE) technology. The resonant wavelength has been observed to vary as a function of the spatial position on the structure. In the fabricated structure, over a length of 30 mm, the grating period increment is measured to be 149.2 nm, whereas the increment of the waveguide film thickness is approximately 100 nm. Experimental results show that a primary reflectance peak is achieved spanning a wavelength range of 805.8-1119.0 nm. The device is designed using the rigorous coupled-wave analysis (RCWA) method, and the proposed device is toward the practical application of GMR filters.

Resonant Wavelength Shift Detection System Based on a Gradient Grating Period Guided-Mode Resonance

A resonant wavelength detection system based on a gradient grating period guided-mode resonance (GGP-GMR) filter and a linear charge-coupled device is demonstrated. The GGP-GMR used in this work consists of a subwavelength grating structure with a grating period that varies from 250 to 550 nm in increments of 2 nm. We successfully demonstrate that by using this system, we can monitor the shift in a sensor's dip wavelength caused by different sucrose concentrations. This technology has the potential to replace the spectrometer used in most optical biosensor systems. Given its compactness, the system can be integrated with lab-on-a-chip systems for numerous biosensing applications.

Wide wavelength range tunable guided-mode resonance filters based on incident angle rotation for all telecommunication bands

The comparison among one-layer, two-layer and three-layer guided-mode resonance filters (GMRFs) has been discussed by the numerical simulations. The rigorous coupled-wave analysis (RCWA) is used to calculate the reflection spectra of the designed GMRFs. As the reflection sidebands of two-layer GMRFs are not satisfactory, tunable three-layer GMRFs for all telecommunication bands have been designed and fabricated. The grating structures of the GMRFs are patterned by interference lithography with two ultraviolet laser beams. The reflection spectra of the GMRF samples at different incident angles are measured by rotating a motorized stage. The negative first-order diffraction resonances located at 1701.4, 1549.3, 1424.4 1309.5, and 1188.9 nm are measured at the incident angles of 3°, 11.4°, 20°, 30.2°, and 45°, respectively. The experimental results are in good agreement with the theoretical simulation ones. We show experimentally a large spectral shift over 510 nm of wavelength that covers all telecommunication bands.

Nonpolarizing guided-mode resonance filter with high tolerance of conical angle

A tunable one-dimensional (1D) nonpolarizing guided-mode resonance filter (GMRF) with high peak efficiencies, narrow spectral linewidths, and low sideband reflections is experimentally demonstrated. The GMRF composed of a 1D grating and two waveguide layers on a glass substrate is designed with rigorous coupled-wave theory. The grating structure of the GMRF is patterned by interference lithography with two ultraviolet laser beams. The reflection resonance wavelengths of nonpolarizing spectra of the GMRF sample with period of 481.9 nm are tuned from 836.6 to 866.3 nm by rotating the angle of incidence. The measured full width at half-maximums of the reflection peaks located at 836.6, 844.1, 851.8, 858.4, and 866.3 nm are 8.1, 8.9, 9.0, 8.6, and 9.4 nm, respectively. The corresponding sidebands of the measured spectra are below 0.2. Moreover, the dependence of the nonpolarizing effect on the conical angle is studied to consider the mounting tolerance. The measured results show that the transmission and reflection spectra of two nonpolarizing GMRFs are insensitive to the conical angle. Compared with previous reported 1D nonpolarizing GMRFs, the tolerances of conical angle of the fabricated structures are remarkably enhanced.

Active optical switches based on polarization-tuned guided-mode resonance filters for optical communication

An active optical switch based on polarization-tuned guided-mode resonance filter (GMRF) for the optical communication wave band is experimentally demonstrated. The proposed active optical switch consists of a linear polarizer, a twisted nematic liquid crystal (TN-LC) polarization rotator and a GMRF from top to bottom. Two fabricated optical switches exhibit high resonance peaks with wavelengths around 1310 and 1550 nm in the voltage-off status. In the voltage-on status, weak light signals without resonance peaks pass through the optical switches. Thus light signal can be tuned by controlling the applied voltage on the TN-LC of the optical switch.

Polarization-Insensitive Filter for Incidence Between Classic and Full Conical Mountings

An angular-dependent polarization-insensitive filter in the telecommunication region is demonstrated in this letter, which is based on a zero-contrast grating for incident plane between classic and full conical mountings. Particle swam optimization combined with the rigorous coupled wave analysis method is applied to design the filter and perform the reflectance spectra. Realization of the polarization-insensitive filter is based on the split feature of a 1D guided mode resonant filter, under oblique incidence in classic mounting. Results show that polarization-independent resonances occur near $1.454~\mu \text{m}$ under the oblique incidences of 4.8°, 5.3°, 6.5°, and 9.3°, with the incident plane angle being set as 15°, 30°, 45°, and 60°, respectively. During the process of varying the incident plane angle from classical mounting to full conical mounting, the mechanism of the increased angle of oblique incidence is also analyzed in detail.

Multiband guided-mode resonance filter in bilayer asymmetric metallic gratings

In this paper, a guided-mode resonances (GMRs) based multiband filter in bilayer asymmetric metallic gratings is presented. Four sharp dips are generated in the frequency range of 1.4–2.0 THz, which are induced by the split of two GMR modes (TE0 and TM0) due to the break of the structure’s symmetry. This symmetry of the structure depends on the relative position between the upper layer and lower layer gratings. Therefore, by choosing proper lateral displacement, the split of TE0 or/and TM0 modes can be eliminated. Two-, three-, and four- GMRs based polarization insensitive or sensitive filters are demonstrated numerically.

Particle swarm optimization and its application to the design of a compact tunable guided-mode resonant filter**Project supported by the National High-Tech Research and Development Program of China (Grant No. 2011 AA050518).

A compact tunable guided-mode resonant filter (GMRF) in the telecommunication region near the 1550 nm wavelength is proposed in this paper. Particle swarm optimization (PSO) is used to design the GMRF. The tunability of the GMRF is achieved by an MEMS-based physical movement (in the horizontal or vertical direction) combined with an incident angle in a certain range. The results show that the resonant wavelength tuning of 110 nm (140 nm) is obtained by horizontal movement of 168 nm (vertical movement of 435 nm) combined with an about 11° variation of incident angle.

A Gradient Grating Period Guided-Mode Resonance Spectrometer

This paper reports a compact spectrometer based on a guided-mode resonance (GMR) filter mounted on a linear charge-coupled device (CCD). The GMR is specially designed to exhibit gradient grating periods (GPPs) laterally to ensure that the GMR functions as a linear-variable bandstop filter. Each period corresponds to a resonant wavelength such that this wavelength is reflected back at its corresponding resonant period and transmitted to all other periods. Consequently, when a resonant wavelength is incident on the GGP-GMR attached to a linear CCD, the CCD pixel underneath its resonant period receives the minimum intensity, and the other pixels receive higher intensities. In terms of the wavelength range of interest, by scanning a single wavelength at a time, a transmission efficiency matrix that contains the transmission efficiency of each wavelength at each pixel can be established. An unknown incident spectrum can be reconstructed using the established transmission efficiency matrix and the intensity measured using the CCD. In this study, a GGP-GMR spectrometer less than 3 mm long that can achieve a wavelength detection range of 200 nm was demonstrated to reconstruct various incident spectra, including a single wavelength of light with a resolution of 0.5 nm, a single wavelength of light with varying intensity levels, and dual incident light sources.

Wavelength division multiplexer based on cavity-resonator-integrated guided-mode resonance filters for a compact multi-wavelength light source

Cavity-resonator-integrated guided-mode resonance filters (CRIGF) consisting of a grating coupler in a waveguide resonator formed by two distributed Bragg reflectors of different reflectances can act as a wavelength-selective reflector and an input waveguide coupler for an incident free-space wave. Integration of CRIGFs in a waveguide is proposed to give an array of external mirrors and a wavelength division multiplexer for constructing a compact multi-wavelength light source. Four CRIGFs of 10-μm-size aperture with a wavelength spacing of 15 nm were designed and fabricated. The reflectance of 62% and output efficiency of higher than 18% were theoretically predicted. Multiplexing of four wavelengths was confirmed experimentally.

Fiber-facet-integrated guided-mode resonance filters and sensors: experimental realization.

Guided-mode resonant (GMR) thin films integrated on fiber tips are known to realize compact filters and sensors. However, limited progress in experimental realization has been reported to date. Here we provide a considerable advance in this technology, as we experimentally demonstrate efficient fiber-facet mounted device prototypes. To retain a large aperture for convenient coupling, we design and fabricate silicon nitride-based resonators on the tip of a multimode fiber. We account for light propagation along the multimode fiber with exact numerical methods. This establishes the correct amplitude and phase distribution of the beam incident on the tip-mounted GMR element, thus enabling us to properly predict the resonance response. To fabricate the integrated GMR structures on the tips of fibers, we employ standard microfabrication processes, including holographic interference lithography and reactive-ion etching. The experimental results agree with simulation with an example device achieving high efficiency of ∼77% in transmission. To investigate fiber sensor operation, an etched silicon nitride fiber tip filter is surrounded with solutions of various refractive indices, yielding an approximate sensitivity of 200 nm/RIU.

High Q reflection filter using a gradient-index membrane with a grating surface

High Q reflection filter using a gradient-index (GI) membrane with a grating surface is proposed. The thickness of GI membrane is very small comparing with the traditional multilayer reflection filter or the GI reflection filter, and the GI membrane can also break the restriction of the resonant excitation condition of the conventional guided-mode resonance (GMR) filter. High Q filtering features can be maintained even on the high-index substrate. The grating thickness of the GI membrane filter can be used to select the resonance wavelength with different quality factors (QFs), the reflection peak is blue-shifted, and the QF is decreased from 554.4 to 207.8 as the grating thickness is increased from 50 nm to 150 nm. The gradient coefficient of the GI membrane filter can be used to tailor the number of the reflection channels. The resonant excitations of high order waveguide modes confined in the GI membrane are responsible for the high Q filtering properties with multiple channels.

Light polarization and color from guided-mode resonance filter

The characteristics of reflected light of a 1-D guided-mode resonance filter (GMRF) are studied in this paper. A triple-layer GMRF is designed by using the finite difference time domain method under non-polarized light illumination. Numerical results show that the reflectance spectra of TE and TM polarizations can be changed by altering the fill factor f of the GMRF. Moreover, by calculating the color of the reflected light with the chromaticity theory, we find that the color of reflected light becomes pure when f is 0.9. The results show that the color and polarization degree of the reflected light of a GMRF are tunable by altering the fill factor.