Guided-mode Resonance Devices Research Articles

Reflection-phase spectra of cavity-resonator-integrated guided-mode resonance devices

A cavity-resonator-integrated guided-mode resonance filter (CRIGF) consisting of waveguide gratings on a transparent substrate can provide not only a narrowband reflection spectrum but also a steep reflection-phase spectrum. Reflection-phase spectra of CRIGFs were discussed in detail theoretically with an analytical expression. It was found that CRIGFs can be categorized into two types showing a phase variation of 2π rad, namely, reflection-phase rotation, or no rotation. On the other hand, the same structure on a high-reflection mirror, instead of the transparent substrate, normally shows the rotation. The two types of CRIGFs were designed and fabricated with different core thicknesses so that theoretically predicted reflection-phase characteristics with and without rotation could be demonstrated experimentally.

光回路表面実装のための共振器集積導波モード共鳴素子

光回路表面実装のための共振器集積導波モード共鳴素子

One-step sol–gel imprint lithography for guided-mode resonance structures

Guided-mode resonance (GMR) structures consisting of sub-wavelength periodic gratings are capable of producing narrow-linewidth optical resonances. This paper describes a sol–gel-based imprint lithography method for the fabrication of submicron 1D and 2D GMR structures. This method utilizes a patterned polydimethylsiloxane (PDMS) mold to fabricate the grating coupler and waveguide for a GMR device using a sol–gel thin film in a single step. An organic–inorganic hybrid sol–gel film was selected as the imprint material because of its relatively high refractive index. The optical responses of several sol–gel GMR devices were characterized, and the experimental results were in good agreement with the results of electromagnetic simulations. The influence of processing parameters was investigated in order to determine how finely the spectral response and resonant wavelength of the GMR devices could be tuned. As an example potential application, refractometric sensing experiments were performed using a 1D sol–gel device. The results demonstrated a refractive index sensitivity of 50 nm/refractive index unit. This one-step fabrication process offers a simple, rapid, and low-cost means of fabricating GMR structures. We anticipate that this method can be valuable in the development of various GMR-based devices as it can readily enable the fabrication of complex shapes and allow the doping of optically active materials into sol–gel thin film.

Guided-mode-resonance-enhanced measurement of thin-film absorption.

We present a numerical and experimental study of a guided-mode-resonance (GMR) device for detecting surface-bound light-absorbing thin films. The GMR device functions as an optical resonator at the wavelength strongly absorbed by the thin film. The GMR mode produces an evanescent field that results in enhanced optical absorption by the thin film. For a 100-nm-thick lossy thin film, the GMR device enhances its absorption coefficients over 26 × compared to a conventional glass substrate. Simulations show the clear quenching effect of the GMR when the extinction coefficient is greater than 0.01. At the resonant wavelength, the reflectance of the GMR surface correlates well with the degree of optical absorption. GMR devices are fabricated on a glass substrate using a surface-relief grating and a titanium-dioxide coating. To analyze a visible absorbing dye, the reflection coefficient of dye-coated GMR devices was measured. The GMR-based method was also applied to detecting acid gases, such as hydrochloric vapor, by monitoring the change in absorption in a thin film composed of a pH indicator, bromocresol green. This technique potentially allows absorption analysis in the visible and infrared ranges using inexpensive equipment.

All-Dielectric Frequency Selective Surface for High Power Microwaves

In this work, an all-dielectric frequency selective surface was developed for high power microwaves. By avoiding the use of metals, arcing at field concentration points and heating in the conductors was avoided. To do this in a compact form factor while still producing a strong frequency response, we based our design on guided-mode resonance (GMR). To make this approach viable for radio and microwave frequencies, we overcame three major challenges. First, conventional GMR devices have less than 1% fractional bandwidth and we extended this to 16%. Second, conventional GMR devices have a field-of-view less than 1 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> and we extended this to over 40 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> . Third, conventional GMR devices must be composed of hundreds of periods to operate, but our device operated very well with only eight. In this paper, we present our design and experimental results at 1.7 GW/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

ALL-DIELECTRIC FREQUENCY SELECTIVE SURFACES WITH FEW NUMBER OF PERIODS

All-dielectric frequency selective surfaces (FSSs) can serve as an alternative to their metallic counterparts when they must operate at very high power, loss must be minimized, or when the surface itself must be low observable. When metals are avoided, there is a weaker interaction with electromagnetic waves and it becomes more di-cult to achieve strong suppression in the stop band while also realizing compact size, wide fleld-of-view or broadband operation. One attractive approach utilizes guided-mode resonance (GMR) as the flltering mechanism, but this phenomenon exhibits several drawbacks that must be overcome for practical application at radio frequencies. This paper introduces the concept of guide-mode resonance for FSSs and describes how they can be made to operate with a dramatically fewer number of periods than conventional GMR devices.

Performance of conformal guided mode resonance filters

Guided mode resonance (GMR) filters are highly functional micro-optics capable of narrowband spectral filtering. GMR devices have previously been demonstrated on flat substrates using a wide range of materials and configurations. In this Letter, we apply a soft lithographic technique followed by the deposition of dielectric layers to generate GMR filters on a concave lens surface. Resonances of the resulting conformal GMR filters are experimentally measured and characterized, and the results are compared to the performance of similar GMR filters fabricated on flat surfaces.