Guided Mode Resonance Structure Research Articles

A model for fast predicting and optimizing the sensitivity of surface-relief guided mode resonance sensors

Abstract A modified waveguide model for predicting the sensitivity of surface-relief guided mode resonance (GMR) biosensors is presented. The proposed model is a convenient and fast calculation method compared to the current optical simulation tools such as the rigorous couple wave analysis (RCWA). A systematic and theoretical discussion of the GMR geometric structure and sensitivity of the modified model for biosensing is also presented. For a given GMR material, the theoretical maximum sensitivity can be achieved by choosing the proper geometric structure from the model simulations. A comparison of the GMR biosensor sensitivity respectively calculated by the model and the RCWA method shows good agreement. Finally, a suspending GMR structure with a 4.5-fold increase in sensitivity compared to the traditional surface-relief GMR is proposed.

Guided mode resonance in subwavelength metallodielectric free-standing grating for bandpass filtering

We present the experimental study of a free-standing metallic guided-mode resonant structure, for bandpass filtering applications in the mid-IR wavelength range. Structure consists of a subwavelength gold grating with narrow slits deposited on a silicon nitride membrane. High optical transmission is measured with up to 78% transmission at resonance. Angularly resolved spectra are presented revealing Fano-type resonance.

Effect of the cladding layer on resonance response in guided mode resonance structures and its sensing applications

The resonance properties in a guided mode resonance (GMR) structure having a cladding layer inserted between the subwavelength grating and the high-index film are studied. The presence of the layer results in a significant reduction of the resonance linewidth where multiple-coupling approximations are implemented to describe this behavior. The sensitivity of the resonance wavelength to the change of the layer’s refractive index demonstrates the feasibility of using this configuration as a high resolution GMR-based sensor (up to 1×10−5 refractive index unit). The improvement is achieved through the waveguide properties with no perturbation of the grating parameters. In this scheme, coupling to a cladding mode increases the sensitivity ∼32 times that of coupling to a guided mode when using high-index substances. For low-index substances, exciting super mode resonances enhances the sensitivity by a factor of 6 compared to the guided-mode resonance.

Enhancing the resonance quality factor in membrane-type resonant grating waveguides

In this Letter, we present a method of reducing the spectral width of guided-mode resonance (GMR) in air-bridged resonant grating-waveguide structures to enhance the Q factor. The posttreatment of adding a dielectric film to the bottom of the membrane to manipulate the resonance behavior is practicable. The introduced underlayer is shown to be capable of effectively reducing the coupling and enhancing the resonant Q factor. The proposed method provides an effective means of adjusting the resonance property without varying the original GMR structure. The results also imply that TM resonance is more feasible for achieving narrow resonance and potentially in sensing applications, because it has higher sensitivity than TE resonance.

Narrow Bandstop Filters with Wide and Flattened Sidebands Using Silicon-Based and Suspended Membrane Type of Guided-Mode Resonance Structures

In this paper, the simple two-layer silicon-based and suspended-membrane-type guided-mode resonance (GMR) filter with a narrow bandstop spectrum as well as wide and flattened sidebands is experimentally demonstrated. The proposed filter based on a free-standing silicon nitride membrane suspended on a silicon substrate is realized by using the anisotropic wet etching to remove the substrate beneath the silicon nitride layer. Both of grating and waveguide structures are fabricated simultaneously on a silicon nitride membrane. Moreover, the silicon dioxide membrane playing a role on modifying the spectral response of proposed GMR filter is deposited beneath the free-standing silicon nitride layer. The resonance wavelength of proposed band-stop filter is controlled at 1580.6 nm with a bandwidth less than 0.92 nm, measured in full-width at half-maximum (FWHM). The improved spectral performance including the sideband can be extended to be 415 nm with the maximum transmittance greater than 93%.

可用作热光传感器和液晶可调滤光片的优化波导管共振结构

Applicability of guided mode resonant structures to tunable optical filtering and sensing is demonstrated using nematic liquid crystals. As a sensor, a minimum refractive index detectivity of 10^{-5} is demonstrated while as a tunable filter, tunability range of few tens of nanometers with 2-nm bandwidth is presented. The optimum design is achieved by maximizing the evanescent field region in the analyte which maximizes the overlap integral. The device can be operated in reflection or transmission modes at normal incidence. It can also be operated at a single wavelength by measuring the angular profile of the light beam.

Multiline two-dimensional guided-mode resonant filters

A novel multiline filter using a two-dimensional guided-mode resonant (GMR) filter is proposed. The filter concept utilizes the multiple planes of diffraction produced by the two-dimensional grating. Multiple resonances are obtained by matching the guided modes in the different planes of diffraction to different wavelengths. It is shown that the location and the separation between resonances can be specifically controlled by modifying the periodicity of the grating and the other physical dimensions of the structure. This is in contrast to the one-dimensional GMR filters where the location of the resonances is material dependent. Two-line reflection filter designs with spectral linewidths less than 1 nm and a controllable spectral separation of up to 23% of the short resonance wavelength are presented using rectangular-grid grating GMR structures. Three-line filters are designed in hexagonal-grid grating GMR structures with two independently controllable resonance locations.