Guided-mode Resonance Effect Research Articles

Multi-functional metasurface: ultra-wideband/multi-band absorption switching by adjusting guided-mode resonance and local surface plasmon resonance effects

This study introduces an innovative dual-tunable absorption film with the capability to switch between ultra-wideband and narrowband absorption. By manipulating the temperature, the film can achieve multi-band absorption within the 30–45 THz range or ultra-wideband absorption spanning 30–130 THz, with an absorption rate exceeding 0.9. Furthermore, the structural parameters of the absorption film are optimized using the particle swarm optimization (PSO) algorithm to ensure the optimal absorption response. The absorption response of the film is primarily attributed to the coupling of guided-mode resonance and local surface plasmon resonance effects. The film’s symmetric structure enables polarization incoherence and allows for tuning through various means such as doping/voltage, temperature and structural parameters. In the case of a multi-band absorption response, the film exhibits good sensitivity to refractive index changes in multiple absorption modes. Additionally, the absorption spectrum of the film remains effective even at large incidence angles, making it highly promising for applications in fields such as biosensing and infrared stealth.

Improving transmittance of long-wave infrared guided-mode resonant filters

The long-wave infrared (LWIR) spectral region spanning from 8 to 12 μm is useful for many scientific and industrial applications. Many of these applications require use of either a bandpass or a bandstop filter that can be realized by the guided-mode resonance (GMR) effect with subwavelength periodic features in layered dielectric materials transparent in the LWIR. The GMR filters operating in the LWIR region are fabricated by depositing an amorphous germanium (Ge) film to form a zero-contrast (ZC) waveguide-grating (WGG) on a polished zinc selenide (ZnSe) substrate. In general, the backside of a ZnSe substrate with refractive index 2.41 is uncoated causing a 17% Fresnel-reflection loss in the light transmitted through the filter due to a large impedance mismatch at the ZnSe/air interface. Because we use such filters in the LWIR laser experiments for notch filtering, to improve the filter transmittance we used ZnSe substrates coated on one-side with broadband antireflection coating (ARC) covering the 7 to 12 μm spectral range to fabricate GMRFs with one-dimensional (1D) Ge ZC WGG. We employed high-spatial resolution e-beam lithography and reactive-ion etching nanofabrication techniques to achieve high-performance large-area (12 × 12 mm2) 1D notch filters with subwavelength periods. We characterized polarization dependent spectral performance of the prototype filters with both coherent and incoherent incident light using a tunable quantum cascade laser system that spans the 7 to 12 μm region, and a Fourier transform infrared spectrometer with collimated incident beam to achieve close to 15% improvement in the peak transmittance as well as significant reduction in coherent noise compared to our earlier results with GMRFs without ARC. Here, we present the filter design simulation and measurement results.

Dual-band tunable filter based on high-Q guided-mode resonance grating

A dual-band tunable filter with a 10.5 nm narrowband based on guided-mode resonance grating is demonstrated. The two filtering working bands around 1200 and 1550 nm can be switched by controlling the TE and TM polarization, respectively. And the Q factor as high as 146.7 at 1550 nm is experimentally realized by optimizing the grating parameters. At TE polarization, an asymmetrical line shape is obtained. In addition, the angle-dependent guided-mode resonance (GMR) effect is well studied in the designed GMR grating filter, in which the tunability and optical bistability based on the thermo-optic effect are first demonstrated.

Guided-mode resonance sensors with ultrahigh bulk sensitivity and figure of merit assisted by a metallic layer and structural symmetry-breaking.

We propose a refractive index sensor with both high bulk sensitivity and figure of merit (FOM) that engages the guided-mode resonance (GMR) effect with the assistance of a metallic layer and structural symmetry-breaking in the grating layer. Owing to the existence of the metallic layer, the electric field at resonance can be reflected to the sensing environment, and enhanced bulk sensitivity is realized. Meanwhile, the full width at half maximum of the GMR mode can be decreased by increasing the asymmetrical degree of the grating, thus obtaining a high FOM which benefits the sensing resolution. A bulk refractive index sensitivity of 1076.7 nm/RIU and an FOM up to 35889 RIU-1 are achieved simultaneously. Other structural parameters such as the refractive index and fill factor of the grating are systematically discussed to optimize the sensing performance. The proposed GMR sensor with both high bulk sensitivity and FOM value has potential uses in applications with more stringent sensing requirements.

Magnetically tunable dual-band terahertz absorption based on guided-mode resonance.

We propose a magnetically tunable dual-band terahertz (THz) absorber by using an InAs substrate with a subwavelength zero-contrast germanium grating. The results demonstrate that the absorption peaks in this absorber can be dynamically tuned by changing the intensity and the rotation angle of the applied transverse magnetic field, which is achievable at a moderate order of magnitude of 0.1 Tesla. In addition, we investigate the distribution of magnetic field intensity and find that the magnetically tunable absorption originates from the combination of the magneto-optical effect and the guided-mode resonance effect, where the absorption peaks shift in different directions at normal incidence and oblique incidence. Furthermore, the absorption intensity of the proposed structure could reach 99% with an ultra-high Q-factor of 258. This work paves the way for actively adjustable high-resolution THz absorption or a nonreciprocal thermal emitter.

High-performance refractive index sensor by nano-cylindrical surface structure

In this work, a two-dimensional grating structure based on the metal assisted guided-mode resonance (MAGMR) effect is proposed, which can be used for near infrared band sensing in an aqueous environment. Following optimization by the finite-difference time-domain method, the structure is able to support MAGMR well, and has an excellent reflection dip. The electromagnetic field shows that the structure not only interacts well with the sensing medium but also has a large penetration depth. Results at different refractive indices of the sensing medium confirm the high sensing performance of the proposed MAGMR sensor, which achieves a sensitivity of 852 nm/RIU. Meanwhile, the sensor has a figure of merit up to 4813 RIU−1 (55 times typical GMR sensors) because of the full width at half maximum is only 0.177 nm. Furthermore, the shape and parameters of the MAGMR sensor have been analyzed in detail in order to gain a comprehensive understanding of its performance. This MAGMR sensor is promising for future applications in biomedicine, chemical measurements and environmental monitoring due to its polarization-independent, non-specific angle of incidence, high penetration depth and high sensing performance.

Longwave infrared polarization independent monolithic guided-mode resonance filters with double-sided orthogonal linear gratings

We present novel polarization independent, high-quality monolithic spectral filters based on the guided-mode resonance (GMR) effect with orthogonal linear gratings on either side of the substrate operating in the longwave infrared (LWIR) spectral region. We employ high-spatial resolution e-beam lithography and reactive-ion etching (RIE) nanofabrication techniques to achieve large-area (10×10 mm2) notch filters with subwavelength features. We fabricated prototype filters and characterized their polarization independent spectral performance with both coherent and incoherent incident light using a tunable quantum cascade laser (QCL) system that spans the ∼8–12 µm spectral band as well as a Fourier transform infrared (FTIR) spectrometer with collimated incident beam.

Controllable lasing behavior enabled by the transmission guided-mode resonance effect in coupled gratings

A new type of dye laser is proposed based on a guided-mode resonance (GMR) transmission structure using coupled gratings. By distributing the laser dye in the coupled gratings, controllable transmission lasing behavior was simulated. The structure excites the transmission GMR effect and causes a strong local electric field in the coupled gratings, inducing the slow light effect, which in turn enhances the interaction between light and matter. The proposed GMR structure guides laser emission in the transmission direction. Two structures with resonant wavelengths of 820 nm and 870 nm were designed and compared. A higher laser intensity can be obtained in the structure with resonance at 870 nm and a corresponding threshold and half-height width of 1.24 × 107 V/m and 0.8 nm, respectively. In addition, the lasing wavelength can be tuned by changing the relative position of the coupled gratings. The proposed structure is desirable for the construction of other light-emitting devices.

Novel Micro-Nano Optoelectronic Biosensor for Label-Free Real-Time Biofilm Monitoring.

According to the World Health Organization forecasts, AntiMicrobial Resistance (AMR) is expected to become one of the leading causes of death worldwide in the following decades. The rising danger of AMR is caused by the overuse of antibiotics, which are becoming ineffective against many pathogens, particularly in the presence of bacterial biofilms. In this context, non-destructive label-free techniques for the real-time study of the biofilm generation and maturation, together with the analysis of the efficiency of antibiotics, are in high demand. Here, we propose the design of a novel optoelectronic device based on a dual array of interdigitated micro- and nanoelectrodes in parallel, aiming at monitoring the bacterial biofilm evolution by using optical and electrical measurements. The optical response given by the nanostructure, based on the Guided Mode Resonance effect with a Q-factor of about 400 and normalized resonance amplitude of about 0.8, allows high spatial resolution for the analysis of the interaction between planktonic bacteria distributed in small colonies and their role in the biofilm generation, calculating a resonance wavelength shift variation of 0.9 nm in the presence of bacteria on the surface, while the electrical response with both micro- and nanoelectrodes is necessary for the study of the metabolic state of the bacteria to reveal the efficacy of antibiotics for the destruction of the biofilm, measuring a current change of 330 nA when a 15 µm thick biofilm is destroyed with respect to the absence of biofilm.

Micro-electromechanical-system-tuned resonant filters spanning the 8-12 µm band.

The spectral band covering ∼8-12µm is atmospherically transparent and therefore important for terrestrial imaging, day/night situational awareness systems, and spectroscopic applications. There is a dearth of tunable filters spanning the band. Here, we propose and demonstrate a new, to the best of our knowledge, tunable-filter method engaging the fundamental physics of the guided-mode resonance (GMR) effect realized with a non-periodic lattice. The polarization-dependent filter is fashioned with a one-dimensional Ge grating on a ZnSe substrate and interrogated with a ∼1.5mm Gaussian beam to show clear transmittance nulls. To expand the tuning range, the device parameters are optimized for sequential operation in TM and TE polarization states. The theoretical model exhibits a tunable range exceeding 4 µm, thus covering the band fully. In the experiment, a prototype device exhibits a spectral range of 8.6-10.0 µm in TM and 9.9-11.7 µm in TE polarization or >3µm total. With additional efforts in fabrication, we expect to achieve the full range.

High-quality large-scale electron-beam-written resonant filters for the long-wave infrared region.

We present new, to the best of our knowledge, large-scale, high-quality spectral filters operating in the long-wave infrared (LWIR) spectral region. We employ high-spatial resolution nanofabrication techniques to achieve large-area (12mm×12mm) spectrally tunable notch filters. Filter operation is based on the guided-mode resonance effect. The device structure consists of a germanium waveguide grating on top of a zinc selenide substrate. The filters reflect the incident broadband light at one (or more) narrow spectral bands while fully transmitting the rest. We tune the reflected wavelength by tilting the filter. Filters based on one-dimensional gratings are polarization sensitive. We fabricate prototype filters and characterize their polarization dependence and spectral tuning performance using a tunable quantum cascade laser system that spans the ∼7-13µm spectral band. We obtain an excellent agreement between the theoretical and experimental results.

Enhanced dye lasing emission by guided-mode resonance grating with mesoporous silica as spacing layer

<sec>The enhancement of lasing emission intensity of dye laser is particularly important and urgently required due to a broad range of optical and electrical applications. The guided-mode resonance (GMR) effect occurs in a periodic waveguide structure where an incident wave is coupled to a leaky waveguide mode, and yields a resonance peak. The resonance wavelength can be easily controlled by adjusting the period of the grating, thickness of the waveguide layer, and refractive index of the covering materials. By using band edge states, one may be able to excite optical resonances extended over the entire structure surface, thereby achieving field enhancement over a large area. In this study, mesoporous silica with low refractive index is introduced between the grating layer and the substrate layer of the GMR structure to significantly enhance the contact between local electric field and gain medium. For comparison, another structure using SU-8 with high refractive index as the spacing layer is also proposed. It is clearly observed that the maximum of the electric field intensity is highly localized inside the SU-8 waveguide grating layer. However, it is shifted upward to the gain medium layer in the mesoporous silica structure due to the reverse symmetry waveguide structure design. Therefore, the interaction between laser dye and electric field is increased to further enhance the lasing emission.</sec><sec>Besides the refractive index, the waveguide layer, other structural parameters such as thickness of each layer and grating period also affect the electric field distribution in the GMR structure. Based on the finite-difference time-domain method, the structural parameters are analyzed and optimized. According to the simulation results, the structure parameters T<sub>WG</sub> = 3.5 μm, <i>Λ</i> = 700 nm, and <inline-formula><tex-math id="Z-20201229080229-1">\begin{document}$ T_{\rm TiO_2} = 20 $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="1-20201017_Z-20201229080229-1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="1-20201017_Z-20201229080229-1.png"/></alternatives></inline-formula> nm are chosen as the guideline for designing the dye laser, which generates the resonance wavelength of 820 nm the same as the absorption wavelength of dye molecules. Additionally, the laser characteristics excited by pump light with the wavelength of 820 nm are studied. The continuous laser output is obtained. The energy threshold is about 2.5 mJ/cm<sup>2</sup>, and the linewidth is about 0.3 nm. The proposed structure can effectively regulate the surface local electric field and enhance the interaction between pump light and gain medium. It can not only be used in lasers, but also provide reference for designing other light-emitting devices.</sec>

Guided-mode resonance-based bandpass filter operating at full conical mounting.

We propose a cost-effective narrow bandpass filter based on a guided-mode resonance (GMR) structure, operating at full conical mounting configuration. Two additional layers above the GMR structure with designed geometry is considered to create a large angle of incidence (AOI) on the GMR structure with an almost normal AOI on the entire structure. In the visible wavelength range, the transmission spectrum contains three peaks: two peaks that are due to the GMR effect and one that is due to thin-film interference. The modal characteristic of the two GMR peaks is identified using a matrix method for the n-layer waveguide structure. The two GMR peaks with bandwidths of ∼1nm and ∼0.5nm correspond to the fundamental TE and TM modes, respectively. The GMR peaks can be pushed away from the thin-film interference peak by modulating the grating depth.

All-dielectric multifunctional transmittance-tunable metasurfaces based on guided-mode resonance and ENZ effect

Electrically tunable metasurfaces open new doors for manipulating the phase, amplitude and polarization of light in ultrathin layers. Compared with metal assisted metasurfaces, all-dielectric transmission metasurfaces—with outstanding feature of low loss, especially incorporating with new electro-optical materials—show great potential for the next generation flat optics. In this study, by combining the epsilon-near-zero effect in indium tin oxide (ITO) with guided-mode resonance, we propose novel electrically tunable all-dielectric metasurface architectures with versatile functions for widespread potential application. The inserted periodic ITO and hafnium oxide layers sandwiched in silicon act as two metal-oxide-semiconductor capacitors in a single period to disturb the resonance wavelength in the near-infrared spectral range under the voltage applied. For the one-dimensional structure, the transmittances of this metasurface at 1512 and 1510 nm change 20 and −14 dB under 0∼5 V bias voltage, respectively. In addition, the bilayer structure performs well in double-waveband applications, indicating that more layers can support more operation wavebands. Meanwhile, the two-dimensional structure works as a polarization insensitive device when setting the same structural parameters in both orthogonal directions. The proposed architecture, with various merits including ultra-compact size, high-speed and complementary metal-oxide-semiconductor compatibility, provides a multifunctional and multi-degree-of-freedom design, as well as enormous potential applications in more complicated flat optics.

Double Electromagnetically Induced Transparency and Its Slow Light Application Based On a Guided-Mode Resonance Grating Cascade Structure.

In recent years, the achievement of the electromagnetically induced transparency (EIT) effect based on the guided-mode resonance (GMR) effect has attracted extensive attention. However, few works have achieved a double EIT-like effect using this method. In this paper, we numerically achieve a double EIT-like effect in a GMR system with a three-layer silicon nitride waveguide grating structure (WGS), using the multi-level atomic system model for theoretical explanation. In terms of slow light performance, the corresponding two delay times reach 22.59 ps and 8.43 ps, respectively. We also investigate the influence of wavelength detuning of different GMR modes on the transparent window and slow light performance. Furthermore, a wide-band flat-top transparent window was also achieved by appropriately adjusting the wavelength detuning between GMR modes. These results indicate that the EIT-like effect in the WGS has potential application prospects in low-loss slow optical devices, optical sensing, and optical communications.

Unpolarized resonant notch filters for the 8-12 µm spectral region.

The long-wave infrared (LWIR) spectral region spanning ∼8-12µm is useful for many scientific and industrial applications. As traditional multilayer film components are not straightforwardly realized at these bands, we provide design, fabrication, and testing of polarization independent bandstop filters based on the guided-mode resonance (GMR) effect. Focusing on the zero-contrast grating architecture, we successfully fabricate prototype filters in the Ge-on-ZnSe materials system. Applying mask-based photolithography and dry etching, photoresist patterns form the desired Ge grating structures. The resulting devices exhibit clean transmittance nulls and acceptably high sidebands. Moreover, we verify polarization independent notch filtering by assembling two identical GMR filters with gratings oriented orthogonally. This approach to realize effective GMR elements will be useful for various fields including photonic and optoelectronic devices operating in the LWIR region.

Acoustic guided-mode resonances in a metamaterial

We theoretically analyze and numerically demonstrate that guided-mode resonance (GMR) effects can be achieved in acoustic systems. Similar to its optical counterpart, the acoustic GMR-like effects can support multiple narrow bandwidth transmission dips at a broad range of frequencies and give rise to strongly localized acoustic pressure fields in the acoustic waveguide layer. The discussed fundamental phenomena will allow a broad range of applications, including the design of filters, sensors, and other novel acoustic devices.

Flat-top Brewster filter based on guided mode resonance effect

We have analyzed and discussed a flat-top Brewster filter that works in full conical mounting. Results reveal that flat-top reflection band can be formed by merging double peaks that corresponded to guided modes with different polarization states. Merging is achieved by adjusting the incident angle in the design. When the proposed single-layer waveguide grating structure is irradiated with transverse magnetic (TM) polarized plane wave at the Brewster angle, the filter has a highly efficient flat-top reflection spectral response with central wavelength of 547 nm, bandwidth of 15.5 nm (R > 90%), and sideband reflectance of <2.3%.

Plasmonic color filter based on a hetero-metal-insulator-metal grating.

Plasmonic color filters are expected to be candidates for application to complementary metal-oxide-semiconductor (CMOS) image sensor arrays with reduced pixel size, owing to the subwavelength mode volume of plasmons. Designs of metallic gratings based on the guided-mode resonance effect suffer from the sideband transmission issue due to high-order diffraction. Here, we propose a plasmonic color filter structure based on a hetero-metal-insulator-metal grating. The guided mode, in resonance with the second-order diffraction, is highly attenuated by the forbidden band, such that the sideband transmission can be suppressed. As calculated by using the transfer matrix method and the finite-difference time-domain method, the Al-ZnO-Ag waveguide-based structure presents a color filter characteristic with the peak transmittance greater than 70% and the peak wavelength tunable in the visible light band. It may find application in displays, image sensors, and biomedical imaging technologies.

Graphene-based dynamically tunable absorbers through guided mode resonance

Abstract Herein, a dynamically tunable absorber based on a guided mode resonance effect is proposed. The device uses the guided mode resonance principle to obtain a narrow bandpass filter and the output light intensity can be adjusted by applying a voltage to the graphene layer. The device simultaneously offers two channels of light in the horizontal and vertical directions separately. To avoid interference of incident and reflected light, the reflected light of the device is designed to emit from the side of the structure thereby effectively improving the detection accuracy. The device indicates a promising application in electromagnetic stealth, biometrics, and photovoltaic devices.