Dual Angular Tunability of 2D Ge/ZnSe Notch Filters: Analysis, Experiments, Physics

Ko, Yeong Hwan; Lee, Kyu Jin; Simlan, Fairooz Abdullah; Gupta, Neelam; Magnusson, Robert

doi:10.1002/adom.202202390

Cited by 5 publications

(3 citation statements)

References 22 publications

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“…In addition, we have successfully fabricated high performance 2D LWIR filters with parameters being Λ = 3.69 μm, F = 0.54, D g = 1.32 μm, and D h = 1.16 μm. The performance of 2D filters has been previously investigated [17]. Figure 8…”

Section: Characterization and Resultsmentioning

confidence: 99%

Design and fabrication of high-performance guided-mode resonance infrared filters

Simlan¹,

Lee²,

Ko³

et al. 2023

Preprint

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This study reports design, fabrication, and characterization of high-performance guided-mode resonance (GMR) infrared filters based on germanium (Ge) operating in the 7 to 15 µm spectral region. The GMR filters exhibit deep transmittance nulls and high sideband efficiency functioning as band-stop filters. There is reasonable agreement between experimental and theoretical spectral results. By modifying design parameters and incorporating an anti-reflection (AR) layer on the substrate backside, the functionality of the filter is significantly enhanced. The measured low transmittance value of the fabricated filters is found to be as low as 0.021% corresponding to an optical density of OD = 3.68. The one-dimensional (1D) GMR filters produced exhibit agile wavelength tunability when the angle of incidence is varied. The results highlight the potential of GMR technology operating at long infrared wavelengths with creating high performance filters with tunable spectral characteristics. Anticipated application domains include the fields of sensing, imaging, and spectroscopy.

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Section: Characterization and Resultsmentioning

confidence: 99%

Design and fabrication of high-performance guided-mode resonance infrared filters

Simlan¹,

Lee²,

Ko³

et al. 2023

Preprint

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“…In 1992, Magnusson and Wang 1 showed that small compact notch filters can be designed based on the guided-mode resonance (GMR) effect in dielectric WGG and since then such filters have been demonstrated from the visible to the LWIR spectral regions 1 – 16 A GMR filter (GMRF) based on one-dimensional (1D) gratings only on one side of the substrate is polarization sensitive, 1 – 10 whereas GMRFs based on two-dimensional gratings are polarization insensitive at normal incidence and polarization sensitive at non-normal incidence 12 – 15 Recently, we demonstrated polarization insensitivity at normal incidence for a double-sided LWIR GMRF with orthogonal 1D gratings on either side of a substrate, 11 as well as a combination of two separate 1D LWIR GMRFs with linear gratings in orthogonal orientations 9 .…”

Section: Introductionmentioning

confidence: 99%

“… – 16 A GMR filter (GMRF) based on one-dimensional (1D) gratings only on one side of the substrate is polarization sensitive, 1 – 10 whereas GMRFs based on two-dimensional gratings are polarization insensitive at normal incidence and polarization sensitive at non-normal incidence 12 – 15 Recently, we demonstrated polarization insensitivity at normal incidence for a double-sided LWIR GMRF with orthogonal 1D gratings on either side of a substrate, 11 as well as a combination of two separate 1D LWIR GMRFs with linear gratings in orthogonal orientations 9 . Our previous work on 1D LWIR GMRFs used flat ZnSe substrates without any ARC 7 , 9 …”

Section: Introductionmentioning

confidence: 99%

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

Gupta

Song

2023

Opt. Eng.

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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 mm 2 ) 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.

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High-Q guided-mode resonance of a crossed grating with near-flat dispersion

Amedalor

Karvinen

Pesonen

et al. 2023

Applied Physics Letters

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Guided-mode resonances in diffraction gratings are manifested as peaks (dips) in reflection (transmission) spectra. Resonances with smaller line widths, i.e., with higher Q-factors, ensure stronger light–matter interactions and are beneficial for field-dependent physical processes. However, these high-Q resonances often suffer from strong angular and spectral dispersions. We demonstrate that a class of resonant modes with extraordinarily weak dispersion and Q-factor ∼1000 can be excited in crossed gratings simultaneously with the modes with well-known linear dispersion. Furthermore, the polarization of the incoming light can be adjusted to engineer the dispersion of these modes, and strong to near-flat dispersion or vice versa can be achieved by switching between two mutually orthogonal linear polarization states. We introduce a semi-analytical model to explain the underlying physics behind these observations and perform full-wave numerical simulations and experiments to support our theoretical conjecture. The results presented here will benefit all applications that rely on resonances in free-space-coupled geometries.

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Dual Angular Tunability of 2D Ge/ZnSe Notch Filters: Analysis, Experiments, Physics

Cited by 5 publications

References 22 publications

Design and fabrication of high-performance guided-mode resonance infrared filters

Design and fabrication of high-performance guided-mode resonance infrared filters

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

High-Q guided-mode resonance of a crossed grating with near-flat dispersion

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