Reversible optical tuning of GeSbTe phase-change metasurface spectral filters for mid-wave infrared imaging

Abstract

Tunable narrowband spectral filtering across arbitrary optical wavebands is highly desirable in a plethora of applications, from chemical sensing and hyperspectral imaging to infrared astronomy. Yet, the ability to reconfigure the optical properties, with full reversibility, of a solid-state large-area narrowband filter remains elusive. Existing solutions require either moving parts, have slow response times, or provide limited spectral coverage. Here, we demonstrate a 1-inch diameter continuously tunable, fully reversible, all-solid-state, narrowband phase-change metasurface filter based on a GeSbTe-225 (GST)-embedded plasmonic nanohole array. The passband of the presented device is ∼ 74 n m with ∼ 70 % transmittance and operates across the 3–5 µm thermal imaging waveband. Continuous, reconfigurable tuning is achieved by exploiting intermediate GST phases via optical switching with a single nanosecond laser pulse, and material stability is verified through multiple switching cycles. We further demonstrate multispectral thermal imaging in the mid-wave infrared using our active phase-change metasurfaces. Our results pave the way for highly functional, reduced power, compact hyperspectral imaging systems and customizable optical filters for real-world system integration.

Nonvolatile, Reconfigurable and Narrowband Mid-Infrared Filter Based on Surface Lattice Resonance in Phase-Change Ge2Sb2Te5

“…Remarkably, results show that as the Ge Sb Te crystallization fraction m increases from 0 (the amorphous state) to 1 (the crystalline state), the reflection spectra are greatly red-shifted: the wavelength for the peak reflectance shifts from 3.197 m to 4.795 m. This corresponds to extremely large spectral tunability of 1.598 m, or , which is slightly larger than the RA wavelength tunability of ∼ . This striking spectral tunability is larger or even much larger than most of the reported Ge Sb Te -based mid-infrared filters, including those based on perfect absorbers [ 13 , 14 , 15 , 16 ], Fabry-Pérot cavities [ 18 , 19 ], extraordinary optical transmission effects [ 8 , 20 ], or SLRs combined with thin Ge Sb Te films [ 26 , 27 ].…”

“…Dynamically tunable narrowband mid-infrared (3 m to 5 m) filters are key devices in a diverse range of applications, including chemical spectroscopy, thermography, multispectral/hyperspectral imaging [ 1 , 2 , 3 ]. It has been accepted that conventional tunable narrowband mid-infrared filters realized by using diffraction gratings, motorized filter wheels, acousto-optic interactions [ 4 , 5 ], or Fabry-Pérot interferometers based on micro-electro-mechanical systems [ 6 ] or liquid-crystals [ 7 ] suffer from different limitations, as summarized by Julian et al [ 8 ]. For example, diffraction gratings and motorized filter wheels have moving parts and slow tuning speed, acousto-optic tunable filters are complex to manufacture and integrate, and Fabry-Pérot interferometer-based filters have limited spectral tunability.…”

“…Later Trimby et al [ 21 ] discussed approaches to modify the filter performance, including the quality factor, the spectral range, and the peak transmission. Quite recently, Julian et al [ 8 ] demonstrated reversible mid-infrared filters with high transmittance (∼70%) and narrowband performance ( ). However, the spectral tunability (500 nm, from 2.91 m to 3.41 m) is still too small to cover the mid-infrared regime.…”

“…The operation principle will be elaborated. Results will show that the reflection spectra of the proposed structure can be dynamically tuned by changing the Ge Sb Te crystallization fraction, which can be achieved with a single nanosecond laser pulse [ 8 ]. Remarkably, we will show that our design has extremely large spectral tunability of 1.598 m (from 3.197 m to 4.795 m), which covers the majority of the mid-infrared regime, high reflection efficiencies and relatively large quality factors ( and at 3.197 m, and at 4.795 m).…”

Phase Change Metasurfaces by Continuous or Quasi-Continuous Atoms for Active Optoelectronic Integration

“…Other than the frequently used nano-antennas, SRRs or crosses for a GST-integrated metasurface hybrid framework, other atoms such as nano-holes, squares and rings were also employed for active tuning, e.g., the tunable extraordinary transmission (EOT) of visible and near-IR light by both electrically and optically induced GST phase transition [ 113 , 114 ], the mid-IR transmissive filter [ 115 ] and the lately reported mid-wave spectral filter [ 116 ], etc. In addition, due to the appreciable visible and UV loss of GST, most GST-based devices were demonstrated in the middle-IR range except a few that covered UV, visible and near-IR range [ 117 , 118 , 119 ].…”