All-optical continuous tuning of phase-change plasmonic metasurfaces for multispectral thermal imaging

TL;DR

This paper introduces a novel all-solid-state, tunable phase-change metasurface filter for mid-infrared thermal imaging, enabling continuous spectral reconfiguration with high stability and potential for compact hyperspectral systems.

Contribution

The work presents the first continuously tunable, spectrally-agnostic phase-change metasurface filter operating in the mid-infrared, achieved via optical switching of GST nanohole arrays.

Findings

Achieved ~74 nm passband tuning with ~70% transmittance in 3-5 μm range.

Demonstrated stable, reversible tuning over multiple cycles.

Enabled multispectral thermal imaging using the metasurface filter.

Abstract

Actively tunable, narrowband spectral filtering across arbitrary optical wavebands is highly desirable in a plethora of applications, from chemical sensing, hyperspectral imaging to infrared astronomy. Yet, the ability to actively reconfigure the optical properties of a solid-state narrowband filter remains elusive. Existing solutions require either moving parts, have slow response times or provide limited spectral coverage. Here, we demonstrate a continuously tunable, spectrally-agnostic, all-solid-state, narrowband phase-change metasurface filter based on a GeSbTe (GST)-embedded plasmonic nanohole array. The passband of the presented tunable filter is ~74 nm with ~70% transmittance and operates across 3 - 5 $\mu$m; the 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 phase-change metasurfaces. Our results pave the way for highly functional, reduced power, compact hyperspectral imaging systems and optical filters.