Tunable mid-wave infrared Fabry-Perot bandpass filters using phase-change GeSbTe
Authors:
Calum Williams,
Nina Hong,
Matthew Julian,
Stephen Borg,
Hyun Jung Kim
Abstract:
We demonstrate spectrally-tunable Fabry-Perot bandpass filters operating across the MWIR by utilizing the phase-change material GeSbTe (GST) as a tunable cavity medium between two (Ge:Si) distributed Bragg reflectors. The induced refractive index modulation of GST increases the cavity's optical path length, red-shifting the passband. Our filters have spectral-tunability of ~300 nm, transmission ef…
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We demonstrate spectrally-tunable Fabry-Perot bandpass filters operating across the MWIR by utilizing the phase-change material GeSbTe (GST) as a tunable cavity medium between two (Ge:Si) distributed Bragg reflectors. The induced refractive index modulation of GST increases the cavity's optical path length, red-shifting the passband. Our filters have spectral-tunability of ~300 nm, transmission efficiencies of 60-75% and narrowband FWHMs of 50-65 nm (Q-factor ~70-90). We further show multispectral thermal imaging and gas sensing. By matching the filter's initial passband to a CO$_{2}$ vibrational-absorption mode (~4.25 $μ$m), tunable atmospheric CO$_{2}$ sensing and dynamic plume visualization of added CO$_{2}$ is realized.
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Submitted 14 February, 2020;
originally announced February 2020.
All-optical continuous tuning of phase-change plasmonic metasurfaces for multispectral thermal imaging
Authors:
Matthew N. Julian,
Calum Williams,
Stephen Borg,
Scott Bartram,
Hyun Jung Kim
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 provid…
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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 $μ$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.
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Submitted 17 December, 2019;
originally announced December 2019.