Near-field resonant photon sorting applied: dual-band metasurface quantum well infrared photodetectors for gas sensing

Abstract

Two photodetectors for measuring transmission and two bulky, separated narrowband filters for picking a target gas absorption line and a non-absorbing reference from broadband emission are typically required for dual-band non-dispersive infrared (NDIR) gas sensing. Metal-dielectric-metal (MDM) metasurface plasmon cavities, precisely controllable narrowband absorbers, suggest a next-generation, nanophotonic approach. Here, we demonstrate a dual-band MDM cavity detector that consolidates the function of two detectors and two filters into a single device by employing resonant photon sorting-a function unique to metasurfaces. Two MDM cavities sandwiching a quantum well infrared photodetector (QWIP) with distinct resonance wavelengths are alternately arranged in a subwavelength period. The large absorption cross section of the cavities ensures ~95% efficient lateral sorting of photons by wavelength into the corresponding detector within a near-field region. The flow of incident photons is thus converted into two independent photocurrents for dual-band detection. Our dual-band photodetectors show competitive external quantum efficiencies up to 38% (responsivity 2.1 A/W, peak wavelength 6.9 5m) at 78 K. By tailoring one resonance to an absorption peak of NO 2 (6.25 5m) and the other to a non-absorbing reference wavelength (7.15 5m), NDIR NO 2 gas sensing with 10 ppm accuracy and 1 ms response times is demonstrated. Through experiment and numerical simulation, we confirm near-perfect absorption at the resonant cavity and suppressed absorption at its non-resonant counterpart, characteristic of resonant photon sorting. Dual-band sensing across the mid-infrared should be possible by tailoring the cavities and quantum well to desired wavelengths.

Supplementary document for Patchwork Metasurface Quantum Well Infrared Photodetectors with Broadened Photoresponse - 4936249.pdf

“…To maximize the bandwidth of our multi-patch detectors, we attempted to increase R near the lower (~ 6.0 μm) and upper bounds (~ 7.5 μm) of our QWIP using four patches resonant at these wavelengths. A red-shift in λ peak has been consistently observed for metasurface QWIPs with stripe cavities in our previous work [2,3] and with patch cavities in this manuscript. Thus, R at wavelengths close to 6.0 μm is consistently low.…”

A quantum well infrared photodetector capable of distinguishing circularly polarized light operating at very long infrared wavelengths

“…This explains the observed difference in coupling efficiency between RCP and LCP light, which is due to the selective excitation of SPP waves and waveguide resonance by circularly polarized light with different spin directions. To evaluate the performance of the QWIP device, the paper calculated the enhancement factor F of the active region of the quantum well and the device's responsivity R. 50,51 Figure 9 shows the enhancement factor F for LCP and RCP light at the incident wavelength of 14.2 µm. The z value of the active region of the quantum well in this device is 0-0.276 µm.…”

Cost‐Effective Nanophotonic Metasurfaces with Spatially Gradient Structures for Ultrasensitive Imaging‐Based Refractometric Sensing

“…Nanophotonic metasurfaces based on metallic and dielectric nanostructures [1][2][3][4][5][6][7][8][9][10] can effectively confine incident light in a nanoscale vicinity to achieve a high electromagnetic field enhancement, which perform on the spectral shift of the resonance peak and is highly sensitive to the refractive index of the medium DOI: 10.1002/smtd.202300873 on the metasurfaces, enabling to detect small refractive index changes of various substances, such as biomolecules, [11][12][13][14][15][16][17][18] toxic gases, [19][20][21] and humidity. [22] However, to identify a tiny spectral shift of resonance peak, bulky and sophisticated spectrometers, with operation of trained professionals, are usually employed.…”