Nanoelectromechanical infrared detector

Markus Piller; Niklas Luhmann; Miao-Hsuan Chien; Silvan Schmid

doi:10.1117/12.2528416

9 September 2019 Nanoelectromechanical infrared detector

Markus Piller, Niklas Luhmann, Miao-Hsuan Chien, Silvan Schmid

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Proceedings Volume 11088, Optical Sensing, Imaging, and Photon Counting: From X-Rays to THz 2019; 1108802 (2019) https://doi.org/10.1117/12.2528416
Event: SPIE Nanoscience + Engineering, 2019, San Diego, California, United States

Abstract

The sensitive detection of infrared (IR) radiation is a essential task in today’s modern world. The sensitivity of the state-of-the-art uncooled thermal infrared detectors is still several orders of magnitude above the fundamental photon noise limit. Thermal detectors based on temperature sensitive micro- and nanomechanical resonators are a promising approach to obtain improved thermal IR detectors. Here, we present an uncooled infrared detector based on a 1 mm×1 mm large nanoelectromechanical drum resonator made of 50 nm thick low-stress silicon nitride (SiN). The detector features a titanium nitride absorber with an absorptivity of ∼30% over the entire mid-IR range. The detector drum is driven at its resonance frequency by means of a phase-locked loop. Absorbed IR radiation results in an observable detuning of the drum’s oscillation frequency. We measured an Allan deviation of σ_A = 5.5 × 10⁻⁷ at room temperature at a noise bandwidth of 25 Hz. With a responsivity of R = 343 W⁻¹ this results in a sensitivity defined as noise equivalent power (NEP) of NEP = 320 pW/rtHz for an IR beam at a wavelength of 9.5 µm. For this measurement, the IR beam focus spot diameter was equal to the drum size. The drum’s responsivity improves by a factor of ten for a focal spot size smaller than ∼ 100 μm. For smaller spots the responsivity remains constant. Based on this analysis we predict a sensitivity of ∼ 30 pW/rtHz for an IR spot size smaller than 100 μm. The detector can be improved further by e.g. optimizing the tensile pre-stress to a lower value or by improving the absorptivity.

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Markus Piller, Niklas Luhmann, Miao-Hsuan Chien, and Silvan Schmid "Nanoelectromechanical infrared detector", Proc. SPIE 11088, Optical Sensing, Imaging, and Photon Counting: From X-Rays to THz 2019, 1108802 (9 September 2019); https://doi.org/10.1117/12.2528416

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