Photopyroelectric Detectors – Chalcogenide Nanogratings

Photopyroelectric detectors can absorb electromagnetic radiation, convert the absorbed energy into thermal energy, and generate a pyroelectric voltage (PEV) across a pyroelectric material. Their applications include energy harvesting, infrared sensing, and thermal imaging.

Conventional narrowband photopyroelectric detectors require a bulky bandpass filter. Alternatively, a narrowband filter, such as a photonic crystal, can be directly integrated with the pyroelectric sensing element. Narrowband photopyroelectric devices can respond to infrared radiation in a specific wavelength range.

The planar photonic crystals can support the guided-mode resonance. They can integrate with most pyroelectric materials and a couple of incident lights into a resonance mode via the grating modulation. For near- and mid-infrared applications, it is possible to use chalcogenide glass to build the photonic crystal grating and achieve resonance modes with a narrow bandwidth and high-quality factor. Researchers have developed resonant-photopyroelectric detectors (R-PED) that combine a free-standing membrane’s narrowband optical absorption and pyroelectric sensing functions. The narrowband optical absorber consists of a 1D chalcogenide (As2S3) grating with a silver cladding layer.

The following aspects will improve photopyroelectric detectors’ performance: response time, bandwidth, and sensitivity. First, higher pyroelectric coefficient materials will be used in R-PEDs to replace the PVDF-TrFE substrate. Second, optimizing the grating structures can reduce the R-PED’s bandwidth and response time even further. Finally, for multi-band sensing applications, an array of R-PEDs with different spectral bands can be integrated on a single chip to detect multiple wavelengths simultaneously.

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