Integrated photodetectors for compact Fourier-transform waveguide spectrometers

Abstract

A Fourier-transform waveguide spectrometer is demonstrated by using HgTe-quantum-dot-based photoconductors with a spectral response up to a wavelength of 2 mu m. The spectral resolution is 50 cm(-1). The total active spectrometer volume is below 100 mu m x 100 mu m x 100 mu m. Extreme miniaturization of infrared spectrometers is critical for their integration into next-generation consumer electronics, wearables and ultrasmall satellites. In the infrared, there is a necessary compromise between high spectral bandwidth and high spectral resolution when miniaturizing dispersive elements, narrow band-pass filters and reconstructive spectrometers. Fourier-transform spectrometers are known for their large bandwidth and high spectral resolution in the infrared; however, they have not been fully miniaturized. Waveguide-based Fourier-transform spectrometers offer a low device footprint, but rely on an external imaging sensor such as bulky and expensive InGaAs cameras. Here we demonstrate a proof-of-concept miniaturized Fourier-transform waveguide spectrometer that incorporates a subwavelength and complementary-metal-oxide-semiconductor-compatible colloidal quantum dot photodetector as a light sensor. The resulting spectrometer exhibits a large spectral bandwidth and moderate spectral resolution of 50 cm(-1) at a total active spectrometer volume below 100 mu m x 100 mu m x 100 mu m. This ultracompact spectrometer design allows the integration of optical/analytical measurement instruments into consumer electronics and space devices.