Abstract

Optical spectroscopic sensing is a technique that is commonly employed for the identification and compositional analysis of a wide variety of substances, from biological samples to greenhouse gases. High-resolution spectrometers are well established, however, attempts to miniaturise the designs can suffer from adverse effects due to the miniaturisation, for both Fourier transform based interferometric designs, as well as dispersive designs. In this work, a linear array of resonant cavity-enhanced photodiodes is realised with spatially chirped resonance wavelength, offering chip-scale free-space hyperspectral sensing. Resonant cavity-enhanced photodiodes sense over a narrow spectral band, which can be tuned by the thicknesses of the heterostructure. Through this work, multiple narrow spectral bands can be sensed by resonant cavity-enhanced photodiodes on a single chip by grading the thicknesses across the wafer. Photocurrent measurements from a fabricated array determine the wavelength of incident light with an accuracy of ± 2 nm.

Highlights

  • The miniaturisation of sensors capable of high-resolution spectroscopic measurements is of significant interest to countless applications where traditional, bulky spectrometers are not feasible

  • An array of resonant cavity-enhanced photodiodes (RCE-PDs) with varied spectral responses has a much reduced overlap of the responses between neighbouring pixels in comparison to broadband detectors and accurate hyperspectral sensing can be achieved without significant post-measurement analysis

  • The results presented here utilise a structure extended from recent work on single-wavelength RCE-PDs sensing in the short-wave infrared

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Summary

Introduction

The miniaturisation of sensors capable of high-resolution spectroscopic measurements is of significant interest to countless applications where traditional, bulky spectrometers are not feasible. An array of RCE-PDs with varied spectral responses has a much reduced overlap of the responses between neighbouring pixels in comparison to broadband detectors and accurate hyperspectral sensing can be achieved without significant post-measurement analysis. This removes the risk of misinterpretation of the incident spectrum and offers a path to miniature high-resolution spectral sensing in simple free-space applications

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