Group IV Mid-infrared waveguide-based bolometers

Abstract

Mid-Infrared (MIR) silicon photonics, known as MIR group IV photonics, is an emerging area which aims to extend silicon photonics to longer wavelengths. MIR silicon photonics can address applications in environmental and biological sensing, homeland security, industrial process control and telecommunications.

To realise MIR lab-on-chip photonic sensors, photodetectors which can operate at any MIR wavelengths are required. As the MIR integrated detectors developed so far are limited by either operation wavelength range or wafer scale fabrication, thermal detectors may be the best options for low-speed applications requiring broadband detection, such as sensing. This thesis presents the investigation of MIR waveguide integrated bolometers.

The first uncooled silicon waveguide-based bolometers in the Silicon-on-Insulator (SOI) and suspended silicon waveguide platforms are presented in this thesis. The bolometers comprise gold plasmonic antennas on the waveguide surface that heat up when they absorb light, and Amorphous Silicon (a-Si) thermometers (formed by ion implantation), whose Temperature Coefficient of Resistance (TCR) is 0.90 % K−1 . The responsivity of bolometers based on suspended silicon waveguides is 1.13 %/mW at 3.8 µm wavelength. To further improve the performance, bolometers based on an a-Si platform have been investigated. The bolometers with p-type a-Si thermometers show a TCR of 1.90 % K−1 and a responsivity of 24.62 %/mW at 3.8 µm wavelength. The thermal conductance of the bolometer is 3.86 × 10−5 W/K and an improvement as large as 3 orders magnitude may be possible in the future through redesign of the device geometry. Moreover, the response of antenna arrays with different input polarisation have been investigated to prove that polarisation-dependent Localized Surface Plasmon Resonance (LSPR) is excited in bolometers.

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Identifiers

ORCID for Goran Mashanovich: orcid.org/0000-0003-2954-5138

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