Abstract
Bolometers are thermal detectors widely applied in the mid-infrared (MIR) wavelength range. In an integrated sensing system on chip, a broadband scalable bolometer absorbing the light over the whole MIR wavelength range could play an important role. In this work, we have developed a waveguide-based bolometer operating in the wavelength range of 3.72-3.88 µm on the amorphous silicon (a-Si) platform. Significant improvements in the bolometer design result in a 20× improved responsivity compared to earlier work on silicon-on-insulator (SOI). The bolometer offers 24.62% change in resistance per milliwatt of input power at 3.8 µm wavelength. The thermal conductance of the bolometer is 3.86×10-5W/K, and an improvement as large as 3 orders magnitude may be possible in the future through redesign of the device geometry.
Highlights
The mid-infrared (MIR) wavelength region is attractive for many applications such as chemical and biological sensing, industrial process control, astronomy and free-space communications [1, 2]
We developed the bolometer on the amorphous silicon (a-Si) platform to significantly improve its performance
The geometry of the bolometer is shown in Figure 1. a-Si is a common material for bolometers
Summary
Nanometallic antenna assisted amorphous silicon waveguide integrated bolometer for mid-infrared. Compared with c-Si, a-Si has an advantage of low thermal conductivity It can better confine the heat in a localised region and achieve a higher temperature change. A-Si is a common material for bolometers It has a high temperature coefficient of resistance (TCR) of 2.5 %/K [19] and a low thermal conductivity of 2.2 W/(m·K) [20], it can confine generated heat in a localised region. We use gold as the material of choice for its excellent plasmonic properties and chemical inertness These antennas absorb the incident light and heat up the localised area including the thermometer arm which is positioned close to these antennas (Figure 1). It is clear that with the same heating power in the antennas, the c-Si waveguide bolometer has a lower temperature change in the thermometer. Assuming the sheet resistance of p-type a-Si is dominant, the TCR of the p-type a-Si is -1.9 %/K from the linear fitting
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