We generate photon pairs in a-Si:H microrings using a CW pump, and find the Kerr coefficient of a-Si:H to be 3.73 ± 0.25 × 10−17m2/W. By measuring the Q factor with coupled power we find that the loss in the a-Si:H micro-rings scales linearly with power, and therefore cannot originate from two photon absorption. Theoretically comparing a-Si:H and c-Si micro-ring pair sources, we show that the high Kerr coefficient of this sample of a-Si:H is best utilized for microrings with Q factors below 103, but that for higher Q factor devices the photon pair rate is greatly suppressed due to the first order loss.
We present a hyperspectral imager with a dual disperser architecture, which is highly re-configurable thanks to the use of a digital micro-mirror device (DMD). The system has over 200 spectral bands in the range 400-700 nm, and 2048 by 2048 spatial pixels. We describe a method to calibrate the instrument and quantify its performance using a simple slit scanning acquisition scheme, and discuss various methods to remove artifacts in the spectral datacube via postprocessing. This prototype instrument is designed for simplicity, and aims to explore new acquisition schemes that exploit the property of colocation and use the programmable nature of the DMD to increase the speed of datacube retrieval and the quality of the hyperspectral data.
We present a novel acquisition scheme based on a dual disperser architecture, which can reconstruct a hyperspectral data cube using many times fewer acquisitions than spectral bands. The reconstruction algorithm follows a quadratic regularization approach, based on the assumption that adjacent pixels in the scene share similar spectra, and if they do not, this corresponds to an edge which is detectable on the panchromatic image. A digital micro-mirror device (DMD) applies reconfigurable spectral-spatial filtering to the scene for each acquisition, and the filtering code is optimized considering the physical properties of the system. The algorithm is tested on simple multi-spectral scenes with 110 wavelength bands, and is able to accurately reconstruct the hyperspectral datacube using only 10 acquisitions.
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