A Total Solid State, Extremely Fast, Highly Sensitive, Rugged, Miniature Spectroradiometer Based on a TeO2 Acousto-optic Tunable Filter (AOTF)

Brimrose proposes to research and build in this Phase I program, a novel miniature spectroradiometer for measuring spectral incident, reflected, and transmitted irradiance of floating ice ocvers at visible wavelength (400-700 nm). This spectroradiometer is incorporated with a Brimrose acousto-optic tunable filter (AOTF). An AOTF uses an ultrasonic wave in a crystal to achieve fast and broadband spectral tuning. AOTFs are totally solid state devices with no moving parts, compact (1 cm cubed), light weight, and low power for battery operation. Because of that, the diameter of the submersible portion of the spectroradiometer is only about 5 cm. Since the AOTF can do self-calibration, no periodic maintenance is needed. In addition, the AOTF can be programmed to simultaneously pass multiple wavelengths, implement powerful matched filtering algorithms and the light throughput is independent of the resolution, which can greatly increase the sensitivity. As a side benefit, this spectroradiometer can also measure the polarization ratio of the light at different wavelength simultaneously. The fast tuning speed (10 ohms), high resolution (1-2 nm), high sensitivity, small size and inherent ruggedness of AOTFs make them ideal for los level light measurement under thick sea ice cover.