Characterization of an Acousto-optic tunable filter for development of a near-IR spectrometer for planetary science.

The development of a spectrometer is being carried out in the Near-Infrared (NIR) wavelength range of 1.0-1.7 μm using an Acousto-Optic Tunable Filter (AOTF). The AOTF is based on Tellurium-di-oxide (TeO) crystal that acts as a dispersing medium and is driven by an external Radio Frequency (RF) signal. The characterization of AOTF is based on the wavelength-tuning frequency relation, spectral bandwidth as a function of wavelength through AOTF Transfer Function (Sinc), their dependence on the angular aperture and the peak diffraction efficiency of the AOTF. To demonstrate the full scanning capability of the AOTF in the wavelength range of 1.0-1.7 μm, Argon (Ar) and Krypton (Kr) line sources are used. The overall functionality of the spectrometer using the wavelength selection capability of AOTF is demonstrated by scanning the RF in the NIR band to detect water vapour absorption signatures in the Earth's atmosphere. This spectrometer is being designed for future interplanetary missions of ISRO with an aim to study the atmospheres of planets such as Mars or Venus. [ABSTRACT FROM AUTHOR]