<title>Bulk And Integrated Acousto-Optic Spectrometers For Molecular Astronomy With Heterodyne Spectrometers</title>

Abstract

One of the most significant developments in radio astronomy has been the recent discovery of over 50 different molecules in the interstellar medium. These observations have changed our picture of the distribution of mass in the galaxy, altered our understanding of the process of star formation, and has also opened up a new and lively field of interstellar chemistry. This achievement was made possible not only by the development of sensitive heterodyne receivers (front-end) in the centimeter and millimeter range, but also by the construction of sensitive RF spectrometers (back-end) which enabled the spectral lines of molecules to be detected and identified. Traditionally, spectrometers have been constructed as banks of discrete adjacently tuned RF filters or as digital autocorrelators. However, a new technique combining acoustic bending of a collimated coherent light beam by a Bragg cell followed by detection by a sensitive array of photodetectors (thus forming a RF acousto-optic spcectrometer (AOS) promises to have distinct advantages over older spectrometer technology. An AOS has wide bandwidth, large number channels, high resolution, and is compact, light weight, and energy efficient. These factors become very important as heterodyne receivers are developed for ever higher frequencies.