Imaging AOTFs with Low RF Power in Deep-UV and Mid-IR

Abstract

Acousto-Optic Tunable Filters (AOTFs) are commonly used for applications where high speed tuning and narrow spectral resolu- tion are required. The RF drive power for peak diffraction efficiency increases as λ2 and depends on the acousto-optic figure of merit (M2), which is material dependent. In the VIS-IR region between 450nm and 4.5μm tellurium dioxide (TeO2) is the common material of choice due to the high M2. At longer wavelengths (up to about 12μm) the mercurous halides and single crystal tellurium show promise. In both cases the λ2 dependency dominates the RF power consumption and for wavelengths beyond 3.5μm the RF power consumption is above the practical limit (>5W) for larger aperture AOTF(> 10mm × 10mm). In the UV range (200nm – 400nm) the λ2 dependency is no longer dominant and the power consumption depends mainly on the M2,however, for most materials transparent in the UV the M2 is poor and thus the drive power will again be excessive (>5W). In order to reduce the RF power requirement to reach peak diffraction efficiency, a resonant configuration in crystal quartz shows promise, especially in the UV range due to its low acoustic attenuation. We describe an AOTF operating in resonance made of crystal quartz, where the reduction of RF power consumption will be reduced by a factor between 15 and 20 compared to a conventional AOTF, thus reducing the power consumption to be within the practical limit (<5W).