Optically Stable, Large Time Bandwidth Acousto-Optic Heterodyne Spectrum Analyzer With Fixed Non-Zero Heterodyne Output.
Patent, Filed 14 Sep 90, patented 2 Jul 91,
DEPARTMENT OF THE NAVY WASHINGTON DC
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A common-path interferometric acoustic-optic heterodyne spectrum analyzer having high immunity to ambient vibration uses two, counter-propagating beams, two Bragg cells for beam diffraction, a series of waveplates and a birefringent quartz wedge. Proper light polarization with the waveplates and Bragg cell geometry allows one Bragg cell to diffract primarily the clockwise beam and the other Bragg cell to diffract the counterclockwise beam. The birefringent quartz wedge shifts the diffracted beams to provide a heterodyne signal with a non-zero IF carrier frequency. The analyzer is highly angle compensated and alignment stable when components are disturbed in position or orientation.
- Electricity and Magnetism