The beat note is used to stabilize the relative frequency between the two optical signals through a simple electronic feedback subsystem that adjusts the voltage applied to the PZT to lock the optical frequency of the COEO to that of the diode laser. The diode laser is frequency stabilized to the atomic absorption of Rb vapor through frequency modulation (FM) saturation spectroscopy. The fractional frequency stability of it has been shown to be 10–12 at 1 second. After further optimization of design to minimize destabilizing effects, it may be possible to attain a longterm stability at 10–13. Such optical frequency stability can be transferred to the microwave in the COEO device where the optical and microwave oscillators are coupled, and hence producing a highly stable microwave signal.
This work was done by Lute Maleki, Nan Yu, and Meirong Tu of Caltech for NASA’s Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Electronics/Computers category. NPO-43026
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