Wideband Fast Switching RF Synthesizer Based on Optical Heterodyne

Fast tuning microwave synthesizer systems are required by the Army for the demodulation of waveforms encoded by spread spectrum techniques. These systems are required as a method of jamming, countermeasures to jamming, secure communications and as low phase noise sources for rapid tuned radar. Our novel approach to these requirements involves the optical heterodyne between two diode laser-pumped, electro-optically tuned, single frequency microlasers operating at 1.3 and/or 1.5 pm. In such a device, the output frequency is tuned simply by applying a voltage to the laser. This is in contrast to slower frequency control techniques that use piezoelectric or temperature control. The anticipated performance of the monolithic device yields a source with a tuning range of 0 to 40 GHZ in less than 500 nsec. The linewidth of microlasers are typically less than 10 kHz; making them ideal for microwave synthesis. Microlaser technology combines this potential with compactness and low cost and represents a substantial improvement over current state-of-the-art non-planar lasers. The Phase I program includes the demonstration of two narrow linewidth, fast tuning microlasers. Fast tuning synthesis will be demonstrated by beat frequency tests between the two independently tuned lasers. Successful demonstration of the proposed fast tuning optical heterodyne synthesizer will lead to the development of compact, sources with potential applications including operation as sources for high-bandwidth fiber-optic and free space communications links, fiber sensors, transmitters for free space coherent communication systems and stable single frequency sources for metrology and wide band fast tuning microwave synthesizers.