Optical generation and self subharmonic injection locking of tunable 10-100 GHz microwave/millimeter signals

Abstract

Summary form only given.Optical techniques for generation of RF signals are becoming increasingly important in applications requiring very high frequencies and narrow linewidth microwave/millimeter signals such as fiber-radio systems for broadband wireless. Two-section distributed-feedback (DFB) lasers exhibiting high frequency self-pulsation signals up to 80 GHz has been reported. The frequency of microwave/millimeter signals from the two-section DFB lasers is controlled via the bias current of the two section. We report on a continuous RF tuning from 10 to a 100 GHz measured electronically by optical downconversion. These microwave/millimeter wave signals have a free running linewidth in the order of a few MHz, unacceptable for many applications. We achieved stabilization and linewidth-reduction by using self subharmonic locking technique, different from ordinary subharmonic injection locking. In ordinary subharmonic locking, frequency multiplication of the subharmonic is achieved by over modulating a master laser with a high-power subharmonic signal. In self subharmonic locking, frequency multiplication of subharmonic is achieved via intracavity nonlinearity. The self subharmonically locked signals have linewidths comparable to that of the injecting subharmonic signal.