Abstract

Optical injection locking is a versatile technique which allows the control of semiconductor lasers and new operational regimes [1, 2]. In dual-tone optical injection, the light of a tunable CW laser is modulated by an electro-optic modulator, creating optical sidebands distanced by the frequency of the RF signal applied (f_gen), before being injected into a slave laser - in our case, a mode-locked laser diode (MLLD). In this way, f_gen can be tuned so that the longitudinal modes of the slave laser become locked to two of the optical sidebands. A type of subharmonic locking can therefore be achieved for f_gen = f_rep/n, where n is a natural integer, and f_rep is the locked pulse repetition rate of the MLLD. This method has shown significant promise for the high-speed control of the repetition rate of MLLD within a wide locking range [2], although most studies have only used n=2 [2-4].

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