Time- and frequency-domain theory of externally synchronised operation of a passively mode-locked laser diode

Abstract

It has been recently proposed, and demonstrated in a fibre laser,1 that synchronising a laser in a passive mode-locking (PML) regime by an external signal can be used to solve an important practical task of the extraction of a clock frequency from a stream of digital data. Monolithic laser diodes (LDs) are known to have a number of advantages for many applications in communications, but since the present application would require a regime of operation and parameter values scarcely studied hitherto, a new insight into the underlying physics looks useful. We present here time- and frequency-domain studies of a PML LD synchronized by an external periodic signal. While both models are fairly general, the specific case in mind is that of a monolithic extended-cavity LD with gain, saturable absorber and passive sections, the external modulation being in the form of a train of optical pump pulses incident on the saturable absorber, encompassing a realistic clock-extraction scheme.