Study of the stabilization of a semiconductor mode-lock laser using hybrid mode-lock and optical feedback

Abstract

In this study we present a scheme for modelocked laser stabilization that narrows the RF linewidth and lowers the timing jitter. The aim of this scheme is to stabilize the pulse repetition frequency (PRF) to be used in an absolute long distance measurement technique. In the most of the stabilization schemes, PRF is kept constant, however in this scheme; the PRF is required to perform a sweep, while achieving a relative error in the order of 10 -8 or better within the tuning range. The laser used is a symmetrical cladding single section InAs/InP quantum dash emitting at 1550 nm and with a pulse repetition frequency of 4.37 GHzThe techniques proposed for stabilization are hybrid mode-locking and optical feed-back. In hybrid modelocking, the PRF is locked to the local oscillator (LO), lowering the RF linewidth and the jitter. By performing a frequency modulation of LO, the PRF is modulated. The optical feedback technique uses a fraction of the output radiation that is fed back into the laser cavity after a certain delay. If the delay line is correctly adjusted, this will reduce the timing jitter of laser. The progress in this technique is in the synchronization of the LO with the delay line, combining the benefits of both techniques. Performing a sweep in PRF, the synchronization circuit adjusts the delay line to match incoming pulses within the cavity. Preliminary results are showed.