Optical Frequency Comb Generation Using Dual-Mode Injection-Locking of Quantum-Dash Mode-Locked Lasers: Properties and Applications

In this paper, we describe generation and application of wide narrow linewidth optical frequency combs using dual-mode injection-locking of InP quantum-dash mode-locked lasers. First, the dependence of the RF locking-range on the device\´s absorber voltage is experimentally investigated. Under optimized absorber voltage, a continuous wide RF locking-range of ${\approx }{\rm 400}~{\rm MHz}$ is achievable for lasers with 21 GHz repetition rate. The total RF locking-range of ${\approx }{\rm 440}~{\rm MHz}$ is possible considering locking-range for positive and negative absorber voltages. This wide tuning ${>}2{%}$ of the repetition rate, a record for a monolithic mode-locked laser, is reported from a two-section device without any additional passive section or extended-cavity for repetition rate tuning. It is shown that the effective RF locking-range in dual-mode injection corresponds to the optical locking-range and repetition rate tuning under CW injection, which is wider when the free-running mode-locking operation is “less stable.” The widest comb consists of 35 narrow lines within 10 dB of the peak, spanning ${\approx }{\rm 0.7}~{\rm THz}$ and generating 3.7 ps pulses. Second, we show the first demonstration of multi pump phase-synchronization of two 10 Gb/s DPSK channels in a phase-sensitive amplifier using dual-mode injection-locking technique. The phase-sensitive amplifier based on the “black box” scheme shows more than 7 dB phase-sensitive gain and error free performance for both input channels with 1 dB penalty.