Electrical subharmonic hybrid mode locking of a colliding pulse mode-locked laser at 28 GHz

This letter discusses electrical subharmonic hybrid mode locking (SHML) of a colliding pulse mode-locked (CPM) laser in InP. The CPM laser fabrication adopts a simple wet etching process and bisbenzocyclobutene planarization process for realizing planarized low-capacitance devices. The experimental results show, for the first time to our knowledge, stable emission of nearly transform-limited pulses at 28 GHz of a CPM laser synchronized to a clock source by SHML. We further describe careful optimization steps of dc and radio-frequency biasing conditions which lead to minimal output pulsewidth of 1.4 ps, limited by the saturable absorber dimension.