100 GHz Multiple Colliding Pulse Generation From Cleaved Facet-Free Multi-Section Semiconductor Laser Diode

We present a monolithically integrated mode-locked laser (MLL) with 25 GHz fundamental repetition rate frequency, which has been designed to operate in a fourth-order colliding regime, to generate 100 GHz. This device has been fabricated within a multi-project wafer (MPW) run in an InP-based active-passive generic foundry. The Fabry-Perot laser resonator, of around 1.66 mm length, is defined by two on-chip reflectors, eliminating the need of cleaved facet. Three saturable absorber sections are symmetrically located by spacing them a quarter of this total length, dividing the cavity into four gain segments. We show that this structure can generate an electrical beat note at 25 GHz as well as 100 GHz, with a linewidth of 350 kHz and 150 kHz, respectively, operating in passive operation regime.