摘要
On-chip ultrafast mode-locking lasers are basic building blocks for the realization of a chip-based optical frequency comb.In this paper,an ultrafast saturable absorber made up of a graphene pad on top of a silicon waveguide is applied to implement an ultrafast pulse laser.Benefiting from the small mode area of the graphene/silicon hybrid waveguide,the saturable pulse energy is reduced by two orders of magnitude compared with the fiber.A mode-locked pulse with a duration of 542 fs and a repetition rate of 54.37 MHz is realized.Pump–probe measurement shows that the carrier relaxation process of free carrier recombination with atomic-thin graphene/silicon junctions is three orders of magnitude faster than silicon,which plays a fundamental role in pulse narrowing.The chip-scale silicon ultrafast laser lays a foundation for a new class of nonlinear devices,in which a combination with multiple functional silicon photonic circuits enables efficient nonlinear interaction at the micrometer scale and less than 1 W of power consumption.
基金
National Natural Science Foundation of China(61775075).
