Integrated saturable-absorber-enhanced power booster for feedback sensitive on-chip pulsed lasers

Abstract

The lack of optical isolators in photonic integrated circuits is a limiting factor for on-chip laser pulse amplification with a Semiconductor Optical Amplifier (SOA) power booster. Indeed, in the absence of optical isolation between an on-chip pulsed laser and the SOA power booster, amplified feedback signals can enter the laser cavity and destabilize the laser output. In this study, we propose an easy-to-implement and effective solution: a fully integrated Saturable Absorber (SA)-enhanced power booster that efficiently amplifies on-chip modelocked laser pulses while isolating the laser cavity from amplified feedback. Our booster design consists of an InP SOA preceded by a short (20?40 ?m) InP SA. We demonstrate both experimentally and numerically that the presence of the short SA between the laser cavity and the SOA indeed prevents feedback-induced laser destabilization while still allowing efficient power amplification. The SA is found to induce a small power penalty of the order of 1 dB but, at the same time, allows using higher booster currents while maintaining stable laser operation. As such, our novel SA-enhanced booster design enables the on-chip generation of high-power stable laser pulses for a wide range of application domains.