Long-wavelength semiconductor ring mode-locked lasers incorporating passive deep-ridge waveguides

Summary form only given. We fabricated semiconductor ring mode-locked lasers using curved passive deep-ridge waveguide. A low threshold current of 25 mA was obtained by a ring laser without a saturable absorber. We also achieved hybrid mode-locking of the R-MLLDs at 29.5, 41.2, and 61.7 GHz with maximum optical modulation indices of 91.4, 87.6 and 42.0%, respectively.

1. Introduction

Optical pulse generation in the millimeter-wave (mm-wave) range is a key technology for future high-bit-rate fiber transmission systems and mm-wave fiber-radio systems. Semiconductor ring mode-locked lasers (R-MLLD)^[1] are promising for these applications because of the controllability of their repetition frequency and facility in monolithic integration. In this paper, we report the fabrication and operation of semiconductor R-MLLDs employing curved passive deep-ridge waveguides (DRWs).