Super-Long Cavity, Monolithically Integrated 1-GHz Hybrid Mode-Locked InP Laser for All-Optical Sampling

High repetition rate (10-50GHz) semiconductor mode-locked lasers (MLL) provide excellent performance in terms of stable output and high optical power and they are commonly investigated for optical frequency comb generation and optical code division multiple access (O-CDMA) networks [1, 2]. However, there have been few studies of monolithically integrated low frequency (< 2-GHz) semiconductor MLLs useful for RF-Photonics and numerous other applications where low-cost electronics and high-speed (short pulses) optics can be leveraged. Photonic ADCs can benefit from short pulse and low repetition rate lasers on a monolithic platform by achieving information quantization in the electrical domain while performing sampling in the optical domain, which entails interfacing low repetition rate lasers with fast all-optical switches with photo-detection [3]. Using many such ADCs in parallel on a monolithic platform provides advantages in cost, power, and equivalent-number-of-bits (ENOBs) compared to very fast electronics ADCs. This paper discusses a 1-GHz hybrid mode-locked (HML) InP laser that can be monolithically integrated with Mach-Zehnder (MZI) modulators that serve as an ultra-compact sampling module. The focus of this paper is to realize an ultra-compact, monolithically integrated high speed sampling module that is compatible with deeply-etched mirrors (DEM) which form the 1-GHz HML laser cavity.