Low noise subpicosecond pulse generation from a 22 GHz AlInGaAs multiple quantum well laser by direct RF modulation

Abstract

Monolithic high-repetition-rate lasers have drawn considerable attention for applications in photonic analog-to-digital conversion, arbitrary waveform generation and high speed optical sampling [1]. These robust and monolithic sources generate subpicosecond pulses at high repetition rates but exhibit large timing jitter. In order to realize a low noise mode-locked laser (MLL) by synchronizing to an external clock at high frequencies (> 20 GHz), several methods such as subharmonic hybrid mode-locking (SHML) [2], fundamental hybrid mode-locking (FHML) using semi-insulating substrate [3] and optical synchronous mode-locking [4] have been presented. The first of the above methods overcomes the shallow radio frequency (RF) modulation issue at high frequencies but introduces unwanted amplitude modulation and excess timing jitter. The second requires a semi-insulating wafer and lengthy fabrication process, while the third typically involves injection of a low noise mode-locked laser into the laser cavity, requiring an additional laser.