Mode locking at terahertz frequencies using a distributed Bragg reflector laser with a sampled grating

We present a highly reproducible method of producing terahertz (THz) optical pulses using a class of mode-locked AlGaInAs/InP laser operating in the 1.55 μm wavelength range. The device uses a sample grating distributed Bragg reflector to provide strong frequency selectivity at the mode-locked frequency while the distributed reflectors relax the fabrication tolerances and ensure the cavity can self adjust to being an integral number of mode-locked periods in length. The measured devices provide nearly transform-limited pulse trains at 640 GHz or 1.28 THz with a high degree of controllability and operate with consistent performance over a wide range of drive conditions. Being low cost and compact sources of THz radiation, these lasers will open up many applications, including systems for high-speed optical communication and THz imaging.