Short optical pulse generation from laser diodes with directional coupler external cavity

We demonstrate picosecond optical pulse (POP) generation from semiconductor laser diodes (LDs) operating in a novel external cavity configuration. The structure uses a looped directional coupler to form an optical cavity whose end reflectivity is controlled by the coupling constant. The end reflectivity can be varied continuously between 0 and 100%, and the cavity length can be adjusted by changing the loop length. A theoretical model and experimental verification of results on the generation of high-repetition POPS are presented.