title: 175 GHz, 400-fs-pulse harmonically mode-locked surface emitting semiconductor laser.
abstract: We report a harmonically mode-locked vertical external cavity surface emitting laser (VECSEL) producing 400 fs pulses at a repetition frequency of 175 GHz with an average output power of 300 mW. Harmonic mode-locking was established using a 300 µm thick intracavity single crystal diamond heat spreader in thermal contact with the front surface of the gain sample using liquid capillary bonding. The repetition frequency was set by the diamond microcavity and stable harmonic mode locking was achieved when the laser cavity length was tuned so that the laser operated on the 117th harmonic of the fundamental cavity. When an etalon placed intracavity next to the gain sample, but not in thermal contact was used pulse groups were observed. These contained 300 fs pulses with a spacing of 5.9 ps. We conclude that to achieve stable harmonic mode locking at repetition frequencies in the 100s of GHz range in a VECSEL there is a threshold pulse energy above which harmonic mode locking is achieved and below which groups of pulses are observed.
authors.affiliation: School of Physics and Astronomy, University of Southampton, Southampton, SO17 1BJ, UK. K.G.Wilcox@soton.ac.uk
authors.forename: Keith G
authors.initials: KG
authors.lastname: Wilcox
authors.forename: Adrian H
authors.initials: AH
authors.lastname: Quarterman
authors.forename: Vasilis
authors.initials: V
authors.lastname: Apostolopoulos
authors.forename: Harvey E
authors.initials: HE
authors.lastname: Beere
authors.forename: Ian
authors.initials: I
authors.lastname: Farrer
authors.forename: David A
authors.initials: DA
authors.lastname: Ritchie
authors.forename: Anne C
authors.initials: AC
authors.lastname: Tropper
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D054023:Lasers, Semiconductor; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*