Patent ID: 8774238

Claim:
Laser apparatus, comprising: a laser-resonator having a resonator length; at least one surface-emitting multilayer semiconductor gain-structure located in the laser-resonator, the at least one and any other gain-structure including a plurality of active-layers spaced apart by spacer-layers and having an excited-state lifetime characteristic of material of the active-layers; means for energizing the gain-structure, thereby causing radiation having a fundamental wavelength characteristic of the active layers of the gain-structure to circulate in the laser-resonator; mode-locking means located in the laser-resonator for causing the circulating radiation to circulate as sequence of mode-locked pulses at a predetermined pulse-repetition frequency determined by the resonator length wherein the pulses have a duration of about 200 femtoseconds or less; and an optical arrangement for causing the circulating radiation to make at least 4 gain-structure incidences during each round trip thereof in the laser-resonator, with a predetermined time between gain-structure incidences less than twice excited-state lifetime of the gain-structure.