Solid state lasers with passive mode coupling and a high pulse repetition frequency

摘要

A passively mode-locked solid-state laser is designed to emit a continuous-wave train of electromagnetic-radiation pulses, the fundamental repetition rate of the emitted pulses exceeding 1 GHz, without Q-switching. The laser comprises an optical resonator (3.1), a solid-state laser gain element (2) placed inside said optical resonator, means (1) for exciting said laser gain element to emit electromagnetic radiation characterized by the effective wavelength, and means for passive mode-locking comprising a saturable absorber. The laser gain element (2) preferably consists of a laser material with a stimulated emission cross section exceeding 0.8x10?-18 cm-2¿ at the effective wavelength; typically, the laser gain element is made of Nd:vanadate. The saturable absorber is preferably a semiconductor saturable absorber mirror device (4). The laser is simple, robust, compact, efficient, and low-cost. It generates a relatively large average power of 100 mW and higher (51, 52), which is useful for a number of optical probing and detection applications, in a beam which is substantially a fundamental spatial mode.