Patent EP-0123198-A1 (EP)
Inventor: LE GOFF DENIS
IPC: H01S3/134
Filed: 1984-04-10
Abstract: 1. A gas laser device capable of emitting pulses of a radiation (22) at a single frequency, comprising : - a gas laser generator (1-5) including : . two reflectors (4, 5) disposed to form a resonant optical cavity along a first axis (2), one of these reflectors (4) being partially transparent, . means (1) for disposing an active laser gas in the cavity, . means for triggering (17, 3) an electric discharge in the gas, these means being capable of creating a radiation at multiple frequencies oscillating in the cavity, the latter comprising means (5) for linearly polarizing this radiation in a first plane, . and means (6) for displacing one of the two reflectors along the first axis so as to modify the frequencies of oscillation of the radiation in predetermined bands by varying the length of the cavity, - a laser emitter (10) suitable for delivering a continuous radiation at a stabilized frequency, said frequency lying in said predetermined bands, - a polarizer (11) disposed at the output of the laser emitter to linearly polarize the continuous radiation in a second plane, - means (9, 5) for injecting the polarized continuous radiation into the cavity, said means receiving this radiation along a second axis (8) and emitting the radiation parallelly to the first axis towards the partially transparent reflector in such a manner that the second plane is perpendicular to the first plane, a portion of this polarized radiation leaving the cavity, - a photoelectric receiver (13) disposed to receive at least a portion of said polarized continuous radiation leaving the cavity, - and a detector (16) connected to the electrical output of the receiver and to said triggering means, said circuit being capable of delivering a signal to the input of the triggering means whenever the laser energy received by the receiver passes through an extreme value, one of the radiation frequencies capable of oscillating in the cavity then being equal to the stabilized frequency of the injected continuous polarized radiation, said signal controlling the triggering of the electrical discharge, a portion of the energy of the radiation oscillating in the cavity passing through the partially transparent reflector to create a pulse of laser radiation whose single frequency is equal to that of the continuous radiation delivered by the emitter, characterized in that - said portion of the polarized continuous radiation received by the receiver (13) leaves the cavity (4-5) along the second axis (8) after being reflected in the opposite direction by the partially transparent reflector (4), - and that it includes an optical plate (21) disposed between the emitter (10) and the polarizer (11) and oriented in such a manner as to direct towards the receiver (13) the radiation leaving the cavity (4-5) along the second axis (8) after having passed through the polarizer (11) in the opposite direction to the radiation (19) emitted by the emitter (10), said extreme value of laser energy received by the receiver (13) for which the detection circuit (16) delivers a detection signal being a minimum value.