Patent ID: 8885246

Claim:
A device for extending the lifetime of at least one frequency-converting non-linear optical crystal subjected to the radiation of an incident laser beam, said at least one frequency-converting non-linear optical crystal being capable of converting the incident laser beam of fundamental optical frequency into an output beam of different optical frequency, the device comprising: a first transmission plate with flat and parallel surfaces, of first thickness and of first optical index, capable of being inserted in the optical path of said incident laser beam and of transmitting a first beam, the normal η 2 to a flat surface of said first transmission plate forming a first angle of inclination with an axis of propagation of the incident laser beam, a second transmission plate with flat and parallel surfaces, of second thickness and of second optical index, capable of being inserted in the optical path of the output beam at the exit of said at least one frequency-converting non-linear crystal and of transmitting the output beam the normal η 3 to said second transmission plate forming a second angle of inclination with respect to an axis of propagation of the output beam, a control system for the first transmission plate and the second transmission plate, the control system performing: (i) transverse rotation of said first transmission plate around at least one axis transverse to the axis of propagation of the incident laser beam, capable of modifying the first angle of inclination over a first angular range to displace the first beam by a first displacement with respect to a first frequency-converting non-linear optical crystal of said at least one frequency-converting non-linear optical crystal, and (ii) transverse rotation of said second transmission plate around at least one axis transverse to the axis of propagation of the output beam ( 17 ), capable of modifying the second angle of inclination over a second angular range, wherein said first and second transmission plates and said control system are capable of minimizing an amplitude of a second displacement of the output beam, in terms of position and of angular direction, over the first angular range of the first plate, wherein the control system causes the transverse rotations of the first and second transmission plates at a first time, the control system causes the transverse rotations of the first and second transmission plates at a second time, and in between the first time and the second time, the control system causes the first beam to remain at a fixed position on the first frequency-converting non-linear optical crystal.