High power optical second harmonic generation in non-linear crystals

Claim 2

A high power, Q-switched, tunable laser providing optical energy at both a fundamental frequency and harmonic frequency thereof, comprising: an optically-resonant cavity having reflective means at either end thereof, one of said reflective means being partially transmissive; an active laser medium disposed within said cavity so as to emit optical energy along an optic axis in a direction normal to the reflecting surface of each of said reflective means; tuning means situated within said cavity in the path of optical energy emitted from said active medium, said tuning means being adapted to alter frequency at which optical energy may pass therethrough in accordance with an electrical voltage supplied thereto; a nonlinear crystal situated astride said optic axis and oriented such that its phase-matching direction coincides with the path of optical energy emerging from said cavity through said partially-transmissive reflective means; transducer means responsive to temperature of said nonlinear crystal for producing an electronic indication of any change in temperature of said nonlinear crystal; and means responsive to said transducer means for supplying an electrical voltage to said tuning means so as to adjust frequency of said optical energy emerging from said cavity in order to maintain substantially perfect phase-matching in said nonlinear crystal irrespective of temperature of said nonlinear crystal.

Claim 3

The apparatus of claim 1 wherein said transducer means comprises a thermocouple.

Claim 4

The apparatus of claim 1 wherein said nonlinear crystal is situated within a constant temperature oven.

Claim 5

The apparatus of claim 2 wherein said nonlinear crystal is situated within a constant temperature oven.

Claim 6

The apparatus of claim 1 wherein said active laser medium comprises neodymium-doped glass and said tuning means comprises electro-optical tuning means.

Claim 7

The apparatus of claim 1 wherein said nonlinear crystal comprises cesium dideuterium arsenate.

Claim 8

The apparatus of claim 3 wherein said nonlinear crystal comprises cesium dideuterium arsenate.

Claim 9

The apparatus of claim 1 wherein said nonlinear crystal is situated outside said cavity.

Claim 10

The apparatus of claim 8 including a constant frequency laser producing optical energy at twice said fundamental frequency, and means directing said optical energy produced by said tunable laser and by said constant frequency laser onto said nonlinear crystal to provide third harmonic optical energy from said crystal.

Claim 11

The apparatus of claim 9 wherein said nonlinear crystal comprises potassium dideuterium phosphate.

Claim 12

A high power, Q-switched, tunable laser producing optical energy at both a fundamental frequency and harmonic frequency thereof, comprising: an optically-resonant cavity having reflective means at either end thereof, one of said reflective means being partially transmissive; an active laser medium disposed within said cavity so as to emit optical energy along an optic axis in a direction normal to the reflecting surface of each of said reflective means; tuning means situated within said cavity in the path of optical energy emitted from said active medium, said tuning means being adapted to alter frequency at which optical energy may pass therethrough in accordance with an electrical voltage supplied thereto; a nonlinear crystal situated astride said optic axis and oriented such that its phase-matching direction coincides with the path of optical energy emerging from said cavity through said partially-transmissive reflective means; optical detecting means producing an output voltage of amplitude varying in accordance with intensity of optical radiation impinging thereon; substantially transparent optical means partially reflective to radiation at said harmonic frequency of optical energy emerging from said optically-resonant cavity, said substantially transparent optical means being situated in the path of optical energy emerging from said nonlinear crystal and oriented such that radiation reflected therefrom impinges on said optical detecting means; and means responsive to said substantially transparent optical means for supplying an electrical voltage to said tuning means so as to adjust frequency of said optical energy emerging from said cavity in order to maintain substantially perfect phase-matching in said nonlinear crystal irrespective of temperature of said nonlinear crystal.

Claim 13

A high power, Q-switched, tunable laser producing optical energy at both a fundamental frequency and harmonic frequency thereof, comprising: an optically-resonant cavity having reflective means at either end thereof, one of said reflective means being partially transmissive; an active laser medium disposed within said cavity so as to emit optical energy along an optic axis in a direction normal to the reflecting surface of each of said reflective means; tuning means situated within said cavity in the path of optical energy emitted from said active medium, said tuning means being adapted to alter frequency at which optical energy may pass therethrough in accordance with an electrical voltage supplied thereto; a nonlinear crystal situated astride said optic axis and oriented such that its phase-matching direction coincides with the path of optical energy emerging from said cavity through said partially-transmissive reflective means; optical detecting means producing an output voltage of amplitude varying in accordance with intensity of optical radiation impinging thereon; substantially transparent optical means partially reflective to radiation at said harmonic frequency of optical energy emerging from said optically-resonant cavity, said substantially transparent optical means being situated in the path of optical energy emerging from said nonlinear crystal and oriented such that radiation reflected therefrom impinges on said optical detecting means; and means responsive to said substantially transparent optical means for supplying an electrical voltage to said tuning means so as to adjust frequency of said optical energy emerging from said cavity in order to maintain substantially perfect phase-matching in said nonlinear crystal irrespective of temperature of said nonlinear crystal.

Claim 14

The apparatus of claim 11 wherein said nonlinear crystal is situated within a constant temperature oven.

Claim 15

The apparatus of claim 11 wherein said nonlinear crystal comprises cesium dideuterium arsenate.

Claim 16

The apparatus of claim 12 wherein said nonlinear crystal comprises cesium dideuterium arsenate.

Claim 17

The apparatus of claim 8 wherein said active laser medium comprises neodymium-doped glass and said tuning means comprises electro-optical tuning means.

Claim 18

The apparatus of claim 11 wherein said nonlinear crystal is situated outside said cavity and said substantially transparent optical means is situated outside said cavity.

Claim 21

The method of claim 17 wherein said step of fine-tuning the output frequency of said tunable laser comprises applying a voltage to an electro-optical tuning element within said laser of amplitude varying in accordance with sensed temperature of said nonlinear crystal.

Claim 24

The method of claim 19 including the step of separating harmonic radiation energy from fundamental radiation energy emerging from said nonlinear crystal.