Control of relaxation oscillations in intracavity optical parametric oscillators

1. A continuous wave intra-cavity optical parametric oscillator, comprising:

a laser gain medium for generating a pump wave;

a non-linear material for generating down converted coherent radiation in response to a pump wave, the down converted radiation comprising a signal wave and an idler wave;

two coupled optical cavities, one of said optical cavities being a pump-wave cavity for resonating the pump wave and the other of said optical cavities being a down converted wave cavity for resonating the signal wave or the idler wave, wherein the non-linear material and the laser gain medium are located in the pump-wave cavity and the non-linear material is located in the down converted wave cavity, and

a non-linear loss element for providing a continuous non-linear loss for suppressing relaxation oscillations, wherein the non-linear loss element is located in the pump-wave cavity and/or the down converted wave cavity.

2. The continuous wave intra-cavity optical parametric oscillator as claimed in claim 1 , wherein said non-linear loss element is located in the pump-wave cavity and is configured to generate a second harmonic of the continuous intra-cavity pump-wave.

3. The continuous wave intra-cavity optical parametric oscillator as claimed in claim 1 , wherein said non-linear loss element is located within both the pump-wave cavity and the down-converted wave cavity and is configured to frequency mix the continuous intra-cavity pump-wave with the continuous wave that is resonated in the down converted wave cavity.

4. The continuous wave intra-cavity optical parametric oscillator as claimed in claim 1 , wherein the non-linear loss element is located within the down-converted wave cavity, and is configured to generate a second harmonic of the continuous wave resonated in the down-converted wave cavity.

5. The continuous wave intra-cavity optical parametric oscillator as claimed in claim 1 , wherein the non-linear loss element comprises a quasi phase-matched crystal.

6. The continuous wave intra-cavity optical parametric oscillator as claimed in claim 1 , wherein the non-linear loss element comprises a crystal that allows a type I birefringent phase match process to occur to thereby provide the continuous non-linear loss.

7. The continuous wave intra-cavity optical parametric oscillator as claimed in claim 1 , wherein the non-linear loss element and the non-linear material for generating down converted coherent radiation are the same element.

8. The continuous wave intra-cavity optical parametric oscillator as claimed in claim 1 , wherein the non-linear loss element is configured to provide a variable loss for suppressing relaxation oscillations.

9. The continuous wave intra-cavity optical parametric oscillator as claimed in claim 8 , wherein the non-linear loss element is variable to suppress relaxation oscillations in response to an electrical signal.

10. The continuous wave intra-cavity optical parametric oscillator as claimed in claim 8 comprising a monitor for monitoring an intensity of an intra-cavity field.

11. The continuous wave intra-cavity optical parametric oscillator as claimed in claim 10 comprising a feedback loop between the monitor and the non-linear loss element for feeding back a signal to cause the non-linear loss element to be varied in response to the monitored instantaneous intensity.

12. The continuous wave intra-cavity optical parametric oscillator as claimed in claim 8 , wherein the non-linear loss element comprises an optical modulator for suppressing relaxation oscillations.

13. A continuous wave intra-cavity optical parametric oscillator, comprising:

a laser gain medium for generating a pump-wave;

a non-linear material for generating down converted coherent radiation in response to a pump-wave, the down converted radiation comprising a signal-wave and an idler-wave; and

two coupled optical cavities, one of said optical cavities being a pump-wave cavity for resonating the pump-wave and the other of said optical cavities being a down-converted wave cavity for resonating the signal-wave or the idler-wave, wherein the non-linear material and the laser gain medium are located in the pump-wave cavity and the non-linear material is located in the down-converted wave cavity,

wherein said non-linear material is configured to induce parasitic effects that create a non-linear loss for suppressing relaxation oscillations.