Coupled-cavity Q-switched laser

Abstract

A Q-switched laser having a gain medium disposed within a first cavity and a second cavity whose optical path length is adjustable such that the quality of the first resonant cavity is affected. One aspect of the invention is the changing of the physical path length of the second cavity so as to effect the reflectivity of a mirror common to both cavities as seen from the first cavity. Another aspect of the invention is the incorporation, within the second cavity, of a material whose refractive index or absorption coefficient can be varied by the application of an electric field, a magnetic field, a temperature change or an applied pressure.

What is claimed is: 
     
       1. A Q-switched laser comprising a gain medium disposed within a first resonant cavity and a second resonant cavity disposed adjacent to the first resonant cavity, the optical path length of the second resonant cavity being adjustable such that the .Iadd.optical length of the second resonant cavity is an integer multiple of the optical length of the first resonant cavity and the net .Iaddend.gain of the first resonant cavity containing said gain medium is affected through optical interactions with the second cavity. 
     
     
       2. The Q-switched laser of claim 1 wherein the optical path length of the second resonant cavity is varied by changes in the physical length of the second resonant cavity. 
     
     
       3. The Q-switched laser of claim 1 wherein the optical path length of the second resonant cavity is varied by changing the index of refraction of a material within the second resonant cavity. 
     
     
       4. The Q-switched laser of claim 3 wherein said material within said second resonant cavity has an index of refraction which varies in response to an external stimulus applied to said material. 
     
     
       5. The Q-switched laser of claim 4 wherein the material within said second cavity comprises an electro-optical material whose index of refraction changes in response to an applied electric field. 
     
     
       6. The Q-switched laser of claim 5 wherein said electro-optical material is a semiconductor. 
     
     
       7. The Q-switched laser of claim 6 wherein said semi-conductor is gallium-aluminum-arsenide. 
     
     
       8. The Q-switched laser of claim 6 wherein said semi-conductor is cadmium sulfide. 
     
     
       9. The Q-switched laser of claim 5 wherein said electro-optical material is lithium niobate. 
     
     
       10. The Q-switched laser of claim 5 wherein said electro-optical material is potassium niobate. 
     
     
       11. The Q-switched laser of claim 4 wherein the material within said second resonant cavity comprises a non-linear optical material which changes its index of refraction in response to a light beam incident upon the non-linear optical material. 
     
     
       12. The Q-switched laser of claim 11 wherein said non-linear optical material is lithium niobate. 
     
     
       13. The Q-switched laser of claim 11 wherein said non-linear optical material is potassium niobate. 
     
     
       14. The Q-switched laser of claim 11 wherein said non-linear optical material is a semiconductor. 
     
     
       15. The Q-switched laser of claim 14 wherein said semiconductor is gallium-aluminum-arsenide. 
     
     
       16. The Q-switched laser of claim 14 wherein said semiconductor is cadmium sulfide. 
     
     
       17. The Q-switched laser of claim 4 wherein the material disposed within said second resonant cavity changes its index of refraction in response to a change in the temperature of the material. 
     
     
       18. The Q-switched laser of claim 4 wherein said material located within said second cavity changes its index of refraction in response to a magnetic field. 
     
     
       19. The Q-switched laser of claim 18 wherein said material located within said second cavity which changes its index of refraction in response to a magnetic field is a magnetic spinel. 
     
     
       20. The Q-switched laser of claim 18 wherein said material located within said second cavity which changes its index of refraction in response to a magnetic field is a magnetic garnet. 
     
     
       21. The Q-switched laser of claim 1 wherein said second resonant cavity comprises an electro-optical material whose absorption coefficient changes in response to an applied electric field. 
     
     
       22. The Q-switched laser of claim 21 wherein said electro-optical material comprises a semiconductor operated near its band edge. 
     
     
       23. The Q-switched laser of claim 1 wherein said second resonant cavity comprises an electro-optical material whose absorption coefficient changes in response to light. 
     
     
       24. The Q-switched laser of claim 23 wherein said electro-optical material comprises a semiconductor operated near its band edge. 
     
     
       25. The Q-switched laser of claim 1 wherein said second resonant cavity further comprises an external coupling mirror whose reflectivity changes in response to an external stimulus to the mirror. 
     
     
       26. The Q-switched laser of claim 25 wherein said external coupling mirror whose reflectivity changes in response to an external stimulus to the mirror comprises an etalon comprising an electro-optical material. 
     
     
       27. The Q-switched laser of claim 1 wherein the intensity of the light produced by the first cavity is changed by changing the optical path length of the second cavity such that the intensity of the light produced by the first cavity is diminished but not turned off. 
     
     
       28. A Q-switched laser comprising a gain medium disposed within a first resonant cavity and a second resonant cavity disposed adjacent to the first resonant cavity, the optical path length of the first resonant cavity being adjustable such that the .Iadd.optical length of the second resonant cavity is an integer multiple of the optical length of the first resonant cavity and the .Iaddend.net gain of the first resonant cavity containing said gain medium is affected through optical interactions with the second cavity. 
     
     
       29. A Q-switched laser comprising a gain medium disposed within a first resonant cavity and a second resonant cavity disposed adjacent to the first resonant cavity, between the first resonant cavity and an optical pump, the optical bath length of the second resonant cavity being adjustable such that the .Iadd.optical length of the second resonant cavity is an integer multiple of the optical length of the first resonant cavity and the .Iaddend.net gain of the first resonant cavity containing said gain medium is affected through interactions with the second cavity.