Nonresonant multiple pass nonlinear structure

1. A laser system comprising:

a seed laser that produces a fundamental frequency light;

a nonresonant multiple pass nonlinear structure which generates a second harmonic light using the fundamental frequency light;

at least one reflecting structure that reflects a remaining portion of the fundamental frequency light from the nonresonant multiple pass nonlinear structure back into the nonresonant multiple pass nonlinear structure to generate an additional second harmonic light; and

at least one second harmonic outcoupler that outputs the second harmonic light and the additional second harmonic light from the laser system.

2. The laser system of claim 1 , wherein the at least one reflecting structure is configured to reflect an incident fundamental frequency light back into the nonresonant multiple pass nonlinear structure in a single reflection.

3. The laser system of claim 1 , wherein the nonresonant multiple pass nonlinear structure is configured to accommodate at least two passes, and wherein each pass through the nonresonant multiple pass nonlinear structure comprises an instance of a light beam passing through at least a portion of the nonresonant multiple pass nonlinear structure with substantially no redirection from a reflective surface or a material boundary.

4. The laser system of claim 1 , wherein the nonresonant multiple pass nonlinear structure comprises a periodically poled crystal with substantially parallel divisional planes.

5. The laser system of claim 1 , wherein an incident fundamental frequency light and a reflected fundamental frequency light both meet a phasematching condition of the nonresonant multiple pass nonlinear structure.

6. The laser system of claim 1 , wherein a first optical path length, of a first pass of fundamental frequency light through the nonresonant multiple pass nonlinear material structure is substantially equivalent to a second optical path length, of a second pass of fundamental frequency light through the nonresonant multiple pass nonlinear structure.

7. The laser system of claim 1 , wherein the seed laser comprises a semiconductor laser.

8. The laser system of claim 1 , wherein substantially no fundamental frequency light is provided to the seed laser as feedback following each pass through the nonresonant multiple pass nonlinear structure.

9. A nonresonant structure comprising:

a nonlinear portion, wherein the dimensions of the nonlinear portion provide for a plurality of passes of fundamental light through the nonlinear portion, each pass through the nonlinear portion comprising an instance of a light beam passing through at least a portion of the nonresonant multiple pass nonlinear structure with substantially no redirection from a reflective surface or a material boundary, and wherein second harmonic light is generated along each of the plurality of passes; and

a reflecting portion, wherein the reflecting portion reflects a fundamental light from a first pass in the nonlinear portion to a second pass in the nonlinear portion.

10. The nonresonant structure of claim 9 , wherein following each pass in the nonlinear portion, substantially no fundamental light comprises a laser gain feedback.

11. The nonresonant structure of claim 9 , wherein the reflecting portion reflects a fundamental light from a first pass in the nonlinear portion to a second pass in the nonlinear portion in a single reflection.

12. The nonresonant structure of claim 9 , wherein the nonlinear portion comprises a nonlinear crystal.

13. The nonresonant structure of claim 9 , wherein the reflecting portion comprises a multilayered coating on the nonlinear crystal.

14. The nonresonant structure of claim 9 , wherein the reflecting portion comprises a mirror structure.

15. A method of generating second harmonic light, the method comprising:

producing a fundamental frequency beam;

inputting the fundamental frequency beam into a nonlinear structure in a first pass, wherein a pass through the nonlinear structure comprises an instance of the fundamental frequency beam passing through at least a portion of the nonlinear structure with substantially no redirection from a reflective surface or a material boundary;

generating a first beam of second harmonic light in the nonlinear structure from a portion of the fundamental frequency beam;

reflecting a remaining fundamental frequency beam from the nonlinear structure into a second pass in the nonlinear structure;

generating a second beam of second harmonic light in the nonlinear structure from a portion of the remaining fundamental beam; and

outputting the first and the second beams of second harmonic light.

16. The method of claim 15 , wherein the reflecting a remaining fundamental frequency beam from the nonlinear structure into a second pass in the nonlinear structure is performed by a single reflection.

17. The method of claim 15 , wherein the nonlinear structure comprises a periodically poled nonlinear crystal.

18. The method of claim 15 , further comprising:

directing an incident fundamental frequency beam in a first angle with respect to the normal of a periodically poled divisional plane of the nonlinear structure; and

reflecting a reflected fundamental frequency beam in a second angle with respect to the normal of a periodically poled divisional plane of the nonlinear structure, wherein the first angle is substantially congruent to the second angle.

19. The method of claim 15 , wherein a first optical path length of an incident fundamental frequency light on a first pass through the nonlinear structure is substantially equivalent to a second optical path length of a reflected fundamental frequency light on a second pass through the nonlinear structure.