Injection seeding of frequency-converted Q-switched laser

1. A method for operating a laser to be seeded having a resonant cavity, the resonant cavity of the laser to be seeded being characterized by a round-trip time, and having a gain medium and a Q-switch disposed within the resonant cavity of the laser to be seeded, the method comprising the steps of: a) producing a single seed pulse with a pulsed seed laser external to the resonant cavity of the laser to be seeded, wherein the pulse length of the seed pulse is shorter than the round-trip time of the resonant cavity of the laser to be seeded, wherein the pulsed seed laser is a pulse-selected mode-locked laser, a passively Q-switched laser (PQSL), an actively Q-switched laser, or a pulsed diode laser, and wherein the pulsed seed laser has a resonant cavity and at most one optical shutter disposed therein; b) opening the Q-switch of the laser to be seeded; c) injection seeding the resonant cavity of the laser to be seeded with only the single seed pulse to produce radiation; and d) non-linearly frequency converting the radiation produced by the gain medium as a result of injection seeding the resonant cavity of the laser to be seeded with the single seed pulse.

2. The method of claim 1 wherein steps a)-d) are repeated at a repetition rate of between about 20 kilohertz and about 1 megahertz and wherein only a single seed pulse is injected into the resonant cavity of the laser to be seeded each time the Q-switch of the laser to be seeded opens.

3. The method of claim 1 wherein non-linearly frequency converting the radiation produced by the gain medium includes generating higher harmonics of the radiation produced by the gain medium.

4. The method of claim 1 wherein, as a result of injection seeding the resonant cavity of the laser to be seeded with the single seed pulse, the radiation produced by the gain medium is characterized by a plurality of sub-pulses, each of which has a duration approximately equal to that of the single seed pulse.

5. The method of claim 1 wherein injection seeding the resonant cavity of the laser to be seeded with the single seed pulse produces a frequency conversion efficiency or peak power of the radiation produced by the gain medium that is at least twice as large compared to free-running operation of the laser to be seeded.

6. The method of claim 1 wherein the pulsed seed laser is a PQSL, the PQSL being characterized by a pulse repetition rate, further comprising the step of synchronizing the production of the single seed pulse to the opening of the Q-switch of the laser to be seeded so that only the single seed pulse arrives at the resonant cavity of the laser to be seeded when the Q-switch of the laser to be seeded is opening.

7. The method of claim 6 wherein the step of synchronizing the production of the single seed pulse to the opening of the Q-switch of the laser to be seeded includes controlling the pulse repetition rate of the PQSL by using the PQSL as a voltage controlled oscillator in a phase-locked loop control circuit.

8. The method of claim 7 wherein the PQSL is pumped by a source of pump power, and wherein the phase-locked loop control circuit controls the pulse repetition rate of the PQSL by controlling the amount of pump power provided to the PQSL.

9. The method of claim 1 wherein injection seeding the resonant cavity of the laser to be seeded with the single seed pulse includes injecting only the single seed pulse through the Q-switch of the laser to be seeded or through a reflecting surface of the resonant cavity of the laser to be seeded.

10. The method of claim 1 wherein non-linearly frequency converting the radiation produced by the gain medium takes place within the resonant cavity of the laser to be seeded.

11. The method of claim 10 wherein non-linearly frequency converting the radiation produced by the gain medium includes generating higher harmonics of the radiation produced by the gain medium.

12. The method of claim 1 wherein non-linearly frequency converting the radiation produced by the gain medium takes place outside the resonant cavity of the laser to be seeded.

13. An injection seeded laser system, comprising: a laser to be seeded having a resonant cavity, the resonant cavity of the laser to be seeded being characterized by a round-trip time, and having a gain medium and a Q-switch disposed within the resonant cavity of the laser to be seeded; a pulsed seed laser, external to the resonant cavity of the laser to be seeded, that is configured to produce a single seed pulse, wherein the pulse length of the seed pulse is shorter than the round-trip time of the resonant cavity of the laser to be seeded, wherein the pulsed seed laser is a pulse-selected mode-locked laser, a passively Q-switched laser (PQSL), an actively Q-switched laser, or a pulsed diode laser, and wherein the pulsed seed laser has a resonant cavity and at most one optical shutter disposed therein; a port through which to inject only the single seed pulse from the pulsed seed laser into the resonant cavity of the laser to be seeded to seed the gain medium to produce radiation; means for opening the Q-switch of the laser to be seeded; and a frequency converting medium optically coupled to the resonant cavity of the laser to be seeded.

14. The system of claim 13 wherein injection seeding the resonant cavity of the laser to be seeded with the single seed pulse from the pulsed seed laser produces a frequency conversion efficiency or peak power of the radiation produced by the gain medium that is at least twice as large compared to free-running operation of the laser to be seeded.

15. The system of claim 13 wherein the frequency converting medium is located within the resonant cavity of the laser to be seeded.

16. The system of claim 15 wherein the frequency converting medium is configured to generate higher harmonics of the radiation produced by the gain medium.

17. The system of claim 13 wherein the frequency converting medium is located outside the resonant cavity of the laser to be seeded.

18. The system of claim 13 wherein the gain medium is a Neodymium-doped solid state material.

19. The system of claim 18 wherein the gain medium is Neodymium-doped Yttrium Aluminum Garnet (Nd:YAG).

20. The system of claim 13 wherein the pulsed seed laser is a PQSL, further comprising a timing controller configured to synchronize the production of the single seed pulse to the opening of the Q-switch of the laser to be seeded so that only the single seed pulse is injected into the resonant cavity of the laser to be seeded when the Q-switch of the laser to be seeded is opening.

21. The system of claim 20 wherein the timing controller includes a phase locked loop control circuit that uses the pulsed seed laser as a voltage controlled oscillator.

22. The system of claim 13 wherein the pulsed seed laser is a PQSL, further comprising one or more additional pulsed seed lasers, wherein each pulsed seed laser is a PQSL configured to produce single seed pulses of different pulse widths and of about the same wavelength as the fundamental wavelength of the laser to be seeded, wherein each pulsed seed laser is adapted to be removably optically coupled to the resonant cavity of the laser to be seeded via the coupling optics.

23. The system of claim 13 wherein, as a result of injection seeding the resonant cavity of the laser to be seeded with the single seed pulse, the radiation produced by the gain medium is characterized by a plurality of sub-pulses, each of which has a duration approximately egual to that of the single seed pulse, wherein the time between sub-pulses is equal to the round-trip-time of the resonant cavity of the laser to be seeded.