Laser-driven light source with electrodeless ignition
An electrodeless laser-driven light source includes a laser source that generates CW sustaining light. A pump laser generates pump light. A Q-switched laser crystal is positioned to receive the pump light and generates pulsed laser light in response to the generated pump light that propagates to a breakdown region in a gas filled bulb comprising an ionizing gas. A detector detects plasma light generated by a CW plasma located at least partly in a CW plasma region in the gas filled bulb comprising the ionizing gas and generates a detection signal. A controller generates control signals that control the pump light to the Q-switched laser crystal so as to extinguish the pulsed laser light within a time delay after the detection signal exceeds a threshold level.
1. An electrodeless laser-driven light source comprising:
a) a gas filled bulb comprising an ionizing gas;
b) a laser source that generates a continuous wave (CW) sustaining light at an output;
c) a pump laser that generates a pump light at an output;
d) a Q-switched laser crystal positioned to receive the pump light generated at the output of the pump laser, the Q-switched laser crystal generating a pulsed laser light in response to the generated pump light and being configured so that the pulsed laser light propagates to a breakdown region in the gas filled bulb comprising the ionizing gas;
e) a detector that detects a plasma light generated by a CW plasma generated at least partly in a CW plasma region in the gas filled bulb comprising the ionizing gas and generates a detection signal at an output; and
f) a controller having an input that is electrically connected to the output of the detector and an output that is electrically connected to a control input of the pump laser, the controller generating control signals that control the pump light so as to extinguish the pulsed laser light within a time delay after the detection signal exceeds a threshold level.
2. The electrodeless laser-driven light source of claim 1 wherein the detection signal generated by the detector represents a power of the plasma light and the threshold level is a desired ratio of the power of the plasma light to an operating power.
3. The electrodeless laser-driven light source of claim 2 wherein the desired ratio is nominally 50%.
4. The electrodeless laser-driven light source of claim 2 wherein the desired ratio is nominally 90%.
5. The electrodeless laser-driven light source of claim 2 wherein the desired ratio falls within a range between 30% and 95%.
6. The electrodeless laser-driven light source of claim 1 wherein the pump laser and the Q-switched laser crystal are configured so that a period between pulses in the pulsed laser light is greater than the time delay.
7. The electrodeless laser-driven light source of claim 1 wherein the pump laser and the Q-switched laser crystal are configured so that a period between pulses in the pulsed laser light is less than the time delay.
8. The electrodeless laser-driven light source of claim 1 wherein the controller is configured so that the time delay is less than one pulse period of the pulsed laser light.
9. The electrodeless laser-driven light source of claim 1 wherein the pump laser and the Q-switched laser crystal are configured so that a pulse repetition rate of the pulsed laser light is in a range of 1 kHz to 20 kHz.
10. The electrodeless laser-driven light source of claim 1 wherein the pump laser and the Q-switched laser crystal are configured so that a pulse repetition rate of the pulsed laser light is less than or equal to 1 kHz.
11. The electrodeless laser-driven light source of claim 1 wherein the pump laser and the Q-switched laser crystal are configured so that a pulse energy of the pulsed laser light is in a range of 50 μJoules to 500 μJoules.
12. The electrodeless laser-driven light source of claim 1 wherein the pump laser and the Q-switched laser crystal are configured so that a pulse energy of the pulsed laser light is in a range of 500 μJoules to 5 mJoules.
13. The electrodeless laser-driven light source of claim 1 wherein the pump laser and the Q-switched laser crystal are configured so that a pulse duration of the pulsed laser light is in a range of 0.1 ns to 10 ns.
14. The electrodeless laser-driven light source of claim 1 wherein the laser source is configured so that a power of the CW sustaining light is in a range of 5 W to 50 W.
15. The electrodeless laser-driven light source of claim 1 wherein the laser source is configured so that a power of the CW sustaining light is in a range of 5 W to 1500 W.
16. The electrodeless laser-driven light source of claim 1 wherein the Q-switched laser crystal comprises a gain section and a saturable absorber section.
17. The electrodeless laser-driven light source of claim 1 wherein the Q-switched laser crystal comprises at least one of a glass host, an yttrium aluminum garnet host, or a spinel host.
18. The electrodeless laser-driven light source of claim 1 wherein the Q-switched laser crystal comprises at least one of a chromium dopant, a cobalt dopant or a vanadium dopant.
19. The electrodeless laser-driven light source of claim 1 wherein the Q-switched laser crystal comprises a narrow-band filter.
20. The electrodeless laser-driven light source of claim 19 wherein the narrow-band filter reflects at least some of the plasma light.
21. The electrodeless laser-driven light source of claim 19 wherein the narrow-band filter blocks wavelengths in the xenon spectrum.
22. The electrodeless laser-driven light source of claim 1 wherein the Q-switched laser crystal comprises a coating on one surface.
23. The electrodeless laser-driven light source of claim 1 wherein the gas-filled bulb comprises xenon gas.
24. The electrodeless laser-driven light source of claim 1 wherein the gas-filled bulb is formed in a spherical shape.
25. The electrodeless laser-driven light source of claim 1 wherein a pressure in the gas-filled bulb comprises a pressure in a range of 20 atm to 50 atm.