Diode pumped laser with intracavity harmonics
View Patent ↗A diode end-pumped solid state laser is provided which produces improved power output, long term stability and improved conversion efficiency from the pumping power, high as well as low power operation while maintaining certain desirable common characteristics such as TEM 00 operation, circular outputs, readily aligned systems and compatibility with long lifetime for all components. The invention intracavity conversion to second, third and higher harmonics in several different spectral regimes. The invention also addresses the aspects of design flexibility, seeking in certain embodiments to provide a single platform for providing several harmonic beams.
1. A diode pumped intracavity converting laser, comprising:
at least two reflector mirrors defining a resonator cavity at a fundamental wavelength;
a first Nd-doped gain medium positioned in the resonator cavity, producing radiation at said fundamental wavelength,
a first diode pump supplying pump beam of up to a maximum power at a pump wavelength to the gain medium,
at least one harmonic wavelength generator situated within said resonant cavity and optically coupled to it through at least one dichroically coated optic,
an outcoupler extracting a desired harmonic wavelength without damage to optical components within said cavity;
said resonator cavity and gain medium adapted to operate in a TEM00 mode with a thermal lens in the cavity that is less than 12 D at all pump power levels up to said maximum, such that the said fundamental beam diameter in the harmonic wavelength generator decreases as the pump power increases.
2. The laser according to claim 1 wherein said Nd-doped gain medium is selected from one of the following materials: vanadate, YAG, YAlO3 or YLF.
3. The laser according to claim 1 wherein harmonic output beam is circular.
4. The laser according to claim 1 wherein the pump wavelength is selected to provide direct excitation of the upper laser level of said gain medium.
5. The laser according to claim 1 wherein the harmonic wavelength generator comprises a non-linear crystal providing radiation at a second harmonic wavelength.
6. The laser according to claim 5 wherein the cavity includes a second nonlinear crystal producing a third harmonic wavelength.
7. The laser according to claim 6 , wherein the fundamental beam diameter in the crystal is large enough to obviate the need for walkoff compensation.
8. The laser according to claim 6 , further including means for walkoff compensation.
9. The laser according to claim 5 , wherein the cavity includes a second and third crystal producing a fourth harmonic.
10. The laser according to claim 5 , wherein the cavity includes a second and third crystal producing a fifth harmonic.
11. The laser according to claim 5 wherein the nonlinear crystal comprises material selected from one of the following: LBO, KTP, KNbO3, CLBO, BBO.
12. The laser according to claim 6 wherein the first crystal comprised Type I LBO and the second crystal is Type II LBO.
13. The laser according to claim 1 wherein the extraction means comprising multiply coated optics.
14. The laser according to claim 1 wherein the extraction means are provided comprising a combination of dispersive surface and a dichroic optic.
15. The laser according to claim 1 wherein the extraction means are provided comprising one or more tilted dichroic optics.
16. The laser according to claim 6 wherein the second harmonic is detuned from optimal conversion efficiency.
17. The laser according to claim 1 further including means for suppressing harmonic feed-back through the gain medium and associated cavity optics.
18. The laser according to claim 5 wherein the third harmonic is obtained with efficiency greater than 180% relative to the absorbed pump power.
19. The laser according to claim 6 wherein the second harmonic is obtained with efficiency greater than 25% relative to the absorbed pump power.
20. The laser according to claim 1 where the fundamental mode size in said gain medium is substantially smaller than about 1 mm.
21. The laser according to claim 6 , where means are provided to utilize multiple harmonics.
22. A diode pumped intracavity tripled laser comprising:
at least two high reflector mirrors defining a resonator cavity at a fundamental wavelength,
a first Nd-doped gain medium positioned in the resonator cavity, producing radiation at said fundamental wavelength,
a first diode pump supplying pump beam of up to a maximum power at a pump wavelength to the gain medium,
a Q-switch for pulsing the laser up to a maximum repetition rate
said resonator cavity and gain medium adapted to operate in a TEM00 mode at all pump power levels up to said maximum power,
a first nonlinear crystal situated within said resonant cavity producing a second harmonic beam;
a second nonlinear crystal situated within said resonant cavity producing a third harmonic beam; and
an outcoupler for extracting the third harmonic wavelength without damage said gain medium or other optical components within said resonant cavity;
wherein the second harmonic conversion efficiency is detuned from its maximum value.
23. The laser according to claim 22 wherein Nd gain medium comprises a material selected from one of the following: vanadate, YAG, YalO3 or YLF.
24. The laser according to claim 22 wherein output is circular.
25. The laser according to claim 22 wherein thermal lens of the laser cavity is less than about 12 D.
26. The laser according to claim 22 wherein the thermal lens is less than about 6 D.
27. The laser according to claim 22 wherein the fundamental beam diameter within the harmonic generator increases as the pump power is increased up to said maximum pump power.
28. The laser according to claim 22 wherein the pump wavelength is selected to provide direct excitation of the upper laser level of said gain medium.
29. The laser according to claim 22 , wherein the cavity includes a third crystal producing a fourth harmonic.
30. The laser according to claim 22 , wherein the cavity includes a second and third crystal producing a fifth harmonic.
31. The laser according to claim 22 wherein the first nonlinear crystal comprises LBO, KTP, KNbO3, CLBO, BBO.
32. The laser according to claim 22 wherein the first crystal comprised Type I LBO and the second crystal is Type II LBO.
33. The laser according to claim 22 wherein the means for outcoupling the third harmonic comprises one or more dichroically coated optic.
34. The laser according to claim 22 wherein the means for outcoupling the third harmonic comprises a combination of dispersive surface and a dichroic optic.
35. The laser according to claim 22 wherein the means for outcoupling the third harmonic comprises a combination of at least two angled dichroically coated optics.
36. The laser according to claim 22 further including means for suppressing harmonic feed-back through the gain medium and associated cavity optics.
37. The laser according to claim 22 wherein the third harmonic is obtained with efficiency greater than 25% relative to the absorbed pump power.
38. The laser according to claim 22 wherein the second harmonic is detuned by means of crystal length selection.
39. A diode pumped intracavity converted laser comprising:
at least two reflector mirrors defining a resonator cavity at a fundamental wavelength,
a first gain medium positioned in the resonator cavity, producing radiation at said fundamental wavelength,
a first diode pump supplying pump beam of up to a maximum power at a pump wavelength to the gain medium,
a Q-switch for pulsing the laser up to a maximum repetition rate,
a first harmonic wavelength generator situated within said resonant cavity and optically coupled to it through at least one high reflecting coated optic,
a second harmonic wavelength generator situated within said resonant cavity and optically coupled to it through at least one high reflecting coated optic, and
means for outcoupling the desired harmonic wavelength without damage to optical components within said cavity,
wherein said resonator cavity and gain medium are adapted to operate in a TEM00 mode in the presence of at least one intracavity lens configured and positioned to create a different spot sizes in said first and second harmonic generators, said spot size selected to optimize overall conversion.
40. A diode pumped intracavity converted laser comprising:
at least two reflector mirrors defining a resonator cavity at a fundamental wavelength,
a first gain medium positioned in the resonator cavity, producing radiation at said fundamental wavelength,
a first diode pump supplying at least one pump beam of up to a maximum power at a pump wavelength to the gain medium,
a Q-switch for pulsing the laser up to a maximum repetition rate,
a first harmonic wavelength generator situated within said resonator cavity and optically coupled thereto through at least one highly reflecting coated optic,
a second harmonic wavelength generator situated within said resonator cavity and optically coupled thereto through at least one highly reflecting coated optic, and
a beam separator element positioned within the resonator cavity and configured to outcouple a desired harmonic wavelength without damage to optical components positioned within said cavity,
wherein the output of a frequency tripled wavelength is achieved with an efficiency greater than about 17% relative to the pump power absorbed in said gain medium.
41. A diode pumped intracavity laser comprising:
at least two mirrors defining a resonator cavity at a fundamental wavelength,
a first gain medium positioned in the resonator cavity, producing radiation at said fundamental wavelength,
a first diode pump supplying at least one pump beam of up to a maximum power -at a pump wavelength to the gain medium,
a Q-switch for pulsing the laser up to a maximum repetition rate,
at least one harmonic wavelength generator situated within said resonator cavity and optically coupled thereto through at least one dichroically coated optic,
at least one angled dichroically coated optic positioned within the resonator cavity and configured to output a selected harmonic wavelength from said resonator cavity without damage to optical components within said resonator cavity,
wherein a beam diameter of the fundamental wavelength in first harmonic wavelength generator is less than about 0.7 mm.
42. A diode pumped intracavity laser comprising:
at least two high reflector mirrors defining a resonator cavity at a fundamental wavelength,
a first gain medium positioned in the resonator cavity, producing radiation at said fundamental wavelength,
a first diode pump supplying at least one pump beam of up to a maximum power at a pump wavelength to the gain medium,
a Q-switch for pulsing the laser up to a maximum repetition rate,
at least one harmonic wavelength generator situated within said resonantor cavity and optically coupled thereto through at least one dichroically coated optic, and
a beam separation element comprising a combination of at least one dispersive surface and at least one dichroic optic positioned within the resonator cavity and configured to deflect a selected harmonic wavelength out of said resonator cavity without producing damaging leakage to said gain medium or optical components within said cavity.