Claims
- 1. A laser beam generating apparatus comprising:
a semiconductor laser for outputting a laser beam having a first wavelength, said semiconductor laser containing gallium nitride; and an external resonator using a nonlinear optical crystal; wherein the output beam from said semiconductor laser is led in said external resonator so as to pass through said nonlinear optical crystal, to generate an ultraviolet beam having a second wavelength shorter than the first wavelength.
- 2. A laser beam generating apparatus according to claim 1, further comprising:
control means for leading the laser beam outputted from said semiconductor laser to said external resonator and keep the resonance state of said resonator; wherein barium borate (β-BaB2O4) crystal allowing phase matching with Type 1 is used as said nonlinear optical crystal.
- 3. A laser beam generating apparatus according to claim 2, further comprising:
temperature control means for keeping the temperature of said barium borate crystal in a range of 0° or less; wherein an ultraviolet laser beam is outputted by second harmonic generation.
- 4. A laser beam generating apparatus according to claim 2, wherein in non critical phase matching of said barium borate, a ratio L/b between a crystal length L set to 10 mm or more and a confocal parameter b=(2πm/λ)·w2 is set to be equal or close to about 2.84, where n is a refractive index of a fundamental harmonic, λ is a wavelength of the fundamental harmonic, and w is a spot radius when light is condensed in crystal, which spot radius is determined as the radius of a spot having an intensity of e−2 on the assumption that the peak of a beam intensity is taken as 1.
- 5. A laser beam generating apparatus according to claim 4, wherein letting k be 2πn/λ), the spot radius w is set to be within +40% around {square root}(L/(2.84 k)).
- 6. A laser beam generating apparatus according to claim 3, wherein in non critical phase matching of said barium borate, a ratio L/b between a crystal length L set to 10 mm or more and a confocal parameter b=(2πn/λ)·w2 is set to be equal or close to about 2.84, where n is a refractive index of a fundamental harmonic, λ is a wavelength of the fundamental harmonic, and w is a spot radius when light is condensed in crystal, which spot radius is determined as the radius of a spot having an intensity of e−2 on the assumption that the peak of a beam intensity is taken as 1.
- 7. A laser beam generating apparatus according to claim 6, wherein letting k be 2πn/λ, the spot radius w is set to be within ±40% around {square root}(L/(2.84 k)).
- 8. A laser beam generating apparatus according to claim 2, wherein in the case of phase matching other than the non critical phase matching, a phase matching angle is set to be in a range of 80° or more and less than 90° or in a range of more than 90° and 100° or less.
- 9. A laser beam generating apparatus according to claim 3, wherein in the case of phase matching other than the non critical phase matching, a phase matching angle is set to be in a range of 80° or more and less than 90° or in a range of more than 90° and 100° or less.
- 10. A laser beam generating apparatus according to claim 2, wherein an effective nonlinear constant is expressed by a term containing an effective nonlinear constant d22 of said barium borate crystal and an effective nonlinear constant d31 of said barium borate crystal, and the phase matching angle including a crystal orientation is set such that both the terms have the same positive or negative sign.
- 11. A laser beam generating apparatus according to claim 2, wherein said barium borate crystal is formed by growth by a direct crystal growth method.
- 12. A laser beam generating apparatus according to claim 1, wherein said semiconductor laser has an output of 50 mmW or more.
- 13. A laser beam generating apparatus according to claim 1, wherein said semiconductor laser oscillates substantially with a longitudinal single mode.
- 14. A laser beam generating apparatus according to claim 13, wherein said semiconductor laser has a structure of a distribution feedback type or a distribution reflection type.
- 15. A laser beam generating apparatus according to claim 13, wherein said apparatus has a configuration of an external control type in which part of the laser beam outputted from said semiconductor laser is fed back by spectral deviation or diffraction.
- 16. A laser beam generating apparatus according to claim 13, wherein an oscillation line width of said semiconductor laser is set to be equal to or less a transmission width of said external resonator.
- 17. A laser beam generating apparatus according to claim 2, wherein said external resonator is formed by only said barium borate crystal, and the resonance state is kept by temperature control of said barium borate crystal.
Priority Claims (1)
Number |
Date |
Country |
Kind |
P2001-237593 |
Aug 2001 |
JP |
|
RELATED APPLICATION DATA
[0001] The present application is a continuation application of U.S. Ser. No. 10/210,644 filed Jul. 31, 2002, which claims priority to Japanese Application(s) No(s). P2001-236237 filed Aug. 3, 2001. This application claims priority to both of the foregoing applications, which application(s) is/are incorporated herein by reference to the extent permitted by law.
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
10210644 |
Jul 2002 |
US |
Child |
10352416 |
Jan 2003 |
US |