Laser system with wavelength converter

Patent metadata

Field	Value
Publication number	US-RE46937-E
Application number	US-201115064420-A
Country	US
Kind code	E1
Filing date	Sep 14, 2011
Priority date	Sep 14, 2010
Publication date	Jul 3, 2018
Grant date	Jul 3, 2018

Abstract

The present invention relates to an apparatus comprising a diode laser ( 10 ) providing radiation in a first wavelength interval, a radiation conversion unit ( 12 ) having an input and an output, the radiation converter configured to receive the radiation in the first wavelength interval from the diode laser at the input, the radiation conversion unit configured to convert the radiation in the first wavelength interval to radiation in a second wavelength interval and the output configured to output the converted radiation, the second wavelength interval having one endpoint outside the first wavelength interval. Further, the invention relates to a method of optically pumping a target laser ( 14 ) in a laser system, the laser system comprising a laser source providing radiation at a first frequency, the laser source being optically connected to an input of a frequency converter, the frequency converter configured to convert the radiation at the first frequency to a second, different frequency, the target laser arranged in optical communication with an output of the frequency converter, the method comprising the steps of emitting radiation from the laser source, receiving the radiation at the frequency converter, converting the radiation from the first frequency to the second frequency in the frequency converter, and providing the radiation at the second frequency at the target laser so that the target laser is optically pumped.

First claim

The invention claimed is:

1. A method for reducing intensity noise of a laser apparatus, the apparatus comprising:
a wavelength-stabilized tapered diode laser providing radiation in a first wavelength interval, the diode laser comprising two separate contacts for controlling injection currents to different sections of the diode laser independently;
a radiation conversion unit having an input and an output, the radiation conversion unit being configured to receive the radiation in the first wavelength interval from the diode laser at the input and to convert the radiation in the first wavelength interval to radiation in a second wavelength interval, and the output being configured to output the converted radiation, the second wavelength interval having one end point outside the first wavelength interval,
wherein the method comprises actively controlling an injection current to the diode laser so as to reduce the intensity noise properties of the diode laser apparatus by performing the following steps:
determining intensity noise in the emitted converted radiation,
comparing the determined noise to a threshold value,
if the determinedin response to determining the noise is above the threshold value, adjusting the injection current supplied to a first one of the contacts until the noise is below the threshold value, and
if the determinedin response to determining the noise is above the threshold value and the injection current supplied to the first contact is at a lowest current threshold level, adjusting the injection current supplied to the second contact.

2. The method according to claim 1 , further comprising optimizing the beam quality of the diode laser by active control of the injection current.

3. The method according to claim 1 , further comprising optimizing the spectral line width of the diode laser by active control of the injection current.

4. The method according to claim 1 , wherein adjusting the injection current supplied to the second contact further comprises, raising the injection current supplied to the first contact so that the two injection currents are within a predetermined range.

5. The method according to claim 1 , wherein the diode laser provides radiation in a single-frequency output.

6. The method according to claim 1 , wherein the wavelength stabilization of the diode laser is achieved using an external cavity.

7. The method according to claim 1 , wherein the wavelength stabilization of the diode laser is achieved by using monolithically integrated structures.

8. The method according to claim 7 , wherein at least one of the monolithically integrated structures is a grating.

9. The method according to claim 1 , wherein the diode laser provides an output of more than 1 watt.

10. The method according to claim 1 , wherein the radiation conversion unit includes a non-linear optical material.

11. The method according to claim 10 , wherein the non-linear optical material is a periodically poled crystal and/or a birefringent crystal and/or a waveguide and/or a photonic crystal and/or non-linear fibre or any combinations thereof.

12. The method according to claim 10 , wherein the radiation conversion unit includes an external resonant cavity wherein the non-linear material is positioned.

13. The method according to claim 1 , wherein the apparatus further comprises a passive cooling system configured to cool the diode laser.

14. The method according to claim 1 , wherein the apparatus further comprises two diode lasers outputting two polarized output beams.

15. The method according to claim 14 , wherein the two polarized output beams have different polarizations.

16. The method according to claim 14 , wherein the apparatus outputs a beam being a combination of two polarized output beams.

17. The method according to claim 14 , wherein the two polarized output beams have different wavelengths.

18. The apparatus method according to claim 14 , wherein the two polarized output beams are combined coherently or incoherently.

19. The method according to claim 1 , wherein the radiation conversion unit doubles the frequency of the radiation from the diode laser.

20. The method according to claim 1 , wherein the radiation conversion unit generates radiation by sum frequency mixing of the radiation in the first spectral region.

21. The method according to claim 1 , wherein the radiation conversion unit generates radiation by second harmonic generation and/or difference frequency mixing and/or sum frequency mixing of the radiation in the first spectral region.

22. The method according to claim 1 , wherein the apparatus further comprises a modulator unit configured to modulate the radiation from the diode laser and wherein the diode laser is modulated directly by injecting modulation current to the diode laser.

23. The method according to claim 22 , wherein the diode laser is modulated directly by injecting modulation current to the diode laser.

24. The method according to claim 1 , wherein the diode laser is a broad-area diode laser and/or a single-mode diode laser.

25. The method according to claim 1 , wherein the diode laser is constituted by an array of diode lasers.

26. The method according to claim 1 , further comprising a wavelength selection device.

27. The method according to claim 26 , wherein the wavelength selection device is an optical band-pass filter, an optical low-pass filter, an optical high-pass filter, a diffraction grating, a volume Bragg grating, a fiber Bragg grating, a prism or an interference filter, or any combination thereof.

28. The method according to claim 1 , wherein the output is coupled to an optical fibre.

29. The method according to claim 1 , wherein the second wavelength interval is 330 nm to 600 nm.

30. The method according to claim 1 , wherein the second wavelength interval is 1500 nm to 6000 nm.

31. The method according to claim 1 , wherein the apparatus further comprises a laser configured to receive radiation at the second wavelength interval.

32. The method according to claim 31 , wherein the laser includes a Ti:sapphire laser and the second wavelength interval includes the peak absorption of Ti:sapphire.

33. A method of optically pumping a Ti:sapphire laser in a laser system, the laser system comprising a tapered diode laser source providing radiation at a first frequency, the diode laser comprising two separate contacts for controlling injection currents to different sections of the diode laser independently, the diode laser source being optically connected to an input of a frequency converter, the frequency converter being configured to convert the radiation at the first frequency to a second, different frequency within an absorption band of the Ti:sapphire laser, the Ti:sapphire laser being arranged in optical communication with an output of the frequency converter, the method comprising the steps of:
emitting radiation from the diode laser source,
receiving the radiation at the frequency converter,
converting the radiation from the first frequency to the second frequency in the frequency converter,
providing the radiation at the second frequency at the target laser so that the target laser is optically pumped, and
wherein the method further comprises actively controlling the injection currents of the dio

Assignees

• Univ Danmarks Tekniske

Inventors

• Jensen Ole Bjarlin
• Andersen Peter Eskil
• Petersen Paul Michael

Classifications

• H01S5/02469

  Passive cooling, e.g. where heat is removed by the housing as a whole or by a heat pipe without any active cooling element like a TEC · CPC title

• H01S5/06817 Primary

  Noise reduction · CPC title

• H01S5/0092

  for nonlinear frequency conversion, e.g. second harmonic generation [SHG] or sum- or difference-frequency generation outside the laser cavity · CPC title

• H01S2301/02

  ASE (amplified spontaneous emission), noise; Reduction thereof · CPC title

• H01S5/1014

  Tapered waveguide, e.g. spotsize converter (H01S5/1064 takes precedence) · CPC title