Laser apparatus having multiple-pass electro-optic modulators

Patent metadata

Field	Value
Publication number	US-11973303-B2
Application number	US-202117360359-A
Country	US
Kind code	B2
Filing date	Jun 28, 2021
Priority date	Jun 28, 2021
Publication date	Apr 30, 2024
Grant date	Apr 30, 2024

Abstract

A laser apparatus includes at least one electro-optic (EO) medium through which a polarized laser beam passes for N times, forming a plurality of first-pass to Nth-pass beams, by reflecting the polarized laser beam from at least one reflection mirror, and a power supplier configured to alternately provide a 1/N of a half-wave (λ/2) or quarter-wave (λ/4) voltage and remove the voltage to the EO medium, λ being a wavelength of the polarized laser beam. The at least one EO medium is tilted at angle θ and/or angle ϕ with respect to one of the plurality of first-pass to Nth-pass beams. The at least one EO medium comprises a M number of EO mediums, and the power supplier is configured to alternately provide a 1/M*N of a half-wave (λ/2) or quarter-wave (λ/4) voltage and remove the voltage to each of the M number of EO mediums.

First claim

What is claimed is:

1. A laser apparatus with a multi-pass configuration, comprising:
an electro-optic (EO) medium through which a polarized laser beam passes;
at least one reflection mirror configured to reflect the polarized laser beam so that the polarized laser beam passes through the EO medium for N times, forming a plurality of first-pass to Nth-pass beams, an optical axis of the EO medium being tilted with respect to at least one of the plurality of first-pass to Nth-pass beams; and
a power supply configured to alternatingly provide a 1/N of a half-wave or quarter-wave voltage and remove the 1/N of the half-wave or quarter-wave voltage to the EO medium, λ being the wavelength of the polarized laser beam.

2. The laser apparatus according to claim 1 , wherein
the optical axis of the EO medium is tilted at a first angle on a first plane and/or a second angle on a second plane with respect to the at least one of the plurality of first-pass to Nth-pass beams.

3. The laser apparatus according to claim 1 , wherein
one of the EO medium or the at least one reflection mirror is tilted in multiple directions.

4. The laser apparatus according to claim 1 , wherein
the plurality of first-pass to Nth-pass beams are slanted at angles of a same magnitude with respect to an optical axis of the EO medium.

5. The laser apparatus according to claim 4 , wherein
the plurality of first-pass to Nth-pass beams are slanted at a first angle of a same magnitude on a first plane and at a second angle of another same magnitude on a second plane with respect to an optical axis of the EO medium.

6. The laser apparatus according to claim 1 , wherein
the plurality of first-pass to Nth-pass beams are slanted with respect to an optical axis of the EO medium such that angles of odd-pass beams in a first plane have a same magnitude as angles of even-pass beams in a second plane and angles of even-pass beams in the first plane have a same magnitude as angles of odd-pass beams in the second plane.

7. The laser apparatus according to claim 6 , wherein
an odd-pass beam is slanted at a first angle with respect to the optical axis on the first plane with respect to the optical axis of the EO medium, and an even-pass beam is slanted at a second angle on the second plane with respect to the optical axis of the EO medium.

8. The laser apparatus according to claim 1 , wherein
even-pass beams and odd-pass beams are symmetric to each other with respect to a pitch plane of the optical axis of the EO medium.

9. The laser apparatus according to claim 1 , wherein
even-pass beams and odd-pass beams are symmetric to each other with respect to a yaw plane of the optical axis of the EO medium.

10. The laser apparatus according to claim 1 , wherein
even-pass beams are along with respect to the optical axis of the EO medium, and odd-pass beams deviate with respect to the optical axis of the EO medium, or
even-pass beams deviate with respect to the optical axis of the EO medium, and odd-pass beams are along with respect to the optical axis of the EO medium.

11. The laser apparatus according to claim 1 , wherein
the polarized laser beam that passed the EO medium for the N times is reflected by a polarizing beam splitter or passes through a thin film polarizer.

12. The laser apparatus according to claim 1 , wherein
the EO medium comprises a M number of Pockels cells, and
the power supplier is configured to alternately provide a 1/M*N of a half-wave (λ/2) or quarter-wave (λ/4) voltage and remove the 1/M*N of the half-wave (λ/2) or quarter-wave (λ/4) voltage to each of the M number of Pockels cells.

13. The laser apparatus according to claim 1 , wherein
the N times is two times,
the polarized laser beam enters the EO medium and passes through the EO medium for a first-pass beam, and
the first-pass beam is reflected back to the EO medium by the at least one reflection mirror and passes through the EO medium for a second-pass beam.

14. The laser apparatus according to claim 1 , wherein
the N times is three times,
the at least one mirror include a first mirror and a second mirror, and
the power supplier is configured to alternately provide a λ/6 voltage and no voltage to the EO medium,
wherein the laser beam enters the EO medium and passes through the EO medium for a first-pass beam,
the first-pass beam is reflected back to the EO medium by the first mirror and passes through Pockels cell for a second-pass beam, and
the second-pass beam is reflected back to the EO medium by the at least one mirror and passes through Pockels cell for a third-pass beam.

15. The laser apparatus according to claim 1 , wherein
the N times is four times, and
the power supplier is configured to alternatingly provide a λ/8 of the half-wave voltage and remove the λ/8 of the half-wave voltage to the EO medium.

16. The laser apparatus according to claim 1 , wherein
the N times is eight times, and
the power supplier is configured to alternately provide a λ/16 of the half-wave voltage and remove the λ/16 of the half-wave voltage to the EO medium.

17. The laser apparatus according to claim 1 , wherein the power supplier is configured to provide the 1/N of a half-wave voltage with a tolerance of up to 10 percent.

18. A method for operating a laser apparatus comprising:
entering a polarized laser beam to an electro-optic (EO) medium;
reflecting, by at least one reflector, the polarized laser beam so that the beam passes through the EO medium for N times, forming a plurality of first-pass to Nth-pass beams, an optical axis of the EO medium being tilted with respect to at least one of the plurality of first-pass to Nth-pass beams; and
alternatingly providing, by a power supplier, a 1/N of a half-wave voltage (λ/2N) and removing the λ/2N voltage to the EO medium, λ being a wavelength of the polarized laser beam.

19. The method according to claim 18 , further comprising:
tilting one of the EO medium, or the at least one reflection mirror with respect to the at least one of the plurality of first-pass to Nth-pass beams in a yaw direction and/or a pitch direction.

20. The laser apparatus according to claim 1 , wherein the half-wave voltage is λ/2 voltage, λ being a wavelength of the polarized laser beam.

21. The laser apparatus according to claim 1 , wherein
the EO medium is made of one of various crystals with electro-optical properties, the various crystals including BBO (Beta Barium Borate), RTP (Rubidium Titanyl Phosphate), KTP (Potassium Titanyl Phosphate), KD*P (Potassium dideuterium phosphate), KDP (Potassium dihydrogen phosphate) and LiNbO 3 (Lithium niobate) crystal.

22. The laser apparatus according to claim 1 , further comprising a laser polarizer configured to output the polarized laser beam.

23. The laser apparatus according to claim 1 , wherein the laser apparatus is placed outside a laser cavity as an electro-optic pulse picker and modulator.

24. The laser apparatus according to claim 1 , wherein the laser apparatus is placed in a laser cavity as an electro-optic Q switch.

Assignees

• Panasonic Ip Man Co Ltd

Inventors

• Chang Liang
• Li Fangqin
• Leto Riccardo

Classifications

• H01S3/115 Primary

  using intracavity electro-optic devices · CPC title

• G02F1/0311 Primary

  Structural association of optical elements, e.g. lenses, polarizers, phase plates, with the crystal · CPC title

• G02F1/0322

  Arrangements comprising two or more independently controlled crystals · CPC title

• H01S3/0071

  Beam steering, e.g. whereby a mirror outside the cavity is present to change the beam direction · CPC title

• H01S3/09

  Processes or apparatus for excitation, e.g. pumping · CPC title