Laser systems and related methods

• US 9,722,392 B2
• Filed: 11/19/2014
• Issued: 08/01/2017
• Est. Priority Date: 11/28/2013
• Status: Active Grant

• Current Assignee: Candela Corporation
• Original Assignee: Candela Corporation
• Inventors: Bhawalkar, Jayant D., Shang, Xiaoming, Qiu, Jinze, Jones, Christopher J., Hsia, James
• Primary Examiner(s): NGUYEN, DUNG T
• Application Number:
  US15/035,765
• Publication Number:
  US 20160294152A1
• Time in Patent Office: 986 Days
• CPC Class Codes: H01S 2301/02 ASE (amplified spontaneous emission), noise; Reduction thereof
• CPC Class Codes: H01S 3/0092 Nonlinear frequency conversion, e.g. second harmonic generation [SHG] or sum- or difference-frequency generation outside the laser cavity nonlinear frequency conversion per se G02F1/35
• CPC Class Codes: H01S 3/061 with elliptical or circular cross-section and elongated shape, e.g. rod
• CPC Class Codes: H01S 3/0617 having a varying composition or cross-section in a specific direction
• CPC Class Codes: H01S 3/0625 Coatings on surfaces other than the end-faces
• CPC Class Codes: H01S 3/0627 the resonator being monolithic, e.g. microlaser
• CPC Class Codes: H01S 3/06754 Fibre amplifiers H01S3/06708 takes precedence
• CPC Class Codes: H01S 3/08081 Unstable resonators
• CPC Class Codes: H01S 3/092 of flash lamp H01S3/0937 takes precedence ; flash lamps per se H01J61/80; circuit arrangements for operating flash lamps in general H05B41/30
• CPC Class Codes: H01S 3/094053 Fibre coupled pump, e.g. delivering pump light using a fibre or a fibre bundle
• CPC Class Codes: H01S 3/094061 Shared pump, i.e. pump light of a single pump source is used to pump plural gain media in parallel
• CPC Class Codes: H01S 3/094069 Multi-mode pumping
• CPC Class Codes: H01S 3/10023 by functional association of additional optical elements, e.g. filters, gratings, reflectors
• CPC Class Codes: H01S 3/109 Frequency multiplication, e.g. harmonic generation
• CPC Class Codes: H01S 3/1115 using intracavity saturable absorbers
• CPC Class Codes: H01S 3/113 using intracavity saturable absorbers
• CPC Class Codes: H01S 3/1312 by controlling the optical pumping
• CPC Class Codes: H01S 3/1611 neodymium
• CPC Class Codes: H01S 3/1633 BeAl2O4, i.e. Chrysoberyl
• CPC Class Codes: H01S 3/1643 YAG
• CPC Class Codes: H01S 3/2308 : Amplifier arrangements, e.g. MOPA

Abstract

A MOPA laser system that includes a seed laser configured to output pulsed laser light, an amplifier configured to receive and amplify the pulsed laser light emitted by the seed laser; and a pump laser configured to deliver a pump laser beam to both the seed laser and the amplifier.

Claims

1. A high-energy, sub-nanosecond laser system comprising:

an amplifier;

a seed laser constructed and arranged to output pulsed laser light towards the amplifier, with the amplifier being constructed and arranged to amplify the pulsed laser light received from the seed laser; and

a pump laser constructed and arranged to pump simultaneously both the seed laser and the amplifier;

wherein the pump laser is a solid state laser pumped by at least one flash lamp and wherein the pump laser emits laser pulses with energies greater than 1J and durations shorter than 0.5 msec; and

wherein the amplifier is constructed and arranged to generate output laser pulses of 0.1 J to 5 J and pulse duration of 10 psec to 900 psec.

2. The laser system according to claim 1, wherein the pump laser is an alexandrite laser and a laser beam emitted by pump laser is delivered to the seed laser and amplifier through a multimode optical fiber.

3. The laser system according to claim 1, wherein a laser beam is split into two laser pumping beams by an uncoated sapphire plate.

4. The laser system according to claim 1, wherein pump laser is an alexandrite laser and the pulses of the pump alexandrite laser beam emitted by the pump laser have constant energy, and further comprising a variable attenuator to adjust the pump beam energy conducted to at least the amplifier.

5. The laser system according to claim 1, further comprising a saturable absorber disposed between the seed laser and the amplifier to prevent self-lasing.

6. The laser system according to claim 1, wherein a seed laser resonator comprises an unstable resonator configured to prevent occurrence of hot spots in a seed laser output beam.

7. The laser system according to claim 6, wherein a first mirror together with a second mirror form the unstable resonator configured to prevent occurrence of hot spots in seed laser output beam.

8. The laser system according to claim 6, wherein a gain length of the seed laser is from 2 mm to 10 mm and wherein the gain length of the seed laser is selected to reduce gain in transverse dimension and to reduce amplified spontaneous emission but to be short enough to support generation of sub-nanosecond pulses.

9. The laser system according to claim 1, wherein the seed laser is a Nd:

YAG rod with a diameter at least three times larger than that of pumped region dimensions and wherein the Nd;

YAG rod diameter is selected to minimize amplified spontaneous emission caused by reflections from a barrel surface of the Nd;

YAG rod.

10. The laser system according to claim 1, further comprising an electronic mechanism configured to ensure a single output laser pulse and terminate a flash lamp drive current in the pump laser upon optical detection of an output pulse from at least one of the seed laser and the amplifier.

11. The laser system according to claim 1, further comprising at least one laser beam frequency doubling device.

12. The laser system according to claim 1, wherein a same optical fiber is used to deliver a pulsed laser beam from the seed laser and a pump laser beam from the pump laser to the amplifier to support spatial overlap between the pulsed laser light and a pumped gain region in the amplifier.

13. A method of generating sub-nanosecond laser pulses comprising:

generating pulsed laser light using a seed laser;

directing the pulsed laser light to an amplifier;

amplifying the pulsed laser light with the amplifier;

operating a pump laser to simultaneously provide pumping energy to both the seed laser and the amplifier; and

employing an electronic mechanism configured to ensure a single output laser radiation pulse by terminating a flash lamp drive current in the pump laser upon optical detection of an output pulse from at least one of the seed laser and the amplifier.

14. The method according to claim 13, further comprising preventing a self-lasing operation mode caused by reflections of an output laser beam from a work material by employing a saturable absorber.

15. The method according to claim 13, wherein operating the pump laser comprises generating the pumping energy of greater than 1 J with a pulse duration of 100 to 200 microseconds.

16. A high-energy, sub-nanosecond laser system comprising:

a seed laser constructed and arranged to output a sub-nanosecond pulsed laser beam;

an amplifier constructed and arranged configured to receive and amplify the pulsed laser light emitted by the seed laser;

a pump laser constructed and arranged to deliver a pump laser beam to both the seed laser and the amplifier; and

a saturable absorber disposed between the seed laser and the amplifier to prevent self-lasing,

wherein the seed laser is a Nd;

YAG rod and the saturable absorber is diffusion-bonded to laser rod.

17. The laser system according to claim 16, wherein to reduce resonator length and generate short pulses, the laser system further comprises laser resonator mirrors deposited directly onto end surfaces of laser rod.

18. The laser system according to claim 16, wherein the laser system is constructed and arranged to generate laser energy pulses of 0.1 to 10 J with a pulse duration of 10 to 900 psec.

19. A laser system comprising:

a seed laser constructed and arranged to output pulsed laser light;

an amplifier constructed and arranged to receive and amplify the pulsed laser light emitted by the seed laser; and

a pump laser constructed and arranged to deliver a pump laser beam to both the seed laser and the amplifier;

wherein the seed laser is a Nd;

YAG rod with a diameter at least three times larger than that of pumped region dimensions; and

wherein the Nd;

YAG rod diameter is selected to minimize amplified spontaneous emission caused by reflections from a barrel surface of the Nd;

YAG rod.