METHOD AND APPARATUS FOR A HYBRID MODE-LOCKED FIBER LASER

• US 20090107962A1
• Filed: 08/29/2008
• Published: 04/30/2009
• Est. Priority Date: 08/31/2007
• Status: Active Grant

• Current Assignee: LadarSystems, Inc.
• Original Assignee: Deep Photonics Corporation
• Inventors: Munroe, Michael J., LaChapelle, Joseph G., Dutton, David A.
• Granted Patent: US 8,630,320 B2
• Time in Patent Office: Days
• US Class Current: 219/121.670
• CPC Class Codes: B23K 26/0624 using ultrashort pulses, i.e. pulses of 1ns or less
• CPC Class Codes: H01S 3/0085 Modulating the output, i.e. the laser beam is modulated outside the laser cavity
• CPC Class Codes: H01S 3/06754 Fibre amplifiers H01S3/06708 takes precedence

Abstract

An apparatus for producing coherent pulsed light with a fiber-based master oscillator/fiber amplifier architecture includes a fiber-coupled mode-locked laser source. The fiber-coupled mode-locked laser source is configured to provide pulses having a pulse duration of less than 1 ns. The apparatus also includes a fiber-coupled amplitude modulator optically coupled to the fiber-coupled mode-locked laser source. The fiber-coupled amplitude modulator is capable of gate durations greater than 1 ns. The apparatus further includes a saturated fiber power amplifier optically coupled to the fiber-coupled amplitude modulator.

Claims

1. An apparatus for producing coherent pulsed light with a fiber-based master oscillator/fiber amplifier architecture, the apparatus comprising:

a fiber-coupled mode-locked laser source configured to provide pulses having a pulse duration of less than 1 ns;

a fiber-coupled amplitude modulator optically coupled to the fiber-coupled mode-locked laser source, wherein the fiber-coupled amplitude modulator is capable of gate durations greater than 1 ns; and

a saturated fiber power amplifier optically coupled to the fiber-coupled amplitude modulator.

2. The apparatus of claim 1 wherein a wavelength of operation of the fiber-coupled mode-locked laser source ranges from about 1015 nm to about 1085 nm.

3. The apparatus of claim 1 wherein a wavelength of operation of the fiber-coupled mode-locked laser source ranges from about 1500 nm to about 1575 nm.

4. The apparatus of claim 1 wherein the fiber-coupled mode-locked laser source comprises a rare earth doped active fiber.

5. The apparatus of claim 1 wherein the fiber-coupled amplitude modulator comprises at least one of a Mach-Zehnder modulator an acousto-optic modulator.

6. The apparatus of claim 1 wherein the fiber power amplifier comprises:

a preamplifier fiber gain stage optically coupled to the fiber-coupled amplitude modulator; and

an amplifier fiber gain stage optically coupled to the preamplifier fiber gain stage.

7. The apparatus of claim 1 further comprising a pulse compressor optically coupled to the saturated fiber power amplifier.

8. The apparatus of claim 1 further comprising one or more frequency conversion stages optically coupled to the saturated fiber power amplifier.

9. The apparatus of claim 8 wherein the one or more frequency conversion stages comprises a nonlinear crystal.

10. A method of providing a set of amplified optical pulse packets, the method comprising:

providing a train of optical pulses, each of the optical pulses being characterized by a pulse width of less than 1 ns;

gating the train of optical pulses to provide a set of optical pulse packets having a first average power, wherein each of the optical pulse packets is characterized by a time duration of greater than 1 ns and includes more than one optical pulse; and

amplifying the set of optical pulse packets to provide the set of amplified optical pulse packets having a second average power, wherein the second average power is substantially independent of the first average power.

11. The method of claim 10 wherein providing the train of optical pulses comprises use of a fiber-coupled mode-locked laser source comprises a rare earth doped active fiber.

12. The method of claim 10 wherein gating the train of optical pulses comprises passing the train of optical pulses through a fiber-coupled amplitude modulator.

13. The method of claim 12 wherein the fiber-coupled amplitude modulator comprises at least one of a Mach-Zehnder modulator or an acousto-optic modulator.

14. The method of claim 10 wherein gating the train of optical pulses is performed asynchronously with providing a train of optical pulses.

15. The method of claim 10 wherein the second average power varies by less than 1 dB for a change in the first average power by 3 dB.

16. The method of claim 10 wherein amplifying the set of optical pulse packets comprises:

preamplifying the set of optical pulse packets in a fiber preamplifier gain stage; and

amplifying the preamplified set of optical pulse packets in a fiber gain stage.

17. The method of claim 10 further comprising compressing the optical pulses in the set of amplified optical pulse packets.

18. The method of claim 17 wherein a pulse duration between each of the optical pulses remains unchanged.

19. The method of claim 10 further comprising frequency converting the set of amplified optical pulse packets.

20. The method of claim 19 wherein frequency converting comprises at least one of second harmonic generation, sum frequency generation.

21. A micro-machining system for processing of a workpiece, the micro-machining system comprising:

a laser configured to provide gated envelopes including a plurality of linearly-polarized, mode-locked pulses, each of the mode-locked pulses having a duration of less than 1 ns, wherein each of the gated envelopes has a duration greater than 1 ns;

an optical system coupled to the laser and configured to direct the gated envelopes along an optical path; and

a workpiece support disposed along the optical path and configured to support the workpiece.

22. The micro-machining system of claim 21 wherein the laser comprises a saturated fiber power amplifier.

23. The micro-machining system of claim 21 further comprising a pulse compressor disposed along the optical path.

24. The micro-machining system of claim 21 further comprising a frequency conversion stage disposed along the optical path.

25. The micro-machining system of claim 24 wherein the frequency conversion stage is configured to provide an output including an wavelength in a range from about 507-542 nm or from about 253-271 nm.

26. The micro-machining system of claim 21 further comprising a controller coupled to the laser, wherein a signal from the controller results in a change in at least one of a duty cycle or a duration of the gated envelopes.