Algorithms for rapid gating of seed suspendable pulsed fiber laser amplifiers

Patent metadata

Field	Value
Publication number	US-10096965-B2
Application number	US-201514657791-A
Country	US
Kind code	B2
Filing date	Mar 13, 2015
Priority date	Mar 13, 2014
Publication date	Oct 9, 2018
Grant date	Oct 9, 2018

Abstract

Pulsed fiber lasers that amplify seed laser pulses include pump laser drivers that produce simmer currents during periods in which the seed pulse is suspended, and forward currents associated with steady state pulse amplification. By suitable selection of simmer currents, initiation of a series of seed pulses produces pulse-to-pulse output powers with suitable power variation.

First claim

We claim:

1. A laser system, comprising:
a seed laser;
a doped fiber situated to receive optical pulses from the seed laser;
a pump laser coupled to the doped fiber and configured to deliver pump optical radiation to the doped fiber to produce optical gain; and
a pulse controller coupled to the seed laser and configured to signal initiation of a series of seed pulses, and coupled to the pump laser and configured to switch a pump laser drive current from a simmer current to a forward current upon initiation of the optical pulses from the seed laser, wherein the simmer current is selected to produce a gain for a first seed laser pulse in the series of seed pulses that corresponds to a saturated gain associated with exposure to the series of seed pulses produced with a forward current.

2. The laser system of claim 1 , further comprising:
a memory that stores simmer current values; and
programmable logic configured to obtain a simmer current value based on the stored simmer current values.

3. The laser system of claim 2 , wherein the programmable logic is configured to obtain the simmer current value based on interpolation using two or more simmer current values stored in the memory.

4. The laser system of claim 3 , wherein the programmable logic obtains the simmer current values based on at least one of a pulse repetition frequency, a pulse power, pulse duration, a pulse energy, and an average power.

5. The laser system of claim 1 , wherein the simmer current is selected so that a first pulse in a pulse sequence has a pulse power that is within ±10% of a steady state pulse power produced with a selected forward current.

6. The laser system of claim 1 , wherein the doped fiber includes an active fiber that is an erbium, ytterbium, neodymium, dysprosium, praseodymium, or thulium-doped single mode optical fiber.

7. The laser system of claim 1 , wherein the pulse controller is coupled to the seed laser to signal cessation of seed pulse generation, and to the pump laser so as to switch a pump laser drive current from the forward current to the simmer current in association with cessation of the optical pulses from the seed laser.

8. The laser system of claim 1 , further comprising a digital to analog convertor that receives a digital value associated with the forward current or the simmer current, and an analog mux, coupled to the pulse controller that selects the forward current or the simmer current.

9. The laser system of claim 1 , further comprising:
a memory that stores simmer current values; and
programmable logic configured to obtain a simmer current value based on two or more simmer current and average power pairs stored in the memory.

10. The laser system of claim 1 , further comprising:
a memory that stores simmer current values; and
a processor configured to obtain a simmer current value based on the stored simmer current values.

11. A laser processing system, comprising:
a workpiece stage; and
a laser system as disclosed in claim 1 , wherein the laser system is situated to direct a laser beam comprising a series of amplified pulses based on the series of seed pulses to a substrate situated at the workpiece stage.

12. A laser system, comprising:
a pump laser driver coupled to switchably provide a forward drive current and a simmer drive current; and
a laser system controller that initiates a seed laser pulse sequence and communicates switching from the simmer drive current to the forward drive current in the pump laser driver.

13. The laser system of claim 12 , wherein the laser system controller is coupled to a memory and establishes the simmer drive current based on a simmer current database.

14. The laser system of claim 13 , wherein the simmer and forward drive currents are selected so that a first pulse in an initiated pulse sequence has pulse power that is within at least ±10%, least ±5%, or least ±1% of a steady state pulse power.

15. The laser system of claim 14 , further comprising a digital to analog convertor that receives a digital value associated with the simmer drive current, and converts the digital value into an analog value so that the simmer drive current is provided by the pump laser driver.

16. The laser system of claim 15 , wherein the laser system controller determines a selected simmer current by retrieving two or more simmer current values and interpolating based on the retrieved values.

17. The laser system of claim 16 , wherein the selected simmer current is determined based on two or more simmer current/average power pairs, and interpolating based on the retrieved values and the desired steady state average power.

18. A method, comprising:
applying a simmer drive current to a pump laser current of a fiber amplifier with a pump laser driver, the pump laser driver coupled to switchably provide a forward drive current and the simmer drive current; initiating a series of seed pulses of a seed laser pulse sequence with a laser system controller and directing the series of seed pulses to the fiber amplifier; and with the laser system controller, communicatively switching the pump laser current of the fiber amplifier from the simmer drive current to the forward drive current in association with initiating the series of seed pulses.

19. The method of claim 18 , wherein the pump laser current is switched prior to initiating the series of seed pulses.

20. The method of claim 18 , wherein the pump laser current is switched after initiating the series of seed pulses.

21. The method of claim 18 , further comprising determining the simmer drive current based on stored simmer current values.

22. The method of claim 18 , further comprising determining simmer current values based on interpolation among stored simmer current values.

23. The method of claim 18 , wherein the applied simmer drive current is selected based on a desired average or pulse output power.

24. The method of claim 18 , wherein the applied simmer drive current is selected based on a desired forward current.

25. The method of claim 18 , further comprising directing an amplified series of seed pulses associated with the simmer drive current and the forward drive current to a workpiece.

26. The method of claim 18 , wherein the fiber amplifier includes an active single mode optical fiber that is doped with erbium, ytterbium, neodymium, dysprosium, praseodymium, or thulium.

27. The method of claim 18 , wherein the simmer and forward drive currents are selected so that a first pulse in the series of seed pulses has pulse power that is within at least ±10%, least ±5%, or least ±1% of a steady state pulse power.

Assignees

• Nlight Photonics Corp
• Nlight Inc

Inventors

• Fanning C Geoffrey
• Kutscha Timothy N

Classifications

• H01S3/1001

  by controlling the optical pumping · CPC title

• H01S3/09415

  the pumping beam being parallel to the lasing mode of the pumped medium, e.g. end-pumping · CPC title

• H01S3/10069

  Memorized or pre-programmed characteristics, e.g. look-up table [LUT] · CPC title

• H01S3/06758

  Tandem amplifiers · CPC title

• H01S3/094076 Primary

  Pulsed or modulated pumping (H01S3/1024 takes precedence) · CPC title