High power femtosecond laser with repetition rate adjustable according to scanning speed

1. A method of scanning with a laser system, the method comprising:

generating femtosecond seed pulses by an oscillator;

stretching a duration of the seed pulses by a stretcher;

amplifying stretched seed pulses by an amplifier into laser pulses;

compensating a group delay dispersion of the laser pulses in the range of 5,000-20,000 fs 2 with a dispersion compensator between end-mirrors of the amplifier;

outputting the laser pulses from the amplifier by an electro-optical modulator;

compressing a duration of the laser pulses to the range of 1-1,000 fs by a compressor;

focusing the laser pulses to a focus spot in a target region with a scanning laser delivery system;

scanning the focus spot with a scanning speed in the target region with the scanning laser delivery system;

changing the scanning speed by a processor of the scanning laser delivery system; and

adjusting the repetition rate according to the changed scanning speed with a repetition-rate controller.

2. The method of claim 1 , wherein:

the stretcher and the compressor are part of a stretcher-compressor.

3. The method of claim 1 , comprising:

adjusting the repetition rate to approximately maintain a density of laser-generated bubbles in the target region around a selected value.

4. The method of claim 3 , wherein:

the density of bubbles is one of a linear density, an areal density, and a volume density.

5. The method of claim 3 , the adjusting the repetition rate step comprising:

adjusting the repetition rate proportionally to the scanning speed.

6. The method of claim 1 , the adjusting the repetition rate comprising:

adjusting the repetition rate from a first value to a second value in a time in the range of 1 μsec-1 sec.

7. The method of claim 1 , comprising:

XY scanning the focus spot along a switchback path; and

slowing down the repetition rate when approaching the switchback portion of the path.

8. The method of claim 1 , comprising:

scanning the laser beam along a spiral; and

slowing down the repetition rate when the scanning approaches the center of the spiral.

9. The method of claim 1 , the adjusting the repetition rate comprising:

receiving information by the repetition-rate controller about the changed scanning speed by one of

sensing the changing scanning speed, and

getting electronic information about the changing scanning speed from a processor or a memory; and

adjusting the repetition rate according to the received information about the changed scanning speed.

10. The method of claim 1 , wherein the outputting the laser pulses comprises:

outputting the laser pulses with an 1-100 μJ energy per pulse.

11. A variable repetition rate laser scanning system, comprising:

an oscillator that generates and outputs a beam of femtosecond seed pulses;

a stretcher-compressor configured

to stretch a duration of the seed pulses,

to receive amplified stretched pulses from an amplifier,

to compress a duration of the amplified stretched pulses, and

to output a laser beam of femtosecond pulses with a repetition rate;

the amplifier configured

to receive the stretched seed pulses from the stretcher-compressor,

to amplify an amplitude of selected stretched seed pulses with a gain medium between end-mirrors to create amplified stretched pulses,

to compensate a dispersion of the amplified stretched pulses in the range of 5,000-20,000 fs 2 with a dispersion compensator between the end-mirrors of the amplifier; and

to output the amplified stretched pulses towards the stretcher-compressor with an electro-optical modulator; and

a scanning laser delivery system that scans a focal spot of the laser beam in a target region with a variable scanning speed to generate spots of photodisruption; wherein

the laser scanning system is configured to changes the repetition rate to create the spots of photodisruption with a predetermined density profile.

12. The laser scanning system of claim 11 , the amplifier comprising:

a switchable polarizer that rotates a polarization plane of the stretched pulses in the amplifier, wherein

a rise time of the switchable polarizer is less than 5 ns.

13. The laser scanning system of claim 12 , the laser scanning system comprising:

a control electronics that applies control signals to the switchable polarizer to cause the switchable polarizer to switch with a rise time of less than 5 ns.

14. The variable repetition rate laser scanning system of claim 11 , wherein:

the amplifier is configured to output the amplified stretched pulses with an 1-100 μJ energy per pulse.

15. A method of scanning with a laser engine, the method comprising:

generating femtosecond seed pulses by an oscillator;

stretching a duration of the seed pulses by a stretcher;

amplifying stretched seed pulses by an amplifier into laser pulses;

compensating a group delay dispersion of the laser pulses with a dispersion compensator between end-mirrors of the amplifier;

outputting the laser pulses from the amplifier by an electro-optical modulator having a repetition rate in the range of 50 kHz-1 MHz;

compressing a duration of the laser pulses to the range of 1-1,000 fs by a compressor;

focusing the laser pulses to a focus spot in a target region to generate spots of photodisruption with a scanning laser delivery system;

scanning the focus spot in the target region with a scanning speed with a scanning laser delivery system; and

adjusting the repetition rate during the scanning to create spots of photodisruption with a density profile.

16. The method of claim 15 , the adjusting comprising:

creating the spots of photodisruption with one of a linear spot density, an areal spot density and a volume spot density being kept essentially even in a target region.

17. The method of claim 15 , the adjusting comprising:

adjusting the repetition rate according to a variation of the scanning speed.

18. The method of claim 15 , the adjusting comprising:

adjusting the repetition rate approximately proportionally to the scanning speed.

19. The method of claim 15 , the adjusting the repetition rate comprising:

adjusting the repetition rate from a first value to a second value in a time in the range of 1 μsec-1 sec.

20. The method of claim 15 , wherein:

the stretcher and the compressor are part of a stretcher-compressor.

21. The method of claim 15 , comprising:

scanning the focus spot along a switchback path; and

slowing down the repetition rate when approaching the switchback portion of the path.

22. The method of claim 15 , comprising:

scanning the laser beam along a spiral; and

slowing down the repetition rate according to the scanning approaching the center of the spiral.

23. The method of claim 15 , comprising:

scanning the laser beam along one of an end of a line and a corner of a line; and

slowing down the repetition rate according to the scanning approaching one of the end of the line and corner of the line.

24. The method of claim 15 , comprising:

receiving stored or sensed information about the scanning speed; and

adjusting the repetition rate according to the received information regarding the scanning speed.

25. The method of claim 15 , comprising:

receiving sensed or imaged information about the target region; and

adjusting the repetition rate according to the received information regarding the target region.