LASER SYSTEM FOR OUTPUT MANIPULATION

• US 20110211600A1
• Filed: 02/28/2011
• Published: 09/01/2011
• Est. Priority Date: 03/01/2010
• Status: Active Grant

• Current Assignee: The Board of Trustees of Michigan State University (Michigan State University)
• Original Assignee: The Board of Trustees of Michigan State University (Michigan State University)
• Inventors: Lozovoy, Vadim, Dantus, Marcos
• Granted Patent: US 8,630,322 B2
• Time in Patent Office: Days
• US Class Current: 372/25
• CPC Class Codes: G02B 21/16 adapted for ultraviolet illumination ; Fluorescence microscopes G02B21/0076 takes precedence
• CPC Class Codes: G02B 2207/114 Two photon or multiphoton effect
• CPC Class Codes: H01S 3/0057 Temporal shaping, e.g. pulse compression, frequency chirping soliton generation and propagation G02F1/3513, H01S3/063 and H01S3/108
• CPC Class Codes: H01S 3/0078 Frequency filtering
• CPC Class Codes: H01S 3/0085 Modulating the output, i.e. the laser beam is modulated outside the laser cavity
• CPC Class Codes: H01S 3/0092 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

Abstract

A laser system capable of phase and/or amplitude manipulation of the output pulses is provided. In another aspect, a laser system includes a self-referenced pulse characterization method. A further aspect uses spectral amplitude modulation to isolate spectral bands by scanning one or more transmission slits or openings, and measuring and/or calculating the first derivative of a phase (group delay) across an entire spectrum. A single-beam pulse shaper-based technique for spectrometer-free measurement and compensation of laser pulse phase distortions is also provided in an additional aspect.

Claims

1. A laser system comprising:

a laser source operably emitting laser pulses;

a pulse shaper operably shaping the pulses;

a detector operably receiving the shaped pulses, the pulses following a single path between the source and the detector; and

a controller operably causing the shaper to transmit a reference spectral portion of at least one of the pulses through the shaper;

the controller operably causing the shaper to transmit different scanned spectral portions of at least one of the same pulses through a different spectral location in the shaper; and

the controller, detector and shaper operably measuring and correcting an undesired distortion in at least some of the pulses by comparing detected values associated with the reference and scanned spectral portion transmissions.

2. The system of claim 1, wherein:

the pulse shaper is programmable; and

the detector has a nonlinear optical response.

3. The system of claim 1, wherein the detector is a photodiode with a nonlinear optical response caused by the output pulses.

4. The system of claim 1, further comprising a microscope receiving at least some of the laser pulses transmitted through the pulse shaper.

5. The system of claim 1, wherein the reference spectral portion of the laser pulses transmitted through a fixed opening in the pulse shaper, acts as a reference against which scanned spectral portions of the laser pulses, transmitted through at least one moving opening in the pulse shaper, is compared by the controller.

6. The system of claim 1, further comprising software instructions within the controller automatically measuring phase distortion in the laser pulses by determining a local first derivative of a phase across a spectrum of the pulses.

7. The system of claim 1, further comprising software instructions within the controller automatically compensating for measured phase distortions by introducing a corresponding phase that cancels the distortions.

8. The system of claim 1, further comprising software instructions within the controller automatically repeating measurement and compensation instructions to refine the quality of the output pulses, a first iteration achieving at least 80% elimination of phase distortions.

9. The system of claim 1, wherein the laser pulses each have a duration of less than 1 picosecond.

10. The system of claim 1, wherein the laser pulses each have a duration of less than 15 femtoseconds.

11. The system of claim 1, further comprising:

a multilayer dielectric mirror located in the beam path;

the controller automatically measuring phase introduced by the dielectric mirror in a calculated manner without a learning algorithm, and by collecting the integrated second harmonic generation from the output pulse.

12. A laser system comprising:

a laser operably emitting laser pulses;

a pulse shaper operably shaping the pulses;

a detector operably receiving the shaped pulses, the detector having a frequency integrated non-linear optical response; and

a controller operably causing the shaper to select at least one spectral portion of the pulses through the shaper less than half of the full spectrum;

the controller, detector and shaper operably measuring and automatically correcting an undesired phase distortion in at least some of the pulses.

13. The system of claim 12, further comprising a microscope receiving at least some of the laser pulses transmitted through the pulse shaper.

14. The system of claim 12, wherein the reference spectral portion of the laser pulses selected by the pulse shaper, acts as a reference against which scanned spectral portions of the laser pulses, selected by at least one moving region of the pulse shaper, is compared by the controller.

15. The system of claim 12, further comprising software instructions within the controller automatically compensating for measured phase distortions by introducing a corresponding phase that cancels the distortions.

16. The system of claim 12, further comprising:

at least one optic of;

(a) a multilayer dielectric mirror, and (b) a Bragg grating, located in the beam path;

the controller automatically measuring phase introduced by the optic in a calculated manner without a genetic learning algorithm, and by collecting second harmonic generation from only portions of the spectrum instead of using the entire spectrum.

17. The system of claim 12, wherein the shaper selection of spectral portions of the pulses through the shaper includes transmission.

18. The system of claim 12, wherein the shaper selection of spectral portions of the pulses through the shaper includes shaping of at least one of:

(a) phase, and (b) polarization, to reduce nonlinear response from undesired portions of the spectrum.

19. The system of claim 12, wherein the detector is a photodiode with a nonlinear optical response caused by the output pulses.

20. The system of claim 12, further comprising software instructions within the controller automatically measuring phase distortion in the laser pulses by determining a local first derivative of a phase across a spectrum of the pulses.

21. The system of claim 12, further comprising software instructions within the controller automatically repeating measurement and compensation instructions to refine the quality of the output pulses, a first iteration achieving at least 80% elimination of phase distortions.

22. The system of claim 12, wherein the laser pulses each have a duration of less than 1 picosecond.

23. The system of claim 12, wherein the laser pulses each have a duration of less than 15 femtoseconds.

24. The system of claim 12, wherein phase corrections measured on a low intensity portion of a laser beam output are implemented on a second programmable pulse shaper acting on the main output laser beam.

25. A laser system comprising:

at least one input laser beam;

at least one modulator operably selecting at least one portion of a spectrum of the input beam while blocking the rest of the spectrum, this portion being a reference portion;

the at least one modulator operably selecting at least one other portion of the spectrum of the input beam while blocking the other spectral regions; and

a controller operably causing the modulator to adjust a time delay between at least one of the other transmitted portions of the beam with respect to the reference portion, the controller operably selecting and independently adjusting a time delay of different spectral portions of the beam with respect to the reference portion.

26. The system of claim 25, further comprising an output laser beam for which all the spectral components of the input beam are synchronized.

27. The system of claim 25, wherein phase corrections measured on a low intensity portion of a laser beam output are implemented on a second programmable pulse shaper acting on the main output laser beam.

28. The system of claim 25, further comprising a fiber optic communication line, the controller causing measuring and correcting of the fiber optic communication line.

29. The system of claim 25, wherein the laser beam is a series of pulses each having a duration of less than 51 fs, further comprising a laser operably emitting the pulses, and the controller providing data used to optimize the laser.

30. The system of claim 25, further comprising a multilayer coated optic, wherein the controller provides data used to optimize the optic.

31. The system of claim 25, wherein the laser beam is a series of pulses each having a duration of less than 51 fs, further comprising a laser operably emitting the pulses, and a microscope receiving at least one of the pulses, the controller providing data used to optimize the microscope.

32. The system of claim 25, wherein the selection by the at least one modulator includes transmission.

33. The system of claim 25, wherein the selection by the at least one modulator includes shaping of at least one of:

(a) phase, and (b) polarization, to reduce nonlinear response from undesired portions of the spectrum.

34. The system of claim 25, wherein phase corrections measured on a low intensity portion of a laser beam output are implemented on a second modulator, which includes a programmable pulse shaper acting on the main output laser beam.

35. Computer software for a laser system, the software being stored in non-transient memory, and the software comprising:

a first set of instructions creating pulse shaper selection spectral windows;

a second set of instructions causing pulse shaper reduction of spectral portions of at least one laser pulse in the regions other than those selected through the windows;

a third set of instructions setting at least one of the windows as a reference;

a fourth set of instructions scanning phase values across at least one of the windows;

a fifth set of instructions recording values from a detector capable of measuring a nonlinear optical response from an output beam;

a sixth set of instructions comparing the detected values as a function of the scanned values;

a seventh set of instructions determining the phase that maximizes the response of the detector for a given set of windows; and

an eighth set of instructions gathering essentially all of the values and from the values determining the distortion of the at least one pulse.

36. The computer software of claim 35, further comprising a set of instructions compensating for the phase distortion.

37. The computer software of claim 35, further comprising a set of instructions causing a laser to emit the at least one pulse including the reference and scanning windows to travel as a single beam manner between the laser and the detector.

38. The computer software of claim 35, further comprising a set of instructions recording the frequency integrated second harmonic generation spectrum, wherein the detector includes a second harmonic generation crystal and a spectrometer.

39. The computer software of claim 35, wherein the detector is a photodiode, further comprising a set of instructions receiving spectrum measurement values from the photodiode.