# US 7,609,731 B2 · Laser system using ultra-short laser pulses

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- Number: US 7,609,731 B2
- Document ID: US7609731B2
- Status: Granted
- Kind: B2
- Application number: 10/791,377
- Filed: 2004-03-02
- Published: 2004-11-25
- Granted: 2009-10-27
- Earliest claimed: 2001-01-30
- Assignees: Board of Trustees operating Michigan State University
- Inventors: Marcos Dantus; Vadim V. Lozovoy; Matthew Comstock
- Web page: https://patentgrep.com/patent/US7609731B2

## CPC

- H01S 3/0057: {Temporal shaping, e.g. pulse compression, frequency chirping (soliton generation and propagation G02F1/3513, H01S3/063 and H01S3/108)}
- G01B 9/02014: {by using pulsed light}
- G01B 9/02091: Tomographic interferometers, e.g. based on optical coherence
- G01N 21/4795: {spatially resolved investigating of object in scattering medium (in vivo A61B)}
- H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## Abstract

A laser system using ultrashort laser pulses is provided. In another aspect of the present invention, the system includes a laser, pulse shaper and detection device. A further aspect of the present invention employs a femtosecond laser and binary pulse shaping (BPS). Still another aspect of the present invention uses a laser beam pulse, a pulse shaper and a SHG crystal.

## Claims

### Claim 1

A system comprising:
a) a laser operable to emit a femtosecond laser beam pulse;
b) a phase shaper operable to shape the pulse with binary phase values; and
c) a controller operable to automatically control the laser and the shaper, the controller including software instructions operable causing and controlling multiphoton intrapulse interference in the laser beam pulse.

### Claim 2 (depends on 1)

The system of claim 1, wherein the shaper employs two phase values separated by π.

### Claim 3 (depends on 1)

The system of claim 1 further comprising multiphoton intrapulse interference phase scan software, for pulse characterization and compensation, used by the controller.

### Claim 4 (depends on 1)

The system of claim 1 further comprising evolutionary learning calculations used by the controller.

### Claim 5 (depends on 1)

The system of claim 1, wherein the system is employed in multiphoton microscopy.

### Claim 6 (depends on 1)

The system of claim 1, wherein the system is employed in an optical communications system.

### Claim 7 (depends on 1)

The system of claim 1, wherein the pulse shaper has one of the following pixel resolutions: (a) about 128; (b) about 512; (c) about 640; and (d) about 1024.

### Claim 8 (depends on 7)

The system of claim 7, wherein the bandwidth of the laser is dispersed across all pixels of the phase modulator.

### Claim 9 (depends on 1)

The system of claim 1, wherein the system is employed in optical coherence tomography.

### Claim 10 (depends on 1)

The system of claim 1, wherein the system is employed in microlithography.

### Claim 11 (depends on 1)

The system of claim 1, wherein the system is employed in functional imaging.

### Claim 12 (depends on 1)

The system of claim 1, wherein the system is employed in quantum information processing.

### Claim 13 (depends on 1)

The system of claim 1, wherein the system is employed in nonlinear optical excitation spectroscopy.

### Claim 14 (depends on 1)

The system of claim 1, wherein the system is employed in photodynamic therapy.

### Claim 15

A system comprising:
a) a laser beam pulse;
b) a phase shaper operable to shape the laser beam pulse with encoded characteristics and with binary phase value;
c) a nonlinear optical medium operable to separate multiple frequencies of the pulse;
d) software instructions operable causing and controlling multiphoton intrapulse interference in the laser beam pulse;
e) a detection device operable to detect the characteristics of the shaped laser beam pulse as separated by the nonlinear optical medium; and
f) a unit connected to the device operably decoding the characteristics.

### Claim 16 (depends on 15)

The system of claim 15, wherein the laser beam pulse is encoded with a routing address.

### Claim 17 (depends on 15)

The system of claim 15 further comprising:
a main transmitting controller; and
multiple remote initial-transmitting sources connected to the transmitting controller;
the main transmitting controller operably causing the pulse shaper to encode multiple successive laser beam pulses differently in an active manner.

### Claim 18 (depends on 15)

The system of claim 15 further comprising a fiber optic cable carrying the laser beam pulse from the pulse shaper.

### Claim 19

A system for use with living tissue, the system comprising:
a high peak intensity laser beam pulse;
software instruction operable causing and controlling multiphoton intrapulse interference in the laser beam pulse;
a device operable to change a characteristic of the pulse prior to emission of the pulse upon the living tissue through use of multiphoton intrapulse interference; and
wherein nonlinear transitions induced by each pulse are controlled by binary phase shaping and the software instructions.

### Claim 20 (depends on 19)

The system of claim 19 wherein the device uses a pulse shaper and the desired excited substances in the tissue undergo two photon absorption.

### Claim 21 (depends on 19)

The system of claim 19 wherein the pulse has a duration of less than fifty one femtoseconds and values used in the binary phase shaping are predetermined.

### Claim 22 (depends on 19)

The system of claim 19 further comprising generating an optical tomography image produced by the shaped pulse passing through the tissue.

### Claim 23 (depends on 19)

The system of claim 19 wherein the device is a pulse shaper which enhances two photon absorption by a therapeutic substance and substantially prevents three photon induced damage of adjacent healthy tissue.

### Claim 24 (depends on 19)

The system of claim 19 wherein the device includes a phase modulation mask operably modifying the beam.

### Claim 25 (depends on 19)

The system of claim 19 wherein the pulse is shaped to enhance targeted multiphoton damage to modify or destroy certain molecules in the living tissue.

### Claim 26 (depends on 19)

The system of claim 19 wherein the multiphoton intrapulse interference operably activates desired photodynamic therapy agents at desired tissue depths.

### Claim 27

A system for multiphoton microscopy, the system comprising:
a) a femtosecond laser operable to emit a laser pulse;
b) a target operable to hold a sample in the pulse;
c) the sample operably labeled with at least one fluorescent probe;
d) software instructions operable causing and controlling multiphoton intrapulse interference in the pulse;
e) a phase shaper operable to shape the pulse in the binary manner to cause selective excitation of the probe and to correct for phase distortions; and
f) a detector operably detecting an emission from the sample.

### Claim 28 (depends on 27)

The system of claim 27, further comprising multiple probes.

### Claim 29 (depends on 28)

The system of claim 28, wherein the shaper operably shapes a probe to selectively excite each of the multiple probes.

### Claim 30 (depends on 27)

The system of claim 27, wherein the probe includes fluorescent nanoparticles.

### Claim 31 (depends on 27)

The system of claim 27, wherein the probe is a chemically sensitive fluorescent probe for detecting at least one of: H+, Na+, and Ca++ ions.

### Claim 32 (depends on 27)

The system of claim 27, further comprising learning calculations.

### Claim 33 (depends on 27)

The system of claim 27, further comprising a controller operably controlling the laser, the shaper, the target and the detector.

### Claim 34 (depends on 33)

The system of claim 33, wherein the controller is part of a microprocessor, and the controller controls multiphoton intrapulse interference in the pulse with binary pulse values used with the binary phase shaper.

### Claim 35 (depends on 34)

The system of claim 34, further comprising a data collector operably collecting data from the detector.

### Claim 36 (depends on 35)

The system of claim 35, further comprising a data analyzer operably analyzing the data that is collected.

### Claim 37 (depends on 27)

The system of claim 27, wherein the shaper is comprised of different phase masks permanently created in a substrate.

### Claim 38 (depends on 27)

The system of claim 27, wherein the detector operably converts the emission so that it is viewable by a human eye.

### Claim 39 (depends on 27)

The system of claim 27, wherein the sample is labeled with quantum dots.

### Claim 40

A method for microscopy of a target material containing probes that are excitable by multiphoton multi-photon excitation, the method comprising:
a) generating a laser pulse;
b) using programmable instructions to cause and control multiphoton intrapulse interference in the pulse;
c) shaping the pulse using a binary phase shaper employing binary phase functions so that the pulse selectively excites a desired probe by the multiphoton excitation;
d) directing the shaped pulse at the target; and
e) detecting emissions from the target.

### Claim 41 (depends on 40)

The method of claim 40, further comprising shaping the pulse by the use of learning calculations.

### Claim 42 (depends on 40)

The method of claim 40, wherein the target has multiple probes.

### Claim 43 (depends on 42)

The method of claim 42, further comprising shaping a pulse to selectively excite each of the multiple probes.

### Claim 44 (depends on 40)

The method of claim 40, further comprising shaping the pulse with a spatial light modulator.

### Claim 45 (depends on 40)

The method of claim 40, wherein the laser pulse is less than 51 femtoseconds, further comprising observing the target with a confocal microscope.

### Claim 46

A method of pulse shaping, the method comprising:
a) emitting a laser pulse having a duration less than 110 femtoseconds;
b) directing the pulse into a pulse shaper;
c) characterization of the pulse using multiphoton intrapulse interference phase software, the software including instructions operable causing and controlling multiphoton intrapulse interference in the pulse if desired; and
d) shaping the pulse by only two phase values.

### Claim 47 (depends on 46)

The method of claim 46, further comprising using the shaped pulse in multi-photon microscopy.

### Claim 48 (depends on 46)

The method of claim 46, further comprising using the shaped pulse in optical communications.

### Claim 49 (depends on 46)

The method of claim 46, further comprising using the shaped pulse in non-linear optical excitation spectroscopy.

### Claim 50 (depends on 46)

The method of claim 46, further comprising using two phases separated by π.

### Claim 51 (depends on 46)

The method of claim 46, wherein the pulse contains data.

### Claim 52 (depends on 51)

The method of claim 51, further comprising using a spatial light modulator.

### Claim 53 (depends on 52)

The method of claim 52, further comprising shaping the pulse with the spatial light modulator having one of the following pixel resolutions: (a) about 128; (b) about 512; (c) about 640; and (d) about 1024.

### Claim 54 (depends on 51)

The method of claim 51, wherein the amount of data transmitted in the pulse is equal to or less than 128 bytes per pulse.

### Claim 55 (depends on 46)

The method of claim 46, further comprising using the shaped pulse in microlithography.

### Claim 56

A method of pulse shaping, the method comprising:
a) emitting at least one laser pulse;
b) directing the at least one pulse into a pulse shaper;
c) shaping the at least one pulse in a binary manner and
d) characterization of the at least one pulse using multiphoton intrapulse interference phase scan software, the software including instructions operable to cause and control multiphoton intrapulse interference in the pulse if desired.

### Claim 57 (depends on 56)

The method of claim 56, further comprising using the shaped pulse in nonlinear optical excitation spectroscopy.

### Claim 58 (depends on 46)

The method of claim 46, further comprising using the shaped pulse in optical coherence tomography.

### Claim 59 (depends on 56)

The method of claim 56, further comprising using the shaped pulse in multiphoton microscopy.

### Claim 60 (depends on 46)

The method of claim 46, further comprising using the shaped pulse in quantum computing.

### Claim 61 (depends on 46)

The method of claim 46, further comprising using the shaped pulse in photodynamic therapy.

### Claim 62 (depends on 46)

The method of claim 46, further comprising using the shaped pulse in microfabrication.

### Claim 63 (depends on 46)

The method of claim 46, further comprising shaping by binary phase shaping.

### Claim 64 (depends on 56)

The method of claim 56, further comprising using the shaped pulse in photodynamic therapy on living tissue.

### Claim 65 (depends on 56)

The method of claim 56, wherein the at least one pulse has a duration less than 51 femtoseconds.

### Claim 66 (depends on 56)

The method of claim 56 further comprising automatically compensating for undesired pulse characteristics.

### Claim 67 (depends on 56)

The method of claim 56 further comprising selectively reducing three or more photon excitation.

### Claim 68

A system comprising:
a laser operably emitting at least one laser beam pulse of less than 51 femtoseconds;
a pulse shaper operably controlling a spectral phase of the at least one pulse, the shaper shaping the at least on pulse by only two phase values;
a detector operably detecting a spectrally dispersed second harmonic of the at least one shaped pulse; and
a controller connected to the shaper and detector, the controller operably controlling multiphoton intrapulse interference in the at least one pulse, the controller being operable to use software instructions to cause and control multiphoton intrapulse interference in the at least one pulse.

### Claim 69 (depends on 68)

The system of claim 68 wherein the at least one pulse has a duration less than 10 femtoseconds.

### Claim 70 (depends on 68)

The system of claim 68 further comprising selectively reducing three or more photon excitation.

### Claim 71 (depends on 68)

The system of claim 68 wherein a calibrated reference spectral phase in the pulse shaper is used to retrieve an unknown spectral phase in subsequent pulses.

### Claim 72 (depends on 68)

The system of claim 68 further comprising using a reference spectral phase including a sinusoidal function with the pulse shaper.

### Claim 73 (depends on 68)

The system of claim 68 further comprising using a reference spectral phase including a cubic function with the pulse shaper.

### Claim 74 (depends on 68)

The system of claim 68 further comprising a retrieved unknown spectral phase in the at least one pulse in used to calculate a compensation phase that cancels spectral phase distortions in subsequent laser beam pulses.

### Claim 75 (depends on 68)

The system of claim 68 further comprising using the shaper and controller to conduct multiphoton intrapulse interference phase scans on subsequent laser beam pulses in an iterative manner to improve the quality of pulse control.

### Claim 76 (depends on 1)

The system of claim 1, wherein the controller controls multiphoton intrapulse interference in the pulse with the assistance of the binary phase values.

### Claim 77 (depends on 1)

The system of claim 1, wherein the binary phase values are predetermined prior to emission of the pulse without an evolutionary learning algorithm.

### Claim 78 (depends on 19)

The system of claim 19, wherein the controller uses multiphoton intrapulse interference phase scan software for pulse characterization and compensation.

### Claim 79 (depends on 19)

The system of claim 19, wherein the controller uses evolutionary learning calculations in combination with the binary phase values.

### Claim 80 (depends on 56)

The method of claim 56, further comprising creating a transform-limited pulse with the pulse shaper.

### Claim 81 (depends on 56)

The method of claim 56, further comprising creating a user-specified shaped pulse with the pulse shaper.

### Claim 82 (depends on 56)

The method of claim 56, further comprising obtaining a second harmonic spectrum of the at least one pulse with a second-harmonic generation crystal land spectrometer.

### Claim 83 (depends on 56)

The method of claim 56, further comprising:
(a) introducing a reference phase function into the at least one pulse by the pulse shaper;
(b) frequency doubling an output;
(c) detecting the second harmonic spectrum in a spectrometer;
(d) determining the phase distortion with a controller and
(e) subtracting the phase distortion when subsequent phase functions are introduced by the pulse shaper to compensate for phase distortions of the input laser pulse.

### Claim 84 (depends on 56)

The method of claim 56, wherein the pulse shaper includes a spatial light modulator which both introduces a reference phase and compensates for phase distortions.

### Claim 85 (depends on 56)

The method of claim 56, further comprising automatically calculating the second derivative of a spectral phase from a collection of second harmonic spectra obtained as a referenced phase is scanned, and obtaining the spectral phase by integration.

### Claim 86 (depends on 56)

The method of claim 56, further comprising introducing a binary phase function to the at least one pulse in addition to a compensation phase.

### Claim 87

A system comprising:
(a) a laser emitting a laser beam pulse;
(b) a shaper operably shaping the pulse with binary phase values; and
(c) a controller including software instructions being operable to cause and control multiphoton intrapulse interference in the pulse with the assistance of the binary phase values.

### Claim 88 (depends on 87)

The system of claim 87, wherein the controller uses multiphoton intrapulse interference phase scan software for pulse characterization and compensation.

### Claim 89 (depends on 87)

The system of claim 87, wherein the controller uses evolutionary learning calculations in combination with the binary phase values.

### Claim 90 (depends on 87)

The system of claim 87, wherein the bandwidth of the laser is dispersed across all pixels of the phase modulator.

### Claim 91 (depends on 87)

The system of claim 87, wherein the system is employed in optical coherence tomography.

### Claim 92 (depends on 87)

The system of claim 87, wherein the system is employed in functional imaging.

### Claim 93 (depends on 87)

The system of claim 87, wherein the system is employed in photodynamic therapy.

### Claim 94 (depends on 87)

The system of claim 87, wherein the pulse has a duration of less than fifty one femtoseconds and values used in the binary phase shaping are predetermined.

### Claim 95 (depends on 87)

The system of claim 87, further comprising generating an optical tomography image produced by the shaped pulse passing through the tissue.

### Claim 96 (depends on 87)

The system of claim 87, wherein the device is a pulse shaper which enhances two photon absorption by a therapeutic substance and substantially prevents three photon induced damage of adjacent healthy tissue.

### Claim 97 (depends on 87)

The system of claim 87, wherein the device includes a phase modulation mask operably modifying the beam.

### Claim 98 (depends on 87)

The system of claim 87, wherein the pulse is shaped to enhance targeted multiphoton damage to modify or destroy certain molecules in the living tissue.

### Claim 99 (depends on 87)

The system of claim 87, wherein the multiphoton intrapulse interference operably activates desired photodynamic therapy agents at desired tissue depths.