EP2089767A2 - Système laser faisant appel à une génération d'harmoniques - Google Patents

Système laser faisant appel à une génération d'harmoniques

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Publication number
EP2089767A2
EP2089767A2 EP07862112A EP07862112A EP2089767A2 EP 2089767 A2 EP2089767 A2 EP 2089767A2 EP 07862112 A EP07862112 A EP 07862112A EP 07862112 A EP07862112 A EP 07862112A EP 2089767 A2 EP2089767 A2 EP 2089767A2
Authority
EP
European Patent Office
Prior art keywords
pulse
laser
harmonic generation
phase
operably
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP07862112A
Other languages
German (de)
English (en)
Inventor
Marcos Dantus
Don Ahmasi Harris
Vadim V. Lozovoy
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Michigan State University MSU
Original Assignee
Michigan State University MSU
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Michigan State University MSU filed Critical Michigan State University MSU
Publication of EP2089767A2 publication Critical patent/EP2089767A2/fr
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/35—Non-linear optics
    • G02F1/37—Non-linear optics for second-harmonic generation
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/35—Non-linear optics
    • G02F1/353—Frequency conversion, i.e. wherein a light beam is generated with frequency components different from those of the incident light beams
    • G02F1/354—Third or higher harmonic generation
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F2201/00—Constructional arrangements not provided for in groups G02F1/00 - G02F7/00
    • G02F2201/16—Constructional arrangements not provided for in groups G02F1/00 - G02F7/00 series; tandem
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • 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
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
    • H01S3/0057—Temporal shaping, e.g. pulse compression, frequency chirping
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • 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
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/23—Arrangements of two or more lasers not provided for in groups H01S3/02 - H01S3/22, e.g. tandem arrangements of separate active media
    • H01S3/2308—Amplifier arrangements, e.g. MOPA

Definitions

  • the present invention generally pertains to laser systems and more particularly to harmonic generation of a laser beam pulse.
  • a laser system provides harmonic generation in a laser beam pulse.
  • a laser operably emits a laser pulse
  • a gaseous optical medium operably creates third or greater harmonic generation in the pulse
  • a controller characterizes and compensates for distortions in the pulse.
  • a further aspect of the present invention employs multiple optical media arranged to cause cascading harmonic generations in a laser pulse, where at least one is: zero order harmonic generation, third harmonic generation or greater than third harmonic generation.
  • a method of shaping, focusing in a gas, and minimizing distortion in a laser pulse is also provided.
  • a method of using plasma, created by the pulse itself, to generate harmonics of the pulse is additionally provided.
  • the laser system of the present invention is advantageous over prior devices since the present invention allows for the elimination of second harmonic generation crystals in some embodiments. This reduces cost, complexity and maintenance of the laser system of the present invention. This can also eliminate the use of autocorrelation or interferometry for measuring phase distortions and compensating for them.
  • the present invention is further advantageous by automatically characterizing and compensating for undesirable distortions in ultra-fast laser pulses, especially those incorporating third harmonic generation.
  • MIIPS air-Multiphoton Intrapulse Interference Phase Scan
  • MIIPS air-Multiphoton Intrapulse Interference Phase Scan
  • the present invention has a clear advantage when there are no crystals suitable for generating the second harmonic of the wavelength of the laser. Cascading of harmonic generation optical media additionally achieves useful harmonic generation at wavelengths that are otherwise difficult to obtain. Additional advantages and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.
  • Figure 1 is a diagrammatic view showing a first preferred embodiment of a laser system of the present invention, employed in a laboratory;
  • Figure 2 is a diagrammatic view showing a second preferred embodiment of the laser system, also employed in a laboratory;
  • Figure 3 is a diagrammatic view showing a third preferred embodiment of the laser system, used on a specimen
  • Figure 4 is a diagrammatic view showing an alternate embodiment of the laser system, employed for remote uses;
  • Figure 5 is a series of traces comparing expected results for SHG crystal -MIIPS (in the left column) to THG air-MIIPS (in the right column) employing the first preferred embodiment laser system;
  • Figure 6 is a graph comparing expected extracted phases for SHG crystal-MIIPS and THG air-MIIPS employing the first preferred embodiment laser system
  • Figure 7 is a diagrammatic view showing a fourth preferred embodiment of the laser system, employing cascading optical media for multiplied harmonic generation;
  • Figure 8 is a diagrammatic view showing a temporal symmetry feature of the first preferred embodiment laser system;
  • Figure 9 is a flow chart showing a computer program for a variation of MIIPS employed in the present invention laser system;
  • Figure 10 is a theoretical graph corresponding to the computer program of Figure 9;
  • Figure 11 is a graph showing a self-diffraction MIIPS variation employed in the present invention laser system;
  • Figure 12 is a diagrammatic view, corresponding to Figure 11, showing a self-diffraction MIIPS variation employed in the present invention laser system.
  • the present invention laser system preferably employs a noninterferometric single beam method for automated characterization and compression of amplified ultrashort femtosecond pulses that takes advantage of third order nonlinear processes in a gas, such as air.
  • the method compensates high-order phase distortions based on Multiphoton Intrapulse Interference Phase Scan (hereinafter "MIIPS").
  • MIIPS Multiphoton Intrapulse Interference Phase Scan
  • the accurate measurement of the spectral phase in femtosecond laser pulses is paramount to the use of phase-modulated laser pulses for femtochemistry, control of chemical reactions, and optical communications.
  • Multiphoton Intrapulse Interference Phase Scan takes advantage of the influence that phase modulation has on the intensity of nonlinear optical processes.
  • the MIIPS equipment and method are disclosed in U.S. Patent
  • a first preferred embodiment of a laser system 11 of the present invention is ideally suited for use in a laboratory.
  • An amplified titanium:sapphire, Legend model laser 13, which can be obtained from Coherent Inc., is used to produce 1 mJ, 40 fs laser beam pulses 12 at a 1 kHz repetition rate.
  • the laser amplifier is seeded with a Micra model titanium:sapphire oscillator 15 which can also be obtained from Coherent Inc.
  • the seed pulses are shaped by an all -reflective folded 4f pre-amplification pulse shaper 17 with a phase only spatial light modulator (hereinafter "SLM") which can be obtained from CRi as SLM 128, before amplification by an amplifier 19.
  • a computer controller 22 is connected to and automatically controls the pulse shaper.
  • the output laser pulse intensity is reduced to 20 ⁇ J and focused in air with a 50mm focal length concave mirror 23.
  • the air focal point is also designated as a gaseous, nonlinear optical medium 24, and may alternately include argon, nitrogen or helium gas in a housing.
  • Low incident power is required to diminish the effects of self phase modulation on the measured phase. It is possible to increase the incident power to 250 ⁇ J with a 250 mm focal length concave mirror.
  • the third harmonic is collimated and separated from the fundamental beam by a fused-silica prism pair 25.
  • the light is then coupled into an Ocean Optics USB 2000 spectrometer 27, which is also connected to controller 21.
  • the third harmonic spectrum is then detected by the spectrometer and recorded as a function of ⁇ to produce the air-MIIPS traces illustrated in Figure 5.
  • Figure 5 illustrates expected air-MIIPS measurements taken alongside SHG MIIPS measurements using a BBO crystal for the purpose of comparing the extracted phase.
  • the MIIPS traces are first shown for the initially uncompensated phase of the laser pulse, then for the compensated phase producing transform limited pulses.
  • the figure also shows the effect of +2000 fs positive and -2000 fs 2 negative chirp on both types of MIIPS traces.
  • Figure 6 shows the flat phase of the compressed/compensated pulse by SHG crystal-MIIPS (shown with solid lines) and THG air-MIIPS (shown with phantom lines).
  • Figure 6 also shows the retrieved phase for +/-2000 fs 2 chirp imparted on the phase by the SLM in the pulse shaper.
  • air-MIIPS works by scanning a reference phase function, f( ⁇ , ⁇ ), across the pulse's spectral width by the spectrometer.
  • the parameters, ⁇ and ⁇ are fixed parameters representing the binary values of ⁇ and the pulse duration respectively.
  • the phase shift ⁇ is scanned from 0 to 4 ⁇ by the spectrometer, the third harmonic spectrum is recorded by the computer controller.
  • the ⁇ value that produces the maximum third harmonic intensity for each frequency, ⁇ m ( ⁇ ), is found for each order n, and the second derivative of the unknown phase is calculated using:
  • the second derivative is used by the controller to determine the spectral phase ⁇ ( ⁇ ), which is added to f( ⁇ , ⁇ ) at the shaper for another iteration of the above process, resulting in a refined result for ⁇ ( ⁇ ).
  • the phase is calculated directly from the data via an iterative analytical approach.
  • Another preferred variation uses a quadratic phase function in place of the sinusoidal phase function.
  • a small portion of the THG is thereafter scattered by dust, water droplets, a prism, etc. toward a spectrometer with a CCD detector 43.
  • the remainder of the ultraviolet and infrared spectrum continues to propagate for use with measurements.
  • a photomultiplier tube or simplified spectrometer could be used in place of the CCD/spectrometer disclosed in this embodiment. This set-up is ideally suited for a laboratory environment.
  • Figure 3 shows a third preferred embodiment of the present invention laser system well suited for a field or industrial environment.
  • This embodiment is similar to the first preferred system except a 99% reflective splitter 61 reflects a majority of the pulse 63 to a specimen or object 65 being identified or worked upon (such as through micromachining, protein sequencing, communications, or OCT) and a small amount of the pulse 67 to concave mirror 21 for the air-MIIPS.
  • An antireflective coating is on the backside of splitter 61.
  • a remote sensing or remote working laser system of the present invention is shown in Figure 4.
  • This alternate embodiment laser system 71 is similar to the third preferred embodiment except that the main laser pulse 63 is focused by a telescope 73 to a gaseous nonlinear optical medium 75, such as atmospheric air, to create third harmonic generation in the pulse 63.
  • the THG, MIIPS compensated pulse is remotely transmitted 5 or more meters (most likely greater than 10 meters) from the laser system to a targeted object or specimen. Ideally, the THG focal point should be at or near the targeted object.
  • Such a system is used for remote identification of an undesired biological or chemical specimen, or to ablate the surface of an aerospace object 77 such as a missile, airplane, satellite or the like for identification or other purposes. It is also envisioned that this exemplary embodiment can be employed as a visible light-emitting filament, elongated along a portion of the pulse's path.
  • a fourth preferred embodiment of the present invention includes a cascading laser system 91 and is illustrated in Figure 7.
  • This system is similar to that disclosed hereinabove for the third preferred embodiment.
  • the differences include a first gaseous, nonlinear optical medium 93, a second concave mirror 95, and a second gaseous, nonlinear optical medium 97.
  • This arrangement of two or more in-line harmonic generation units creates a cascading and harmonic generation multiplying effect on the pulse.
  • a gas is employed in each optical medium 93 and 97 to cause third harmonic generation at each location.
  • an argon gas is used for the optical media and a pulse duration of about 30-40 fs is employed centered about 800 nm.
  • Argon is desirable due to its atomic and highly polarizable nature.
  • the first optical medium creates THG at about 266 nm and the second optical medium creates THG at about 89 nm.
  • the cascading allows for "nonlinear wave mixing" of the pulse.
  • combinations of crystals and a gaseous optical medium can be used in a cascading and harmonic generation multiplying process.
  • a 0.1 mm thick crystal of Potassium Dihydrogen Phosphite (KDP) or a BBO crystal having a thickness of 0.05 mm is used at either the first or second optical medium location to create second harmonic generation, and a gas is used at the other optical medium location to create third harmonic generation.
  • KDP Potassium Dihydrogen Phosphite
  • BBO crystal having a thickness of 0.05 mm is used at either the first or second optical medium location to create second harmonic generation
  • a gas is used at the other optical medium location to create third harmonic generation.
  • three or more optical media can be cascaded in-line and a second amplifier may be optionally provided between any pairs of optical media.
  • the features in the MIIPS trace show an alternating intensity pattern.
  • the changes in the intensity are due to the fact that sinusoidal phase modulation can be used to prepare pulses with a temporal asymmetry.
  • Time-asymmetric pulses are those that change if time is reversed.
  • the phase function is one period of the sine function in the frequency domain
  • the pulse, in the time domain can be described as a progression of increasingly stronger pulses ending with one that is greatest in intensity.
  • the phase between the sub-pulses alternates.
  • the temporal symmetry is reversed, in this case the most intense feature precedes the sub-pulses. This feature is well suited for use with micromachining or for medical surgery.
  • a multiplier changes the intensity of the sub-pulses.
  • ⁇ Binary phase functions (0- ⁇ ): always produce pulses that are temporally symmetric.
  • Cubic phase modulation produces temporal asymmetry similar to sine functions, a multiplier can be used to control the spacing between the sub- pulses and for how long they extend.
  • a positive pre-factor causes the appearance of trailing sub-pulses, and a negative pre-factor causes sub-pulses to appear before the strongest pulse.
  • temporally asymmetric pulses increase or decrease in intensity as a function to time. They can be created using a cubic or a sinusoidal phase function. Pulses that start with high intensity and then decrease are ideal when there is a threshold; for example, in micromachining, ablation, plasma generation, and fi lamentation. Pulses that start with a lower intensity are ideal when the process requires molecular alignment. Then the slow increase of the laser intensity gives the molecules a chance to align before the more intense part of the laser arrives and ionizes them. PLASMA HARMONIC GENERATION
  • An alternate embodiment of the present invention laser system uses plasma to cause harmonic generation rather than a crystal.
  • the plasma is created through ionization of the workpiece or targeted specimen, and otherwise acts like the air focal point and air-MIIPS described with the previous embodiments herein. Odd or even numbered harmonic generation can be created depending upon the type of transmission and specimen interface. For example, an air transmission and an airborn, gaseous chemical specimen can create third harmonic generation from the associated plasma. As a further example, a liquid transmission and silicon wafer specimen can create SHG from the associated plasma.
  • the plasma is created by the pulse itself ablating the specimen through ionization. The plasma generates harmonics in the pulse that can subsequently be used for MIIPS characterization and compensation of the phase distortions.
  • MIEPS variation is as follows.
  • MIIPS is based on the observation that for a given frequency ⁇ , the SHG is maximized when the second derivative of the phase is zero.
  • Mil only constructive multiphoton intrapulse interference
  • NLO nonlinear optical
  • This condition provides a direct measurement of the second derivative of the unknown phase in terms of the reference phase, because when the NLO is maximized is known. Therefore, for every frequency Q), the reference phase f(Q), ⁇ IIW ⁇ ) that maximizes the NLO process is found in the measured scan.
  • programmed computer software instructions 101 for MIIPS use a pulse shaper to successively introduce a set of calibrated reference spectral phases f( ⁇ , ⁇ ) to the pulses, with unknown phase distortion ⁇ (QJ), and measures the resulting NLO spectra.
  • the reference phase can be introduced by scanning a prism or a grating.
  • the NLO process can be second harmonic generation, third harmonic generation, terahertz generation, or any higher harmonic generation.
  • the material is, for example, zinc oxide or gallium nitride powder.
  • ⁇ "( ⁇ ) double integration results in ⁇ ( ⁇ ), which can be used for accurate phase compensation by subtraction to achieve TL pulses.
  • a MIIPS scan can be visualized in a two dimensional contour plot showing the NLO intensity as a function of ⁇ and ⁇ , as is illustrated in Figure 10.
  • the reference function is the quadratic reference phase
  • a £ scan results directly in ⁇ "( ⁇ ).
  • the cubic reference phase a ⁇ scan results in diagonal lines with a slope proportional to ⁇ , when correcting for that slope on obtains two measurements for ⁇ "(( ⁇ ), each corresponding to the plus or minus sign of ⁇ .
  • the sinusoidal reference phase where ⁇ is a parameter scanned across a 4 ⁇ range, the features corresponding to ⁇ ma ⁇ ( ⁇ ) for TL pulses are diagonal parallel lines separated by ⁇ .
  • the choice of reference phase is determined by the user, however, sinusoidal phases are preferred for very accurate results. Nevertheless, a quadratic phase is very simple to implement and gives an excellent first scan. The accuracy of the cubic phase should be as good as that of the sinusoidal phase. It is preferred to run one iteration with the quadratic phase and then run subsequent iterations with the cubic phase.
  • the target phase residue is set as the minimum deviations tolerable by the user. Typically, distortions are reduced to 0.1 rad across the spectrum.
  • T/X JL the parameter that ⁇ and X TL are the calculated pulse duration by Fourier transform of the spectrum of the laser with and without the residual phase distortion. MIIPS values with this embodiment should routinely reach the 1.01 level and in some cases are even lower than 1.001.
  • MIIPS unit can use the amplifier and compressor gratings.
  • a fixed shaper can be employed for correcting the pulse distortion based on the new MIIPS software calculations.
  • pulse durations of 5 fs or less when MIIPS is used with a quadratic phase function instead of a sinusoidal function, a single scan is needed to measure the phase distortions with an accuracy similar to 0.5%.
  • the present invention laser system and method are ideally suited for use in performing dentistry.
  • a Ti:Sa femtosecond laser using a pulse energy of about 300-400 ⁇ J and a pulse repetition rate of about 3 kHz is expected to achieve an ablation rate of about 1 mm 3 /min on the dentine surface of a human tooth.
  • the laser pulse is shaped and MIIPS is preferably employed to reduce undesired pulse distortions.
  • the pulse creates plasma which can optionally be employed instead of a crystal.
  • a pulse duration equal to or less than 120 fs is preferred for dental surgery which includes drilling.
  • FIG. 11 Another variation of the laser system of the present invention employs self-diffraction Multiph ⁇ ton Intrapulse Interference Phase Scan methods and systems.
  • Self-diffraction is essentially the same as four wave mixing and transient grating.
  • Self-diffraction MIIPS is particularly useful in characterizing ultraviolet pulses for which SHG crystals are unavailable.
  • Self diffraction removes the wavelength restrictions of SHG crystals, making it work for any wavelength from the hard-UV to the far-infrared.
  • Figure 11 shows infrared, transform limited pulses expected with self-diffraction MIIPS.
  • a laser system 103 includes an emitted fs laser pulse 105 which is self-diffracted by a mask 107 having a pair of apertures.
  • Mask 107 blocks all but two small regions of the amplified pulse (although additional apertures can alternately be used).
  • the resulting beams are then focused on a nonlinear medium 111 by a lens 109 and the self-diffracting signal 113 is detected by a compact fiber-coupled spectrometer.
  • a 100 ⁇ m quartz plate and a 250 ⁇ m sapphire plate are used for the IR and UV pulses, respectively.
  • the gaseous nonlinear optical medium can be used to generate zero order harmonic generation (known as optical rectification), fifth order harmonic generation or seventh or greater harmonic generation, in a compensated pulse. Further for example, it may be desirable to provide a 1 ⁇ m Yittrium or 1.5 ⁇ m Erbium laser to create fifth harmonic generation in a gas.
  • the dual beam FROG procedure can be used in combination with cascading optical media although various advantages of the preferred embodiment may not be realized. It is alternately envisioned to employ a pulse duration of less than 5 fs with air-MIIPS or other nonlinear gaseous optical media, and without a crystal. It is intended by the following claims to cover these and any other departures from the disclosed embodiments which fall within the true spirit of this invention.

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  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
  • Lasers (AREA)

Abstract

L'invention concerne un système laser assurant une génération d'harmoniques dans une impulsion de faisceau laser. Dans un autre aspect de la présente invention, un laser émet fonctionnellement une impulsion laser, un support optique gazeux assure fonctionnellement une génération d'harmoniques d'ordre 3 ou supérieur dans l'impulsion, et un dispositif de commande caractérise et compense les distorsions dans l'impulsion. Un aspect supplémentaire de la présente invention fait appel à de multiples supports optiques conçus pour provoquer des générations d'harmoniques en cascade dans une impulsion laser.
EP07862112A 2006-11-16 2007-11-16 Système laser faisant appel à une génération d'harmoniques Withdrawn EP2089767A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US85942106P 2006-11-16 2006-11-16
PCT/US2007/024171 WO2008063602A2 (fr) 2006-11-16 2007-11-16 Système laser faisant appel à une génération d'harmoniques

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EP2089767A2 true EP2089767A2 (fr) 2009-08-19

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US8633437B2 (en) 2005-02-14 2014-01-21 Board Of Trustees Of Michigan State University Ultra-fast laser system
FR2887334B1 (fr) 2005-06-20 2007-08-24 Centre Nat Rech Scient Dispositif et procede de caracterisation de structure par effet de longueur d'onde dans un systeme photo-acoustique
US8618470B2 (en) 2005-11-30 2013-12-31 Board Of Trustees Of Michigan State University Laser based identification of molecular characteristics
US9202678B2 (en) 2008-11-14 2015-12-01 Board Of Trustees Of Michigan State University Ultrafast laser system for biological mass spectrometry
US8675699B2 (en) 2009-01-23 2014-03-18 Board Of Trustees Of Michigan State University Laser pulse synthesis system
WO2010141128A2 (fr) * 2009-03-05 2010-12-09 Board Of Trustees Of Michigan State University Système d'amplification laser

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US5341236A (en) * 1992-12-03 1994-08-23 Northrop Corporation Nonlinear optical wavelength converters with feedback
US6498801B1 (en) * 1999-08-05 2002-12-24 Alexander E. Dudelzak Solid state laser for microlithography
US7583710B2 (en) * 2001-01-30 2009-09-01 Board Of Trustees Operating Michigan State University Laser and environmental monitoring system
US7450618B2 (en) * 2001-01-30 2008-11-11 Board Of Trustees Operating Michigan State University Laser system using ultrashort laser pulses
US6816520B1 (en) * 2001-11-30 2004-11-09 Positive Light Solid state system and method for generating ultraviolet light

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WO2008063602A2 (fr) 2008-05-29
WO2008063602A3 (fr) 2008-11-06

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