WO2021260051A1 - Appareil laser et procédé de commande d'un appareil laser - Google Patents

Appareil laser et procédé de commande d'un appareil laser Download PDF

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Publication number
WO2021260051A1
WO2021260051A1 PCT/EP2021/067224 EP2021067224W WO2021260051A1 WO 2021260051 A1 WO2021260051 A1 WO 2021260051A1 EP 2021067224 W EP2021067224 W EP 2021067224W WO 2021260051 A1 WO2021260051 A1 WO 2021260051A1
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Prior art keywords
laser
modulator
resonator
output beam
medium
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PCT/EP2021/067224
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German (de)
English (en)
Inventor
Marc Eichhorn
Christelle Kieleck
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Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
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Priority to EP21737017.0A priority Critical patent/EP4173091A1/fr
Publication of WO2021260051A1 publication Critical patent/WO2021260051A1/fr

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    • 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
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/11—Mode locking; Q-switching; Other giant-pulse techniques, e.g. cavity dumping
    • H01S3/1103—Cavity dumping
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
    • B23K26/0604—Shaping the laser beam, e.g. by masks or multi-focusing by a combination of beams
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
    • B23K26/067—Dividing the beam into multiple beams, e.g. multifocusing
    • 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
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/08—Construction or shape of optical resonators or components thereof
    • H01S3/08072—Thermal lensing or thermally induced birefringence; Compensation thereof
    • 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
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/13—Stabilisation of laser output parameters, e.g. frequency or amplitude
    • H01S3/136—Stabilisation of laser output parameters, e.g. frequency or amplitude by controlling devices placed within the cavity
    • 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
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/08—Construction or shape of optical resonators or components thereof
    • H01S3/08054—Passive cavity elements acting on the polarization, e.g. a polarizer for branching or walk-off compensation
    • 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
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/08—Construction or shape of optical resonators or components thereof
    • H01S3/081—Construction or shape of optical resonators or components thereof comprising three or more reflectors
    • H01S3/0813—Configuration of resonator
    • 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
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/08—Construction or shape of optical resonators or components thereof
    • H01S3/081—Construction or shape of optical resonators or components thereof comprising three or more reflectors
    • H01S3/082—Construction or shape of optical resonators or components thereof comprising three or more reflectors defining a plurality of resonators, e.g. for mode selection or suppression
    • 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
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/08—Construction or shape of optical resonators or components thereof
    • H01S3/081—Construction or shape of optical resonators or components thereof comprising three or more reflectors
    • H01S3/083—Ring lasers
    • 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
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/105—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling the mutual position or the reflecting properties of the reflectors of the cavity, e.g. by controlling the cavity length
    • H01S3/1051—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling the mutual position or the reflecting properties of the reflectors of the cavity, e.g. by controlling the cavity length one of the reflectors being of the type using frustrated reflection
    • 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
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/106—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity
    • H01S3/1068—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity using an acousto-optical device
    • 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
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/106—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity
    • H01S3/107—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity using electro-optic devices, e.g. exhibiting Pockels or Kerr effect
    • H01S3/1075—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity using electro-optic devices, e.g. exhibiting Pockels or Kerr effect for optical deflection
    • 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
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/13—Stabilisation of laser output parameters, e.g. frequency or amplitude
    • H01S3/1305—Feedback control systems
    • 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
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/13—Stabilisation of laser output parameters, e.g. frequency or amplitude
    • H01S3/1306—Stabilisation of the amplitude
    • 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
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/13—Stabilisation of laser output parameters, e.g. frequency or amplitude
    • H01S3/131—Stabilisation of laser output parameters, e.g. frequency or amplitude by controlling the active medium, e.g. by controlling the processes or apparatus for excitation
    • H01S3/1312—Stabilisation of laser output parameters, e.g. frequency or amplitude by controlling the active medium, e.g. by controlling the processes or apparatus for excitation by controlling the optical pumping

Definitions

  • the present invention relates to a laser device and a method for controlling a laser device according to the independent claims.
  • a time-variable mean power and pulse energy for applications in the field of optronic countermeasures with lasers, laser communication and laser material processing, it is often desirable to emit a time-variable mean power and pulse energy, as desired in accordance with an electronic specification signal, and to split it into, for example, two output beams, such as two channels .
  • a Q-switched laser source could be variably adjustable in its output power and pulse energy from pulse to pulse.
  • a Q-switched laser source often does not have a stable beam position and divergence that does not fluctuate from pulse to pulse, regardless of the selected average output power, repetition rate or pulse energy.
  • the Q-switched laser source is often operated with constant power in continuous, repetitive operation.
  • the laser power and thus the pulse energy is subsequently attenuated in its amplitude by a modulator introduced into the output beam, whereby the desired intensity modulation is impressed on the output beam.
  • the component complementary to this appears in the second beam generated by the modulator, for example a second polarization in an electro-optical modulator or a diffracted portion in an acousto-optical modulator.
  • Such a Q-switched laser source often works at full power, which can result in high energy consumption and the need for a corresponding waste heat management with additional power and space requirements.
  • the modulator in the output beam can cause a change in the beam position depending on the thermal load, in particular with varying modulation formats.
  • the laser pulse duration and peak power also depend significantly on the selected repetition rate, which is why this is often fixed.
  • the object of the invention is thus to create an improved laser device and an improved method for controlling a laser device, with which a reduction in the waste heat generated when generating a laser beam and / or an optimization of the beam properties of the generated laser beam can be achieved.
  • This object is achieved by a laser device according to claim 1 and a method for controlling a laser device according to claim 20.
  • Advantageous refinements and developments are described in the dependent claims.
  • the present invention is based on the knowledge that the above object can be achieved by arranging two modulators in a laser resonator, and depending on the desired power distribution on the channels, pulse energy and pulse duration, these modulators are specifically controlled.
  • a laser resonator of this type two output beams which can form channels can be generated.
  • a first output beam can be a useful beam to be used for the specific application, for example in the area of optronic countermeasures with lasers, laser communication and laser material processing, which beam has predetermined beam properties.
  • excess laser power can be decoupled from the laser resonator via the second output beam in order to keep the laser resonator in its middle operating point and / or to ensure the specified beam properties of the useful beam.
  • Both output beams can also represent useful beams to be used in the specific application.
  • a laser device comprising a laser resonator.
  • the laser resonator has a laser medium.
  • the laser device comprises a first modulator.
  • the first modulator is arranged in the laser resonator.
  • the first modulator is designed to couple a first output beam from the laser resonator.
  • the laser device comprises a second modulator.
  • the second modulator is arranged in the laser resonator.
  • the second modulator is designed to couple a second output beam from the laser resonator. Since the two output beams can form channels, they can in particular be decoupled from the laser device, for example emerge from a housing of the laser device.
  • the laser resonator can be a linear resonator or a ring resonator. Furthermore, the laser resonator can have at least two mirrors which spatially delimit the laser resonator and have a reflectivity of more than 80%, preferably more than 90%, preferably more than 95%, preferably more than 99%. For example, the mirrors are highly reflective mirrors with a reflectivity of more than 99.9%.
  • the laser medium can be arranged between two mirrors of the laser resonator. Furthermore, the laser medium can be a laser-active medium. In addition, the laser medium can be a solid, for example a doped crystal or a doped glass, a doped light-guiding fiber, a liquid, for example a dye solution, or a gas.
  • the first modulator and the second modulator can each be designed to couple the respective output beams out of the laser resonator by deflecting laser radiation.
  • the first output beam and / or the second output beam can be a laser pulse or a continuous wave laser beam.
  • the first output beam can be a useful beam to be used in the specific application, while excess power is coupled out of the laser resonator via the second output beam.
  • the first modulator and the second modulator can be controllable modulators.
  • the laser device can also include a control device.
  • the control device can be designed to control the first modulator and the second modulator independently of one another.
  • the independent control of the respective modulators has the advantage that the power of the respective output beams can be adjusted individually. This allows the beam properties of the respective output beams to be optimized.
  • the control device can comprise a microcontroller or a processor.
  • the first modulator and / or the second modulator can be an acousto-optical modulator, an electro-optical modulator, a frustrated total reflection switch or a mechanically moved wave plate.
  • the control device can be designed to control the first modulator and the second modulator in such a way that a total decoupling rate of laser radiation from the laser resonator into the first output beam and into the second output beam is constant in continuous operation, or in pulsed operation During the pulse generation of each individual pulse over several pulses, a total decoupling degree of laser radiation from the laser resonator into the first output beam and into the second output beam is constant or that a pulse duration of the first output beam or the second Output beam is constant.
  • control device can be designed to control the first controllable modulator and the second controllable modulator and the pump power of the laser in such a way that, in continuous operation, a beam position or beam divergence of laser radiation from the laser resonator into the first output beam or into the second output beam is constant, or in pulsed operation during the pulse generation of each individual pulse over several pulses a beam position or beam divergence of laser radiation from the laser resonator in the first output beam or in the second output beam is constant.
  • This has the advantage that the beam properties of the respective output beams can be optimized.
  • the total degree of coupling of the respective modulators can be through
  • T oc 1 ⁇ (1 - ⁇ 1 ) 2 * (1 ⁇ ⁇ 2 ) 2 with double passage of the laser radiation through the first modulator and the second modulator per cycle or during one cycle of the resonator, for example in a standing wave resonator, if each Passage on the way there and back leads to a decoupling, or through
  • T oc 1 ⁇ (1 - ⁇ 1 ) * (1 ⁇ ⁇ 2 ) with a single passage of the laser radiation through the first modulator and the second modulator per cycle or during one cycle of the resonator, for example in a ring resonator.
  • ⁇ 1 is the proportion of the power coupled out into the first output beam during a modulator passage.
  • ⁇ 2 is the proportion of the power coupled out into the second output beam during a modulator passage.
  • a suitable choice of ⁇ 1 and ⁇ 2 has the advantage that the laser resonator can be kept in its mean operating point.
  • the first modulator and the second modulator can be acted upon by the laser mode one after the other in the running direction or circumferential direction of a laser mode in the laser resonator without passing through the laser medium and / or when passing through the Laser radiation through the first modulator or the second modulator, the first modulator and the second modulator in the running direction or circumferential direction of a laser mode in the laser resonator are acted upon one after the other with the laser mode traversing the laser medium.
  • the laser resonator can additionally have further decoupling points, for example for measurement and control purposes, or due to unavoidable losses L.
  • the laser device can furthermore have a detection device for detecting an effective inversion of the laser medium.
  • the control device can also be designed to control the first modulator and / or the second modulator and / or the pump power on the basis of the detected effective inversion of the laser medium. This has the advantage that a desired inversion of the laser medium can be set.
  • the detection device can be designed to detect fluorescence of the laser medium and to determine the effective inversion of the laser medium on the basis of the detected fluorescence of the laser medium. This has the advantage that the effective inversion of the laser medium can be determined particularly precisely.
  • the control device can also be designed to control the first modulator and / or the second modulator and / or the pump power on the basis of the detected fluorescence.
  • the detection device can be designed to detect laser radiation from the laser medium and to determine the effective inversion of the laser medium on the basis of the detected laser radiation from the laser medium. This has the advantage that the effective inversion of the laser medium can be determined particularly precisely.
  • the control device can also be designed to control the first modulator and / or the second modulator and / or the pump power on the basis of the detected laser radiation.
  • the detection device can be designed to detect a beam position or beam divergence of the laser radiation of the laser medium and to determine a beam position or beam divergence of the laser radiation of the laser medium on the basis of the detected laser radiation of the laser medium. This has the advantage that the one beam position or beam divergence of the laser radiation of the laser medium can be determined particularly precisely.
  • the laser device can also have a detection device for detecting a laser power.
  • the control device can also be designed to control the first modulator and / or the second modulator and / or the pump power on the basis of the detected laser power.
  • the detected laser power can be a power of the first output beam, a power of the second output beam or a power of a laser beam decoupled at a further decoupling point, such as a decoupling mirror, of the laser resonator.
  • the laser device can have a detection device for detecting a beam position or a beam divergence of the laser radiation.
  • the control device can be designed to control the first modulator and / or the second modulator and / or the pump power on the basis of the detected beam position or beam divergence.
  • the laser resonator can have a coupling-out mirror which has a reflectivity of more than 80%, preferably more than 90%, preferably more than 95%, preferably more than 99%.
  • the detection device can be designed to detect the power decoupled by the output mirror and thus to determine the laser power or a beam position or a beam divergence of the laser radiation on the basis of the detected output power.
  • the coupling-out mirror can be a mirror delimiting the laser resonator or a deflecting mirror arranged in the laser resonator or a beam splitter arranged in the laser resonator or a polarizer arranged in the laser resonator.
  • the respective modulators can be arranged in the laser resonator in such a way that the respective modulators in the laser resonator are acted upon one after the other by laser radiation circulating in the laser resonator without passing through the laser medium.
  • the laser resonator can have a mirror.
  • the first modulator and the second modulator can be arranged between the laser medium and the mirror.
  • the mirror can spatially delimit the laser resonator.
  • the mirror can have a reflectivity of more than 80%, preferably more than 90%, preferably more than 95%, preferably more than 99%.
  • the mirror can be a highly reflective mirror with a reflectivity of more than 99.9%.
  • Optical elements for example lenses, beam splitters, etalons, filters, polarizers or retardation plates, can be arranged between the mirror and the first or the second modulator or the laser medium.
  • the second modulator can be arranged at a distance from a common straight line on which the first modulator and the laser medium lie.
  • the first modulator can also be designed to generate a laser beam directed in the direction of the second modulator.
  • the second modulator can also be designed to generate the second output beam from the laser beam generated by the first modulator. This has the advantage that frequency shifts generated by coupling out the respective output beams can be reduced.
  • the respective modulators can be arranged on different sides of the laser medium.
  • the laser resonator can have a first mirror and a second mirror.
  • the laser medium can be arranged between the first mirror and the second mirror.
  • the first modulator can be arranged between the laser medium and the first mirror.
  • the second modulator can be arranged between the laser medium and the second mirror.
  • the respective mirrors can spatially delimit the laser resonator.
  • the respective mirrors can have a reflectivity of more than 80%, preferably more than 90%, preferably more than 95%, preferably more than 99%.
  • the respective mirrors can be highly reflective mirrors with a reflectivity of more than 99.9%.
  • the respective mirrors, the laser medium and the respective modulators can lie on a common straight line.
  • At least one of the respective modulators can be designed in such a way that the radiation decoupled in the opposite direction of rotation in the direction opposite to the output beam defined as the decoupling channel is reflected back. This has the advantage that the direction of rotation of the laser mode in the laser resonator can be determined by the respective modulators.
  • the laser resonator can be designed in such a way that the laser medium is traversed four times in one cycle of the resonator. As a result, an amplification of the radiation in the laser resonator can be increased per resonator revolution. This also enables shorter laser pulses to be made possible.
  • the laser device comprises a laser resonator which has a laser medium, a first controllable modulator which is arranged in the laser resonator and which is designed to couple a first output beam from the laser resonator, and a second controllable modulator which is in the laser resonator is arranged, and which is designed to couple a second output beam from the laser resonator.
  • the method comprises controlling the first controllable modulator and the second controllable modulator and / or the laser pump power in such a way that, in continuous operation, a total decoupling rate of laser radiation from the laser resonator into the first output beam and into the second output beam is constant, or in the pulsed mode During the pulse generation of each individual pulse over several pulses, a total decoupling rate of laser radiation from the laser resonator into the first output beam and into the second output beam is constant or that a pulse duration of the first output beam or the second output beam is constant.
  • the method includes controlling the first controllable modulator and the second controllable modulator and the pump power of the laser in such a way that, in continuous operation, a beam position or beam divergence of laser radiation from the laser resonator into the first output beam or into the second Output beam is constant, or in pulsed operation during the pulse generation of each individual pulse over several pulses a beam position or beam divergence of laser radiation from the laser resonator into the first output beam or into the second output beam is constant.
  • the method can be a computer-implemented control method based, for example, on direct calculations or the use of a hash table or the use of artificial intelligence.
  • the method can also detect an effective inversion of the laser medium or fluorescence or laser radiation or laser power or a beam position or beam divergence of the laser radiation of the laser medium and control the first controllable modulator and / or the second controllable modulator and / or the pump power of the laser based on the detected effective inversion of the laser medium or the fluorescence or the laser radiation or the laser power or the beam position or the beam divergence of the laser radiation of the laser medium.
  • the method can be carried out with the laser device according to the invention.
  • FIGS. 1a to 1c laser devices according to different exemplary embodiments
  • FIGS. 2a to 2e laser resonators according to further exemplary embodiments
  • FIGS. 3a to 3f laser resonators according to further exemplary embodiments
  • FIGS. 4a and 4b laser resonators according to further exemplary embodiments.
  • Figure 5 a functional principle of a frustrated total reflection
  • FIGS. 1a to 1c show laser devices according to different exemplary embodiments.
  • the laser devices each have a laser resonator 1 which is delimited by a mirror 2.
  • Laser resonator 1 is a ring resonator while the laser resonators 1 shown in FIGS. 1b and 1c are linear resonators or standing wave resonators.
  • a laser medium 3, a first modulator 4 and a second modulator 5 are arranged in each of the laser resonators 1.
  • the first modulator 4 is designed to couple a first output beam 6 from the laser resonator 1.
  • the second modulator 5 is designed to couple a second output beam 7 from the laser resonator 1.
  • the respective modulators 4, 5 couple the respective output beams 6, 7 from the laser radiation 8 located in the laser resonator 1.
  • the laser radiation 8 is reflected by the mirrors 2.
  • the mirrors 2 can each have a reflectivity of more than 80%, preferably of more than 90%, preferably of more than 95%, preferably of more than 99%.
  • the mirrors 2 are highly reflective mirrors with a reflectivity of more than 99.9%.
  • the first modulator 4 and the second modulator 5 are each arranged between the laser medium 3 and the mirror 2-1, while the first modulator 4 in the laser resonator 1 shown in FIG is arranged between the mirror 2-2 and the laser medium 3 and the second modulator 5 between the laser medium 3 and the mirror 2-1.
  • the laser medium 3 and the respective modulators 4, 5 are arranged on a common straight line.
  • the laser radiation 8 can form a standing wave between the mirrors 2, while in the laser resonator 1 shown in FIG.
  • the direction of rotation 9 can be determined by further, not shown elements in the laser resonator 1 or by external injection.
  • the respective modulators 4, 5 can be acousto-optical modulators. In this case, for example, forming the diffracted by the acoustic wave in the respective acousto-optical modulator beam to the respective coupled-out output beam 6, 7. The proportion of the coupled power ⁇ 1 for the first output beam 6, as a channel 1, by suitable choice of the acoustic power of the modulator can be set.
  • the respective modulators 4, 5 can be electro-optical modulators (EOM) consisting of an electro-optical cell and at least one polarizing beam splitter.
  • EOM electro-optical modulators
  • the combination of one EOM with the beam splitter each forms an adjustable decoupling ⁇ 1 for the laser radiation 8 passing through this EOM when it hits the respective beam splitter, for example for the first output beam 6.
  • the respective decoupled portion represents one of the two output radiate 6, 7 or output channels.
  • the portion transmitted by the beam splitter or the reflected portion can be the decoupled portion.
  • the respective modulators 4, 5 can use the change in distance between two optical media in order to achieve a decoupling through frustrated total internal reflection (FTIR).
  • FTIR frustrated total internal reflection
  • the first output beam 6 forms a channel 1 and the second output beam 7 forms a channel 2.
  • at least one of the two modulators 4, 5 or both are first activated in such a way that there is sufficient one large overall decoupling occurs, so that the laser resonator 1 does not start to oscillate and during this time inversion is built up in the laser medium 3 by pumping. This can also be achieved by controlling only one of the modulators 4, 5.
  • the effective inversion increases as a function of the residual inversion of the laser medium 3 that may exist before the pumping process of the laser medium 3 due to the pumping process:
  • ⁇ a is the spectroscopic absorption cross-section and ⁇ e is the spectroscopic emission cross-section of the laser transition, R p is the pumping rate, ⁇ f is the fluorescence lifetime and (N) is the mean concentration of the laser-active dopant in the laser medium 3.
  • the effective inversion results mathematically by shifting the population inversion around a value that depends on the spectroscopic cross sections and the mean active concentration:
  • the laser device thus runs in a manner comparable to a normal, Q-switched laser and generates a pulse with the pulse duration
  • ⁇ c is the photon lifetime in the laser resonator
  • ⁇ (r) the extraction efficiency and the ratio of the logarithmic gain when the pulse is triggered for logarithmic amplification of a comparable continuous wave laser at the laser threshold g th (threshold amplification)
  • P 2 ⁇ 2 (1 - ⁇ 1 ) P inc, 1 (t)
  • P inc, 1 (t) is the power that falls over the pulse and varies over time within the laser resonator 1 on the modulator 4 for channel 1. So the circumstances are regardless of the pulse shape P inc, 1 (t).
  • the corresponding ratio ⁇ of the output power and pulse energy between the two output channels or output beams 6, 7 can thus be freely set with a constant total pulse energy and pulse duration from pulse to pulse. If the modulators 4, 5 were controlled and responded quickly, it would even be possible to change the distribution during a pulse. The component that is complementary to the power emitted in channel 1 is then always emitted in the other channel.
  • decoupling points or modulators 4, 5 are on different sides of the laser medium 3, for example, the decoupling point for channel 1 or the first modulator 4, then the laser medium 3 and then the decoupling point for channel 2 or the second, is first in the direction of rotation 9 Applied to modulator 5 or, for example, in the laser resonator 1 shown in FIG. 1c, applies
  • the amplification G (t) which is time-dependent over a pulse, also determines the time profile of the power P 2 emitted in channel 2. In this case it would be
  • hv is the photon energy of a laser photon (h: Planck's quantum of action, v: frequency of the photon) and V is the active volume of the laser medium.
  • the current effective inversion of the laser medium 3 can be determined and, with a given pumping rate, the inversion curve before the next pulse or, with a given time up to the next pulse, the necessary pumping rate, ie the pump power to be applied , in order to achieve the desired inversion when the next pulse is triggered.
  • the necessary pumping rate ie the pump power to be applied
  • the pulse duration are then set.
  • an arbitrarily selectable complementary division of the laser emission into two channels with a minimal number of additionally required components can be effected with the laser device.
  • the advantages are that the laser device can be operated at a constant working point and thus the beam position and beam quality remain unchanged due to constant thermal effects regardless of the modulation Limitation of this flexibility to operate with different pump capacities or repetition rates and by choosing the total decoupling as far as physically possible the original pulse duration or pulse energy to keep constant.
  • the pump power or the decoupling of the first modulator or the decoupling Development of the second modulator can be determined and controlled in such a way that the desired power or energy distribution and / or pulse duration results in the two channels and a predetermined beam position and / or beam divergence or a tolerance of a deviation from a desired beam position and / or beam divergence as possible is achieved.
  • FIGS. 2a to 2e show laser resonators 1 according to further exemplary embodiments.
  • the laser resonators 1 shown in FIGS. 2a to 2e can be designed in a manner similar to the laser resonators described in connection with FIGS. 1a to 1c.
  • Two Pockels cells 10 and a polarizer 11 are arranged in the laser resonator 1 shown in FIG. 2a.
  • the Pockels cell 10 - 1 and the polarizer 11 form the first modulator 4, which decouples the first output beam 6.
  • the Pockels cell 10 - 2 and the polarizer 11 form the second modulator 5, which decouples the second output beam 7.
  • the number of components required to manufacture the laser resonator 1 can be reduced. Since the Pockels cells 10 are arranged on the same side of the laser medium 3, the advantage can also be achieved that a fixed relationship of the degrees of coupling can be brought about.
  • the laser resonator 1 shown in FIG. 2b has two Pockels cells 10 and two polarizers 11.
  • the Pockels cell 10-1 and the polarizer 11-1 form the first modulator 4, while the Pockels cell 10-2 and the polarizer 11-2 form the second modulator 5.
  • the modulators 4, 5 are arranged on different sides of the laser medium 3. In this case, the advantage can also be achieved that a fixed polarization state can be brought about in the laser medium.
  • the laser resonator 1 shown in FIG. 2c has two Pockels cells 10, two polarizers 11 and a quarter-wave retardation plate 12.
  • the Pockels cell 10-1 and the polarizer 11-1 form the first modulator 4, while the Pockels cell 10-2 and the polarizer 11-2 form the second modulator 5.
  • the running directions 13 of the laser radiation with different polarizations are shown in FIG. 2c.
  • the second modulator 5 is arranged at a distance from a common straight line on which the first modulator 4 and the laser medium 3 are arranged.
  • the first modulator 4 or the polarizer 11-1 generates a further laser beam 14, from which the second modulator 5 generates the second output beam 7.
  • This arrangement has the advantage that the laser medium 3 is traversed four times with each cycle in the laser resonator 1. As a result, a gain can be twice as high as in the case of the laser resonator 1 shown in FIG. 2b. This also enables shorter laser pulses to be generated.
  • the laser resonator 1 shown in FIG. 2d is a unidirectional ring resonator.
  • the direction of rotation 9 in the laser resonator 1 is set here by an optical isolator 15 arranged in the laser resonator 1.
  • the laser resonator 1 shown in FIG. 2e differs from the laser resonator 1 shown in FIG. 2d in that, instead of the optical isolator 15, at least one of the mirrors 16 is arranged on the polarizers 11 to move around the direction of rotation 9 or a unidirectional direction of rotation force.
  • FIGS. 3a to 3f show laser resonators 1 according to further exemplary embodiments.
  • the laser resonators 1 shown in FIGS. 3 a to 3 f can be designed in a manner similar to the laser resonators described in connection with FIGS. 1 a to 1 c.
  • the first modulator 4 is formed by an acousto-optical modulator 17-1 and a further mirror 16-1.
  • the second modulator 5 is formed by an acousto-optical modulator 17-2 and a further mirror 16-2.
  • the respective modulators 4, 5 are arranged on the same side of the laser medium 3, while in the laser resonator 1 shown in FIG Modulators 4, 5 are arranged on different sides of the laser medium 3.
  • a device can be realized in which there are four output channels.
  • the two channels generated by the first modulator are complementary to the two channels generated by the second modulator.
  • the two channels of each modulator have a different output, depending on the degree of decoupling of the respective modulator. Depending on the application, this can be an advantage.
  • the laser resonator 1 shown in FIG. 3c has two spherical mirrors 18 which spatially delimit the laser resonator 1.
  • two acousto-optical modulators 17 are arranged in the laser resonator 1.
  • the radius of the spherical mirror 18-1 corresponds to the distance between the spherical mirror 18-1 and the acousto-optical modulator 17-1 in such a way that the diffracted beam is reflected back into itself regardless of the diffraction angle.
  • the radius of the spherical mirror 18-2 corresponds to the distance between the spherical mirror 18-2 and the acousto-optical modulator 17-2 in such a way that the diffracted beam is reflected back into itself regardless of the diffraction angle.
  • the acousto-optical modulator 17-1 and the spherical mirror 18-1 form the first modulator 4, while the acousto-optical modulator 17-2 and the spherical mirror 18-2 form the second modulator 5.
  • the spherical mirrors 18 can be highly reflective mirrors, for example mirrors with a reflectivity of more than 99%.
  • the laser resonator 1 shown in FIG. 3d differs from the laser resonator 1 shown in FIG. 3b in that the acousto-optical modulator 17-2 is spaced from a common straight line on which the laser medium 3 and the acousto-optical modulator 17-1 are arranged, is arranged.
  • the laser resonator 1 shown in FIG. 3e differs from the laser resonator 1 shown in FIG. 3a in that the laser resonator 1 shown in FIG. 3e is designed as a unidirectional ring resonator with an optical isolator 15.
  • the laser resonator 1 shown in FIG. 3f differs from that in FIG Figure 3d laser resonator 1 shown in that the laser resonator 1 shown in Figure 3f is designed as a unidirectional ring resonator.
  • orders 19 of the diffracted laser beams are shown in FIG. 3f.
  • the laser resonators 1 shown in FIGS. 3d and 3f have the advantage that the 1st order diffracted by the acousto-optical modulator 17-1 is reduced by the acousto-optical modulator 17-2 from the -1. Order is bent again into the 0th order. As a result, the frequency shifts caused by the diffraction carried out in the acousto-optical modulators 17-1, 17-2 can cancel each other out. As a result, the light circulating in the laser resonator 1 does not experience any frequency shift.
  • FIGS. 4a and 4b show laser resonators 1 according to further exemplary embodiments.
  • the laser resonators 1 shown in FIGS. 4a and 4b can be designed similarly to the laser resonators described in connection with FIGS. 1a to 1c.
  • the first modulator 4 is formed by a frustrated total reflection switch 20-1 and a further mirror 16-1.
  • the second modulator 5 is formed by a frustrated total reflection switch 20-2 and a further mirror 16-2.
  • the laser resonator 1 shown in FIG. 4a is designed as a linear resonator
  • the laser resonator 1 shown in FIG. 4b is designed as a unidirectional ring resonator.
  • the direction of rotation 9 results automatically from self-injection by the further mirror 16.
  • FIG. 5 shows a functional principle of a frustrated total reflection switch 20.
  • the frustrated total reflection switch 20 comprises two bodies 21 made of an optically dense material, which are arranged at a distance d from one another.
  • An optically thin material 22 is arranged between the bodies 21.
  • a beam 23 incident in the body 21 - 1 is reflected at an interface 24 between the body 21 - 1 and the optically thin material 22.
  • a reflected beam 25 is thereby formed.
  • the distance d between the bodies 21 is small enough, for example less than twice the wavelength of the incident beam 23, a portion of the incident beam 23 can enter the body Transmit 21-2. Such a transmission is also referred to as an optical tunnel effect.
  • the portion of the incident beam 23 transmitted into the body 21-2 forms an optically tunneled steel 26.
  • the power of the optically tunneled beam 26 can be modulated.
  • the optical tunnel effect can also take place in the opposite direction.

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Electromagnetism (AREA)
  • Plasma & Fusion (AREA)
  • Mechanical Engineering (AREA)
  • Lasers (AREA)

Abstract

La présente invention concerne un appareil laser et un procédé de commande d'un appareil laser. L'appareil laser comprend un résonateur laser (1) qui comporte un milieu laser (3). En outre, l'appareil laser comprend un premier modulateur (4) qui est disposé dans le résonateur laser (1) et qui est conçu pour découpler un premier faisceau de sortie (6) du résonateur laser (1). L'appareil laser comprend en outre un second modulateur (5) qui est disposé dans le résonateur laser (1) et qui est conçu pour découpler un second faisceau de sortie (7) du résonateur laser (1).
PCT/EP2021/067224 2020-06-26 2021-06-23 Appareil laser et procédé de commande d'un appareil laser WO2021260051A1 (fr)

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DE102020207949.8A DE102020207949A1 (de) 2020-06-26 2020-06-26 Laservorrichtung und Verfahren zum Ansteuern einer Laservorrichtung

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Citations (3)

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Publication number Priority date Publication date Assignee Title
JPS63204682A (ja) * 1987-02-19 1988-08-24 Nec Corp レ−ザパルス制御方式
US5128949A (en) * 1989-05-31 1992-07-07 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Method and circuit for controlling the evolution time interval of a laser output pulse
US20080273559A1 (en) * 2007-05-04 2008-11-06 Ekspla Ltd. Multiple Output Repetitively Pulsed Laser

Family Cites Families (1)

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Publication number Priority date Publication date Assignee Title
DE102014013567B3 (de) 2014-09-18 2015-10-08 Iai Industrial Systems B.V. Gütegeschaltetes CO2-Laser-Materialbearbeitungssystem mit akustooptischen Modulatoren

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Publication number Priority date Publication date Assignee Title
JPS63204682A (ja) * 1987-02-19 1988-08-24 Nec Corp レ−ザパルス制御方式
US5128949A (en) * 1989-05-31 1992-07-07 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Method and circuit for controlling the evolution time interval of a laser output pulse
US20080273559A1 (en) * 2007-05-04 2008-11-06 Ekspla Ltd. Multiple Output Repetitively Pulsed Laser

Non-Patent Citations (1)

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Title
CHENGHUI H ET AL: "A Q-switched Nd:YAlO"3 laser emitting 1080 and 1342nm", OPTICS COMMUNICATIONS, ELSEVIER, AMSTERDAM, NL, vol. 281, no. 14, 15 July 2008 (2008-07-15), pages 3820 - 3823, XP022699484, ISSN: 0030-4018, [retrieved on 20080411], DOI: 10.1016/J.OPTCOM.2008.03.037 *

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