WO2009037039A1 - Production d'impulsions doubles dans un laser à corps solide monolithique à plusieurs segments à déclenchement passif - Google Patents

Production d'impulsions doubles dans un laser à corps solide monolithique à plusieurs segments à déclenchement passif Download PDF

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Publication number
WO2009037039A1
WO2009037039A1 PCT/EP2008/059787 EP2008059787W WO2009037039A1 WO 2009037039 A1 WO2009037039 A1 WO 2009037039A1 EP 2008059787 W EP2008059787 W EP 2008059787W WO 2009037039 A1 WO2009037039 A1 WO 2009037039A1
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laser
region
laser device
active
regions
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PCT/EP2008/059787
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German (de)
English (en)
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Heiko Ridderbusch
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Robert Bosch Gmbh
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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
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/0627—Construction or shape of active medium the resonator being monolithic, e.g. microlaser
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
    • F02P23/00—Other ignition
    • F02P23/04—Other physical ignition means, e.g. using laser rays
    • 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
    • H01S3/06—Construction or shape of active medium
    • H01S3/07—Construction or shape of active medium consisting of a plurality of parts, e.g. segments
    • 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
    • H01S3/1123—Q-switching
    • H01S3/113—Q-switching using intracavity saturable absorbers
    • 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
    • H01S3/06—Construction or shape of active medium
    • H01S3/0602—Crystal lasers or glass lasers
    • H01S3/0612—Non-homogeneous structure
    • 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
    • H01S3/08086—Multiple-wavelength emission
    • H01S3/0809—Two-wavelenghth emission
    • 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
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
    • H01S3/094076—Pulsed or modulated pumping
    • 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
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
    • H01S3/094096—Multi-wavelength pumping
    • 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
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
    • H01S3/0941—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light of a laser diode
    • H01S3/09415—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light of a laser diode the pumping beam being parallel to the lasing mode of the pumped medium, e.g. end-pumping
    • 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
    • H01S3/10038—Amplitude control
    • H01S3/10046—Pulse repetition rate control
    • 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
    • H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
    • H01S3/16—Solid materials
    • H01S3/1601—Solid materials characterised by an active (lasing) ion
    • H01S3/1603—Solid materials characterised by an active (lasing) ion rare earth
    • H01S3/1611—Solid materials characterised by an active (lasing) ion rare earth neodymium
    • 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
    • H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
    • H01S3/16—Solid materials
    • H01S3/163—Solid materials characterised by a crystal matrix
    • H01S3/164—Solid materials characterised by a crystal matrix garnet
    • H01S3/1643—YAG
    • 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
    • H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
    • H01S3/16—Solid materials
    • H01S3/163—Solid materials characterised by a crystal matrix
    • H01S3/1645—Solid materials characterised by a crystal matrix halide
    • H01S3/1653—YLiF4(YLF, LYF)

Definitions

  • the invention relates to a laser device having at least one passive laser circuit having laser-active solid.
  • the invention further relates to an operating method for a laser device of the aforementioned type in which pumping light is applied to the laser device in order to generate a laser pulse.
  • Such laser devices and operating methods are known and have the disadvantage that they can produce only a very limited temporally short successive laser pulses with substantially the same, relatively large pulse energy, as required in particular for efficient laser ignition of internal combustion engines or the like.
  • a first type of the known laser devices makes it possible to generate highly repetitive laser pulses which, however, each have only a very low pulse energy, so that such systems are not suitable, for example, for laser ignition systems.
  • the laser-active solid has at least a first region and a second region, wherein the first region has a first cross section for the stimulated emission, which is different from a second cross section for the stimulated emission of the second region and / or wherein a first emission wavelength at which the first region stimulates stimulated radiation emitted is different from a second emission wavelength at which the second region stimulates emits radiation.
  • Emission wavelength for the stimulated emission is achieved that the stimulated emission occurring under the application of pump light initially in a first of the two areas is sufficiently large to bleach a saturable absorber of the passive Q-switching and thus enable a laser operation, in which the previously by the optical pumping generated population inversion of the respective first area is reduced in the form of a first laser pulse.
  • the population inversion produced by optical pumping of the second region can then be reduced in the form of a second laser pulse, with the second laser pulse following the first laser pulse very closely in time.
  • the time interval between the two laser pulses generated according to the invention is significantly lower than in the case of a conventional laser system with only one laser-active region.
  • a population inversion in the single laser-active region must first be completely reconstructed-by optical pumping-before a subsequent second laser pulse can be generated.
  • the laser device according to the invention provides for two separate memories in the form of the two different regions, which initially store the pump energy radiated by pump light in the form of a respective population inversion and can deliver it again almost simultaneously in the form of the laser pulses.
  • the time difference between the pulses generated according to the invention depends i.a. from the properties of the passive Q-switching and is preferably less than 100 microseconds.
  • the laser pulses produced according to the invention are particularly suitable for use in ignition systems for internal combustion engines because, on the one hand, a single, first laser pulse can reliably ignite an air / fuel mixture and, on the other hand, the subsequent second laser pulse so closely follows the first laser pulse in time that it is almost completely absorbed by the plasma, which has formed as a result of the irradiation of the first laser pulse.
  • the invention allows the targeted introduction of multiple high-energy laser pulses in the same flame kernel and thereby the overall provision of an increased compared to conventional systems, yet time concentrated amount of ignition energy.
  • more than two different laser-active regions can also be provided, it also being possible to provide a plurality of passive Q-circuits in the laser device, which enable the generation of further, cascaded laser pulses.
  • both regions of the laser-active solid have an ytterbium-doped host material or also a neodymium-doped host material.
  • the two regions may advantageously comprise at least one of the following laser-active materials: Nd: YAG, Nd: YALO, Nd: YLF, Nd: YSGG, Nd: LuAG, Nd: GGG, Nd: GSGG, Nd: KYW, Nd: KGW, Yb: YAG, Yb: KGW, Yb: KYW, Yb: YLF, Yb: NGW, Yb: GGG, Yb: GSGG.
  • the following laser-active materials Nd: YAG, Nd: YALO, Nd: YLF, Nd: YSGG, Nd: LuAG, Nd: GGG, Nd: GSGG, Nd: KYW, Nd: KGW, Yb: YAG, Yb: KGW, Yb: KYW, Yb: YLF, Yb: NGW, Yb: GGG, Yb: GSGG.
  • a very particularly preferred embodiment of the invention provides that the first region comprises Nd: YAG material, and that the second region comprises Nd: YLF material.
  • At least one non-laser-active, in particular undoped, region which on the one hand is used for mechanical spacing, e.g. the sensitive coupling mirror and output mirror of the laser device of areas with laser-active material is used, which heats up accordingly when exposed to pump light.
  • the sensitive coupling mirror and output mirror of the laser device of areas with laser-active material is used, which heats up accordingly when exposed to pump light.
  • the laser device can advantageously be monolithic, that is, all the laser-active regions and optionally the passive Q-switching and the undoped regions are integrally formed.
  • the laser device according to the invention may also have a plurality of discrete components.
  • a saturable absorber of the passive Q-switching is arranged between different laser-active regions and / or between a laser-active region and an undoped region.
  • This variant of the invention advantageously enables an individual direct irradiation of pumping light into the respective laser-active region and a temporary optical separation of the regions from one another by the Q-switching. That is, the pump light provided for a first region does not first have to pass through another region before it can act on the first region.
  • a particularly preferred variant of the invention provides that the first and second cross section for the stimulated emission of the regions at most by about 60% from each other differ.
  • the first and second emission wavelengths of the regions may differ by up to about 10%.
  • an operating method according to claim 11 is given.
  • the inventive method provides that in the laser device according to the invention both areas are optically pumped to allow the generation of a plurality of temporally close successive laser pulses.
  • the time interval between a first pump start time and a second pump start time at which the application of pump light is started in each case and / or further parameters of the pumping process in question, in particular an intensity and / or a time profile of the pump light used be selected as a function of a desired time interval between two laser pulses, which are generated as a result of the application of the areas with the pump light, and / or in dependence of the desired pulse energy.
  • the laser device according to the invention can be advantageously used to construct a laser-based ignition device for an internal combustion engine of a motor vehicle or a stationary motor, or generally for all other applications in which laser pulses with high pulse energy and pulse frequency must be provided.
  • FIG. 1 shows a first embodiment of the laser device according to the invention
  • FIG. 2a to 2c show a time course of different operating variables of the laser device according to the invention according to FIG. 1, FIG.
  • FIGS. 3a to 3c show different variants of a second embodiment of the laser device according to the invention
  • FIG. 5 shows an ignition device for an internal combustion engine with the invention
  • FIG. 1 schematically shows a first embodiment of the laser device 26 according to the invention.
  • the laser device 26 has a laser-active solid 44, to which a passive Q-switching 46, also referred to as Q-switch, is optically arranged downstream.
  • the laser-active solid 44 forms here, together with the passive Q-switching circuit 46 and the coupling mirror 42 arranged on the left thereof in FIG. 1 and the output mirror 48, a laser oscillator whose Oscillation behavior of the passive Q-switching circuit 46 depends and thus at least indirectly controllable in a conventional manner.
  • the laser device according to the invention or the laser-active solid 44 is acted upon by the coupling mirror 42 with pumping light 60a, 60b which is generated in a remotely located pumping light source 30 (FIG. 5) and by the optical waveguide device 28 to the laser device 26 is transmitted.
  • the pumping light 60a, 60b excites electrons in the laser-active solid 44 and thus leads to a known population inversion.
  • the coupling mirror 42 has a relatively large transmission coefficient for the pumping light 60a, 60b.
  • the passive Q-switching circuit 46 While the passive Q-switching circuit 46 has its basic state in which it has a relatively low transmission coefficient, laser operation is avoided in the laser-active solid 44 or in the solid 44, 46 bounded by the coupling-in mirror 42 and the output mirror 48. However, as the pumping time increases, that is to say during continued application of the pumping light 60a, 60b, the radiation intensity in the laser oscillator 42, 44, 46, 48 also increases, so that the passive Q-switching circuit 46 finally fades. That is, its transmission coefficient increases, and laser operation in the laser oscillator 42, 44, 46, 48 begins.
  • the laser pulse 24 is then decoupled from the laser oscillator 42, 44, 46, 48 by the outcoupling mirror 48 arranged on the right in FIG. 1 and is for example used in a laser-based ignition device 27 (FIG. 5) for an internal combustion engine 10 for igniting a combustion chamber 14 the internal combustion engine 10 located air / fuel mixture usable.
  • the laser pulse 24 can be coupled into the combustion chamber 14 of the internal combustion engine 10, for example, by a corresponding optical fiber device or directly by a combustion chamber window arranged downstream of the output mirror 48.
  • a focusing optics for focusing the laser pulse 24 on an ignition point may possibly also be present, in particular also integrally formed with the combustion chamber window.
  • the laser-active solid 44 of the laser device 26 has at least two regions 44a, 44b of laser-active material which have mutually different cross sections ⁇ a, ⁇ b for the stimulated emission and / or different emission wavelengths at which stimulated radiation is emitted.
  • the stimulated emission occurring under the application of pumping light 60a, 60b initially becomes sufficiently large in the first region 44a to form a saturable absorber of the passive one Ruscrien 46 bleach and thus to allow laser operation in which the previously generated by the optical pumping inversion of the respective first region 44a is degraded in the form of a first laser pulse.
  • the population inversion produced by the optical pumping of the second region 44b until then can then be reduced in the form of a second laser pulse, the second laser pulse following the first laser pulse very closely in time.
  • the time interval between the two laser pulses generated according to the invention is significantly lower than in the case of a conventional laser system with only one laser-active region.
  • a population inversion in the single laser-active region must first be completely reconstructed-by optical pumping-before a subsequent second laser pulse can be generated.
  • the laser device 26 according to the invention provides two separate memories in the form of the two different regions 44a, 44b, which initially store the pump energy irradiated by the pump light 60a, 60b in the form of a respective population inversion and release it again almost simultaneously in the form of the laser pulses.
  • the time difference between the pulses generated according to the invention depends i.a. from the properties of the passive Q 46.
  • sufficiently high pump energy can also be stored in the pumped regions 44a, 44b in order to generate high-energy laser pulses, e.g. for an ignition system of an internal combustion engine to produce.
  • FIGS. 2a, 2b, 2c illustrate the operating method according to the invention described above.
  • FIG. 2 a shows the time profile of the transmission coefficient T of the saturable absorber contained in the passive Q-switching circuit 46 (FIG. 1).
  • the optical pumping of the laser-active material of the first area 44a begins first with the pumping light 60a (FIG 1).
  • a corresponding increase in the inversion density Na in the region 44a can also be seen from FIG. 2b.
  • the optical pumping of the laser-active material of the second region 44b begins with the pump light 60b (FIG. 1) provided for this purpose at the second pump start time t ⁇ 'according to FIG. 2c.
  • a corresponding increase in the inversion density Nb in the region 44b can be seen in FIG. 2c.
  • the transmission coefficient T maintains its output value TO until approximately the time t1. From the time t1, the intensity of the stimulated emitted radiation in the first region 44a is sufficiently large to cause the saturable absorber to fade and thus to increase the transmission coefficient T (FIG. 2a), so that the inversion density Na degrades as shown in FIG. 2b which results in the generation of the first laser pulse 24 1 at time t2.
  • the inversion density Nb which has since been built up in the second area 44b, can also be reduced, which leads to the generation of the second laser pulse 24 2 at the time t3.
  • the time interval t3 - 12 may advantageously be less than about 100 ⁇ s, for example.
  • the inventively generated laser pulses 24 1, 24 2 are due to their high pulse energy and their short time interval t3 - 12 in a special way for use in ignition systems for internal combustion engines, because on the one hand already the first laser pulse 24 1 safe firing of an air / fuel mixture can cause, and because on the other hand, the subsequent, second laser pulse 24 2 temporally so close to the first laser pulse 24 1 follows that it is almost completely absorbed by the plasma, which has formed as a result of the irradiation of the first laser pulse 24 1.
  • the invention allows the targeted introduction of multiple high-energy laser pulses 24 1, 24 2 in the same flame kernel and thereby the overall provision of an increased compared to conventional systems, yet time concentrated ignition energy.
  • pumping light 60a, 60b of the same wavelength can be provided for both regions 44a, 44b, for example.
  • the optical pumping of the two regions 44a, 44b can also be carried out such that For example, only a single pump start time t ⁇ results, from which both areas 44a, 44b are optically pumped.
  • the first region 44a has a material which has a larger stimulated emission cross-section ⁇ a than the material of the second region 44b. Therefore, emissions emanating from the first region 44a cause the described fading of the saturable absorber of the passive Q-switch 46.
  • the materials used here emit laser light of the same or similar wavelength.
  • FIG. 3 a shows an embodiment of the invention comparable to the laser device 26 already illustrated in FIG.
  • the laser-active material of the first region 44a is a neodymium-doped
  • FIG. 3b An alternative embodiment of the laser device 26 according to the invention is shown in FIG. 3b.
  • the laser device 26 shown in FIG. 3b has a different sequence of the regions 44a, 44b.
  • the second region 44b is now arranged directly downstream of the coupling-in mirror 42, and the second region 44b is followed, according to FIG. 3b, by the first region 44a.
  • FIG. 3c Another very advantageous variant of the invention is illustrated in FIG. 3c.
  • the passive Q-switching 46 is located between the regions 44a, 44b.
  • This configuration advantageously makes it possible for the pumping light 60a, 60b provided for the respective region 44a, 44b to be irradiated longitudinally, in particular on opposite end faces of the laser device 26, such that the respective region 44a, 44b is directly illuminated by the pump light 60a, 60b associated therewith can be applied.
  • a corresponding pumping light supply is symbolized in Figure 3c by the arrows 60a, 60b.
  • FIG. 4a shows a further advantageous embodiment of the laser device 26 according to the invention, in which, in addition to the regions 44a, 44b of laser-active material, an undoped region 50a is also provided, which accordingly is not laser-active.
  • an undoped region 50a into the laser device 26 according to the invention advantageously provides, firstly, a degree of freedom with regard to the geometric length of the device 26 to be achieved.
  • the pulse duration of the generated laser pulses 24 1, 24 2 is directly associated with this in a manner known to those skilled in the art.
  • a further advantage of the undoped region 50a between the coupling-in mirror 42 and the second region 44b is that the region 44b which heats up under the influence of pumping light 60b is spaced from the coupling-in mirror 42 by the thickness of the undoped region 50a, for example as a thin dielectric layer is formed and, accordingly, is sensitive to high temperatures.
  • the undoped region 50a may advantageously be arranged such that it effects an at least partial thermal decoupling or an influencing of the heat conditions in the laser device 26.
  • FIG. 4b shows a further advantageous variant of the laser device 26 according to the invention, in which two undoped regions 50a, 50b are provided in such a way that they are optically arranged upstream and downstream of the second laser-active region 44b.
  • FIG. 4 c shows a further variant of the invention, in which a total of three undoped regions 50 a, 50 b, 50 c are provided.
  • a saturable absorber provided in the passive Q-switching circuit 46 of the laser device 26 according to the invention can comprise, for example, Cr 4+ or V 3+ -doped garnets such as YAG, GGG, GSGG, LuAG, YSGG and have an initial transmission TO (FIG is less than 5%, and less than 99.5%.
  • the coupling-in mirror 42 is for example highly transparent for the wavelength (n) of the pumping light 60a, 60b, which for the presently used Nd-doped material is between about 780 nm to about 820 nm and about 880 nm to about 885 nm be.
  • pumped light having a wavelength of about 940 nm and / or from about 970 nm to about 980 nm is used to form the regions 44a, 44b with Yb-doped material.
  • the coupling mirror 42 is also highly reflective for the wavelength (s) of the generated laser pulses 24 1, 24 2, which are between about 1020 nm and about 1080 nm. Accordingly, for this wavelength (s), the output mirror 48 is partially reflective (between about 15% and about 99.5% reflectivity) so that the generated laser pulses 24 1, 24 2 can exit the laser device 26. Furthermore, the output mirror 48 is possibly highly reflective for the wavelength (n) of the pumping light 60a, 60b used.
  • the invention it is also conceivable to integrate a plurality of saturable absorbers (not shown) into the laser device 26 in order to realize the functionality of the passive Q-switch 46.
  • the saturable absorbers may be provided at different locations of the laser device 26, the aggregate initial transmission TO again corresponding to the initial transmission specified above by way of example.
  • FIG. 5 schematically shows an ignition device 27 for an internal combustion engine 10, in which the laser device 26 according to the invention and the above-described operating method according to the invention are used to generate laser pulses 24 and 24 1, 24 2, respectively, for igniting one in the combustion chamber 14 of the internal combustion engine 10 located air / fuel mixture serve.
  • the internal combustion engine 10 comprises a plurality of cylinders, of which only one is designated by the reference numeral 12 in FIG.
  • a combustion chamber 14 of the cylinder 12 is limited by a piston 16.
  • Fuel enters the combustion chamber 14 directly through an injector 18, which is connected to a designated also as a rail or common rail fuel pressure accumulator 20.
  • injected fuel 22 is ignited by means of the above-described high-energy laser pulse 24 or 24 1, 24 2, which is emitted from the laser device 26 of the ignition device 27 according to the invention in the combustion chamber 14, see. also Figure 2b, 2c.
  • the laser device 26 via a light guide device 28 with the
  • Pump light 60a, 60b ( Figure 1), which is provided by the pumping light source 30.
  • the pump light source 30 is controlled by a control and regulating device 32, which also controls the injector 18.
  • the pumping light source 30 may comprise one or more semiconductor diodes, not shown, which emit pump light 60a, 60b of corresponding intensity as a function of a control current via the optical waveguide device 28 to the laser device 26.
  • semiconductor Laser diodes and other small-sized pumping light sources are preferably used for use in the automotive sector, for the operation of the ignition device 27 according to the invention, in principle, any type of pumping light source can be used.
  • the laser device 26 according to the invention can be advantageously used to construct a laser-based ignition device 27 for an internal combustion engine of a motor vehicle or a stationary motor, or generally for all other applications in which laser pulses 24 1, 24 2 must be provided with high pulse energy and temporally in short succession.
  • the materials for the laser-active regions 44a, 44b are selected such that their cross-sections ⁇ a, ⁇ b differ slightly for the stimulated emission, preferably by a maximum of up to 60%. Alternatively or additionally, a corresponding difference in emission wavelengths for stimulated emitted radiation of up to about 10% may be provided.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Electromagnetism (AREA)
  • Optics & Photonics (AREA)
  • Plasma & Fusion (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Lasers (AREA)

Abstract

La présente invention concerne un dispositif laser (26) comprenant au moins un corps solide (44) à action laser à déclenchement passif (46). Selon l'invention, le corps solide (44) à action laser présente au moins une première zone (44a) et une deuxième zone (44b), la première zone (44a) présentant une première section active (σa) destinée à l'émission stimulée, qui est différente d'une deuxième section active (σb) destinée à l'émission stimulée de la deuxième zone (44b); et/ou une première longueur d'onde d'émission pour laquelle la première zone (44a) émet un rayonnement sous l'effet de la stimulation, étant différente d'une deuxième longueur d'onde pour laquelle la deuxième zone (44b) émet un rayonnement sous l'effet de la stimulation. De cette manière, des impulsions laser (24_1, 24_2) fortement énergétiques qui se succèdent très rapidement dans le temps peuvent être produites en soumettant le dispositif laser (26) à une lumière de pompage.
PCT/EP2008/059787 2007-09-14 2008-07-25 Production d'impulsions doubles dans un laser à corps solide monolithique à plusieurs segments à déclenchement passif WO2009037039A1 (fr)

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DE200710044008 DE102007044008A1 (de) 2007-09-14 2007-09-14 Lasereinrichtung und Betriebsverfahren hierfür
DE102007044008.3 2007-09-14

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DE102009028337A1 (de) * 2009-08-07 2011-02-10 Robert Bosch Gmbh Laserzündeinrichtung und Betriebsverfahren hierfür
DE102010008170A1 (de) * 2010-02-16 2011-08-18 Du, Keming, Dr., 52078 Optische Oszillator/Verstärker-Anordnungen
DE102013221553A1 (de) * 2013-10-23 2015-04-23 Robert Bosch Gmbh Laserzündsystem

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US5756924A (en) * 1995-09-28 1998-05-26 The Regents Of The University Of California Multiple laser pulse ignition method and apparatus
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WO2006102084A1 (fr) * 2005-03-18 2006-09-28 Pavilion Integration Corporation Microlaser monolithique a combinaison intracavite de faisceaux et melange de frequence somme et de frequence difference
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US5756924A (en) * 1995-09-28 1998-05-26 The Regents Of The University Of California Multiple laser pulse ignition method and apparatus
US20040218652A1 (en) * 2003-05-01 2004-11-04 Raytheon Company Eye-safe solid state laser system and method
WO2006102084A1 (fr) * 2005-03-18 2006-09-28 Pavilion Integration Corporation Microlaser monolithique a combinaison intracavite de faisceaux et melange de frequence somme et de frequence difference
DE102006031947A1 (de) * 2006-07-11 2008-01-17 Robert Bosch Gmbh Lasereinrichtung

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