EP1861902A1 - Dual wavelength laser device, and system comprising same - Google Patents

Dual wavelength laser device, and system comprising same

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Publication number
EP1861902A1
EP1861902A1 EP06726016A EP06726016A EP1861902A1 EP 1861902 A1 EP1861902 A1 EP 1861902A1 EP 06726016 A EP06726016 A EP 06726016A EP 06726016 A EP06726016 A EP 06726016A EP 1861902 A1 EP1861902 A1 EP 1861902A1
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EP
European Patent Office
Prior art keywords
level
laser
medium
laser beam
crystal
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.)
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EP06726016A
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German (de)
French (fr)
Inventor
Thierry Georges
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OXXIUS
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OXXIUS
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Classifications

    • 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
    • H01S3/108—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 non-linear optical devices, e.g. exhibiting Brillouin or Raman scattering
    • 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
    • H01S3/05—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
    • 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
    • H01S2302/00—Amplification / lasing wavelength
    • 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
    • H01S3/0604—Crystal lasers or glass lasers in the form of a plate or disc
    • 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
    • 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
    • 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
    • H01S3/1671—Solid materials characterised by a crystal matrix vanadate, niobate, tantalate
    • H01S3/1673—YVO4 [YVO]

Definitions

  • Tro-wavelength laser device and system comprising such a device.
  • the present invention relates to a laser device with two wavelengths or two frequencies. It relates more particularly to the generation of a laser beam from a sum of two different frequencies.
  • the wavelengths obtained by solid state lasers are basically in the near infrared.
  • Such a laser comprises an amplifying medium (solid-state-doped solid state laser) associated with a non-linear crystal converting a fundamental near-infrared signal emitted by the amplifying medium into a visible signal by doubling the frequency of the fundamental.
  • an amplifying medium solid-state-doped solid state laser
  • a non-linear crystal converting a fundamental near-infrared signal emitted by the amplifying medium into a visible signal by doubling the frequency of the fundamental.
  • some of the visible wave lengths do not correspond to a frequency doubling of a transition of a rare earth.
  • Frequency doubling makes it possible, for example, to obtain a wave at 532 nm (1064 nm doubled, Nd: YAG or Nd: YVO 4 ), or for example at 514 nm (1029 nm doubled / Yb: YAG).
  • the wavelengths not obtained by doubling frequency can however be approximated by the sum of two frequencies.
  • 488 nm can be approximated by the sum of 1064 nm and 915 nm (two transitions of Nd: YV0 4 ) or by the sum of 1053 nm and 907 nm (two transitions of Nd / YLF).
  • WO 02/103863 proposes to mix the emission of a three-level laser with that of a four-level laser, possibly including a frequency doubling crystal within the four-level laser cavity.
  • the non-linear crystal is explicitly out of the three-level laser cavity.
  • this arrangement has the disadvantage of mixing at least one low-power laser signal and thus greatly reducing the nonlinear conversion efficiency or requiring a non-linear crystal of high efficiency, the latter being generally very expensive.
  • this arrangement is rather complex because it requires two pumps, two pump injections and multiplexing of the four-level laser pump with the three-level laser signal.
  • the present invention aims to overcome the aforementioned drawbacks by proposing a new laser device simple to implement and inexpensive.
  • a laser device comprising: a three-level amplifying medium capable of emitting a first fundamental wavelength laser beam;
  • a four-level amplifying medium capable of emitting a second laser beam of fundamental wavelength
  • a nonlinear crystal capable of mixing the first and second laser beams and generating a third beam whose frequency is the sum of the frequencies of said first and second laser beams.
  • the three-level amplifying medium and at least one non-linear crystal constitute a resonant cavity for the first laser beam
  • the four-level amplifying medium and at least the non-linear crystal constitute a resonant cavity for the second laser beam
  • the two amplifying media and the non-linear crystal forming a linear cavity
  • the two laser beams oscillate through the non-linear crystal.
  • the mixing takes place between two beams of high power.
  • the nonlinear crystal can be of average efficiency, thus inexpensive.
  • two wavelengths coming from two different emission bands can oscillate simultaneously, since at least one of the two laser beams (or wavelength) is provided with an exclusive gain zone. .
  • the two amplifying media and the non-linear crystal constitute a monolithic resonant linear cavity.
  • a system comprising a laser device as described above and a pumping means consisting of a single laser diode.
  • the pumping means emits a laser beam able to excite both the three-level amplifying medium and the four-level amplifying medium.
  • a portion of the pump is absorbed by the three-level amplifying medium and the pump residue is absorbed by the four-level amplifying medium.
  • This requires joining the two amplifying media, the cavity ending in the non-linear crystal.
  • the three-level amplifying medium and the non-linear crystal are placed side by side on two opposite sides of the four-level amplifying medium, respectively.
  • the output mirrors of the two lasers that is to say the two amplifying media with three and four levels, are then on the output of the nonlinear crystal. Furthermore, the focus of the pump is optimized so that the four-level amplifying medium is pumped by the laser diode and the three-level laser emission.
  • the pumping means emits a laser beam able to excite only the three-level amplifying medium.
  • the latter is fully pumped by the emission of the laser at three levels.
  • the three-level amplifying medium and the four-level amplifying medium are advantageously constituted by an identical rare earth and crystal. From the thermal point of view, the second variant is probably better than the previous one because the quantum defect for the four-level laser is lower.
  • the adaptation between the pump and the signal for the four-level laser is perfect. This also makes it possible to sandwich the doubling crystal and to transfer the dielectric treatments only to the laser crystals, which corresponds to an inexpensive treatment.
  • the two amplifying media are contiguous on two opposite sides of the non-linear crystal, which is preferably a birefringent crystal.
  • the nonlinear crystal being inserted between the two amplifying media, the walls of the various elements of the device are treated in such a way that:
  • the input of the three-level amplifier medium and the output of the four-level amplifier medium comprise a reflective dielectric treatment for said first laser beam
  • the output of the three-level amplifier medium and the output of the four-level amplifier medium comprise a reflective dielectric treatment for said second laser beam
  • the output of the three-level amplifier medium and the input of the four-level amplifier medium comprise a transmission dielectric processing for said first laser beam
  • the output of the four-level amplifier medium comprises a dielectric transmission processing for said third laser beam.
  • the two amplifying media and the non-linear crystal constitute a resonant linear cavity for the first laser beam.
  • the four-level amplifying medium and the non-linear crystal constitute a resonant linear cavity for the second laser beam.
  • the population inversion necessary for the oscillation of a three-level laser is greater than that required for a four-level laser (mirroring comparable mirrors).
  • the population inversion no longer increases, which makes it impossible to reach the oscillation threshold of the three-level laser.
  • the pump excites the exclusive gain medium of the three-level laser.
  • Population inversion increases to the threshold of the three-level laser. Beyond the threshold of this three-level laser, the second gain medium (laser at four levels) begins to be excited by the partial absorption of the three-level laser emission. The increase of the pump power then makes it possible to reach the threshold of the four-level laser.
  • the power distribution between the three- and four-level laser emissions follows the distribution of the three-level emission losses out of and into the four-level laser amplifying medium.
  • the two powers are equal when the absorption of the three-level laser emission in the four-level laser amplifier is equal to the other losses, ie the non-resonant losses and the doubling losses.
  • the four-level amplifying medium then has an absorption of the order of 1% at the wavelength of the three-level laser.
  • two strong laser beams are obtained because the nonlinear crystal is located inside the two laser cavities (resonant cavities for the first and second laser beams).
  • Another advantage of an arrangement according to the present invention is that the transverse modes of the amplifying media have a similar transverse size, which optimizes the conversion efficiency.
  • FIG. 1 illustrates a laser device forming a monolithic linear cavity according to the invention, the nonlinear crystal being disposed between the two amplifying media;
  • FIG. 2 is a graph illustrating schematically the evolution of the excitation and power levels of the two amplifying media of the device according to FIG. 1; and FIG. 3 illustrates a laser device according to the present invention with the four-level amplifying medium disposed between the three-level amplifying medium and the nonlinear crystal.
  • a laser device 1 according to the invention forming a linear cavity. This laser device is pumped by a single laser diode 2. The laser beam emitted by the laser diode 2 is collinear with the device.
  • the laser device 1 consists of a nonlinear crystal 4 coupled between, input, a three-level amplifier medium 3 and, at the output, a four-level amplifier medium 5.
  • the three-level amplifier medium 3 is a laser crystal emitting around 915 nm such as Nd: YVO 4 and receiving the beam emitted by the laser diode.
  • the sole objective of the laser beam emitted by the laser diode 2 is the excitation of this three-level amplifying medium 3.
  • the non-linear crystal consists of KNbO 3 potassium niobate.
  • the four-level amplifying medium 5 is a laser crystal emitting around 1064 nm such as Nd: YVO 4 .
  • the device 1 is designed to output a laser beam 14 at 491 nm from the summation of the two laser beams of the two amplifying media.
  • the cavity at 915 nm is closed by the dielectric treatments HR915, ie reflecting at 915 nm, at the input 8 of the first amplifier crystal 3 and at the output 11 of the second amplifier crystal 5.
  • the laser beam 6 at 915nm is confined between walls 8 and 11.
  • the cavity at 1064 nm is closed by the dielectric treatments HR1064, that is to say reflective at 1064 nm / output 9 of the first amplifier crystal 3 and output 11 of the second amplifier crystal.
  • the laser beam 7 at 1064 nm is confined between the walls 9 and 11.
  • the dielectric treatment at the output 9 of the first amplifier crystal 3 is of the HT915 type, that is to say transmitter at 915 nm.
  • the dielectric treatment at the output 11 of the second amplifier crystal 5 is of type HT491 in order to let the blue emission of the laser beam 14 to 491 nm,
  • each cavity at 915 nm and at 1064 nm comprises the non-linear crystal.
  • the table below shows the refractive indices determined in the nonlinear crystal doubler KNbO 3 of the device 1 according to the invention, at 303K for the wavelengths 915nm, 1064nm and 491.7nm:
  • n (915) + n (1064) 2n c (491.7), which corresponds to a non-critical phase matching type I.
  • the device 1 uses the Nd: YVO 4 with a 915nm emission in the three-level laser, and a 1064nm emission in the four-level laser. Nd can also be used. 1 GdVO 4 with a 912nm emission in the three-level laser, and a 1062.6nm emission in the four-level laser.
  • FIG. 2 shows the evolution of the excitation and power levels of the two amplifying media 3 and 5.
  • the pump 2 excites (excitation level 1) exclusively the three-level amplifying medium 3.
  • the oscillation threshold of the latter is reached (1 on the abscissa in FIG. 2)
  • the laser power emitted makes it possible to excite ( excitation level 2) the four-level amplifier medium 5.
  • the latter then emits a laser power when its oscillation threshold is reached (1.5 on the abscissa).
  • Figure 3 is shown a variant 13 of the device according to the present invention. Both amplifying media 3 and 5 are directly coupled to each other.
  • the non-linear crystal 4 is coupled to the four-level amplifier medium 5 so that the emissions of the three-level and four-level lasers are superimposed.
  • the device 13 emits a laser beam 15 at the output of the nonlinear crystal.
  • the 915nm cavity is closed by the dielectric treatments HR.915, ie reflecting at 915nm, at the input 8 of the first amplifier crystal 3 and at the output 12 of the nonlinear crystal 4.
  • the laser beam 6 at 915 nm is confined between the walls 8 and
  • the cavity at 1064 nm is closed by the dielectric treatments HR.1064, that is, reflecting at 1064 nm, at the input 10 of the second amplifier crystal 5 and at the output 12 of the nonlinear crystal 4.
  • the laser beam 7 to 1064nm is confined between walls 10 and 12.

Landscapes

  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Optics & Photonics (AREA)
  • Nonlinear Science (AREA)
  • Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
  • Lasers (AREA)

Abstract

The invention concerns a laser device (1, 13) comprising: a three-level amplifying medium (3) adapted to emit a first laser beam (3) of fundamental wavelength; a four-level amplifying medium (5) adapted to emit a second laser beam (7) of fundamental wavelength; a non-linear crystal (4) adapted to mix the first and second beams and to generate a third beam (14, 15) whereof the frequency is the sum of the frequencies of said first and second laser beams. Said device is characterized in that the three-level amplifying medium (3) and at least the non-linear crystal (4) form a resonant cavity for the first laser beam (6), and the four-level amplifying medium (5) and at least the non-linear crystal (4) form a resonant cavity for the second laser beam (7), the two amplifying media and the non-linear crystal forming a linear cavity.

Description

" Dispositif laser à deux longueurs d'onde, et système comprenant un tel dispositif." "Two-wavelength laser device, and system comprising such a device."
La présente invention se rapporte à un dispositif laser à deux longueurs d'onde ou deux fréquences. Elle concerne plus particulièrement la génération d'un faisceau laser à partir d'une somme de deux fréquences différentes.The present invention relates to a laser device with two wavelengths or two frequencies. It relates more particularly to the generation of a laser beam from a sum of two different frequencies.
D'une façon générale, les longueurs d'ondes obtenues par des lasers à solide sont fondamentalement dans le proche infrarouge. Pour obtenir des longueurs d'onde dans le visible plusieurs techniques sont possibles dont notamment celle du laser doublé intra-cavité. Un tel laser comporte un milieu amplificateur (laser à solide à base d'un cristal dopé par une terre rare) associé à un cristal non-linéaire convertissant un signal fondamental proche infrarouge émis par le milieu amplificateur en un signal visible par doublage de la fréquence du fondamental. Cependant/ certaines longueurs d'onde du visible ne correspondent pas à un doublage de fréquence d'une transition d'une terre rare. Le doublage de fréquence permet d'obtenir par exemple une onde à 532 nm (1064 nm doublé, Nd :YAG ou Nd :YVO4), ou par exemple à 514 nm (1029 nm doublé/ Yb :YAG). Les longueurs d'ondes non obtenues par doublage de fréquence peuvent cependant être approchées par la somme de deux fréquences. Par exemple, 488 nm peut être approchée par la somme de 1064 nm et 915 nm (deux transitions de Nd :YV04) ou par la somme de 1053 nm et 907 nm (deux transitions de Nd/YLF).In general, the wavelengths obtained by solid state lasers are basically in the near infrared. To obtain wavelengths in the visible several techniques are possible, including that of the lined laser intra-cavity. Such a laser comprises an amplifying medium (solid-state-doped solid state laser) associated with a non-linear crystal converting a fundamental near-infrared signal emitted by the amplifying medium into a visible signal by doubling the frequency of the fundamental. However / some of the visible wave lengths do not correspond to a frequency doubling of a transition of a rare earth. Frequency doubling makes it possible, for example, to obtain a wave at 532 nm (1064 nm doubled, Nd: YAG or Nd: YVO 4 ), or for example at 514 nm (1029 nm doubled / Yb: YAG). The wavelengths not obtained by doubling frequency can however be approximated by the sum of two frequencies. For example, 488 nm can be approximated by the sum of 1064 nm and 915 nm (two transitions of Nd: YV0 4 ) or by the sum of 1053 nm and 907 nm (two transitions of Nd / YLF).
Le principe de la somme de fréquence dans le niobate de potassium KNbO3 a déjà été énoncé dans un premier article : « Efficient intracavity sum-frequency génération of 490nm radiation by use of potassium niobate », S. Shichijyo et a!., Opt. Lett. 19, p.1022 (1994). Dans cet article, l'émission continue d'un laser Ti :saphir autour de 910 nm est mélangée à l'émission continue à 1064 nm d'un laser Nd :YV04 contenant un cristal de niobate de potassium. La présence intra-cavité du cristal non linéaire augmente fortement la puissance à 1064 nm (16W pour 400 mW de pompe). En revanche, l'émission du laser Ti :saphir est faible (typiquement 100 mW), ce qui limite la puissance émise à 490 nm.The principle of the frequency sum in KNbO 3 potassium niobate has already been stated in a first article: "Efficient intracavity sum-frequency generation of 490 nm of radiation of potassium niobate use", S. Shichijyo et al., Opt. Lett. 19, p.1022 (1994). In this article, the continuous emission of a Ti: sapphire laser around 910 nm is mixed with the 1064 nm continuous emission of an Nd: YVO 4 laser containing a potassium niobate crystal. The intra-cavity presence of the non-linear crystal greatly increases the power at 1064 nm (16W for 400 mW of pump). On the other hand, the emission of the Ti: sapphire laser is low (typically 100 mW), which limits the power emitted at 490 nm.
On connaît également un second article : « All-solid-state continuous- wave doubly résonant' all-intracavity sum-frequency mixer », Hanno M. Kretshmann et al., Optics Letters Lett Vol 22, No 19, October 1, 1997. Les auteurs décrivent un disposition pour sommer deux fréquences de façon à obtenir un signal émis dans le rouge autour de 620nm. Pour ce faire, on utilise deux lasers à quatre niveaux de fréquence de résonance respectivement de 1080nm et 1444nm. On inclut un milieu non linéaire dans la cavité résonante de chaque laser à quatre niveaux. Un inconvénient de ce dispositif est donc l'utilisation de deux lasers à quatre niveaux, ce qui nécessite la mise en œuvre de deux pompes, une pompe pour chaque laser à quatre niveaux.A second article is also known: "All-solid-state continuous-wave doubly resonant ' all-intracavity sum-frequency mixer," Hanno M. Kretshmann et al., Optics Letters Lett Vol 22, No 19, October 1, 1997. The authors describe a provision for summing two frequencies so as to obtain a signal emitted in the red around 620 nm. To do this, two lasers with four resonance frequency levels of 1080 nm and 1444 nm respectively are used. A nonlinear medium is included in the resonant cavity of each four-level laser. A disadvantage of this device is the use of two lasers at four levels, which requires the implementation of two pumps, a pump for each four-level laser.
Le document WO 02/103863 propose de mélanger l'émission d'un laser trois niveaux avec celle d'un laser à quatre niveaux, en incluant éventuellement un cristal doubleur de fréquence à l'intérieur de Ia cavité du laser à quatre niveaux. Le cristal non linéaire est explicitement sorti de la cavité du laser à trois niveaux. Comme dans Ie premier article, cet arrangement a l'inconvénient de mélanger au moins un signal laser de faible puissance et donc de réduire fortement l'efficacité de conversion non linéaire ou de nécessiter un cristal non linéaire de forte efficacité, ce dernier étant en général très onéreux. D'autre part, cet arrangement est plutôt complexe, car il nécessite deux pompes, deux injections de pompe et le multiplexage de la pompe du laser à quatre niveaux avec le signal du laser à trois niveaux. La présente invention a pour but de remédier aux inconvénients précités en proposant un nouveau dispositif laser simple à mettre en œuvre et peu onéreux.WO 02/103863 proposes to mix the emission of a three-level laser with that of a four-level laser, possibly including a frequency doubling crystal within the four-level laser cavity. The non-linear crystal is explicitly out of the three-level laser cavity. As in the first article, this arrangement has the disadvantage of mixing at least one low-power laser signal and thus greatly reducing the nonlinear conversion efficiency or requiring a non-linear crystal of high efficiency, the latter being generally very expensive. On the other hand, this arrangement is rather complex because it requires two pumps, two pump injections and multiplexing of the four-level laser pump with the three-level laser signal. The present invention aims to overcome the aforementioned drawbacks by proposing a new laser device simple to implement and inexpensive.
On atteint au moins l'un des objectifs précités avec un dispositif laser comprenant : - un milieu amplificateur à trois niveaux apte à émettre un premier faisceau laser de longueur d'onde fondamentale;At least one of the aforementioned objectives is achieved with a laser device comprising: a three-level amplifying medium capable of emitting a first fundamental wavelength laser beam;
- un milieu amplificateur à quatre niveaux apte à émettre un second faisceau laser de longueur d'onde fondamentale;a four-level amplifying medium capable of emitting a second laser beam of fundamental wavelength;
- un cristal non-linéaire apte à mélanger les premier et second faisceaux laser et à générer un troisième faisceau dont la fréquence est la somme des fréquences desdits premier et second faisceaux laser.a nonlinear crystal capable of mixing the first and second laser beams and generating a third beam whose frequency is the sum of the frequencies of said first and second laser beams.
Selon l'invention, Ie milieu amplificateur à trois niveaux et au moins le cristal non-linéaire constituent une -cavité résonante pour le premier faisceau laser, et le milieu amplificateur à quatre niveaux et au moins le cristal non- linéaire constituent une cavité résonante pour le second faisceau laser; les deux milieux amplificateurs et le cristal non-linéaire formant une cavité linéaire.According to the invention, the three-level amplifying medium and at least one non-linear crystal constitute a resonant cavity for the first laser beam, and the four-level amplifying medium and at least the non-linear crystal constitute a resonant cavity for the second laser beam; the two amplifying media and the non-linear crystal forming a linear cavity.
Avec le dispositif selon l'invention, les deux faisceaux laser oscillent à travers le cristal non linéaire. Le mélange s'effectue entre deux faisceaux de forte puissance. Contrairement au système de l'art antérieur, le cristal non- linéaire peut être d'efficacité moyenne, donc peu onéreux.With the device according to the invention, the two laser beams oscillate through the non-linear crystal. The mixing takes place between two beams of high power. Unlike the system of the prior art, the nonlinear crystal can be of average efficiency, thus inexpensive.
Avec un tel dispositif selon l'invention, deux longueurs d'onde provenant de deux bandes d'émissions différentes peuvent osciller simultanément, car on prévoit pour au moins un des deux faisceaux laser (ou longueur d'onde), une zone de gain exclusive.With such a device according to the invention, two wavelengths coming from two different emission bands can oscillate simultaneously, since at least one of the two laser beams (or wavelength) is provided with an exclusive gain zone. .
De préférence, les deux milieux amplificateurs et le cristal non-linéaire constituent une cavité linéaire résonante monolithique.Preferably, the two amplifying media and the non-linear crystal constitute a monolithic resonant linear cavity.
Suivant un autre aspect de l'invention, il est proposé un système comprenant un dispositif laser tel que décrit ci-dessus et un moyen de pompage constitué par une unique diode laser. Suivant une première variante de l'invention, le moyen de pompage émet un faisceau laser apte à exciter à la fois Ie milieu amplificateur à trois niveaux et le milieu amplificateur à quatre niveaux. Ainsi, une partie de la pompe est absorbée par le milieu amplificateur à trois niveaux et Ie résidu de la pompe est absorbé par le milieu amplificateur à quatre niveaux. Cela nécessite d'accoler les deux milieux amplificateurs, la cavité se terminant par le cristal non linéaire. Autrement dit, le milieu amplificateur à trois niveaux et le cristal non linéaire sont accolés sur respectivement deux faces opposées du milieu amplificateur à quatre niveaux. Les miroirs de sortie des deux lasers, c'est à dire les deux milieux amplificateurs à trois et quatre, niveaux, se trouvent alors sur Ia sortie du cristal non linéaire. Par ailleurs, on optimise la focalisation de la pompe de telle sorte que le milieu amplificateur à quatre niveaux est pompé par la diode laser et par l'émission laser à trois niveaux.According to another aspect of the invention, there is provided a system comprising a laser device as described above and a pumping means consisting of a single laser diode. According to a first variant of the invention, the pumping means emits a laser beam able to excite both the three-level amplifying medium and the four-level amplifying medium. Thus, a portion of the pump is absorbed by the three-level amplifying medium and the pump residue is absorbed by the four-level amplifying medium. This requires joining the two amplifying media, the cavity ending in the non-linear crystal. In other words, the three-level amplifying medium and the non-linear crystal are placed side by side on two opposite sides of the four-level amplifying medium, respectively. The output mirrors of the two lasers, that is to say the two amplifying media with three and four levels, are then on the output of the nonlinear crystal. Furthermore, the focus of the pump is optimized so that the four-level amplifying medium is pumped by the laser diode and the three-level laser emission.
Suivant une seconde variante avantageuse de l'invention, le moyen de pompage émet un faisceau laser apte à exciter uniquement le milieu amplificateur à trois niveaux. Ce qui laisse toute la latitude sur Ie positionnement du milieu amplificateur à quatre niveaux. Ce dernier est entièrement pompé par l'émission du laser à trois niveaux. Pour ce faire, le milieu amplificateur à trois niveaux et le milieu amplificateur à quatre niveaux sont avantageusement constitués par une terre rare et un cristal identiques. Du point de vue thermique, la seconde variante est probablement meilleure que la précédente car le défaut quantique pour le laser à quatre niveaux est plus faible. Par ailleurs, l'adaptation entre la pompe et le signal pour le laser à quatre niveaux est parfaite. Cela permet également de mettre en sandwich le cristal doubleur et de ne reporter les traitements diélectriques que sur les cristaux laser, ce qui correspond à un traitement peu onéreux. En effet, dans un mode de réalisation préféré de l'invention, les deux milieux amplificateurs sont accolés sur respectivement deux faces opposées du cristal non linéaire, qui est de préférence un cristal biréfringent. Selon une caractéristique avantageuse de l'invention, le cristal non linéaire étant inséré entre les deux milieux amplificateurs, les parois des différents éléments du dispositif sont traités de telle sorte que :According to a second advantageous variant of the invention, the pumping means emits a laser beam able to excite only the three-level amplifying medium. This leaves all the latitude on the positioning of the four-level amplifier medium. The latter is fully pumped by the emission of the laser at three levels. To do this, the three-level amplifying medium and the four-level amplifying medium are advantageously constituted by an identical rare earth and crystal. From the thermal point of view, the second variant is probably better than the previous one because the quantum defect for the four-level laser is lower. In addition, the adaptation between the pump and the signal for the four-level laser is perfect. This also makes it possible to sandwich the doubling crystal and to transfer the dielectric treatments only to the laser crystals, which corresponds to an inexpensive treatment. Indeed, in a preferred embodiment of the invention, the two amplifying media are contiguous on two opposite sides of the non-linear crystal, which is preferably a birefringent crystal. According to an advantageous characteristic of the invention, the nonlinear crystal being inserted between the two amplifying media, the walls of the various elements of the device are treated in such a way that:
- l'entrée du milieu amplificateur à trois niveaux et la sortie du milieu amplificateur à quatre niveaux comprennent un traitement diélectrique réfléchissant pour ledit premier faisceau laser;the input of the three-level amplifier medium and the output of the four-level amplifier medium comprise a reflective dielectric treatment for said first laser beam;
- la sortie du milieu amplificateur à trois niveaux et la sortie du milieu amplificateur à quatre niveaux comprennent un traitement diélectrique réfléchissant pour ledit second faisceau laser;the output of the three-level amplifier medium and the output of the four-level amplifier medium comprise a reflective dielectric treatment for said second laser beam;
- la sortie du milieu amplificateur à trois niveaux et l'entrée du milieu amplificateur à quatre niveaux comprennent un traitement diélectrique de transmission pour ledit premier faisceau laser; etthe output of the three-level amplifier medium and the input of the four-level amplifier medium comprise a transmission dielectric processing for said first laser beam; and
- la sortie du milieu amplificateur à quatre niveaux comprend un traitement diélectrique de transmission pour ledit troisième faisceau laser.the output of the four-level amplifier medium comprises a dielectric transmission processing for said third laser beam.
En d'autres termes, les deux milieux amplificateurs et le cristal non- linéaire constituent une cavité linéaire résonante pour Ie premier faisceau laser. Le milieu amplificateur à quatre niveaux et le cristal non-linéaire constituent une cavité linéaire résonante pour le second faisceau laser.In other words, the two amplifying media and the non-linear crystal constitute a resonant linear cavity for the first laser beam. The four-level amplifying medium and the non-linear crystal constitute a resonant linear cavity for the second laser beam.
En général, l'inversion de population nécessaire à l'oscillation d'un laser à trois niveaux est supérieure à celle nécessaire d'un laser à quatre niveaux (à réflexion des miroirs comparables). Lorsque l'oscillation du laser à quatre niveaux débute, l'inversion de population n'augmente plus, ce qui interdit d'atteindre le seuil d'oscillation du laser à trois niveaux. Dans Ia seconde variante, la pompe excite le milieu de gain exclusif du laser à trois niveaux.In general, the population inversion necessary for the oscillation of a three-level laser is greater than that required for a four-level laser (mirroring comparable mirrors). When the oscillation of the four-level laser begins, the population inversion no longer increases, which makes it impossible to reach the oscillation threshold of the three-level laser. In the second variant, the pump excites the exclusive gain medium of the three-level laser.
L'inversion de population augmente jusqu'au seuil du laser à trois niveaux. Au-delà du seuil de ce laser à trois niveaux, le deuxième milieu de gain (laser à quatre niveaux) commence à être excité par l'absorption partielle de l'émission du laser à trois niveaux. L'augmentation de la puissance de pompe permet alors d'atteindre le seuil du laser à quatre niveaux.Population inversion increases to the threshold of the three-level laser. Beyond the threshold of this three-level laser, the second gain medium (laser at four levels) begins to be excited by the partial absorption of the three-level laser emission. The increase of the pump power then makes it possible to reach the threshold of the four-level laser.
Des modélisations ont montrées que au-delà du seuil, la répartition de puissance entre les émissions lasers à trois et quatre niveaux suit la répartition des pertes de l'émission à trois niveaux, hors et dans le milieu amplificateur du laser à quatre niveaux. Ainsi, les deux puissances sont égales lorsque l'absorption de l'émission laser à trois niveaux dans l'amplificateur du laser à quatre niveaux est égale aux autres pertes, c'est à dire les pertes non résonantes et les pertes par doublage. C'est la situation qu'il faut rechercher lorsqu'on désire maximiser l'efficacité de la sommation des fréquences. De préférence, le milieu amplificateur à quatre niveaux présente alors une absorption de Tordre de 1% à la longueur d'onde du laser à trois niveaux. Dans chaque variante, on obtient deux faisceaux lasers forts car Ie cristal non linéaire se trouve à l'intérieur des deux cavités lasers (cavités résonantes pour les premier et second faisceaux lasers).Modeling has shown that beyond the threshold, the power distribution between the three- and four-level laser emissions follows the distribution of the three-level emission losses out of and into the four-level laser amplifying medium. Thus, the two powers are equal when the absorption of the three-level laser emission in the four-level laser amplifier is equal to the other losses, ie the non-resonant losses and the doubling losses. This is the situation to look for when trying to maximize the efficiency of frequency summation. Preferably, the four-level amplifying medium then has an absorption of the order of 1% at the wavelength of the three-level laser. In each variant, two strong laser beams are obtained because the nonlinear crystal is located inside the two laser cavities (resonant cavities for the first and second laser beams).
Un autre avantage d'une disposition selon la présente invention, est le fait que les modes transverses des milieux amplificateurs ont une taille transverse similaire, ce qui optimise le rendement de conversion.Another advantage of an arrangement according to the present invention is that the transverse modes of the amplifying media have a similar transverse size, which optimizes the conversion efficiency.
D'autres avantages et caractéristiques de l'invention apparaîtront à l'examen de la description détaillée d'un mode de mise en œuvre nullement limitatif, et des dessins annexés sur lesquels :Other advantages and features of the invention will appear on examining the detailed description of a non-limiting embodiment, and the attached drawings in which:
- la figure 1 illustre un dispositif laser formant une cavité linéaire monolithique selon l'invention, le cristal non linéaire étant disposé entre les deux milieux amplificateurs;- Figure 1 illustrates a laser device forming a monolithic linear cavity according to the invention, the nonlinear crystal being disposed between the two amplifying media;
- la figure 2 est un graphe illustrant de façon schématique l'évolution des niveaux d'excitation et de puissance des deux milieux amplificateurs du dispositif selon la figure 1; et - la figure 3 illustre un dispositif laser selon la présente invention avec le milieu amplificateur à quatre niveaux disposé entre le milieu amplificateur à trois niveaux et le cristal non linéaire. Sur la figure 1, on voit un dispositif laser 1 selon l'invention, formant cavité linéaire. Ce dispositif laser est pompé par une unique diode laser 2. Le faisceau laser émis par la diode laser 2 est colinéaire au dispositif. Le dispositif laser 1 est constitué par un cristal non-linéaire 4 accolé entre, en entrée, un milieu amplificateur à trois niveaux 3 et, en sortie, un milieu amplificateur à quatre niveaux 5. Le milieu amplificateur à trois niveaux 3 est un cristal laser émettant autour de 915 nm tel que le Nd : YVO4 et recevant le faisceau émis par la diode laser. L'unique objectif du faisceau laser émis par la diode laser 2 est l'excitation de ce milieu amplificateur à trois niveaux 3. Le cristal non-linéaire est constitué par du niobate de potassium KNbO3. Le milieu amplificateur à quatre niveaux 5 est un cristal laser émettant autour de 1064nm tel que le Nd:YV04. Le dispositif 1 est conçu pour émettre en sortie un faisceau laser 14 à 491 nm provenant de la sommation des deux faisceaux laser des deux milieux amplificateurs.FIG. 2 is a graph illustrating schematically the evolution of the excitation and power levels of the two amplifying media of the device according to FIG. 1; and FIG. 3 illustrates a laser device according to the present invention with the four-level amplifying medium disposed between the three-level amplifying medium and the nonlinear crystal. In Figure 1, there is shown a laser device 1 according to the invention forming a linear cavity. This laser device is pumped by a single laser diode 2. The laser beam emitted by the laser diode 2 is collinear with the device. The laser device 1 consists of a nonlinear crystal 4 coupled between, input, a three-level amplifier medium 3 and, at the output, a four-level amplifier medium 5. The three-level amplifier medium 3 is a laser crystal emitting around 915 nm such as Nd: YVO 4 and receiving the beam emitted by the laser diode. The sole objective of the laser beam emitted by the laser diode 2 is the excitation of this three-level amplifying medium 3. The non-linear crystal consists of KNbO 3 potassium niobate. The four-level amplifying medium 5 is a laser crystal emitting around 1064 nm such as Nd: YVO 4 . The device 1 is designed to output a laser beam 14 at 491 nm from the summation of the two laser beams of the two amplifying media.
La cavité à 915nm est fermée par les traitements diélectriques HR915, c'est à dire réfléchissant à 915nm, en entrée 8 du premier cristal amplificateur 3 et en sortie 11 du second cristal amplificateur 5. En d'autres termes, Ie faisceau laser 6 à 915nm est confiné entre les parois 8 et 11.The cavity at 915 nm is closed by the dielectric treatments HR915, ie reflecting at 915 nm, at the input 8 of the first amplifier crystal 3 and at the output 11 of the second amplifier crystal 5. In other words, the laser beam 6 at 915nm is confined between walls 8 and 11.
La cavité à 1064nm est fermée par les traitements diélectriques HR1064, c'est à dire réfléchissant à 1064nm/ en sortie 9 du premier cristal amplificateur 3 et en sortie 11 du second cristal amplificateur. En d'autres termes, le faisceau laser 7 à 1064nm est confiné entre les parois 9 et 11. Le traitement diélectrique en sortie 9 du premier cristal amplificateur 3 est de type HT915, c'est à dire transmetteur à 915nm. Le traitement diélectrique en sortie 11 du deuxième cristal amplificateur 5 est de type HT491 afin de laisser sortir l'émission bleue du faisceau laser 14 à 491nm,The cavity at 1064 nm is closed by the dielectric treatments HR1064, that is to say reflective at 1064 nm / output 9 of the first amplifier crystal 3 and output 11 of the second amplifier crystal. In other words, the laser beam 7 at 1064 nm is confined between the walls 9 and 11. The dielectric treatment at the output 9 of the first amplifier crystal 3 is of the HT915 type, that is to say transmitter at 915 nm. The dielectric treatment at the output 11 of the second amplifier crystal 5 is of type HT491 in order to let the blue emission of the laser beam 14 to 491 nm,
Avantageusement, avec une telle disposition, chaque cavité à 915nm et à 1064nm comporte le cristal non-linéaire.Advantageously, with such an arrangement, each cavity at 915 nm and at 1064 nm comprises the non-linear crystal.
Le tableau ci-dessous reprend les indices de réfraction déterminés dans le cristal doubleur non-linéaire KNbO3 du dispositif 1 selon l'invention, à 303K pour les longueurs d'ondes 915nm, 1064nm et 491.7nm:The table below shows the refractive indices determined in the nonlinear crystal doubler KNbO 3 of the device 1 according to the invention, at 303K for the wavelengths 915nm, 1064nm and 491.7nm:
On constate que : na(915)+na(1064)=2nc(491.7) , ce qui correspond à un accord de phase non critique de type I . It is found that: n (915) + n (1064) = 2n c (491.7), which corresponds to a non-critical phase matching type I.
Le dispositif 1 utilise le Nd :YVO4 avec une émission à 915nm dans le laser à trois niveaux, et une émission à 1064nm dans le laser à quatre niveaux. On peut aussi utiliser Ie Nd .1GdVO4 avec une émission à 912nm dans le laser à trois niveaux, et une émission à 1062.6nm dans le laser à quatre niveaux.The device 1 uses the Nd: YVO 4 with a 915nm emission in the three-level laser, and a 1064nm emission in the four-level laser. Nd can also be used. 1 GdVO 4 with a 912nm emission in the three-level laser, and a 1062.6nm emission in the four-level laser.
Sur la figure 2, on voit l'évolution des niveaux d'excitation et de puissance des deux milieux amplificateurs 3 et 5. En abscisse se trouve la puissance de pompe en unité arbitraire, et en ordonnée, la concentration d'ions excités ainsi que la puissance laser en unités arbitraires. La pompe 2 excite (niveau d'excitation 1) exclusivement le milieu amplificateur à trois niveaux 3. Lorsque le seuil d'oscillation de ce dernier est atteint (1 en abscisse sur la figure 2), la puissance laser émise permet d'exciter (niveau d'excitation 2) le milieu amplificateur à quatre niveaux 5. Ce dernier émet ensuite à son tour une puissance laser lorsque son seuil d'oscillation est atteint (1,5 en abscisse).FIG. 2 shows the evolution of the excitation and power levels of the two amplifying media 3 and 5. On the abscissa is the pump power in arbitrary units, and on the ordinate, the concentration of excited ions as well as laser power in arbitrary units. The pump 2 excites (excitation level 1) exclusively the three-level amplifying medium 3. When the oscillation threshold of the latter is reached (1 on the abscissa in FIG. 2), the laser power emitted makes it possible to excite ( excitation level 2) the four-level amplifier medium 5. The latter then emits a laser power when its oscillation threshold is reached (1.5 on the abscissa).
Sur la figure 3 est représentée une variante 13 du dispositif selon la présente invention. Les deux milieux amplificateurs 3 et 5 sont directement accolés l'un à l'autre. Le cristal non linéaire 4 est accolé au milieu amplificateur à quatre niveaux 5 de telle sorte que les émissions des lasers à trois niveaux et à quatre niveaux sont superposées. Le dispositif 13 émet un faisceau laser 15 en sortie du cristal non linéaire.In Figure 3 is shown a variant 13 of the device according to the present invention. Both amplifying media 3 and 5 are directly coupled to each other. The non-linear crystal 4 is coupled to the four-level amplifier medium 5 so that the emissions of the three-level and four-level lasers are superimposed. The device 13 emits a laser beam 15 at the output of the nonlinear crystal.
Dans ce cas, la cavité à 915nm est fermée par les traitements diélectriques HR.915, c'est à dire réfléchissant à 915nm, en entrée 8 du premier cristal amplificateur 3 et en sortie 12 du cristal non linéaire 4. En d'autres termes, le faisceau laser 6 à 915nm est confiné entre les parois 8 etIn this case, the 915nm cavity is closed by the dielectric treatments HR.915, ie reflecting at 915nm, at the input 8 of the first amplifier crystal 3 and at the output 12 of the nonlinear crystal 4. In other words , the laser beam 6 at 915 nm is confined between the walls 8 and
12.12.
La cavité à 1064nm est fermée par les traitements diélectriques HR.1064, c'est à dire réfléchissant à 1064nm, en entrée 10 du second cristal amplificateur 5 et en sortie 12 du cristal non linéaire 4. En d'autres termes, le faisceau laser 7 à 1064nm est confiné entre les parois 10 et 12.The cavity at 1064 nm is closed by the dielectric treatments HR.1064, that is, reflecting at 1064 nm, at the input 10 of the second amplifier crystal 5 and at the output 12 of the nonlinear crystal 4. In other words, the laser beam 7 to 1064nm is confined between walls 10 and 12.
Bien sûr, l'invention n'est pas limitée aux exemples qui viennent d'être décrits et de nombreux aménagements peuvent 'être apportés à ces exemples sans sortir du cadre de l'invention. Of course, the invention is not limited to the examples just described and numerous adjustments can be made to these examples without exceeding the scope of the invention.

Claims

REVENDICATIONS
1. Dispositif laser comprenant :A laser device comprising:
- un milieu amplificateur à trois niveaux (3} apte à émettre un premier faisceau laser (6) de longueur d'onde fondamentale;a three-level amplifying medium (3) capable of emitting a first laser beam (6) of fundamental wavelength;
- un milieu amplificateur à quatre niveaux (5) apte à émettre un second faisceau laser (7) de longueur d'onde fondamentale;a four-level amplifying medium (5) capable of emitting a second laser beam (7) of fundamental wavelength;
- un cristal non-linéaire (4) apte à mélanger les premier et second faisceaux laser et à générer un troisième faisceau (14) dont la fréquence est la somme des fréquences desdits premier et second faisceaux laser; caractérisé en ce que le milieu amplificateur à trois niveaux (3) et au moins le cristal non-linéaire (4) constituent une cavité résonante pour le premier faisceau laser (6), et le milieu amplificateur à quatre niveaux (5) et au moins le cristal non-linéaire (4) constituent une cavité résonante pour le second faisceau laser (7); les deux milieux amplificateurs et le cristal non- linéaire formant une cavité linéaire.a nonlinear crystal (4) capable of mixing the first and second laser beams and generating a third beam (14) whose frequency is the sum of the frequencies of said first and second laser beams; characterized in that the three-level amplifier medium (3) and at least one non-linear crystal (4) constitute a resonant cavity for the first laser beam (6), and the four-level amplifier medium (5) and at least the non-linear crystal (4) constitutes a resonant cavity for the second laser beam (7); the two amplifying media and the nonlinear crystal forming a linear cavity.
2. Dispositif selon la revendication 1, caractérisé en ce que les deux milieux amplificateurs et le cristal non-linéaire constituent une cavité linéaire résonante monolithique.2. Device according to claim 1, characterized in that the two amplifying media and the non-linear crystal form a monolithic resonant linear cavity.
3. Dispositif (1) selon la revendication 1 ou 2, caractérisé en ce que les deux milieux amplificateurs sont accolés sur respectivement deux faces opposées du cristal non linéaire.3. Device (1) according to claim 1 or 2, characterized in that the two amplifying media are contiguous respectively on two opposite sides of the nonlinear crystal.
4. Dispositif selon la revendication 3, caractérisé en ce que le milieu amplificateur à quatre niveaux présente une absorption de Tordre de 1% à la longueur d'onde du laser à trois niveaux.4. Device according to claim 3, characterized in that the four-level amplifying medium has an absorption of the order of 1% at the wavelength of the three-level laser.
5. Dispositif selon la revendication 3 ou 4, caractérisé en ce que :5. Device according to claim 3 or 4, characterized in that:
- l'entrée (8) du milieu amplificateur à trois niveaux (3) et la sortie (11) du milieu amplificateur à quatre niveaux (5) comprennent un traitement diélectrique réfléchissant pour ledit premier faisceau laser (6); - la sortie (9) du milieu amplificateur à trois niveaux (3) et la sortie (11) du milieu amplificateur à quatre niveaux (5) comprennent un traitement diélectrique réfléchissant pour ledit second faisceau laser (7);the input (8) of the three-level amplifier medium (3) and the output (11) of the four-level amplifier medium (5) comprise a reflective dielectric processing for said first laser beam (6); the output (9) of the three-level amplifier medium (3) and the output (11) of the four-level amplifier medium (5) comprise a reflective dielectric treatment for said second laser beam (7);
- la sortie (9) du milieu amplificateur à trois niveaux (3) et l'entrée (10) du milieu amplificateur à quatre niveaux (5) comprennent un traitement diélectrique de transmission pour ledit premier faisceau laser (6); etthe output (9) of the three-level amplifier medium (3) and the input (10) of the four-level amplifier medium (5) comprise a transmission dielectric processing for said first laser beam (6); and
- la sortie (11) du milieu amplificateur à quatre niveaux (Ξ) comprend un traitement diélectrique de transmission pour ledit troisième faisceau (14).the output (11) of the four-level amplifier medium (Ξ) comprises a transmission dielectric processing for said third beam (14).
6. Dispositif (13) selon la revendication 1 ou 2, caractérisé en ce que le milieu amplificateur à trois niveaux et le cristal non linéaire sont accolés sur respectivement deux faces opposées du milieu amplificateur à quatre niveaux.6. Device (13) according to claim 1 or 2, characterized in that the three-level amplifying medium and the nonlinear crystal are contiguous respectively on two opposite faces of the four-level amplifier medium.
7. Dispositif selon l'une quelconque des revendications précédentes, caractérisé en ce que le milieu amplificateur à trois niveaux et le milieu amplificateur à quatre niveaux sont constitués par une terre rare et un cristal identiques.7. Device according to any one of the preceding claims, characterized in that the three-level amplifying medium and the four-level amplifying medium consist of an identical rare earth and crystal.
8. Système comprenant un dispositif laser selon l'une quelconque des revendications précédentes/ caractérisé en ce qu'il comprend en outre un moyen de pompage constitué par une unique diode laser (2).8. System comprising a laser device according to any preceding claim / characterized in that it further comprises a pumping means consisting of a single laser diode (2).
9. Système selon la revendication 8, caractérisé en ce que, les deux milieux amplificateurs étant accolés sur respectivement deux faces opposées du cristal non linéaire, le moyen de pompage émet un faisceau laser apte à exciter uniquement le milieu amplificateur à trois niveaux (3).9. System according to claim 8, characterized in that, the two amplifying media being contiguous on respectively two opposite faces of the non-linear crystal, the pumping means emits a laser beam able to excite only the three-level amplifying medium (3). .
10. Système selon la revendication 8, caractérisé en ce que, le milieu amplificateur à trois niveaux et Ie cristal non linéaire étant accolés sur respectivement deux faces opposées du milieu amplificateur à quatre niveaux; Ie moyen de pompage émet un faisceau laser apte à exciter Ie milieu amplificateur à trois niveaux (3) et le milieu amplificateur à quatre niveaux (5). 10. System according to claim 8, characterized in that the three-level amplifying medium and the non-linear crystal being contiguous on respectively two opposite faces of the four-level amplifying medium; The pumping means emits a laser beam capable of exciting the three-level amplifying medium (3) and the four-level amplifying medium (5).
EP06726016A 2005-03-04 2006-03-03 Dual wavelength laser device, and system comprising same Withdrawn EP1861902A1 (en)

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FR0502228A FR2882860B1 (en) 2005-03-04 2005-03-04 "TWO WAVELENGTH LASER DEVICE AND SYSTEM COMPRISING SUCH A DEVICE"
PCT/FR2006/000478 WO2006092509A1 (en) 2005-03-04 2006-03-03 Dual wavelength laser device, and system comprising same

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JP5343699B2 (en) * 2009-05-18 2013-11-13 株式会社島津製作所 Optical resonator
CN102185247B (en) * 2011-04-08 2012-04-25 山东大学 537 nm and 556 nm double-wavelength laser device
IL236339A0 (en) * 2014-12-18 2015-04-30 Ocuwave Ltd Laser system

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CN101138137B (en) 2010-09-29
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WO2006092509A1 (en) 2006-09-08
IL185698A0 (en) 2008-01-06
JP2008532305A (en) 2008-08-14
FR2882860B1 (en) 2009-05-22
US20080192782A1 (en) 2008-08-14

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