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.

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• 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)

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• 2005
  • 2005-03-04 FR FR0502228A patent/FR2882860B1/fr not_active Expired - Lifetime
• 2006
  • 2006-03-03 JP JP2007557543A patent/JP2008532305A/ja active Pending
  • 2006-03-03 CN CN2006800069509A patent/CN101138137B/zh not_active Expired - Fee Related
  • 2006-03-03 EP EP06726016A patent/EP1861902A1/de not_active Withdrawn
  • 2006-03-03 US US11/817,695 patent/US20080192782A1/en not_active Abandoned
  • 2006-03-03 WO PCT/FR2006/000478 patent/WO2006092509A1/fr not_active Ceased
• 2007
  • 2007-09-04 IL IL185698A patent/IL185698A0/en unknown

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