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
  • H01S3/14—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
• • 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
• • 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
• • 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
  • H01S3/1605—Solid materials characterised by an active (lasing) ion rare earth terbium
• • 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
  • H01S3/1631—Solid materials characterised by a crystal matrix aluminate
• • 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
  • H01S3/1631—Solid materials characterised by a crystal matrix aluminate
  • H01S3/1638—YAlO3 (YALO or YAP, Yttrium Aluminium Perovskite)
• • 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
  • H01S3/1655—Solid materials characterised by a crystal matrix silicate
• • 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
  • H01S3/1668—Solid materials characterised by a crystal matrix scandate
• • 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
  • H01S3/1691—Solid materials characterised by additives / sensitisers / promoters as further dopants
  • H01S3/1698—Solid materials characterised by additives / sensitisers / promoters as further dopants rare earth
• • 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
  • H01S5/00—Semiconductor lasers
  • H01S5/30—Structure or shape of the active region; Materials used for the active region
  • H01S5/32—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures
  • H01S5/323—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser
  • H01S5/32308—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser emitting light at a wavelength less than 900 nm
  • H01S5/32341—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser emitting light at a wavelength less than 900 nm blue laser based on GaN or GaP

Definitions

• the present invention relates to a solid-state laser comprising a gain medium of a solid-state host material, which is doped with rare-earth ions.
• US 6,816,532 B2 discloses a laser diode exited laser apparatus in which the gain medium is doped with rare-earth ions, in particular with Ho 3+ -, Sm 3+ -, Eu 3+ -, Dy 3+ -, Er 3+ - and Tb 3+ - ions.
• the solid gain medium is pumped by a GaN based laser diode. Both the excitation and the laser emission of the disclosed laser involve transitions between 4f states of the rare-earth ion. Since the absorption at these transitions is relatively weak, the efficiency of the devices is limited and long interaction lengths like for example in fiber lasers are required.
• the proposed solid-state laser comprises a gain medium of a solid-state host material, which is co-doped with the Ce 3+ - ions and with ions of a further rare-earth material.
• the host material is selected such that a lower edge of the 5d band of the Ce 3+ - ion is energetically higher than an upper lasing state of the ions of the further rare-earth material.
• the proposed all solid-state laser can be pumped efficiently with GaN laser diodes in the wavelength range of for example between 400 and 450 nm.
• the gain medium absorbs the radiation of the pump laser via the 4f-5d transitions in the Ce 3+ - ion. From the 5d band of the Ce 3+ - ion the energy is transferred to the upper lasing state of the further rare-earth ion which then emits the desired laser radiation through a transition between the upper lasing state and a lower lasing state.
• the emitted laser wavelength is influenced by the selection of the further rare-earth ions and may further be influenced by the spectral characteristics of the resonator mirrors of the solid-state laser.
• Ce 3+ - ions with further trivalent rare- earth ions are combinations of Ce 3+ -ions with Pr 3+ , Sm 3+ , Eu 3+ , Dy 3+ and Tm 3+ to design lasers emitting with different wavelengths in the visible wavelength range.
• the proposed solid-state laser comprises a gain medium of a solid-state host material, which is co-doped with Ce 3+ - ions and Tb 3+ - ions.
• the laser pumping scheme involves 4f-5d-transitions in Ce 3+ , energy transfer from the Ce 3+ 5d band to the 5 D 4 -state of Tb 3+ , from which laser emission takes place.
• This scheme is very attractive since it combines the high absorption of 4f-5d-transitions with the known laser properties of rare-earth 4f-4f lasers. Highly integrated, efficient laser devices are therefore possible.
• the Tb 3+ - ion is very attractive to provide an optically pumped solid-state laser in the green wavelength range, since it has a well isolated 5 D 4 state with a long lifetime in many hosts. From this 5 D 4 -level green emission around 543 nm is very pronounced.
• the dopant concentration Cce for the Ce 3+ -ions is preferably in the range of 0.01% wt to 5% wt.
• the appropriate selection of this host material is important in order to achieve the desired laser action.
• Very advantageous laser operation has been observed when using host materials with an energy gap of at least 6 eV.
• the host materials also have to ensure the energy transfer between the 5d-band of the Ce 3+ -ions and, for example, the 5 D 4 state of the Tb 3+ ions.
• the Ce 3+ -ions act as a sensitizer and provide a good absorption of the pump radiation via the 4f-5d transitions, whereas the further rare-earth ions act as the laser active ions.
• solid-state host materials doped with Ce 3+ -ions are not suited for laser action due to very strong excited state absorption, it was surprisingly found by the inventors of the present invention, that by co-doping the Ce 3+ -ions with further trivalent rare-earth ions and by selecting an appropriate host material, laser action can be achieved in an efficient manner.
• an all-solid-state laser is realized which can be efficiently pumped by GaN based laser diodes to emit in the green wavelength range.
• Such all-solid-state laser systems including the pump laser can be manufactured in a highly integrated manner and are in particular suited as light sources for projection systems in display or illumination applications.
• the optical design of the all-solid-state laser can be chosen as known in the art.
• a laser can be set up for example in the form of an end pumped rod, similar to other diode pumped solid-state lasers known in the art.
• the proposed laser can also be designed in the form of a planar waveguide laser, in which the co-doped material is brought to the form of a planar waveguide that is adapted in its geometry to the emission profile of the laser diode.
• the laser diode and the co-doped conversion medium are preferably placed on a shared cooling structure, which allows for a highly integrated device.
• the high absorption of the Ce 3+ -ions allows also for transversal pump geometries, in which the laser radiation emerges in a direction perpendicular to the direction of the pump radiation.
• Fig. 1 an excitation scheme of a preferred embodiment of the proposed laser
• Fig. 2 an example for an end pumped geometry of the proposed laser
• Fig. 3 an example of a transversally pumped geometry of the proposed laser.
• the gain medium of the proposed laser is co-doped with Ce 3+ - and Tb 3+ -ions.
• the Ce-Tb-laser is pumped with a GaN based laser diode.
• Figure 1 shows the pumping and lasing scheme of such a solid-state laser.
• the blue pump radiation 1 of the GaN based laser diode is absorbed via the 4f-5d transition of the Ce 3+ -ions.
• energy transfer 2 takes place between the 5d band of the Ce 3+ -ions and the upper lasing state ( 5 D 4 state) of the Tb 3+ - ions as is indicated in the figure. From this 5 D 4 state of the Tb 3+ -ions laser emission 3 around 543 nm starts by transition to a lower state of the Tb 3+ -ions.
• the laser emission 3 is very pronounced in this laser scheme.
• Figure 2 shows an example for an end pumped geometry of the proposed Ce-Tb-laser.
• the pump radiation emitted by a GaN laser diode 4 is focused by appropriate optics 5 through the first resonator end mirror 7 of the solid-state laser into the Ce 3+ -Tb 3+ co-doped gain material 6.
• the first resonator end mirror 7 used for end pumping is highly reflective for radiation in the green wavelength region and antireflective for the pump radiation wavelength.
• the second resonator end mirror 8 on the other hand is highly reflective for the wavelength of the pump radiation and sufficiently reflective for the green wavelength emitted by the gain material 6 in order to achieve lasing action. On the other hand this second resonator end mirror 8 allows the outcoupling of a portion of the laser emission 3 in the green wavelength region.
• FIG 3 shows another example for the design of the proposed solid-state laser.
• a transversally pumped geometry is used for the Ce-Tb-laser.
• the gain medium 6 of the Ce-Tb-laser in this case has two resonator end mirrors 10 which reflect a sufficiently high portion of the generated green radiation to maintain laser action. Both resonator end mirrors 10 also serve as outcoupling mirrors for the laser radiation 3.
• the gain medium 6 is transversally pumped by a GaN diode laser module 9 composed of several GaN laser diodes side by side in order to achieve emission of the pump radiation 1 over the whole length of the gain medium 6 as indicated in Figure 3.

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

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• 2007
  • 2007-10-15 JP JP2009533997A patent/JP2010507920A/ja not_active Withdrawn
  • 2007-10-15 WO PCT/IB2007/054188 patent/WO2008050258A2/en not_active Ceased
  • 2007-10-15 CN CNA2007800396257A patent/CN101529672A/zh active Pending
  • 2007-10-15 EP EP07826745A patent/EP2084792A2/de not_active Withdrawn
  • 2007-10-19 TW TW96139348A patent/TW200830652A/zh unknown

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