WO2020132043A1 - High power laser converter based on patterned srb4bo7 or pbb407 crystal - Google Patents

High power laser converter based on patterned srb4bo7 or pbb407 crystal Download PDF

Info

Publication number
WO2020132043A1
WO2020132043A1 PCT/US2019/067135 US2019067135W WO2020132043A1 WO 2020132043 A1 WO2020132043 A1 WO 2020132043A1 US 2019067135 W US2019067135 W US 2019067135W WO 2020132043 A1 WO2020132043 A1 WO 2020132043A1
Authority
WO
WIPO (PCT)
Prior art keywords
laser
sbo
laser system
crystal
harmonic
Prior art date
Application number
PCT/US2019/067135
Other languages
French (fr)
Other versions
WO2020132043A8 (en
Inventor
Valentin GAPGNTSEV
Original Assignee
Ipg Photonics Corporation
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Ipg Photonics Corporation filed Critical Ipg Photonics Corporation
Priority to CN201980083902.7A priority Critical patent/CN113196596B/en
Priority to US17/415,090 priority patent/US11719993B2/en
Priority to KR1020217021906A priority patent/KR102707500B1/en
Priority to EP19898599.6A priority patent/EP3881402B1/en
Priority to JP2021535150A priority patent/JP2022514745A/en
Publication of WO2020132043A1 publication Critical patent/WO2020132043A1/en
Publication of WO2020132043A8 publication Critical patent/WO2020132043A8/en

Links

Classifications

    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/35Non-linear optics
    • G02F1/355Non-linear optics characterised by the materials used
    • G02F1/3551Crystals
    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/35Non-linear optics
    • G02F1/3501Constructional details or arrangements of non-linear optical devices, e.g. shape of non-linear crystals
    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/35Non-linear optics
    • G02F1/353Frequency conversion, i.e. wherein a light beam is generated with frequency components different from those of the incident light beams
    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/35Non-linear optics
    • G02F1/353Frequency conversion, i.e. wherein a light beam is generated with frequency components different from those of the incident light beams
    • G02F1/354Third or higher harmonic generation
    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/35Non-linear optics
    • G02F1/355Non-linear optics characterised by the materials used
    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/35Non-linear optics
    • G02F1/355Non-linear optics characterised by the materials used
    • G02F1/3558Poled materials, e.g. with periodic poling; Fabrication of domain inverted structures, e.g. for quasi-phase-matching [QPM]
    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/35Non-linear optics
    • G02F1/37Non-linear optics for second-harmonic generation
    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/35Non-linear optics
    • G02F1/37Non-linear optics for second-harmonic generation
    • G02F1/377Non-linear optics for second-harmonic generation in an optical waveguide structure
    • G02F1/3775Non-linear optics for second-harmonic generation in an optical waveguide structure with a periodic structure, e.g. domain inversion, for quasi-phase-matching [QPM]
    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/35Non-linear optics
    • G02F1/39Non-linear optics for parametric generation or amplification of light, infrared or ultraviolet waves
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01SDEVICES 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
    • H01S3/00Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/106Controlling 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
    • H01S3/108Controlling 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
    • H01S3/109Frequency multiplication, e.g. harmonic generation
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01SDEVICES 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
    • H01S3/00Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/11Mode locking; Q-switching; Other giant-pulse techniques, e.g. cavity dumping
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01SDEVICES 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
    • H01S3/00Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/23Arrangements of two or more lasers not provided for in groups H01S3/02 - H01S3/22, e.g. tandem arrangements of separate active media
    • H01S3/2308Amplifier arrangements, e.g. MOPA
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01SDEVICES 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
    • H01S3/00Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/005Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
    • H01S3/0092Nonlinear frequency conversion, e.g. second harmonic generation [SHG] or sum- or difference-frequency generation outside the laser cavity

Definitions

  • the disclosure relates to a high power solid state laser provided with at least one nonlinear converter based on patterned Strontium Tetraborate SrB4B07 (SBO) and Lead
  • UV ultraviolet
  • DUV deep UV
  • the copending US patent application No. discloses a method for fabricating a patterned non-ferromagnetic nonlinear SBO or PBO fully incorporated herein by reference.
  • This subgroup of borates has some remarkable properties.
  • the SBO should be very transparent in VIS near infrared (IR). Its absorption should be in a single ppm/cm range. It is mechanically stable and non- hydroscopic. It is easy to grow this crystal by the known conventional techniques.
  • these crystals have a very high (for borate) thermal conductivity of ⁇ 16 W/m*K, It is an order of magnitude higher than that of BBO and LBO.
  • the SBO crystal is one of a very few non-linear materials (if not the only one) which does not have two-photon absorption (TP A) at 266 nm - a nonlinear effect increasing the power loss and light- induced damage.
  • TP A two-photon absorption
  • the SBO/PbBO crystal is probably the only non-linear material capable of withstanding sustainable multi-watt operation (pulsed and CW) at 266 nm with fluencies typical for non-linear conversion regimes (-100-500 MW/cm 2 ).
  • this group of borates is an ideal material for nonlinear interactions.
  • a group of high power laser systems capable of operating in a UV frequency range. All of the disclosed systems have a common general optical schematic. The latter is provided with a laser source and at least one frequency converter so as to output sub-nanosecond, preferably picosecond pulses in a UV spectral region.
  • ps fiber lasers participating in generating higher harmonics, such as UV light are advantageous over ns fiber lasers because the nonlinear crystals in the ps pulsed regime have longer useful life than that of crystals irradiated by ns pulses. This advantage becomes even more prominent when the SBO or PBO is used since there is no 2 -photon absorption is these crystals.
  • FIG. 1 is a general optical schematic of the inventive laser system
  • FIG. 2 shows a patterned SBO/PBO crystal of the inventive system
  • FIG. 3 is an exemplary schematic of the inventive system of FIG. 1 used for generation of the FH.
  • FIG. 4 is an exemplary schematic of the inventive system of FIG. 1 used for generation of the third and higher harmonics.
  • FIG. 5 is an exemplary schematic of the inventive system of FIG. 1 used for generation of the fifth harmonic.
  • FIG. 6 is an exemplary schematic of the inventive system of FIG. 1 used for parametric conversion.
  • FIG. 7 is the SBO/PBO crystal of FIG. 2 configured from a single slab to provide a frequency conversion of the fundamental frequency into a plurality of successive harmonics.
  • FIG. 1 illustrates a general optical schematic 40 of the inventive laser system.
  • the schematic 40 is configured as a source of electromagnetic (EM) radiation 42 incident on a frequency converter 44 which is based, at least in part, on patterned SBO or PBO nonlinear crystal 10 and configured to convert a fundamental frequency into a higher harmonic.
  • the converters are placed in a single-pass or multi-pass resonator.
  • the EM source 42 is a laser system operating in various regimes which includes continuous a wave (CW) mode, quasi-continuous wave (QCW) mode and pulsed modes.
  • source 42 is a high power source with the output of at least 1 kW and as high as of MWs.
  • laser systems operating under a kW power level are also part of the disclosed subject matter.
  • the configuration of source 42 is not limited to any particular lasing medium.
  • it is a solid state laser system including fiber and yttrium aluminum glass (Y AG) lasing media, with the disk lasers being a subclass of YAGs.
  • the light emitting ions doped in the lasing media include various rare-earth metals. Since an industrial range of fundamental wavelengths and their higher harmonics is mostly associated with laser sources emitting light in a 1 - 2 mm range, ions of ytterbium (Yb), erbium (Er), neodymium (Nd), and Thulium perhaps are most frequently used.
  • the mentioned elements are however do not represent the exclusive list of all rare earth elements that may be used for light generation in the inventive system.
  • the architecture of laser source 42 may be represented by a variety of specific configurations.
  • the laser source may have a MOP A configuration including a combination of master oscillator (MO) 43 and power amplifier (PA) 44.
  • the MO 43 may include semiconductors or fibers preferably operating at a single frequency.
  • MO 43 can be configured in accordance with the schematics disclosed in PCT/US 15/65798 and PCT/US 15/52893 which are owned by the assignee of the current applications and incorporated here by reference in their entirety. Considering that modem power levels of known oscillators have reached a kW level, the architecture of source 42 may be represented only by lasers omitting thus the amplifier.
  • laser source 42 preferably outputs a single frequency, single transverse mode sub-nanosecond output in the QCW and pulsed regime.
  • a beam quality factor M 2 may be higher than 1, for example 1.5.
  • frequency converter 44 operates to generate a second harmonic (SH), third harmonic (TH), fourth harmonic (FH), and other higher harmonics as well as to perform optical parametric interactions.
  • the crystal SBO or PBO 10 is configured with a periodic structure 12 of domains 30 and 32 having respective opposite polarities +/- which alternate one another. These domains have highly parallel walls.
  • the periodic structure 12 allows the use of a QPM technique to generate high harmonic of the pump light.
  • Recent experiments conducted by the Applicants resulted in crystal 10 provided with a volume periodic pattern which includes a sequence of uniformly dimensioned 3D-domains 30, 32 having respective positive and negative polarities which alternate one another and provide the crystal with a clear aperture having a diameter of up to a few centimeters.
  • the domains each are configured with a uniform thickness corresponding to the desired coherence length 1 and ranging from about 0.2 mm to about 20 mm and a clear aperture which has a dimeter varying from about 1 mm to about 5 cm.
  • the crystal 10 can be utilized as an optical element, such as a frequency converter incorporated in a laser which operates in a variety of frequency ranges.
  • crystal 10 configured to convert a fundamental frequency of laser source 42 to a DUV range, has a coherence length 1 ranging between 0.2 to about 5 nm.
  • the volume pattern may extend through the entire thickness of crystal block 10 between faces +C and -C, or terminate at a distance from one of these faces.
  • the crystal 10 is based on the discussed above unique qualities and disclosed in copending, co-owned US application 62781371which is filed concurrently with the subject matter application which incorporates it by reference in its entirety.
  • the SBO/PBO 10 is characterized by a short UV absorption cut-off (l cutoff ) or wide energy bandgap (E g ) which guarantee the transmittance in the UV and DUV spectra.
  • the large bandgap significantly decreases the two-photon absorption or multi-photon absorption, and thus, in turn, increases the laser-induced damage threshold in a crystal and results in reduced non-desirable thermo-optical effects. Linear absorption of borates is typically very low as well.
  • SBO/PBO crystal 10 is particularly attractive when used in laser systems operating in ultraviolet/deep ultraviolet (UV/DUV) frequency ranges.
  • UV/DUV lasers are widely employed in various applications. For instance, a DUV at 266 nm has been utilized as an external seed of a free-electron laser with outputs as short as about 4 nm so useful in the scientific research beyond the carbon K-edge.
  • the industrial applications, laser machining of wide bandgap materials, microelectronics and many other are direct beneficiaries of the DUV lasers owing to their high photon energy.
  • the conversion schemes are numerous and examples thereof are disclosed hereinbelow.
  • an exemplary schematic setup of system 40 includes converter 46 configured with SHG 46 and FHG 48 stages.
  • the SHG 46 doubles the frequency of the pump wave in a 1 mm wavelength range to Green light and the latter continuing frequency conversion to obtain ultraviolet/deep UV (UV/DUV 50) light at or lower than a 2xx nm wavelength.
  • a pump wavelength at a 1060 nm output by source 42 (fundamental frequency w)
  • a second harmonic 2w (532 nm wavelength) in SHG 46
  • the SHG 46 may be based on BBO, LBO CLBO, SBO, PBO and other nonlinear crystals.
  • the FHG 48 includes SBO/PBO crystal 10.
  • FIG. 4 exemplifies a schematic configured to generate the third harmonic (THG) 50.
  • the system 40 includes source 42 outputting light at fundamental frequency w which is incident on SHG 46.
  • the latter 46 converts the fundamental frequency into second harmonic 2w.
  • the THG 50 receives a remaining portion of light at the fundament frequency and second harmonic and combines these frequencies to create the third harmonic.
  • the SHG 46 may have the configuration of FIG. 3, and so does THG 50 including SBO/PBO crystal 10.
  • a non- inclusive example can be illustrated by a fundamental wavelength of 1064 nm which eventually is converted into the TH of about 355 nm.
  • the system 40 may be further provided with a FiHG 52 combining the unused SH and generated TH.
  • FIG. 5 illustrates still another example of system 40 with converter 44 configured to generate the fifth harmonic (FiHG).
  • the converter 44 operates by initially generating the SH in SHG 46.
  • the unused light at the fundamental (pump) is separated from the SH at the output of SHG 46 and further guided to the fifth harmonic generator (FiHG) 52 along a path defined by reflective elements, such as mirrors or prisms. If desired, the unconverted light at the fundamental frequency can be guided through FHG 48.
  • SBO/PBP quasi phase matched crystal 10 can be used for frequency doubling, tripling etc, as well as for sum and difference frequency generation. It also can be used for parametric amplification. Referring to FIG. 6, light at a signal wavelength propagates through crystal 10 together with a pump beam of shorter wavelength resulting in several outputs which include an idler, residual pump beam and signal separate outputs, as well known to one of ordinary skill.
  • FIG. 7 illustrates another configuration of system 40 including laser source 42 of FIG. 1, which is a diode laser in this schematic, and SBO/PBO 10.
  • the latter is configured from a monolithic slab which can first double the fundamental frequency and further generate a higher harmonic at for example 355 nm and 266 nm. For this reason, the domain period along a path of light at the fundamental frequency through the slab varies from one for SHG and, then, for example, the FHG.
  • Such a configuration can be used in a microchip of no longer than 5 - 10 mm and including a laser diode on vanadate and SBO/PBO 10 to produce a mW output.
  • the configuration of crystal 10 may include more than two periods.
  • the pulsed regime of the disclosed systems can be implemented by utilizing a chirp pulse amplification technique.
  • the pulse laser sources further may be based on a passively mode locked or actively mode locked lasers outputting nanosecond, and sub nanosecond, i.e., femtosecond and picosecond pulses.
  • the average power of the output of the disclosed pulsed systems may vary between milliwatts (mW) and about 100 W in UV/DUV frequency ranges.
  • the disclosed schematic can operate generating harmonics higher than the fifth harmonic. Accordingly, other aspects, advantages, and modifications are within the scope of the following claims.

Landscapes

  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • Optics & Photonics (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
  • Lasers (AREA)

Abstract

The disclosed laser system is configured with a laser source outputting light at a fundamental frequency. The output light is incident on a frequency converter operative to convert the fundamental frequency to a higher harmonic including at least one frequency converting stage. The frequency converter is based on a SrΒ4O7 (SBO) or PbB4O7 (PBO) nonlinear crystal configured with a plurality of domains. The domains have periodically alternating polarity of the crystal axis enabling a QPM use and formed with each with highly parallel walls which deviate from one another less than 1 micron over a 10 mm distance.

Description

HIGH POWER LASER CONVERTER BASED ON PATTERNED SrB4BO7 OR PbB4O7
CRYSTAL
BACKGROUND OF THE DISCLOSURE
Field of the Disclosure
[001] The disclosure relates to a high power solid state laser provided with at least one nonlinear converter based on patterned Strontium Tetraborate SrB4B07 (SBO) and Lead
Tetraborate PbB407 (PBO) crystals.
Background of the Disclosure
[002] The demand for laser tools in the ultraviolet (UV) and particularly high power deep UV (DUV) range is growing enormously to address the needs experienced by heavy industries, medicine, data storage, optical communication, entertainment and others Advances in semiconductor photolithography, micromachining and material-processing applications, for example, are driving demand for coherent light sources operating in UV and DUV spectral regions.
[003] Although some gas lasers, such as excimer lasers can emit isolated wavelengths of coherent light in the UV and DUV spectral regions with a high average output power, compact and efficient solid-state lasers with nonlinear optical (NLO) crystals in this spectral range are still needed due to their well-known high efficiency, low maintenance, small footprint and overall low cost. The performance of solid-state lasers in the UV and DUV spectral regions depends mostly on advances in the fabrication of efficient and reliable NLO crystals discovered over the last two decades.
[004] The copending US patent application No. discloses a method for fabricating a patterned non-ferromagnetic nonlinear SBO or PBO fully incorporated herein by reference. This subgroup of borates has some remarkable properties. First, it has a uniquely large (even among borates) bandgap of ~9 eV and its UV cut-off is about 130 nm. There is no literature data, but very likely (as many other borates) the SBO should be very transparent in VIS near infrared (IR). Its absorption should be in a single ppm/cm range. It is mechanically stable and non- hydroscopic. It is easy to grow this crystal by the known conventional techniques.
[005] In addition, these crystals have a very high (for borate) thermal conductivity of ~16 W/m*K, It is an order of magnitude higher than that of BBO and LBO. Last but not least, the SBO crystal is one of a very few non-linear materials (if not the only one) which does not have two-photon absorption (TP A) at 266 nm - a nonlinear effect increasing the power loss and light- induced damage. Combined with the unique optical transparency and high LIDT, the SBO/PbBO crystal is probably the only non-linear material capable of withstanding sustainable multi-watt operation (pulsed and CW) at 266 nm with fluencies typical for non-linear conversion regimes (-100-500 MW/cm2). Clearly with the periodic phase matching structure method of fabrication disclosed in the copending application this group of borates is an ideal material for nonlinear interactions.
[006] It is, therefore, desirable to provide a laser based on SBO or PBO.
SUMMARY OF THE DISCLOSURE
[007] This need is satisfied by a group of high power laser systems capable of operating in a UV frequency range. All of the disclosed systems have a common general optical schematic. The latter is provided with a laser source and at least one frequency converter so as to output sub-nanosecond, preferably picosecond pulses in a UV spectral region. As one of ordinary skill readily knows, ps fiber lasers participating in generating higher harmonics, such as UV light, are advantageous over ns fiber lasers because the nonlinear crystals in the ps pulsed regime have longer useful life than that of crystals irradiated by ns pulses. This advantage becomes even more prominent when the SBO or PBO is used since there is no 2 -photon absorption is these crystals.
BRIEF DESCRIPTION OF THE DRAWINGS
[008] The above and other aspects and feature will become more readily apparent in conjunction with the following drawings, in which:
[009] FIG. 1 is a general optical schematic of the inventive laser system;
[010] FIG. 2 shows a patterned SBO/PBO crystal of the inventive system;
[01 1] FIG. 3 is an exemplary schematic of the inventive system of FIG. 1 used for generation of the FH.
[012] FIG. 4 is an exemplary schematic of the inventive system of FIG. 1 used for generation of the third and higher harmonics.
[013] FIG. 5 is an exemplary schematic of the inventive system of FIG. 1 used for generation of the fifth harmonic. [014] FIG. 6 is an exemplary schematic of the inventive system of FIG. 1 used for parametric conversion.
[015] FIG. 7 is the SBO/PBO crystal of FIG. 2 configured from a single slab to provide a frequency conversion of the fundamental frequency into a plurality of successive harmonics.
SPECIFIC DESCRIPTION
[016] Reference will now be made in detail to the disclosed inventive concepts. Wherever possible, same or similar reference numerals are used in the drawings and the description to refer to the same or like parts or steps. The drawings are in simplified form being far from precise scale.
[017] FIG. 1 illustrates a general optical schematic 40 of the inventive laser system. The schematic 40 is configured as a source of electromagnetic (EM) radiation 42 incident on a frequency converter 44 which is based, at least in part, on patterned SBO or PBO nonlinear crystal 10 and configured to convert a fundamental frequency into a higher harmonic. Typically, the converters are placed in a single-pass or multi-pass resonator.
[018] The EM source 42 is a laser system operating in various regimes which includes continuous a wave (CW) mode, quasi-continuous wave (QCW) mode and pulsed modes. For many applications, source 42 is a high power source with the output of at least 1 kW and as high as of MWs. However, laser systems operating under a kW power level are also part of the disclosed subject matter.
[019] The configuration of source 42 is not limited to any particular lasing medium. Preferably, it is a solid state laser system including fiber and yttrium aluminum glass (Y AG) lasing media, with the disk lasers being a subclass of YAGs. The light emitting ions doped in the lasing media include various rare-earth metals. Since an industrial range of fundamental wavelengths and their higher harmonics is mostly associated with laser sources emitting light in a 1 - 2 mm range, ions of ytterbium (Yb), erbium (Er), neodymium (Nd), and Thulium perhaps are most frequently used. The mentioned elements are however do not represent the exclusive list of all rare earth elements that may be used for light generation in the inventive system.
[020] The architecture of laser source 42 may be represented by a variety of specific configurations. For example, the laser source may have a MOP A configuration including a combination of master oscillator (MO) 43 and power amplifier (PA) 44. The MO 43 may include semiconductors or fibers preferably operating at a single frequency. For example, MO 43 can be configured in accordance with the schematics disclosed in PCT/US 15/65798 and PCT/US 15/52893 which are owned by the assignee of the current applications and incorporated here by reference in their entirety. Considering that modem power levels of known oscillators have reached a kW level, the architecture of source 42 may be represented only by lasers omitting thus the amplifier. As to the amplifier, its examples can be found in PCT/US2017/064297 disclosing an Yb/YAG system or USP 8068705 disclosing a fiber amplifier and many others owned by the assignee of the current application and fully incorporated herein by reference. Regardless of its configuration, laser source 42 preferably outputs a single frequency, single transverse mode sub-nanosecond output in the QCW and pulsed regime. However, a beam quality factor M2 may be higher than 1, for example 1.5.
[021] Referring to FIGs. 1 and 2, frequency converter 44 operates to generate a second harmonic (SH), third harmonic (TH), fourth harmonic (FH), and other higher harmonics as well as to perform optical parametric interactions. The crystal SBO or PBO 10 is configured with a periodic structure 12 of domains 30 and 32 having respective opposite polarities +/- which alternate one another. These domains have highly parallel walls. The periodic structure 12 allows the use of a QPM technique to generate high harmonic of the pump light. Recent experiments conducted by the Applicants resulted in crystal 10 provided with a volume periodic pattern which includes a sequence of uniformly dimensioned 3D-domains 30, 32 having respective positive and negative polarities which alternate one another and provide the crystal with a clear aperture having a diameter of up to a few centimeters. The domains each are configured with a uniform thickness corresponding to the desired coherence length 1 and ranging from about 0.2 mm to about 20 mm and a clear aperture which has a dimeter varying from about 1 mm to about 5 cm. The crystal 10 can be utilized as an optical element, such as a frequency converter incorporated in a laser which operates in a variety of frequency ranges. For example, crystal 10, configured to convert a fundamental frequency of laser source 42 to a DUV range, has a coherence length 1 ranging between 0.2 to about 5 nm. The volume pattern may extend through the entire thickness of crystal block 10 between faces +C and -C, or terminate at a distance from one of these faces. The crystal 10 is based on the discussed above unique qualities and disclosed in copending, co-owned US application 62781371which is filed concurrently with the subject matter application which incorporates it by reference in its entirety. [022] The SBO/PBO 10 is characterized by a short UV absorption cut-off (lcutoff) or wide energy bandgap (Eg) which guarantee the transmittance in the UV and DUV spectra. Moreover, the large bandgap significantly decreases the two-photon absorption or multi-photon absorption, and thus, in turn, increases the laser-induced damage threshold in a crystal and results in reduced non-desirable thermo-optical effects. Linear absorption of borates is typically very low as well.
[023] Accordingly, SBO/PBO crystal 10 is particularly attractive when used in laser systems operating in ultraviolet/deep ultraviolet (UV/DUV) frequency ranges. UV/DUV lasers are widely employed in various applications. For instance, a DUV at 266 nm has been utilized as an external seed of a free-electron laser with outputs as short as about 4 nm so useful in the scientific research beyond the carbon K-edge. The industrial applications, laser machining of wide bandgap materials, microelectronics and many other are direct beneficiaries of the DUV lasers owing to their high photon energy. The conversion schemes are numerous and examples thereof are disclosed hereinbelow.
[024] Referring to FIG. 3, an exemplary schematic setup of system 40 includes converter 46 configured with SHG 46 and FHG 48 stages. The SHG 46 doubles the frequency of the pump wave in a 1 mm wavelength range to Green light and the latter continuing frequency conversion to obtain ultraviolet/deep UV (UV/DUV 50) light at or lower than a 2xx nm wavelength. For example, a pump wavelength at a 1060 nm output by source 42 (fundamental frequency w), is converted into a second harmonic 2w (532 nm wavelength) in SHG 46 which, in turn, is converted into the fourth harmonic 4w (266 nm wavelength.) The SHG 46 may be based on BBO, LBO CLBO, SBO, PBO and other nonlinear crystals. The FHG 48 includes SBO/PBO crystal 10.
[025] FIG. 4 exemplifies a schematic configured to generate the third harmonic (THG) 50. The system 40 includes source 42 outputting light at fundamental frequency w which is incident on SHG 46. The latter 46 converts the fundamental frequency into second harmonic 2w. The THG 50 receives a remaining portion of light at the fundament frequency and second harmonic and combines these frequencies to create the third harmonic. The SHG 46 may have the configuration of FIG. 3, and so does THG 50 including SBO/PBO crystal 10. A non- inclusive example can be illustrated by a fundamental wavelength of 1064 nm which eventually is converted into the TH of about 355 nm. The system 40 may be further provided with a FiHG 52 combining the unused SH and generated TH.
[026] FIG. 5 illustrates still another example of system 40 with converter 44 configured to generate the fifth harmonic (FiHG). The converter 44 operates by initially generating the SH in SHG 46. The unused light at the fundamental (pump) is separated from the SH at the output of SHG 46 and further guided to the fifth harmonic generator (FiHG) 52 along a path defined by reflective elements, such as mirrors or prisms. If desired, the unconverted light at the fundamental frequency can be guided through FHG 48.
[027] Based on the foregoing, SBO/PBP quasi phase matched crystal 10 can be used for frequency doubling, tripling etc, as well as for sum and difference frequency generation. It also can be used for parametric amplification. Referring to FIG. 6, light at a signal wavelength propagates through crystal 10 together with a pump beam of shorter wavelength resulting in several outputs which include an idler, residual pump beam and signal separate outputs, as well known to one of ordinary skill.
[028] As known to one of ordinary skill, it is impractical to use standard crystals, such as PPKTP or PIPLIN for generating the FH because this harmonic of 1- 2” fundamental wavelength coincides with (or even falls beyond) the cutoff wavelength of these materials. The crystals that may generate the mentioned FH have very low nonlinearity. The SBO/PBO, however, is highly nonlinear and has a cutoff wavelength around 130 nm which obviously extends its conversion abilities way into the DUV frequency range allowing thus inventive laser system 40 operate way below 200 nm and even below 160 nm.
[029] FIG. 7 illustrates another configuration of system 40 including laser source 42 of FIG. 1, which is a diode laser in this schematic, and SBO/PBO 10. The latter is configured from a monolithic slab which can first double the fundamental frequency and further generate a higher harmonic at for example 355 nm and 266 nm. For this reason, the domain period along a path of light at the fundamental frequency through the slab varies from one for SHG and, then, for example, the FHG. Such a configuration can be used in a microchip of no longer than 5 - 10 mm and including a laser diode on vanadate and SBO/PBO 10 to produce a mW output. The configuration of crystal 10 may include more than two periods.
[030] It is to be understood that while the invention has been described in conjunction with the detailed description thereof, the foregoing description is intended to illustrate and not limit the scope of the invention, which is defined by the scope of the appended claims. For example, the pulsed regime of the disclosed systems can be implemented by utilizing a chirp pulse amplification technique. The pulse laser sources further may be based on a passively mode locked or actively mode locked lasers outputting nanosecond, and sub nanosecond, i.e., femtosecond and picosecond pulses. The average power of the output of the disclosed pulsed systems may vary between milliwatts (mW) and about 100 W in UV/DUV frequency ranges. The disclosed schematic can operate generating harmonics higher than the fifth harmonic. Accordingly, other aspects, advantages, and modifications are within the scope of the following claims.

Claims

1. A laser system, comprising:
a laser source outputting light at a fundamental frequency; and
a frequency generator operative to convert the fundamental frequency into a higher harmonic and including at least one frequency converting stage which is based on a SrB40v (SBO) or PbB4O7 (PBO) crystal, wherein the SBO/PBO crystal is configured with a plurality of domains with respective periodically alternating polarity of the crystal axis enabling QPM use, the domains having parallel walls deviating from one another less than 1 micron over a 10 mm distance.
2. The laser system of claim 1 , wherein the SBO/PBO crystal is configured to generate the higher harmonic selected from the group consisting of a second harmonic, third harmonic, fourth harmonic, and fifth harmonic and a combination of the higher harmonics.
3. The laser system of claim 1 , wherein the SBO/PBO crystal is configured to provide optical parametric interactions.
4. The laser system of claim 1, wherein the SBO/PBO has a thickness of each domain for a VIS-DUV light ranges varying between 0.2 mm and about 20 mm, and a clear aperture with a minimal dimeter ranging from about 1 mm to about 5 cm.
5. The laser system of claim 1 , wherein the laser source includes a laser system operating in a continuous wave (CW), quasi-continuous wave (QCW) or pulsed regimes.
6. The laser system of claim 5, wherein the laser source includes a solid-state laser selected from the group consisting of a fiber laser, yttrium aluminum glass (YAG) and disk laser, the solid state laser being configured with a gain medium doped with light emitting dopants, which are selected from rare-earth elements, and outputting light in a 1 to 2 mm wavelength range.
7. The laser system of claim 5, wherein the laser source has a master-oscillator (MO) power amplifier (PA) configurations.
8. The laser system of claim 7, wherein the laser source outputs a train of pulses in a nano - subnanosecond pulse duration range.
9. The laser system of claim 1, wherein the converter includes a single, monolithic slab of SBO/PBO formed with at least two different domain periods, wherein light at the fundamental frequency propagates along a path through the slab which has an upstream end thereof provided with the period for a SHG and a downstream stream end of the slab having the period for the higher harmonic.
10. The laser system of claim 2, wherein the SBO outputs a single mode light at a wavelength of about 130 nm and average power of at least 10 W at the high harmonic.
PCT/US2019/067135 2018-12-18 2019-12-18 High power laser converter based on patterned srb4bo7 or pbb407 crystal WO2020132043A1 (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
CN201980083902.7A CN113196596B (en) 2018-12-18 2019-12-18 High power laser converter based on patterned SRB4BO7 or PBB4O7 crystals
US17/415,090 US11719993B2 (en) 2018-12-18 2019-12-18 High power laser converter based on patterned SRB4B07 or PBB407 crystal
KR1020217021906A KR102707500B1 (en) 2018-12-18 2019-12-18 High-power laser converters based on patterned SRB4BO7 or PBB4O7 crystals
EP19898599.6A EP3881402B1 (en) 2019-12-18 High power laser converter based on patterned srb4bo7 or pbb407 crystal
JP2021535150A JP2022514745A (en) 2018-12-18 2019-12-18 High power laser transducer based on patterned SrB4O7 or PbB4O7 crystals

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US201862781386P 2018-12-18 2018-12-18
US62/781,386 2018-12-18

Publications (2)

Publication Number Publication Date
WO2020132043A1 true WO2020132043A1 (en) 2020-06-25
WO2020132043A8 WO2020132043A8 (en) 2021-06-10

Family

ID=71101653

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US2019/067135 WO2020132043A1 (en) 2018-12-18 2019-12-18 High power laser converter based on patterned srb4bo7 or pbb407 crystal

Country Status (5)

Country Link
US (1) US11719993B2 (en)
JP (1) JP2022514745A (en)
KR (1) KR102707500B1 (en)
CN (1) CN113196596B (en)
WO (1) WO2020132043A1 (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11237455B2 (en) * 2020-06-12 2022-02-01 Kla Corporation Frequency conversion using stacked strontium tetraborate plates
US11567391B1 (en) 2021-11-24 2023-01-31 Kla Corporation Frequency conversion using interdigitated nonlinear crystal gratings
WO2023107298A1 (en) * 2021-12-11 2023-06-15 Kla Corporation Deep ultraviolet laser using strontium tetraborate for frequency conversion

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20210103502A (en) * 2018-12-18 2021-08-23 아이피지 포토닉스 코포레이션 Method for making patterned SrB4BO7 and PbB4O7 crystals
US11719993B2 (en) 2018-12-18 2023-08-08 Ipg Photonics Corporation High power laser converter based on patterned SRB4B07 or PBB407 crystal

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8068705B2 (en) 2009-09-14 2011-11-29 Gapontsev Valentin P Single-mode high-power fiber laser system
WO2013043842A1 (en) * 2011-09-23 2013-03-28 Kla-Tencor Corporation Solid-state laser and inspection system using 193nm laser
CN108683072A (en) * 2018-05-18 2018-10-19 北方工业大学 A method of improving SBO deep ultraviolet double-frequency laser delivery efficiencies
US20220066283A1 (en) 2018-12-18 2022-03-03 Ipg Photonics Corporation High power laser converter based on patterned srb4b07 or pbb407 crystal

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1255331A1 (en) * 2001-05-01 2002-11-06 Coherent, Inc. CW far-UV laser system with two active resonators
JP2010256659A (en) * 2009-04-27 2010-11-11 National Institute For Materials Science Wavelength conversion element, wavelength conversion device, and lithium tantalate single crystal used for the same
DE102009028819B4 (en) * 2009-08-21 2012-07-19 Forschungsverbund Berlin E.V. Apparatus and method for amplifying or frequency converting laser radiation using quasi-phase matching in four-wave mixing
US9318870B2 (en) * 2011-05-06 2016-04-19 Kla-Tencor Corporation Deep ultra-violet light sources for wafer and reticle inspection systems
US20130313440A1 (en) * 2012-05-22 2013-11-28 Kla-Tencor Corporation Solid-State Laser And Inspection System Using 193nm Laser
US9509112B2 (en) * 2013-06-11 2016-11-29 Kla-Tencor Corporation CW DUV laser with improved stability
AU2015383603B2 (en) * 2015-02-17 2018-10-25 Alcon Inc. Femtosecond ultraviolet laser
WO2019222263A1 (en) * 2018-05-14 2019-11-21 Cornell University Generation of broadband coherent laser pulses based on adiabatic four-wave mixing in waveguides and fiber
KR20210103502A (en) * 2018-12-18 2021-08-23 아이피지 포토닉스 코포레이션 Method for making patterned SrB4BO7 and PbB4O7 crystals

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8068705B2 (en) 2009-09-14 2011-11-29 Gapontsev Valentin P Single-mode high-power fiber laser system
WO2013043842A1 (en) * 2011-09-23 2013-03-28 Kla-Tencor Corporation Solid-state laser and inspection system using 193nm laser
CN108683072A (en) * 2018-05-18 2018-10-19 北方工业大学 A method of improving SBO deep ultraviolet double-frequency laser delivery efficiencies
US20220066283A1 (en) 2018-12-18 2022-03-03 Ipg Photonics Corporation High power laser converter based on patterned srb4b07 or pbb407 crystal

Non-Patent Citations (6)

* Cited by examiner, † Cited by third party
Title
A.S. ALEKSANDROVSKY ET AL.: "Deep UV generation and fs pulses characterization using strontium tetraborate", NONLINEAR OPTICS AND APPLICATIONS V, vol. 8071, no. 1, 2011, pages 1 - 9, XP060014012, DOI: 10.1117/12.886189
A.S. ALEKSANDROVSKY ET AL.: "Observation of spontaneously grown domain structure in SBO crystals via nonlinear diffraction", SOLID STATE LASERS AND NONLINEAR FREQUENCY CONVERSION, vol. 6610, 2007
ALEKSANDROVSKIY A.S. ET AL.: "Generation of far ultraviolet radiation in an SBO crystal with an irregular domain structure", QUANTUM ELECTRONICS, no. 8, 2011, pages 748 - 753, XP009528488, ISSN: 0368-7147 *
See also references of EP3881402A4
VYUNYSHEV ANDREY MIKHAILOVICH: "Nonlinear optical conversion of radiation in irregular domain structures of strontium tetraborate", ABSTRACT OF THE DISSERTATION FOR THE DEGREE OF CANDIDATE OF PHYSICAL AND MATHEMATICAL SCIENCES, 30 November 2008 (2008-11-30), pages 1 - 19, XP009528715 *
ZAITSEV A.I. ET AL.: "Growth, optical and microstructural properties of PbB407 plate crystals", OPTICAL MATERIALS, vol. 37, 7 November 2014 (2014-11-07), pages 298 - 301, XP029082633, DOI: 10.1016/j.optmat.2014.06.012 *

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11237455B2 (en) * 2020-06-12 2022-02-01 Kla Corporation Frequency conversion using stacked strontium tetraborate plates
US11543732B2 (en) 2020-06-12 2023-01-03 Kla Corporation Frequency conversion using stacked strontium tetraborate plates
US11567391B1 (en) 2021-11-24 2023-01-31 Kla Corporation Frequency conversion using interdigitated nonlinear crystal gratings
US11815784B2 (en) 2021-11-24 2023-11-14 Kla Corporation United states frequency conversion using interdigitated nonlinear crystal gratings
WO2023107298A1 (en) * 2021-12-11 2023-06-15 Kla Corporation Deep ultraviolet laser using strontium tetraborate for frequency conversion
US11899338B2 (en) 2021-12-11 2024-02-13 Kla Corporation Deep ultraviolet laser using strontium tetraborate for frequency conversion

Also Published As

Publication number Publication date
KR20210102390A (en) 2021-08-19
EP3881402A4 (en) 2022-09-07
JP2022514745A (en) 2022-02-15
US20220066283A1 (en) 2022-03-03
KR102707500B1 (en) 2024-09-13
US11719993B2 (en) 2023-08-08
EP3881402A1 (en) 2021-09-22
CN113196596A (en) 2021-07-30
WO2020132043A8 (en) 2021-06-10
CN113196596B (en) 2024-08-20

Similar Documents

Publication Publication Date Title
US11719993B2 (en) High power laser converter based on patterned SRB4B07 or PBB407 crystal
JP6665106B2 (en) Ultra-high power single-mode green fiber laser operating in continuous-wave and quasi-continuous-wave modes
Soh et al. A 980-nm Yb-doped fiber MOPA source and its frequency doubling
JP2011193029A (en) Laser resistant to internal ir-induced damage
CN101202405A (en) Method for obtaining 192 nm ultraviolet laser by 1342 nm laser 7 frequency multiplication
EP3881402B1 (en) High power laser converter based on patterned srb4bo7 or pbb407 crystal
US20150316831A1 (en) Diamond-based supercontinuum generation system
RU2809331C2 (en) HIGH POWER LASER CONVERTER BASED ON STRUCTURED CRYSTAL SrB4O7 OR PbB4O7
McKay et al. High average power (11 W) eye-safe diamond Raman laser
Creeden et al. Multi-watt mid-IR fiber-pumped OPO
Croitoru et al. Buried Depressed-Cladding Waveguides Fabricated in RE3+: CLNGG Laser Crystals using Direct Laser Writing Technique
Hong et al. High-beam-quality all-solid-state 355 nm ultraviolet pulsed laser based on a master-oscillator power-amplifier system pumped at 888 nm
Kubecek et al. Lithium triborate picosecond optical parametric oscillator
Fu et al. High efficiency and high power 260 nm deep UV laser pumped by an all-fiberized ytterbium-doped fiber laser
Vasilyev et al. 7 W few-cycle mid-infrared laser source at 79 MHz repetition rate
Dehn et al. Phase conjugation for improvement of solid state and excimer lasers
Xuan et al. High power Yb: YAG ceramics laser and diamond Raman laser for frequency conversion to DUV
Donelan et al. OPG and OPO Nonlinear Conversion in OP-GaAs using 2 μm Single Oscillator Pump Sources
Popov et al. High power, seeded, fiber-amplifiers and non-linear conversion in periodically-poled crystals
Simons et al. Compact diode-pumped 598-nm laser source
Soh et al. An 18-mW 488.7-nm cw frequency-doubled fiber MOPA source
Oku et al. High power all-fiber picosecond laser system for UV light generation
Shcheslavskiy et al. Third-harmonic generation from Rayleigh particles: breaking all the rules
Cocuzzi et al. Fiber-guided seeding of narrow bandwidth, sub-nanosecond optical parametric pulse generation in PPLN
Kaneda et al. All-solid-state sub-200-nm pulsed deep ultraviolet source

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 19898599

Country of ref document: EP

Kind code of ref document: A1

ENP Entry into the national phase

Ref document number: 2021535150

Country of ref document: JP

Kind code of ref document: A

NENP Non-entry into the national phase

Ref country code: DE

ENP Entry into the national phase

Ref document number: 2019898599

Country of ref document: EP

Effective date: 20210617

ENP Entry into the national phase

Ref document number: 20217021906

Country of ref document: KR

Kind code of ref document: A