WO2022016224A1 - Laser pulsé pour traitements dermatologiques - Google Patents

Laser pulsé pour traitements dermatologiques Download PDF

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WO2022016224A1
WO2022016224A1 PCT/AU2021/050790 AU2021050790W WO2022016224A1 WO 2022016224 A1 WO2022016224 A1 WO 2022016224A1 AU 2021050790 W AU2021050790 W AU 2021050790W WO 2022016224 A1 WO2022016224 A1 WO 2022016224A1
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harmonic
generator
idler
crystal
laser
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Alexandre Francois
Nathan Holmes
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Norseld Pty Ltd
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Norseld Pty Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/005—Optical 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
    • H01S3/0092—Nonlinear frequency conversion, e.g. second harmonic generation [SHG] or sum- or difference-frequency generation outside the laser cavity
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B18/18—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves
    • A61B18/20—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves using laser
    • A61B18/203—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves using laser applying laser energy to the outside of the body
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL 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
    • G02F1/00—Devices 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
    • G02F1/35—Non-linear optics
    • 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
    • H01S3/1083—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 using parametric generation
    • 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
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B2018/00315—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body for treatment of particular body parts
    • A61B2018/00452—Skin
    • A61B2018/00458—Deeper parts of the skin, e.g. treatment of vascular disorders or port wine stains
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B2018/00315—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body for treatment of particular body parts
    • A61B2018/00452—Skin
    • A61B2018/0047—Upper parts of the skin, e.g. skin peeling or treatment of wrinkles
    • 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
    • H01S3/109—Frequency multiplication, e.g. harmonic generation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/11—Mode locking; Q-switching; Other giant-pulse techniques, e.g. cavity dumping
    • H01S3/1106—Mode locking
    • H01S3/1109—Active mode locking
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/11—Mode locking; Q-switching; Other giant-pulse techniques, e.g. cavity dumping
    • H01S3/1106—Mode locking
    • H01S3/1112—Passive mode locking
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/11—Mode locking; Q-switching; Other giant-pulse techniques, e.g. cavity dumping
    • H01S3/1123—Q-switching

Definitions

  • Lasers are now commonly used for the treatment of a large range of benign pigmented and vascular skin pathologies, as well as in cosmetic procedures such as skin whitening and tattoo and hair removal.
  • Most laser-based treatments involve an intense laser light source directed at the affected skin tissue, enabling, in most cases, a photothermal reaction and occasionally a photochemical reaction targeting specific chromophores, resulting in their elimination and/or downregulation as shown by R. Anderson et al. (“Selective photothermolysis: precise microsurgery by selective absorption of pulsed radiation” Science 20, 524-527 (1983)).
  • Tattoo-removal lasers are typically operated at wavelengths between 670 nm and 1200 nm with picosecond to sub-nanosecond pulse durations, while hair-removal lasers use wavelengths between 700 nm and 1 .064 pm.
  • Shorter wavelengths typically ranging from 400 nm to 700 nm, have also been extensively used for treating pigmented and vascular lesions such as melasma, lentigines, seborrhoeic keratoses, cafe-au-lait macules, port-wine stain birthmarks, telangiectasiae, rosacea, spider angiomas, cherry angiomas, venous lakes and others and for treating variations of skin pigmentation (i.e. skin whitening).
  • FIG. 1 shows the absorption spectra of both melanin and haemoglobin, exploited for the treatment of abnormal skin pigmentation and vascular lesions respectively.
  • Examination of both spectra reveals that while melanin exhibits a monotonous decay of its absorption with increasing wavelengths, haemoglobin is characterized by three distinct absorption peaks - at 412 nm and 542 nm - and again at 577 nm, where the haemoglobin absorption is greater than melanin. Otherwise, melanin absorption is always higher than haemoglobin.
  • This unique behaviour allows for specifically targeting either melanin or haemoglobin as a function of wavelength for photothermal or photochemical treatment, enabling selective treatment of either pigmented or vascular tissue.
  • UV wavelengths Shorter wavelengths, especially in the UV (below 300 nm) and in the visible (around 490nm) are well suited for the treatment of melanin, as the melanin absorption at these wavelengths is high and haemoglobin absorption low. UV wavelengths are, however, best avoided for skin treatments as they could induce ionising damage as shown by R. Kaufmann et al. (“Pulsed Er.YAG and 308 nm UV-excimer laser: an in vitro and in vivo study of skin-ablative effects” Laser Surg. Med. 9, 132-140 (1989)), leaving the wavelength in the visible region, centred around 490 nm, as the most viable option.
  • Pulsed laser regimes have the advantage that the shorter the pulse duration - typically tens of nanosecond to hundreds of picoseconds - the higher the energy peak delivered per pulse when compared with the same average power in CW or long pulse duration laser sources.
  • the combination of wavelength and pulse energy duration results in much greater penetration depth in tissue which is advantageous for evoking photochemical processes throughout the thickness of the epidermis without collateral thermal damage to surrounding tissue.
  • the aforementioned wavelengths, centred around 490 nm and 577 nm, are notoriously difficult to produce, especially when both high repetition rate and pulse energies are required for photothermal damage.
  • the most efficient laser sources for yellow wavelengths are gas plasma copper vapour and copper bromide lasers, which coincidently emit two wavelengths simultaneously at 511 nm and 578 nm, making them the perfect tool for treating both pigmented and vascular skin lesions with a single laser system as shown in multiple reports from by H.l.
  • Moulton et al. (“Three-color Coherent Light System” US005740190A) developed a laser system capable of generating 3 different wavelengths in the blue (455 nm), green (532 nm) and red (618 nm), produced by a combination of non-linear effects including second harmonic generation and optical parametric oscillation, which can be subsequently recombined to generate any visible colour for illumination and display applications.
  • this complex system requires 2 different pump laser sources and does not generate light at the wavelengths of interest (490 nm and 576 nm) for the specific excitation of both melanin and haemoglobin required for the treatment of pigmented and vascular lesions, respectively.
  • Hunziker et al. (“Dermatological picosecond laser treatment systems and method using optical parametric oscillator”, US2019/0151019A1 ) also used a combination of second harmonic generation and optical parametric oscillation to create a laser system capable of generating multiple wavelengths suitable for dermatological treatment including tattoo removal and pigmented lesions.
  • the different wavelengths can not be produced simultaneously but are instead collected after each non-linear process stage to produce either the fundamental of pump laser (1 OOOnm to 1200nm, preferably between 1050 and 1070 nm), after the first second harmonic generation (500nm to 600nm, preferably between 525 and 535nm) and after the optical parametric oscillation spectra (i.e.
  • US 2016/0143692A1 (Laser System for skin treatment) describes a laser system skin treatment using a second harmonic generation stage to produce the 2nd harmonic from a YLF crystal (1048nm) at 524nm.
  • the YLF crystal is pumped by a Alexandrite laser and passively Qswitch (Cr:YAG), and so there is no control over the repetition rate.
  • the temporal output is a train of short pulses (1 to 200ns) produced by the passive Qswitch. This train of pulses is further modulated by the operation of the Alexandrite laser which typically has a 1 to 10 Hz repetition rate.
  • the output wavelengths are 524nm (2nd harmonic) for the treatment of vascular lesions and 1064nm for collagen stimulation.
  • US2019/0336213A1 High power tuneable optical parametric oscillator for selective photothermolysis laser surgery discloses operation of multiple identical Optical Parametric Oscillator in parallel (One pump laser with multiple beam output pump multiple Optical Parametric Oscillator which produce identical wavelengths subsequently recombined). The output is continuously tuneable but requires each Optical Parametric Oscillator crystal to be rotated simultaneously which requires precise control of movement.
  • the invention provides a light emitting apparatus for the dermatological treatment of a patient comprising a pulsed laser generator; an optical parametric generator to produce an idler laser beam and a signal laser beam, and comprising a non-linear crystal; a first harmonic generator to produce from the idler its nth harmonic; a second harmonic generator to produce from the signal its nth harmonic; an applicator arranged to receive and apply either the nth harmonic of the idler, the nth harmonic of the signal or both to the skin of the patient.
  • the invention provides a light emitting apparatus for the dermatological treatment of a patient comprising: a pulsed laser generator; an optical parametric generator to produce an idler laser beam and a signal laser beam, and comprising a plurality of light redirectors and a non-linear crystal; a first harmonic generator comprising a crystal to produce from the idler its nth harmonic; a second harmonic generator comprising a crystal to produce from the signal its nth harmonic; wherein the non-linear crystal, the first harmonic generator crystal and the second harmonic generator crystal each comprise a crystal selected from one or more of LBO, CLBO, BBO, BIBO, BBO,SBBO, KAB, LiNb03, LiTa03, KNb03, KTP, KTA, RTP, RTA; an applicator arranged to receive and apply either the nth harmonic of the idler, the nth harmonic of the signal or both to the skin of the patient.
  • the invention provides a light emitting apparatus for the dermatological treatment of a patient comprising: a pulsed pump laser generator comprising a laser emitting at 500nm to 850 nm with a pulse duration of between 700 picoseconds to 30 nanoseconds and a repetition rate of between 100 Hz to 100 kHz; an optical parametric generator comprising a plurality of light redirectors selected from reflectors and refractors and a non-linear crystal positioned between a first and a second light redirector, the optical parametric generator to produce an idler laser beam and a signal laser beam, and comprising a non-linear crystal having a high second order susceptibility; a first harmonic generator comprising a crystal to produce from the idler its nth harmonic; a second harmonic generator comprising a crystal to produce from the signal its nth harmonic; wherein the non-linear crystal, the first harmonic generator crystal and the second harmonic generator crystal each comprise a crystal selected from one or more of LBO, CLBO, BBO, BI
  • KTP, KTA, RTP, RTA an applicator arranged to receive and apply either the nth harmonic of the idler, the nth harmonic of the signal or both to the skin of the patient; the apparatus comprising a resonator.
  • the invention provides a light emitting apparatus for the dermatological treatment of a patient comprising: a pulsed pump laser generator comprising a laser emitting at 500nm to 550 nm, Q-switched to produce about 10-100 mJ per pulse with a pulse duration of between 5-30 nanoseconds and a repetition rate of between 100 Hz to 22 kHz; an optical parametric generator comprising a plurality of reflectors: a non-linear crystal positioned between a first and a second reflector, the optical parametric generator to produce an idler laser beam and a signal laser beam, and comprising a non-linear crystal having a high second order susceptibility; a first harmonic generator comprising a crystal to produce from the idler its 2nd harmonic; a second harmonic generator comprising a crystal to produce from the signal its 2nd harmonic; wherein the non-linear crystal, the first harmonic generator crystal and the second harmonic generator crystal each comprise a crystal selected from one or more of LBO, CLBO, BBO, BIBO, B
  • the invention provides a light emitting apparatus for the dermatological treatment of a patient comprising: a pulsed pump laser generator comprising a laser emitting at 500nm to 532 nm, Q-switched to produce about 10-100 mJ per pulse with a pulse duration of between 5-30 nanoseconds and a repetition rate of between 100 Hz to 22 kHz; wherein the laser is selected from frequency doubled Nd:YAG laser, Nd:YV04, Nd:LuV04 or Nd:GdV04, Yb:YAG, Yb:YV04, Yb:GdV04 or Yb:LuV04; a diverter comprising a reflector to direct the output of the pulsed pump laser generator into the optical parametric generator; an optical parametric generator comprising a plurality of reflectors: a non-linear crystal positioned between a first and a second reflector, the optical parametric generator to produce an idler laser beam and a signal laser beam, and comprising a
  • a light emitting apparatus for the dermatological treatment of a patient comprising: a pulsed pump laser generator comprising a laser emitting at 500nm to 532 nm, Q-switched to produce about 10-100 mJ per pulse with a pulse duration of between 5-30 nanoseconds and a repetition rate of between 100 Hz to 22 kHz; wherein the laser is selected from frequency doubled Nd:YAG laser, Nd:YV04, Nd:LuV04 or Nd:GdV04, Yb:YAG, Yb:YV04, Yb:GdV04 or Yb:LuV04; a diverter comprising a reflector to direct the output of the pulsed pump laser generator into the optical parametric generator; an optical parametric generator comprising a plurality of reflectors: a non-linear crystal positioned between a first and a second reflector, the optical parametric generator to produce an idler laser beam and a signal laser beam, and comprising a non-linear crystal having a
  • a light emitting apparatus for the dermatological treatment of a patient comprising: a pulsed pump laser generator comprising a frequency doubled Nd:YAG laser emitting at 532 nm, actively Q-switched to produce about 10 mJ per pulse with a pulse duration of between 5-10 nanoseconds and a repetition rate of between 10 kHz to 20 kHz; a diverter comprising a reflector to direct the output of the pulsed pump laser generator into the optical parametric generator; an optical parametric generator comprising: a back reflector, an output reflector, a non-linear crystal positioned between the back and output reflectors, the optical parametric generator to produce an idler laser beam and a signal laser beam, and comprising a non-linear crystal having a high second order susceptibility (c2), as defined in equation 2: where P(t) is the dielectric polarization density, E(t) is the electric field and eq the vacuum permittivity (8.854x10-12 F/m); wherein the non-linear crystal comprises
  • a first harmonic generator comprising a BBO crystal cut at 21 .7 degrees to produce from the idler its 2nd harmonic at 578nm
  • a second harmonic generator comprising a BBO crystal cut at 24.2 degrees to produce from the signal its 2nd harmonic at 492.5nm
  • an applicator arranged to receive and apply either the 2nd harmonic of the idler, the 2nd harmonic of the signal or both to the skin of the patient
  • the apparatus comprising two reflective surfaces arranged as a singly resonant Optical Parametric Oscillator cavity.
  • the invention provides a light emitting apparatus for the dermatological treatment of a patient comprising: a pulsed pump laser generator comprising a frequency doubled Nd:YAG laser emitting at 532 nm, actively Q-switched to produce about 10 mJ per pulse with a pulse duration of between 5-10 nanoseconds and a repetition rate of between 10 kHz to 20 kHz; a diverter comprising a reflector to direct the output of the pulsed pump laser generator into the optical parametric generator; an optical parametric generator comprising: a back reflector, an output reflector, a non-linear crystal positioned between the back and output reflectors, the optical parametric generator to produce an idler laser beam and a signal laser beam, and comprising a non-linear crystal having a high second order susceptibility (c2), as defined in equation 2: where P(t) is the dielectric polarization density, E(t) is the electric field and eq the vacuum permittivity (8.854x10-12 F/m); where
  • a first harmonic generator comprising a BBO crystal cut at 21 .7 degrees to produce from the idler its 2nd harmonic at 578nm; a second harmonic generator comprising a BBO crystal cut at 24.2 degrees to produce from the signal its 2nd harmonic at 492.5nm; an applicator arranged to receive and apply either the 2nd harmonic of the idler, the 2nd harmonic of the signal or both to the skin of the patient; the apparatus comprising two reflective surfaces arranged as a singly resonant Optical Parametric Oscillator cavity.
  • the invention provides a light emitting apparatus for the dermatological treatment of a patient comprising: a pulsed pump laser generator comprising a frequency doubled Nd:YAG laser emitting at 532 nm, actively Q-switched to produce about 10 mJ per pulse with a pulse duration of between 5-10 nanoseconds and a repetition rate of between 10 kHz to 20 kHz; a diverter comprising a reflector to direct the output of the pulsed pump laser generator into the optical parametric generator; an optical parametric generator comprising: a back reflector, an output reflector, a non-linear crystal positioned between the back and output reflectors, the optical parametric generator to produce an idler laser beam and a signal laser beam, and comprising a non-linear crystal having a high second order susceptibility (c2), as defined in equation 2: where P(t) is the dielectric polarization density, E(t) is the electric field and eq the vacuum permittivity (8.854x10-12 F/m); where
  • a first harmonic generator comprising a BBO crystal cut at 21 .7 degrees to produce from the idler its 2nd harmonic at 578nm; a second harmonic generator comprising a BBO crystal cut at 24.2 degrees to produce from the signal its 2nd harmonic at 492.5nm; an applicator arranged to receive and apply either the 2nd harmonic of the idler, the 2nd harmonic of the signal or both to the skin of the patient; the apparatus comprising two reflective surfaces arranged as a singly resonant Optical Parametric Oscillator cavity.
  • the present invention provides a system for producing both high pulse energy and repetition rate yellow and green laser light simultaneously from a single laser system for dermatological treatment.
  • the invention relies on a combination of optical parametric generation and harmonic generation to produce two laser outputs in the visible portion of the optical spectrum.
  • a light emitting system for the dermatological treatment of a patient comprising: a pulsed laser generator to generate a pulsed light; an optical parametric generator; a first harmonic generator; a second harmonic generator; an applicator, arranged to receive and apply either the n th harmonic of the idler, the n th harmonic of the signal or both to the skin of the patient.
  • the invention provides a light emitting system for the treatment of abnormal skin pigmentation, skin pigmentation variations and vascular lesion comprising: a pulsed laser generator to generate a first pulsed light train with a 700 picoseconds to 30 nanoseconds pulse duration, a repetition rate of 100 Hz to 100 kHz and a wavelength ranging from 500nm to 850nm; an optical parametric generator, comprising a non-linear crystal inside an optical cavity formed by at least two reflectors, arranged to receive the first pulsed light train and generate two other pulse light trains, the idler and the signal, with their respective wavelengths higher than the first pulsed light train; a first harmonic generator comprising at least one non-linear crystal to generate the n th harmonic of the idler with an output fluence ranging from 5x10 4 W/cm 2 to 5x10 7 W/cm 2 ; a second harmonic generator comprising at least one non linear crystal to generate the n th harmonic of the signal with an output fluence ranging from 5x10 4
  • the wavelength of n th harmonic of the idler is ranging from 565nm to 595nm and the wavelength of n th harmonic of the signal is ranging from 480nm to 535nm. In some embodiments, the wavelength of n th harmonic of the idler is ranging from 480nm to 535nm and the wavelength of n th harmonic of the signal is ranging from 565nm to 595nm.
  • a light emitting system for the treatment of abnormal skin pigmentation, skin pigmentation variations and vascular lesion comprising: a pulsed laser generator to generate a first pulsed light train with a 700 picoseconds to 30 nanoseconds pulse duration, a repetition rate of 100 Hz to 100 kHz and a wavelength of 532 nm; an optical parametric generator, comprising a b-Barium Borate (BBO) non-linear crystal inside an optical cavity formed by at least two reflectors, arranged to receive the first pulsed light train and generate two other pulse light trains, the idler and the signal, with their respective wavelengths higher than the first pulsed light train; a 1 st harmonic generator being a Second Harmonic Generator (SHG) comprising a BBO non-linear crystal to double the frequency of the idler with an output fluence ranging from 5x10 4 W/cm 2 to 5x10 7 W/cm 2 ; a 2 nd harmonic generator being a SHG comprising a BBO
  • SHG Second Harmonic Generator
  • the wavelength of second harmonic of the idler is 578nm and the wavelength of second harmonic of the signal is 492.5nm. In some preferred embodiments the wavelength of second harmonic of the idler is 492.5nm and the wavelength of second harmonic of the signal is 578nm.
  • the pulse laser generator may be actively or passively Q-switched.
  • the optical parametric generator may be located in a number of positions, and in some preferred embodiments it is located within the optical cavity of the pulse laser generator.
  • An optical parametric generator can take a variety of forms.
  • OPO Optical Parametric Oscillator
  • it is an optical cavity formed by at least two mirrors surrounding a non-linear crystal.
  • a pump source can only be a coherent light source such as a laser source.
  • the pump laser once launched into the cavity, interacts with the non-linear crystal to generate two other wavelengths - the signal and idler.
  • the pump wavelength, signal and idler wavelengths are related to each other by the equation 1 . Phase matching between the pump, idler and signal wavelength is simply tuned by rotating the non-linear crystal, resulting into the generation of different pairs of signal and idler wavelengths satisfying equation 1 .
  • optical parametric generator architectures for example Optical Parametric Amplifier (OPA)
  • OPA Optical Parametric Amplifier
  • the optical parametric generator used in this invention could be either an Optical Parametric Oscillator or an Optical Parametric Amplifier, both fulfilling the required function.
  • a harmonic generator is a device also exploiting the optical properties of a non-linear crystal to generate the n th harmonic of the wavelength passing through.
  • the different harmonics i.e. 2 nd harmonic, 3 rd harmonic, 4 th harmonic and so on
  • 2 nd harmonic, 3 rd harmonic, 4 th harmonic and so on are produced through a combination of different non-linear effects with increasing complexity and decreasing efficiency as the harmonic order increases:
  • the pulsed laser generator is a frequency doubled near infra-red laser emitting a first pulsed light train - typically between 515 nm and 532 nm.
  • This first pulsed light train is directed into the optical parametric generator, where it may for example pass through a first non-linear crystal, set at a fixed incidence angle, to generate the idler and signal.
  • the incidence angle is set in such a way that the idler wavelength is 1156nm and the signal wavelength is 985nm.
  • Both the idler and signal wavelengths are then directed toward two harmonic generators, being SHG in this example, thereby doubling their respective frequencies. This results in the simultaneous generation of both 576nm and 492.5nm which can be used independently through an applicator for treatment of the patient’s skin.
  • FIG. 1 shows the relative absorption of two naturally occurring chromophores, haemoglobin and melanin.
  • FIG. 2 shows the depth of which a variety of wavelengths penetrate human skin.
  • FIG. 3 shows the system for generating two wavelengths using a combination of second harmonic generation and optical parametric generator.
  • FIG. 4 shows the tuning curve of a b-barium borate (BBO) type II crystal at room temperature with a 532nm pump laser input.
  • BBO b-barium borate
  • FIG. 5 shows the tuning curve of a potassium titanyle arsenate (KTA) type II crystal at room temperature with a 532nm pump laser input.
  • KTA potassium titanyle arsenate
  • FIG. 6 shows the details of the optical parametric generator arranged with a ring cavity.
  • a pump laser 1 emitting a coherent laser beam 2 at the wavelength l R is directed by a diverter (comprising reflectors 6 and 7) into the optical parametric generator, which comprises a back reflector 3 and output reflector 4 and a first non-linear crystal 5 positioned between the reflectors 3 and 4.
  • the optical parametric generator in turn produces two coherent laser beams 8 and 9, named the idler and signal respectively.
  • the wavelength of the idler, signal and the pump laser are related by equation 1 .
  • the idler 8 is then passed through a first harmonic generator 10 to produce its n th harmonic 11
  • the signal 9 is passed through a second harmonic generator 12 to generate its n th harmonic 13.
  • the resulting signal 11 and 13 are then directed into an applicator 14, allowing their delivery to the patient’s skin.
  • the pump laser 1 is a diode pumped, frequency doubled Nd:YAG laser emitting at 532 nm, actively Q-switched to produce 1 to 100 mJ per pulse with a pulse duration of 700 picoseconds to 30 nanoseconds and a repetition rate of 100 Hz to 100 kHz.
  • the pulse duration is in the range 5-30ns and the repetition rate is in the range 15kHz to 22kHz.
  • the pulse duration is 30ns, in another it is 25ns and in another it is in the range 5-10ns.
  • the repetition rate is 22 kHz, in another it is 18kHz and in another it is 15 kHz.
  • a frequency doubled Nd:YAG laser such as but not limited to a frequency doubled Nd:YV04, Nd:LuV04 or Nd:GdV04.
  • a frequency doubled Yb:YAG, Yb:YV04, Yb:GdV04 or Yb:LuV04 emitting at 515nm or any other harmonic of a crystal rod doped with a gain medium emitting in the infra-red could be used.
  • Another alternative is to use the second harmonic of a fiber laser such as a Nd 3+ doped fiber laser or Yb 3+ doped fiber laser or any other pump source emitting between 500 nm and 550 nm.
  • the pump laser could be either actively Q- switched, requiring an acousto-optic or electro-optic actuator, or passively Q-switched with a saturable absorber, for generating the appropriate pulse duration and repetition rate.
  • non-linear materials defined here as having a high second order susceptibility (X 2 ), as defined in equation 2, can be used as non-linear crystal 5 in the optical parametric generator or in the harmonic generators in this invention.
  • non-linear material is dictated by a number of considerations such as its optical transparency at the considered wavelengths (i.e. visible and near infra-red wavelengths for this invention), its chromatic dispersion and birefringence which determines the necessary phase matching conditions and phase matching bandwidth and its optical damage threshold (i.e. ability to sustain high optical power).
  • non-linear crystals for this invention such as borate based materials (LBO, CLBO, BBO, BIBO, BBO,SBBO, KAB), lithium based materials (LiNbC>3, LiTaOs) or potassium niobate (KNbC>3) and potassium titanyl phosphate (KTP, Potassium Titanyle Arsenate (KTA), RTP, RTA).
  • borate based materials LBO, CLBO, BBO, BIBO, BBO,SBBO, KAB
  • lithium based materials LiNbC>3, LiTaOs
  • potassium titanyl phosphate KTP, Potassium Titanyle Arsenate (KTA), RTP, RTA
  • the second harmonic of a Nd:YAG pump laser is directed into the optical parametric generator with a BBO crystal type II as non-linear crystal 5.
  • the tuning curve of the optical parametric generator using such crystal is shown in the FIG. 4, which exhibits the idler and signal wavelengths, as well as the optical parametric gain, as a function of the incidence angle of the pump laser at 532 nm.
  • FIG. 4 shows that two incidence angles would yield the combination where the resulting wavelength outputs are 1156nm and 985nm.
  • the shorter incidence angle (i.e. 31 .43 deg), where the idler and signal are equal to 1156nm and 985nm respectively is more advantageous as it exhibits the highest optical parametric gain (i.e. 1 .18x10 4 W 1/2 ).
  • the first harmonic generator 10 produces the second harmonic of the idler 8 through its interaction with a BBO crystal cut at 21 .7 deg to generate 578 nm.
  • the second harmonic generator 12 produces the second harmonic of the signal 9 through its interaction with a BBO crystal cut at 24.2 deg to generate 492.5 nm.
  • the optical parametric oscillator uses a Potassium titanyle arsenate (KTA) crystal as non-linear crystal 5.
  • KTA Potassium titanyle arsenate
  • FIG. 5 The tuning curve of the optical parametric generator using such KTA crystal is shown in the FIG. 5, which exhibits the idler and signal wavelengths, as well as the optical parametric gain, as a function of the incidence angle of the pump laser at 532 nm.
  • FIG. 5 shows that only one incidence angle (i.e. 39.66 deg) would yield the combination where the resulting wavelength outputs are 1156nm and 985nm, with an optical parametric gain of 2.02x10 4 W 1/2 , almost twice the optical parametric gain achieved with a BBO crystal.
  • a person skilled in the art will appreciate that a multitude of combinations of non-linear crystals in place of the non-linear crystals 5 or the harmonic generators 10 and 12 are possible to achieve the same outcome.
  • the construction of an optical cavity is required.
  • the cavity is created by two reflectors, which can be flat or curved, surrounding the non-linear crystal, and arranged to have their reflective surfaces parallel to each other.
  • This architecture is often referred as a linear resonator.
  • More complex cavity geometries can be designed with more than 2 reflectors to achieve the same purpose and can be referred to for example as a ring resonator.
  • An example ring resonator is shown in the FIG. 6 where the pump laser beam 2 enters the cavity formed by 4 reflectors 15,16, 17 and 18.
  • the reflectivity of the reflectors is chosen so that they reflect the signal laser beam 9 emerging from the non-linear crystal 5 and transmit both the idler 8 and pump laser 2.
  • This arrangement is often referred to as a singly resonant optical parametric generator.
  • One particularly preferred embodiment is a singly resonant Optical Parametric Oscillator cavity with 2 reflectors. It is relative simple to manufacture and far less sensitive to alignment issues than other configurations as discussed below.
  • a double resonant parametric generator whereby both the signal 9 and idler 8 are reflected into and resonate within the cavity is also possible and is more efficient.
  • it is more complex to implement than a singly resonant Optical Parametric Oscillator cavity as discussed above since the phase for the idler and signal must be matched. This imposes stringent requirements for the design of the cavity which increase the complexity and therefore manufacturing difficulty.
  • ring resonator architecture presented here is merely one example and that this concept can be extended to either a singly or doubly resonant cavity with n reflectors, with n being an integer equal to or greater than 2.
  • the modular design of this invention as shown in the FIG. 3 separates the different cavities involved such as the pump laser 1 and the optical parametric generator cavity and the different harmonic generation stages.
  • the optical parametric generator can be arranged in such a way that it occurs inside the first pump laser cavity. This particular arrangement is referred to as intra-cavity optical parametric generation. Whilst an intra-cavity arrangement may increase the performance of the current invention it is much more complex to implement and maintain and will not fundamentally change its purpose (i.e. generating simultaneously two laser outputs at 492.5nm and 578nm).
  • the repetition rate and pulse duration of both the signal and idler wavelength depend only on the pump laser.
  • the optical parametric generator has only a marginal effect on the pulse duration, generally compressing the pulse temporal width by 10%.
  • the different second harmonic generation stages involved have no effect on both the pulse duration and repetition rate. While the approach developed in this invention might be counterintuitive, especially with an optical parametric generator being used which would allow for tuning the output wavelengths within the same desired spectral range in other circumstances, it offers several key advantages:
  • a single stage optical parametric generator capable of a tuneable output within the required wavelength range necessitates a shorter pump wavelength, usually in the UV range (i.e. below 400nm), such as the third harmonic of a Nd:YAG at 355 nm which are typically used in these circumstances.
  • a shorter pump wavelength usually in the UV range (i.e. below 400nm)
  • frequency tripling i.e. producing the third harmonic
  • frequency doubling i.e. producing the second harmonic
  • Kato Frequency conversion of Nd:YAG laser radiation in RDA” Opt. Comm. 13, 93-95 (1975)
  • An optical parametric generator typically has a threshold below which the optical parametric generation does not work, unlike the other non-linear effects involved in this invention (i.e. harmonic generation).
  • This threshold is strongly dependant on the architecture of the optical parametric generator (i.e. cavity size, reflector spectral response, non-crystal size etc%) and can be difficult to predict.
  • Reports in the literature have shown optical parametric generation threshold in the order of few mJ to tens of mJ per pulse. Therefore, using either second harmonic or the fundamental harmonic in the pump laser, instead of the third harmonic commonly used, allows for a reduction of the pump laser energy output requirement, thereby reducing the complexity and cost associated with the first pump laser.

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Abstract

L'invention concerne un appareil électroluminescent pour le traitement dermatologique d'un patient, comprenant : un générateur laser pulsé ; un générateur paramétrique optique afin de produire un faisceau laser intermédiaire et un faisceau laser de signal, et comprenant un cristal non linéaire ; un premier générateur d'harmonique afin de produire à partir de la roue libre sa nième harmonique ; un second générateur d'harmonique afin de produire à partir du signal sa nième harmonique ; un applicateur agencé afin de recevoir et d'appliquer la nième harmonique de la roue libre, la nième harmonique du signal ou les deux à la peau du patient.
PCT/AU2021/050790 2020-07-24 2021-07-22 Laser pulsé pour traitements dermatologiques Ceased WO2022016224A1 (fr)

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AU2020902592A AU2020902592A0 (en) 2020-07-24 Pulsed Laser for dermatology treatments

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CN115764531A (zh) * 2022-11-18 2023-03-07 威海光子信息技术产业研究院有限公司 一种百皮秒激光放大器

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Publication number Priority date Publication date Assignee Title
CN115513765A (zh) * 2022-10-27 2022-12-23 天津恒宇医疗科技有限公司 基于调q锁模技术的斑块消蚀系统
CN115764531A (zh) * 2022-11-18 2023-03-07 威海光子信息技术产业研究院有限公司 一种百皮秒激光放大器

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