Picosecond optical radiation systems and methods of use

• US 10,245,107 B2
• Filed: 07/25/2014
• Issued: 04/02/2019
• Est. Priority Date: 03/15/2013
• Status: Active Grant

• Current Assignee: Cynosure, LLC (Hologic Incorporated)
• Original Assignee: Cynosure Incorporated
• Inventors: Sierra, Rafael Armando, Mirkov, Mirko Georgiev
• Primary Examiner(s): Niu, Xinning (Tom)
• Application Number:
  US14/340,961
• Publication Number:
  US 20140371730A1
• Time in Patent Office: 1,712 Days
• CPC Class Codes: A61B 18/203 applying laser energy to the outside of the body
• CPC Class Codes: A61B 2018/0047 Upper parts of the skin, e.g. skin peeling or treatment of wrinkles
• CPC Class Codes: A61N 5/0616 Skin treatment other than tanning
• CPC Class Codes: A61N 5/067 using laser light
• CPC Class Codes: H01S 3/0092 Nonlinear frequency conversion, e.g. second harmonic generation [SHG] or sum- or difference-frequency generation outside the laser cavity nonlinear frequency conversion per se G02F1/35
• CPC Class Codes: H01S 3/0627 the resonator being monolithic, e.g. microlaser
• CPC Class Codes: H01S 3/08018 Mode suppression
• CPC Class Codes: H01S 3/08054 Passive cavity elements acting on the polarization, e.g. a polarizer for branching or walk-off compensation quarter-wave plates in a Q-switch laser H01S3/1124, H01S3/115
• CPC Class Codes: H01S 3/093 focusing or directing the excitation energy into the active medium
• CPC Class Codes: H01S 3/094038 End pumping
• CPC Class Codes: H01S 3/094076 Pulsed or modulated pumping H01S3/1024 takes precedence
• CPC Class Codes: H01S 3/094084 with pump light recycling, i.e. with reinjection of the unused pump light, e.g. by reflectors or circulators
• CPC Class Codes: H01S 3/1024 for pulse generation
• CPC Class Codes: H01S 3/107 using electro-optic devices, e.g. exhibiting Pockels or Kerr effect H01S3/1061, H01S3/1063, H01S3/1065 take precedence
• CPC Class Codes: H01S 3/1106 Mode locking
• CPC Class Codes: H01S 3/1109 Active mode locking
• CPC Class Codes: H01S 3/1121 Harmonically mode locking lasers, e.g. modulation frequency equals multiple integers or a fraction of the resonator roundtrip time
• CPC Class Codes: H01S 3/1611 neodymium
• CPC Class Codes: H01S 3/1623 chromium, e.g. Alexandrite
• CPC Class Codes: H01S 3/1633 BeAl2O4, i.e. Chrysoberyl
• CPC Class Codes: H01S 3/1643 : YAG
• CPC Class Codes: H01S 3/1673 : YVO4 [YVO]

Abstract

Methods, systems and apparatus are disclosed for delivery of pulsed treatment radiation by employing a pump radiation source generating picosecond pulses at a first wavelength, and a frequency-shifting resonator having a lasing medium and resonant cavity configured to receive the picosecond pulses from the pump source at the first wavelength and to emit radiation at a second wavelength in response thereto, wherein the resonant cavity of the frequency-shifting resonator has a round trip time shorter than the duration of the picosecond pulses generated by the pump radiation source. Methods, systems and apparatus are also disclosed for providing beam uniformity and a sub-harmonic resonator.

Claims

1. An apparatus for delivery of pulsed treatment radiation comprising:

a pump radiation source generating picosecond pulses at a first wavelength, and

a wavelength-shifting resonator having a lasing medium and resonant cavity configured to receive the picosecond pulses from the pump radiation source at the first wavelength and to emit radiation at a second wavelength in response thereto,

wherein the resonant cavity of the wavelength-shifting resonator has a round trip time shorter than duration of the picosecond pulses generated by the pump radiation source, and the wavelength-shifting resonator operates without use of a modelocker or a Q-switch.

2. The apparatus of claim 1, wherein the wavelength-shifting resonator has a round trip time at least 5 times shorter than the duration of the picosecond pulses generated by the pump radiation source.

3. The apparatus of claim 1, wherein the wavelength-shifting resonator has a round trip time at least 10 times shorter than the duration of the picosecond pulses generated by the pump radiation source.

4. The apparatus of claim 1, wherein the wavelength-shifting resonator has a cavity length less than 10 millimeters.

5. The apparatus of claim 1, wherein the lasing medium of the wavelength-shifting resonator comprises a neodymium-doped crystal.

6. The apparatus of claim 5, wherein the lasing medium of the wavelength-shifting resonator comprises a solid state crystal medium selected from the group consisting of neodymium-doped yttrium-aluminum garnet (Nd:

YAG) crystals, neodymium-doped Perovskite (Nd;

YAP or Nd;

YAlO₃) crystals, neodymium-doped yttrium-lithium-fluoride (Nd;

YAF) crystals, and neodymium-doped, vanadate (Nd;

YVO₄) crystals.

7. The apparatus of claim 1, further comprising a polarizer embedded within the resonant cavity of the wavelength-shifting resonator.

8. The apparatus of claim 1, wherein the lasing medium of the wavelength-shifting resonator is a polarizing medium.

9. The apparatus of claim 1, further comprising a frequency-doubling crystal.

10. The apparatus of claim 9, wherein the frequency-doubling crystal comprises a second harmonic generating, nonlinear crystal material.

11. The apparatus of claim 9, wherein the frequency-doubling crystal comprises one of a lithium triborate (LiB₃O₅) material or a KTP material.

12. The apparatus of claim 1, wherein the pump radiation source is a mode-locked laser.

13. The apparatus of claim 12, wherein the mode-locked laser comprises an alexandrite laser.

14. The apparatus of claim 12, wherein the mode-locked laser generates pulsed laser energy having at least about 100 mJ/pulse.

15. The apparatus of claim 12, wherein the mode-locked laser generates pulsed laser energy has a pulse duration of less than 1000 picoseconds.

16. The apparatus of claim 1, further comprising a treatment beam delivery system configured to apply a treatment beam to a patient'"'"'s skin.

17. The apparatus of claim 16, wherein the treatment beam comprises at least one of picosecond pulses from the pump radiation source at the first wavelength, picosecond pulses emitted by the wavelength-shifting resonator at the second wavelength, and picosecond pulses at a third wavelength, wherein the picosecond pulses at the third wavelength are output by a frequency-doubling crystal that receives the picosecond pulses at the second wavelength.

18. The apparatus of claim 17, wherein the first wavelength is about 755 nm, the second wavelength is about 1064 nm, and the third wavelength is about 532 nm.

27. The apparatus of claim 1, further comprising controlling a temperature of the wavelength-shifting resonator.

19. A method for shifting wavelength of a picosecond optical radiation pulse, the method comprising:

generating a pulse of optical radiation at a first wavelength and having a duration less than 1000 picoseconds,

pumping a wavelength-shifting resonator, operating without use of a modelocker or a Q-switch, with the pulse of optical radiation at the first wavelength, the wavelength-shifting resonator comprising a laser crystal with a high absorption coefficient at the first wavelength,

wherein a round trip time of the wavelength-shifting resonator is shorter than pumping laser pulse duration; and

extracting a pulse of radiation at a second wavelength emitted by the wavelength-shifting resonator, wherein the pulse at the second wavelength also has a duration of less than 1000 picoseconds.

20. The method of claim 19, wherein the wavelength-shifting resonator has a round trip time at least 5 times shorter than the duration of the pumping pulse.

21. The method of claim 19, wherein the wavelength-shifting resonator has a round trip time at least 10 times shorter than the duration of the pumping pulse.

22. The method of claim 19, wherein the wavelength-shifting resonator has a cavity length less than 10 millimeters.

23. The method of claim 19, wherein the laser crystal comprises a neodymium-doped crystal.

24. The method of claim 23, wherein the laser crystal comprises a solid state crystal medium selected from the group comprising neodymium-doped yttrium-aluminum garnet (Nd:

YAG) crystals, neodymium-doped pervoskite (Nd;

YAP or Nd;

YAlO₃) crystals, neodymium-doped yttrium-lithium-fluoride (Nd;

YAF) crystals, and neodymium-doped vanadate (Nd;

YVO₄) crystals.

25. The method of claim 19, further comprising transmitting the pulse of radiation at a second wavelength through a frequency doubling crystal.

28. The method of claim 19 wherein the duration of each pulse is greater than 1 picosecond.

26. A method for treating tattoos or skin pigmentation disorders using a picosecond optical radiation source, the method comprising:

employing a pump radiation source to generate a pulse of optical radiation at a first wavelength, wherein the pulse has a duration of less than 1000 picoseconds,

pumping a wavelength-shifting resonator, operating without use of a modelocker or a Q-switch, with the pulse of optical radiation at the first wavelength, the wavelength-shifting resonator comprising a laser crystal with high absorption coefficient at the first wavelength,

wherein a round trip time of the wavelength-shifting resonator is shorter than the pumping laser pulse duration;

extracting a pulse of radiation at a second wavelength emitted by the wavelength-shifting resonator, wherein the pulse at the second wavelength also has a duration of less than 1000 picoseconds;

delivering the pulse of radiation at the second wavelength to a frequency-doubling crystal so as to generate a pulse of radiation at a third wavelength, wherein the pulse at the third wavelength also has a duration of less than 1000 picoseconds; and

directing the pulse at the third wavelength to a tattoo pigment or a skin pigmentation target to disrupt the target and promote clearance thereof.

29. The method of claim 26 wherein the duration of each pulse is greater than 1 picosecond.