Picosecond laser apparatus and methods for its operation and use

• US 9,028,536 B2
• Filed: 08/03/2009
• Issued: 05/12/2015
• Est. Priority Date: 08/02/2006
• Status: Active Grant

• Current Assignee: Cynosure, LLC (Hologic Incorporated)
• Original Assignee: Cynosure Incorporated
• Inventors: Sierra, Rafael Armando, Mirkov, Mirko, Welches, Richard Shaun
• Primary Examiner(s): ROANE, AARON F
• Application Number:
  US12/534,379
• Publication Number:
  US 20090292277A1
• Time in Patent Office: 2,108 Days
• Field of Search: 128/898, 606 2- 19, 607 88- 95
• US Class Current: 607/88
• CPC Class Codes: A61B 18/203 applying laser energy to the outside of the body
• CPC Class Codes: A61B 2017/00769 Tattoo removal
• CPC Class Codes: A61B 2018/00452 Skin
• 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: G02F 1/0327 Operation of the cell; Circuit arrangements G02F1/05 takes precedence
• CPC Class Codes: H01S 3/00 Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range semiconductors lasers H01S5/00
• 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 3/1103 Cavity dumping
• CPC Class Codes: H01S 3/1109 Active mode locking
• CPC Class Codes: H01S 3/115 using intracavity electro-optic devices

Abstract

Apparatuses and methods are disclosed for applying laser energy having desired pulse characteristics, including a sufficiently short duration and/or a sufficiently high energy for the photomechanical treatment of skin pigmentations and pigmented lesions, both naturally-occurring (e.g., birthmarks), as well as artificial (e.g., tattoos). The laser energy may be generated with an apparatus having a resonator with the capability of switching between a modelocked pulse operating mode and an amplification operating mode. The operating modes are carried out through the application of a time-dependent bias voltage, having waveforms as described herein, to an electro-optical device (e.g., a Pockels cell) positioned along the optical axis of the resonator.

Claims

1. A method for treating a skin pigmentation, the method comprising generating pulsed laser energy by

a) reflecting laser energy generated by a lasing medium between a first mirror at one end of a resonator and a second mirror at the opposite end of said resonator and through a polarizer and one or additional electro-optical devices within said resonator and generating a modelocked pulse within the resonator by applying a periodic voltage waveform to the one or additional electro-optical devices;

and

(b) then amplifying the modelocked pulse by applying to said one or additional electro-optical devices a first constant voltage and maintaining an effective reflectivity of the second mirror at substantially 100%; and

(c) then extracting the amplified modelocked pulse from the resonator, and exposing pigmented skin of a patient to the pulsed laser energy.

2. The method of claim 1 wherein the amplified modelocked pulse is extracted from the resonator by applying a second constant voltage to said one or additional electro-optical devices and maintaining an effective reflectivity of the second mirror at substantially 0%.

3. The method of claim 1, wherein the periodic voltage waveform is equal to the sum of a baseline voltage, V_o, and a time-dependent differential voltage, δ

V(t), that varies periodically with a period substantially equal to the twice the time required for said laser energy to traverse the length of said resonator said baseline voltage V_o is from about 30% to about 70% of the quarter wave voltage of said one or additional electro-optical devices.

4. The method of claim 3, wherein said baseline voltage V_o is from about 40% to about 60% of the quarter wave voltage of said one or additional electro-optical devices.

5. The method of claim 3, wherein said time-dependent differential voltage, δ

V(t), has an amplitude from about 5% to about 35% of the quarter wave voltage of said one or additional electro-optical devices.

6. The method of claim 3, wherein said time-dependent differential voltage, δ

V(t), has an amplitude from about 10% to about 30% of the quarter wave voltage of said one or additional electro-optical devices.

7. The method of claim 1, wherein said one or additional electro-optical devices is a Pockels cell.

8. The method of claim 2, wherein said first constant voltage is substantially 0 and said second constant voltage is substantially equal to the quarter wave voltage of said one or additional electro-optical devices.

9. The method of claim 1, wherein said pulsed laser energy has from about 200 to about 800 mj/pulse.

10. The method of claim 1, wherein said pulsed laser energy has a pulse duration of at most about 150 ps.

11. The method of claim 1, wherein said skin pigmentation is a tattoo or a birthmark.

16. The method of claim 1 wherein the pulsed laser energy includes pulses having a duration of at most about 500 ps.

17. The method of claim 1 wherein the pulsed laser energy includes an energy of at least about 100 mj/pulse.

18. The method of claim 1 wherein the pulsed laser energy includes pulses having a duration of less than about 1 nanosecond.

19. The method of claim 1 wherein the pulsed laser energy includes pulses having a duration of less than about 500 ps.

20. The method of claim 1 wherein the pulsed laser energy includes pulses having a duration of between about 100 ps and about 300 ps.

21. The method of claim 1, wherein said skin pigmentation is a pigmented lesion.

12. A method for removing a tattoo comprising tattoo pigment particles, the method comprising exposing said tattoo pigment particles to pulsed laser energy with pulses having a duration below about twice the acoustic transit time across said tattoo pigment particles.

13. The method of claim 12, wherein said tattoo particles have a diameter from about 1 to about 10 microns.

14. The method of claim 12, wherein said pulses have an energy of at least about 100 mj.

15. The method of claim 12, wherein said duration is at most about 500 ps.

22. The method of claim 12 comprising exposing said tattoo pigment particles to pulsed laser energy with pulses having a duration below about five times the acoustic transit time across said tattoo pigment particles.

23. A method for removing a skin pigmentation comprising pigment particles, the method comprising exposing said pigment particles to pulsed laser energy with pulses having a duration below about twice the acoustic transit time across said pigment particles.

24. The method of claim 23 comprising exposing said pigment particles to pulsed laser energy with pulses having a duration below about five times the acoustic transit time across said pigment particles.

25. The method of claim 23, wherein said particles have a diameter from about 1 to about 10 microns.

26. The method of claim 23, wherein said pulses have an energy of at least about 100 mj.

27. The method of claim 23, wherein said duration is at most about 500 ps.