Picosecond laser apparatus and methods for its operation and use
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.
1. A method for treating a skin pigmentation comprising pigment particles using a photomechanical process, the method comprising exposing at least one pigment particle to pulsed laser energy generated using Nd:YAG, titanium doped sapphire (TIS) crystal, or alexandrite as a lasing medium and with pulses having a duration that is a multiple of the acoustic transit time across said pigment particle to photomechanically disrupt the pigment particle.
2. The method of claim 1 wherein said pulses have an energy of at least 100 mj.
3. The method of claim 1 wherein said duration is less than 1 nanosecond.
4. The method of claim 1 wherein said duration is at most 500 ps.
5. The method of claim 1 wherein said pulses have a duration of between 100 ps and 300 ps.
6. The method of claim 1 wherein said pulses have a duration of between 100 ps and 500 ps.
7. The method of claim 1 wherein the duration is below twice the acoustic transit time across said pigment particle.
8. The method of claim 1 wherein the duration is below five times the acoustic transit time across said pigment particle.
9. The method of claim 1 wherein the duration is from two times to five times the acoustic transit time across the pigment particle.
10. The method of claim 1 wherein the pigment particle is in one of a tattoo, a birthmark, or a pigment particle in a pigmented lesion.
11. The method of claim 1 wherein the at least one pigment particle has a diameter of from 1 micron to 10 microns.
12. The method of claim 1 wherein pulsed laser energy is generated using Nd:YAG as a lasing medium.
13. The method of claim 1 wherein pulsed laser energy is generated using titanium doped sapphire (TIS) crystal as a lasing medium.
14. The method of claim 1 wherein pulsed laser energy is generated using alexandrite as a lasing medium.