Pulsed Nd:YAG lasers are typically operated in a what is called Q-switching mode: An optical switch is inserted in the laser cavity and once a maximum population inversion in the neodymium ions is achieved, it opens. The light wave then runs through the cavity, depopulating the excited laser medium at maximum population inversion. This is Q-switched mode and output powers of 250 megawatts and pulse durations of 10 to 25 nanoseconds are reached. The high-intensity pulses can be frequency doubled to generate laser light at 532 nm, or higher harmonics at 355 and 266 nm.
The Q-Switched ND: Yag laser is designed to emit two different wave lengths of light. One of the wavelengths is an invisible infrared light which is used for deeper penetration. This wavelength can be used to target deeper hair follicles. The second wavelength is a green light which is utilized for treating hair follicles that are closer to the surface of the skin. The Q-switching device in either instance emits rapid bursts of laser light to the area that is being treated.
- Wavelength: 1064
- Pulse width: 10-50
- Spot size: 3-5
- Fluence: 20-100
- Repetition rate: Up to 10 Hz
There are many long-term studies that show these laser systems can achieve a significant delay in hair regrowth. In general, the Nd: YAG 1064 nm system may be best laser system to treat darkly pigmented patients. A big advantage is the availability of surface cooling and epidermal protection due to surface cooling and longer pulse duration of these lasers resulting in less downtime for patients.
The Q Switched Nd: YAG laser is extremely effective for removing both dark and light colored tattoos. The separate wavelengths combine into one laser that is quick and painless; lightening of a tattoo is almost immediate. The 1064nm wavelength works best at removing red and black ink with minimal scarring. This wavelength has the deepest penetration of the lasers and has the least risk of hypo pigmentation. The 532nm wavelength is best for lighter tattoos that have orange and yellow colored ink. The one downside to this laser is that neither of these wavelengths is does a good job of removing green or blue ink.
The one disadvantage is that waxing and carbon lotion application is cumbersome to use and there isn’t any clinical data to support any benefits when pretreatment waxing or carbon suspension is used.