Green laser pointer
Nd:YVO4 is replacing Nd:YAG and Nd:YLF due to lower dependency on the exact parameters of the pump diode (therefore allowing for higher tolerances), wider absorption band, lower lasing threshold, higher slope efficiency, linear polarization of output light, and single mode output.For frequency doubling of higher power lasers, LBO is used instead of KTP. Newer lasers use a composite Nd:YVO4/KTP crystal instead of two discrete ones.
Some green lasers operate in pulse or quasi-continuous wave (QCW) mode, to reduce cooling problems and prolong battery life.
The recent announcement of a direct green laser (not requiring doubling) promises much higher efficiencies and could foster the development of new color video projectors.
Because even a low-powered green laser is visible at night through Rayleigh scattering from air molecules, this type of pointer is used by astronomers to easily point out stars and constellations. Green laser pointers can come in a variety of different output powers. The 5 mW green laser pointers (class llla) are the safest to use, and anything more powerful is usually not necessary for pointing purposes since the beam is still visible in dark lighting conditions.