Lasers emitting in the yellow part of the spectrum are much less common than most other colors.
[19] They are also much more expensive than comparable lasers because the difference in energy levels between the metastable and the ground state required for laser action is difficult to create for yellow photons. In commercial products diode pumped solid state (DPSS) technology is employed to create the yellow light. An infrared laser diode at 808 nm is used to pump a crystal of neodymium-doped yttrium vanadium oxide (Nd:YVO4) or neodymium-doped yttrium aluminium garnet (Nd:YAG) and induces it to emit at two frequencies (1064 nm and 1342 nm) simultaneously. This deeper infrared light is then passed through another crystal containing potassium, titanium and phosphorus (KTP), whose non-linear properties generate light at a frequency that is the sum of the two incident beams; in this case corresponding to the required wavelength of 593.5 nm (yellow).
[