Farbfernsehen
Color television requires light in three distinct wavelengths—red, green, and blue. While red laser diodes are commercially available, there are no commercially available green laser diodes which can provide the required power at room temperature with an adequate lifetime. Instead, frequency doubling can be used to provide the green wavelengths. Several types of lasers can be used as the frequency doubled sources: fibre lasers, inter-cavity doubled lasers, external cavity doubled lasers, eVCSELs, and OPSLs (Optically Pumped Semiconductor Lasers). Among the inter-cavity doubled lasers, VCSELs have shown much promise and potential to be the basis for a mass-produced frequency doubled laser.