Blue laser

A blue laser emits electromagnetic radiation with a wavelength between 400 and 500 nanometers, which the human eye sees in the visible spectrum as blue or violet. Blue lasers can be produced by direct, inorganic diode semiconductor lasers based on quantum wells of gallium(III) nitride at 380-417nm or indium gallium nitride at 450nm diode-pumped solid-state infrared lasers with frequency-doubling to 405nm upconversion of direct diode semiconductor lasers via thullium or paraseodyium doped fibers at 480nm metal vapor, ionized gas lasers of helium-cadmium at 442 nm and 10-200 mW argon-ion lasers at 458 and 488 nm Lasers emitting wavelengths below 445 nm appear violet, but are called blue lasers. Violet light's 405nm short wavelength, on the visible spectrum, causes fluorescence in some chemicals, like radiation in the ultraviolet ("black light") spectrum (wavelengths less than 400 nm). Prior to the 1960s and until the late 1990s, gas and argon-ion lasers were common; suffering from poor efficiencies(0.01%) and large sizes. In the 1960s, advancements in sapphire creation allowed researchers to deposit GaN on a sapphire base to create blue lasers, but a lattice mismatch between the structures of gallium nitride and sapphire created many defects or dislocations, leading to short lifetimes(