Ruby laser weaknesses in the lining. Ruby lasers were used extensively in tattoo and hair removal, but are being replaced by alexandrite and s in this application. The ruby laser was the first laser to be made functional. Built by Theodore Maiman in 1960, the device was created out of the concept of an "optical maser," a maser that could operate in the visual or infrared regions of the spectrum. In 1958, after the inventor of the maser, Charles Townes, and his colleague, Arthur Schawlow, published an article in the "Physical Review" regarding the idea of optical masers, the race to build
Blue laser a longer-wave neodymium laser interposed between diode laser and doubler-crystal. The violet 405 nm laser (whether constructed from GaN or frequency-doubled GaAs laser diodes) is not in fact blue, but appears to the eye as violet, a color for which a human eye has a very limited sensitivity. When pointed at many white objects (such as white paper or white clothes which have been washed in certain washing powders) the visual appearance of the laser dot changes from violet to blue, due to fluorescence of brightening dyes. For display applications which must appear "true blue", a wavelength of 445–450 nm