Infrared lasers based on semiconductors are readily available since decades, for instance as pump source for telecom or solid state lasers. These can be frequency-doubled to the blue range using standard nonlinear crystals. Violet lasers may be constructed directly with GaN (gallium nitride) semiconductors, as noted. However, a few higher-powered (120 mW) 404–405 nm "violet" laser pointers have become available which are not based on GaN, but also use frequency-doubler technology starting from 1 watt 808 nm gallium arsenide infrared diode lasers being directly doubled, without a longer-wave diode-pumped solid state laser interposed between diode laser and doubler-crystal. Highest powers and wavelength tunability can be reached when the frequency doubling process is resonator enhanced, resulting in Watt-class sources spanning across the visible wavelength range. For instance, in  2.6 W of output power around 400 nm were demonstrated. Blue laser pointers, which became available around 2006, have the same basic construction as DPSS green lasers. They most commonly emit light at 473 nm, which is produced by frequency doubling of 946 nm laser radiation from a diode-pumped or crystal. Neodymium-doped crystals usually produce a principal wavelength of 1064 nm, but with the proper reflective coating mirrors can be also made to lase at other non-principal neodymium wavelengths, such as the 946 nm transition used in blue-laser applications. For high output power BBO crystals are used as frequency doublers; for lower powers, KTP is used. Output powers available are up to 5000 mW. Conversion efficiency for producing 473 nm laser radiation is inefficient with some of the best lab produced results coming in at 10-15% efficient at converting 946 nm laser radiation to 473 nm laser radiation. In practical applications, one can expect this to be even lower. Due to this low conversion efficiency, use of a 1000 mW IR diode results in at most 150 mW of visible blue light. Blue lasers can also be fabricated directly with InGaN semiconductors, which produce blue light without frequency-doubling. 445 nm through 465 nm blue laser diodes are currently available on the open market. The devices are significantly brighter than 405 nm laser diodes, since the longer wavelength is closer to the peak sensitivity of the human eye.