Gallium laser technology

Rotating optical disk systems were first demonstrated in the 1960s and paved the way for the Philips Videodisc, introduced in 1973. Less than ten years later, following the successful development of the reliable, low-cost gallium-arsenide laser, the compact disc was launched, leading to the first penetration of laser technology into the consumer market. 

But the nonlinear optics focused on organic frequency doubling crystals and poled polymers was dealt a mortal blow by Nakamura s59 practical development of the "gallium nitride" (InYC,a, YN/GaN) blue laser [149-151], which is revolutionizing lighting and consumer laser technology. 

The lasers in the 670-nm region, from the aluminum indium gallium phosphide [107102-89-6] system are available at center wavelengths from 635 to 690 nm. These wavelengths He at the red end of the visible spectmm. Such lasers, which may compete for appHcations with the helium—neon laser, are under intensive development and represent less mature technology than the other lasers. 

Arsine is used for the preparation of gallium arsenide [1303-00-0] GaAs, (17), and there are numerous patents covering this subject (see Arsenic and ARSENIC alloys). The conversion of a monomeric arsinogaHane to gallium arsenide has also been described (18). GaUium arsenide has important appHcations in the field of optoelectronic and microwave devices (see Lasers Microwave technology Photodetectors). 

New developments relating to the manufacture of thin film transistors (TFT) are being reported from Japan where the Tokyo Institute of Technology has developed a flexible, transparent device on a PETP substrate. This TFT comprises an amorphous oxide semiconductor, which serves as the active layer, and which is made from indium, gallium and zinc oxide deposited by laser ablation to a thickness of 30-60 nm. The TFT, with its transparent electrodes and circuitry, is manufactured in a vacuum at a temperature of 150 "C or less. Because of this low processing temperature it is possible to use low cost PET film, with a thickness of 200 pm, as a substrate thereby enabling transistors to be manufactured at a relatively low cost. 

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