research at IBM led to the first commercial use of SOI in mainstream CMOS technology. SOI was first commercialized in 1995, when Shahidi's work on SOI convinced John Kelly, who ran IBM's server division, to adopt SOI in the AS/400 line of server products, which used 220 nm CMOS with copper metallization SOI devices. IBM began to use SOI in the high-end RS64-IV "Istar" PowerPC-AS microprocessor in 2000. Other examples of microprocessors built on SOI technology include AMD's 130 nm, 90 nm, 65 nm, 45 nm and 32 nm single, dual, quad, six and eight core processors since 2001. In late 2001, IBM was set to introduce 130 nanometer CMOS SOI devices with copper and low-κ dielectric for the back end, based on Shahidi's work. Freescale adopted SOI in their PowerPC 7455 CPU in late 2001. Currently, Freescale is shipping SOI products in 180 nm, 130 nm, 90 nm and 45 nm lines. The 90 nm PowerPC- and Power ISA-based processors used in the Xbox 360, PlayStation 3, and Wii use SOI technology as well. Competitive offerings from Intel however continue to use conventional bulk CMOS technology for each process node, instead focusing on other venues such as HKMG and tri-gate transistors to improve transistor performance. In January 2005, Intel researchers reported on an experimental single-chip silicon rib waveguide Raman laser built using SOI. As for the traditional foundries, in July 2006 TSMC claimed no customer wanted SOI, but Chartered Semiconductor devoted a whole fab to SOI. Use in high-performance radio frequency (RF) applications In 1990, Peregrine Semiconductor began development of an SOI process technology utilizing a standard 0.5 μm CMOS node and an enhanced sapphire substrate. Its patented silicon on sapphire (SOS) process is widely used in high-performance RF applications. The intrinsic benefits of the insulating sapphire substrate allow for high isolation, high linearity and electro-static discharge (ESD) tolerance. Multiple other companies have also applied SOI technology to successful RF applications in smartphones and cellular radios. Use in photonics SOI wafers are widely used in silicon photonics. The crystalline silicon layer on insulator can be used to fabricate optical waveguides and other optical devices, either passive or active (e.g. through suitable implantations). The buried insulator enables propagation of infrared light in the silicon layer on the basis of total internal reflection. The top surface of the waveguides can be either left uncovered and exposed to air (e.g. for sensing