High laser pulse energy, ultrashort pulse lengths, high repetition rates, as well as short wavelengths, have given ultraviolet radiation a prominent role in optics. It is mainly excimer lasers and higher harmonics of diode-pumped solid-state lasers that show potential for future applications such as ultraprecision machining and measurement, minimally invasive brain, vascular, and eye surgery, data communication, and LSI electronic devices. The main problem is efficiency. Very few of the expensively generated UV photons can be used. Stable and efficient UV configurations require stable and efficient optics with extreme technical demands. Efficient optics can only be coated optics and, consequently, stable coatings are one of the most important prerequisites for solving the problem of low efficiency.
Laser fusion and optical lithography are the technology drivers for developing optical components and coatings for increasingly shorter wavelengths. Investigations are being concentrated on excimer laser wavelengths (248 nm, 193 nm, and 157 nm) and the higher harmonics of Nd-YAG lasers. An even shorter wavelength of about 13 nm is becoming important for next-generation lithography. The primary sources of information in the UV-coating field are the proceedings of the annual SPIE conferences on microlithography, the Boulder Conference on Laser- Induced Damage in Optical Materials, and of the SEMATEC meetings.
First of all, basic interaction mechanisms of UV photons with dielectrics are reviewed. Then, results of coatings for deep ultraviolet (DUV: 250–190 nm) and vacuum ultraviolet (VUV: 190–50 nm) are presented. Finally, a preview for extreme ultraviolet (EUV: 50–5 nm) will be given.
Online access to SPIE eBooks is limited to subscribing institutions.