Currently, the actual use of the laser, its output wavelength is mainly concentrated in the infrared, such as the commonly used Nd: YAG laser, its output wavelength is 1060nm; the CO2 laser, its output wavelength is 10600nm. Though there also exist lasers whose output wavelength is in the far ultraviolet and far infrared, their output laser power and energy conversion efficiency are relatively low, and also its working performance is not stable enough, they are not so practical. But in some application areas, such as bio-engineering, micro-electronics industry, chemical industry, especially need some far-ultraviolet laser; astrophysics, solid state physics, plasma diagnostics, agriculture, medicine, need far infrared laser. Therefore, it will be a key point to explore the far-ultraviolet laser (especially X-ray laser) and far-infrared laser technology in the future. The main means:
1. Making use of the molecules¡¯ stimulated emission, excimers and clusters¡¯ electronic level transition can generate far-ultraviolet and X-ray radiation. We have got the shortest wavelength 40nm¡«30 nm. Making use of the molecules¡¯ rotational energy level transition can generate far-infrared radiation. We have got the laser whose wavelength is around 500 ¦Ìm.
2. Making use of nonlinear optical effect, optical frequency doubling and sum frequency can generate coherent UV light: we have got the coherent light whose wavelength is 106nm by Nd: YAG laser¡¯s high optical frequency doubling. Making use of optical differential frequency can generate far infrared coherent light: we have got the coherent light whose wavelength is 5mm by CO2 laser¡¯s differential frequency. Using nonlinear optical phenomena to extended coherent light, we need to develop the nonlinear transparent crystal of UV and infrared relatively.
3. Making use of laser plasma¡¯s stimulated radiation is the main way to generate X-ray wavelength coherent radiation.
4. Making use of the free-electron laser, that is a laser for generating coherent radiation of relativistic electrons by a static magnetic field of the swing movement, can generate coherent light of far-infrared to and far ultraviolet in principle. We have got the coherent light of MMW and visible light. We¡¯ll critically develop UV devices in future.