Nowadays tunable diode laser become main tool for high resolution atomic spectroscopy. The use of frequency doubled lasers extends available wavelength ranges from green to vacuum ultraviolet small linewidth (from 10kHz to tens of MHz) radiation tunable across range from tens to hundreds of nm. It makes possible application of single mode laser diodes in certain specific fields one of them - pumping and high resolution spectroscopy of highly excited long-lived atomic states and selective photo ionization of atoms. Recently studies of highly exited -^s"Rydberg atoms" have obtained second wind in the experiments with laser cooled atoms [1]. It has been pointed out that cold Rydberg atom are most likely candidate as logic gate for quantum computing modeling [2]. Such experiments build up new requirements to the lasers radiation. Because of relatively thin absorption lines of cold atoms the laser should have small linewidth. Furthermore laser radiation should be continuously tunable in certain wavelength range, while laser frequency is stable and have relatively high power of several mW of UV or blue radiation. The one of possible atoms for quantum computation are laser cooled Rb atoms having as alkali atoms simple atomic levels structure and relatively large atomic mass in comparison to lithium, sodium, and potassium, and therefore lower temperatures. There are several ways to excite Rb atoms into Rydberg states. One mostly possible is based on use cascade transition 5S{sub}(1/2)→5P{sub}(3/2)→n(S,D) using two lasers radiation. First pumping cycle is made by using external cavity laser diode working at 780 nm. Second cycle should be made using laser tunable between 479-481 nm. In the selected wavelength range it was possible use frequency doubled Ti:Sa and Dye-lasers, having certain disadvantages related to pumping lasers. Semiconductor lasers are devoid of such disadvantages. Unfortunately up to present day there were no laser diodes available for mentioned above spectral range. Possibly the GaN based laser diodes will extend lasing emission band to this range in nearest future, but in a current work we found only one way for solution. It was based on conventional frequency doubling technique of near infrared laser diode using nonlinear crystal inside a ring cavity [3].
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