realization of Highly coherent and accurately frequency tunable light sources at ultraviolet region using semiconductor lasers.

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TecHnique of coherent addition was developed to increase the fundamental laser light power for nonlinear potical frequency conversion. By applying this technique to semiconductor lasers, the phase error between these lasers was reduced to 0.25 rad. Addition efficiency was increased up to 85%, which is, to our knowledges, the highest record in the world.Coherent light generation at 252 nm was carried out for Silicon atom trapping and single atomic-level crystal growth. Experiments on generating the sum-freQuency between a titanium-sapphire laser and its second-harmonics was carried out for this purpose. A nonlinear optical crystal, LBO,was used for the second-harmonics generation, for which a build-up potical cavity was designed and used to improving the generation efficiency. The build-up factor of larger than 50 was realized and the second-harmonics power of 12 mW was obtained.A nonlinear optical crystal, BBO,was used to generate the sum-frequency. The potical system was potimized to tailor the beam profiles of the fundamental and second-harmonics waves. As the result, the output power of 2.8 nW was obtained. Although this power looks low, it is sufficiently high for trapping a small number of atoms, which was confirmed through calculating potical optential for atom-guiding by a hollow optical fiber.Multiple optical cavity and waveguide were fabricated for the optical frequency comb generator, which is an essential device for modulating the phase of generated ultraviolet light. The output power was increased 15 dB., and the total span of modulation sidebands was expanded to 10 THz. Furthermore, the phase-locking between the modulation sidebands, and stabilization of cavity length was carried out for reliable operation of the comb generator.By the results described above, it was confirmed that the we have reached the goal of the present research.