High-Repetition-Rate UV Light At 355nm Generated By LD CW Side-Pumped Laser

Laser diode (LD) pumped high-power solid-state 355nm ultraviolet (UV) laser was appeared in 1970s. It stimulates the development of UV lights which have the advantages of low cost, compactness and high beam quality become a reality in laser precision processing. As the UV lasers take the advantages of the short wavelength, high processing precision and direct damage to the molecular bond, the application field of laser processing has been widely expanded. And laser processing technology has been rapidly promoted. With the deeper research in 355nm UV laser, the higher technological demand emerge in output power, repetition-rate, beam quality and pulse width, which make the research of LD pumped 355nm UV laser has more profoundly practical meaning.In this paper, high-repetition-rate 355nm UV laser is obtained in purpose. Base on the theory of high-repetition-rate Nd3+:YAG single-pass laser amplifier, which is combined with nonlinear frequency conversion technology. The basic factors of sum frequency conversion efficiency and the relation between them have been studied. High-repetition-rate 355nm UV laser is obtained eventually. The main theoretical and experimental research contents are completed as follows:1. According to reading literatures, different pumped patterns, different frequency conversion structures and different frequency conversion mechanism have been used to achieve high-power and high-repetition-rate UV lasers at 355nm. The difficulties and progresses in high-repetition-rate DPSS UV lasers at 355nm are summarized.2. Combining the rate equation of passively Q-switched with basic theory of resonator, the structure of resonator has been optimized. The best method to obtain high-repetition-rate 1064nm laser is deeply researched. Then high-repetition-rate 1064nm laser generated by LD continuously side-pumped has been designed.3. The related equation of energy density in signal light, the amplifier gain and extraction efficiency are calculated, which is basic on rate equation of pulse amplifier. And effects of amplifier output energy have been separately discussed.4. KTP and LBO are chosen as harmonic generation crystal, which are caused by the analysis of phase-matching conditions and contradistinctions between common nonlinear crystals. We use them in the external cavity experiment of 355nm UV laser. Respectively study the influences of sum frequency conversion efficiency caused by power density of 1064nm and 532nm. The theoretical analysis of optimal photon number ratio also affects sum frequency conversion efficiency.5. Based on the theory analysis of unit technology, experimental research has been carried on. When repetition rate is 4.348 kHz,118.6mW UV laser at 355nm is obtained. And the conversion efficiency of sum frequency is 2.1%.