LD Pumped Nd: YAG Double Frequency Solid-State Blue Laser

LD-pumped all-solid-state laser is the most active branch in the laser technical flied. It also is the ultimate direction for the laser development. LD-pumped all-solid-state green laser is relative mature. However, few all-solid-state blue lasers could be found in market because of its low output power, which confines its application. In order to achieve output laser of TEM₀₀ mode and high conversion efficiency, it's necessary to have a favorable optical coupling system between pump laser and resonator. For this technical difficulty in mode matching, we join the research line, hoping to present some useful exploration.Nd: YAG laser crystal is used in experiment, which is hopeful to give relatively high output power of 473nm blue laser through frequency-doubling technique.Firstly, have analyzed the energy level and Florence spectrum of Nd: YAG, figured out the value of the stimulated cross section and the absorb cross section, studied the reason of 946nm laser operation at room temperature and consequently pointed out it is the most suitable laser crystal to produce blue laser.Secondly, the effect of matching between pumping laser and resonating laser on laser operation is discussed. Applying to the method of the geometrical optics, optical system used for collimating and focusing fast-axis and slow-axis semiconductor laser beam is designed and its simulating results using ZEMAX optical designing software are given. This system using ellipse cylinder lens and cylinder lens at fast-axis and two cylinder lens at slow-axis consist of four toroidal microlenses and focusing spot radius of 86μm is made at the base of collimation of the semiconductor laser beam. This system meets the mode matching between the cavity pump beam and resonating laser. Consequently the output power of 44mW of TEM₀₀ mode at 473nm has been obtained for pumping power of 1.8W. The total optical to optical conversion efficiency is 2.4%.