Abstract Single frequency laser has the advantages of high stability in frequency and low noise. Therefore, single frequency laser is now widely used in applications, such as high precision measurement, holography and data storage. Attempts to generate second harmonic radiation using a linear cavity have typically resulted in significant amplitude fluctuations due to longitudinal mode coupling. Various techniques have been proposed for solving the so called ¡§green(blue) problem¡¨ to achieve single longitudinal mode operation, such as inserting optical component in the conventional linear cavity or use ring cavity instead of linear cavity. Uni-directional ring cavity has shown to be the most robust method for producing single frequency laser. The purpose of this study is to develop compact, low-cost and high-efficiency single frequency IR, green and blue lasers. To continue our preview achievement in single frequency IR and green laser systems, shorter wavelength for 946 nm and blue (473 nm) single frequency laser were attempted. In this thesis, we introduced how could only two spherical mirrors to form the laser cavity for traveling wave oscillation and eliminate ¡§spatial hole burning¡¨ caused by the standing wave operation. And we overcome the thermal problem of quasi-three-level laser by multi-wavelength coating on gain medium and input/output couplers, numerical simulation for mode match, and TE-cooling system for laser crystal. Finally, a non-planar figure ¡§8¡¨ 946-nm ring laser were developed using the multi-reentrant ring cavity, and controlled beam path at uni-directional operation. This symmetrical two-mirror figure ¡§8¡¨ ring cavity has the merit of compact, few optical elements, and easy design. The stable single frequency laser output of our ring cavity promises to make the design widely applicable to solid-state lasers.