By using an extra-cavity-enhanced frequency doubler with a periodically poled KTiOPO4 (PPKTP) crystal, which is pumped by a home-made continuous-wave single-frequency tunable Ti: sapphire laser at 795 nm wavelength, the 397.5 nm violet laser is obtained experimentally with the output power of 103 mW, conversion efficiency of 39.6%, and the beam quality factor M2<1.43. Compared with the intracavity enhanced frequency doubling with the angle matched Bismuth Triborate (BIBO) crystal, the mode matching efficiency of the 397.5 nm lasing to the optical parametric amplifier (OPA) cavity is increased from 76% up to 99%. Meanwhile, in the balanced homodyne detection system, a mode cleaner with the same cavity parameters as OPA, is inserted into the local oscillator to make sure the local oscillator and the signal fields have the identical spatial modes. As a result, the interference efficiency of the two input fields is more than 99%, and the efficiency of the balanced homodyne detection system is improved. By optimizing the design of the 795 nm and 397.5 nm laser system, the laser source can meet the requirement of studying the compact continuous-variable squeezed light source at 795 nm.