Spectral purity improvement of high-power pulsed lasers achieved by manipulating the nonlinear optical frequency conversion

Pulsed lasers usually suffer from the conflict between low spectral purity (SP) and high output power because the mode-selection process is not able to be accomplished within a short pulse period. In order to address this issue, we present a fresh lossless mode-selection method (MSM) that is implemented by manipulating the loss induced by nonlinear optical frequency conversion (LINOFC). Based on this method, the SP up to 3.2 × 10 4 with 9.16 W output power is experimentally obtained, which is attributed to the stronger and faster process of nonlinear optical frequency conversion (NOFC). In the experiment, in order to manipulate the magnitude of LINOFC during the short pulse period, a fast polarization control module based on an electro-optic effect was designed to change the phase-matching condition of fundamental light in the nonlinear crystal. Differing from the traditional MSMs, the NOFC will be more effective when the output power is increased; thus, a higher SP and a large output power can be achieved simultaneously in pulsed lasers, which is a type of necessary source for quantum optics and photonics technologies.