Effective generation tunable femtosecond laser in the visible waveband by one-step frequency conversion of LiB ₃ O ₅ crystal

This study proposes and experimentally verifies a method for generating tunable visible femtosecond lasers based on the cascaded nonlinear effects of a temperature-tuned lithium triborate (LiB₃O₅, LBO) crystal. A femtosecond laser with a central wavelength of 1030 nm was used as a single pump source. By precisely controlling the temperature of the LBO crystal to adjust its phase-matching conditions, the cascaded nonlinear processes of self-phase modulation and second-harmonic generation (SPM-SHG) were successfully excited, enabling efficient frequency conversion from the near-infrared (NIR) to the visible range in one step. Experimental results show that the system can achieve tunable visible laser output in the range of 428-515 nm, with a maximum conversion efficiency of 7.8% at 453 nm. This method of cascaded generation of SPM-SHG provides a high-performance solution for the convenient and rapid one-step generation of tunable visible lasers from the near-infrared and holds significant application prospects.