Brightness-guided adiabatic phase-mismatch engineering for high-power, temperature-robust picosecond green generation in LBO

High-brightness picosecond green lasers are important for precision processing and advanced manufacturing, yet lithium triborate (LBO)-based picosecond secondharmonic generation (SHG) often faces a trade-off between brightness and temperature bandwidth.Here we treat the longitudinal phase-mismatch trajectory as a design degree of freedom and propose a brightness-oriented adiabatic trajectory that jointly optimizes conversion efficiency and beam quality.Through parametric trajectory screening and longitudinal temperature-profile mapping, the proposed trajectory was implemented in a 50mm-long LBO crystal.Experiments produced 79.87 W of picosecond green output at 532.286 nm, corresponding to a light-to-light conversion efficiency of 62.4%, with a beam Downloaded from https://www.cambridge.org/core.31 Jul 2026 at 20:59:15, subject to the Cambridge Core terms of use.quality factor of 2 1.24 M  .Compared with a conventional efficiency-oriented adiabatic trajectory, the proposed trajectory increased brightness by suppressing beam quality degradation rather than maximizing conversion efficiency alone.We further introduce the brightness temperature bandwidth, which reached 25°C for the proposed trajectory, 39% larger than the 18°C value obtained with the conventional trajectory, but smaller than the corresponding efficiency temperature bandwidth of 34°C.This difference indicates that an efficiency-defined bandwidth can overestimate the practically usable operating range.