Instability and ultra-high frequency spectrum pulse train in passively Q-switched Yb:LuAG ceramic laser.

The ultra-high-frequency pulse trains in a Yb:LuAG passively Q-switched laser with a Yb ratio of 15 at. % are experimentally investigated. The pulse trains consist of a low-frequency harmonic spectrum pulse train with a fundamental frequency below 500 KHz as the source and an ultra-high-frequency harmonic spectrum pulse train with an exciting fundamental frequency above 10⁴ KHz. The basic frequency of the low spectrum increases approximately linearly with increasing pump power. The change law of the fundamental frequency of the ultra-high frequency spectrum with the increase in pump power conforms to the frequency-doubling principle of the harmonic spectrum changing to a higher frequency, and increases exponentially with A × 2ⁿ (n is a natural number, A = 1.25 × 10⁸, 1.552 × 10⁸, or 1.0 × 10⁸ Hz). In this paper, the base frequency range of the ultra-high-frequency spectrum was 0.077 73 GHz–0.66 THz. The maximum average peak power of an ultra-high-frequency pulse was 18.25 mW, and the minimum width of an ultra-high-frequency pulse was 3.2 ps. [ABSTRACT FROM AUTHOR]