Observation of spectral modulation coupled with broadband transverse-mode-locking in an Yb:CALGO frequency-degenerate cavity

A frequency-degenerate cavity(FDC) is the resonator that the ratio of transverse and longitudinal mode frequency spacings is a simple rational number. When an optical resonator is close to the FDC, transverse-mode-locking(TML) takes place with drastic changes of laser mode. We report for the first time, to the best of our knowledge,the multi-frequency emission and spectral modulation effects coupled with TML in FDC. The Yb:CaGdAlO_4(Yb:CALGO) crystal with large gain bandwidth was used as a gain medium in an off-axis-pumped hemispherical FDC for realizing broadband emission. Interestingly, the spectrum can transform from a single smooth packet shape to a multi-peak structure; meanwhile, the transverse pattern accordingly transforms into some exotic wave-packet profiles through controlling off-axis displacement in a special degenerate state.     

516 mW,nanosecond Nd:LuAG laser Q-switched by gold nanorods

Q-switched operation of an Nd:LuAG laser using gold nanorods(GNRs) as the saturable absorber(SA) is reported, which also produces the highest average power among the nanosecond Nd-doped Q-switched lasers by GNRs-based SA. The applied GNRs are prepared using a seed-mediated growth method and then dropped onto the quartz substrate to fabricate the SA. The average power of the Q-switched laser is 516 mW with the shortest pulse duration of 606.7 ns and the repetition rate of 265.1 kHz.