Multi-GHz Femtosecond Mode-Locking and Noise Characterization of fs-Laser-Inscribed Waveguide Lasers

Fundamental GHz mode-locking of waveguide (WG) lasers have recently attracted tremendous interest owing to their unique properties and own potential applications with an ultra-compact cavity utilizing fs-laser-inscribed active WGs [1], [2]. However, although the understanding of noise characteristics is a critical parameter for advanced applications [3], there is an absence of study on noise measurements of mode-locked WG lasers so far. Here, we report on multi-GHz femtosecond mode-locked operation of Yb
³⁺
-doped KLu(WO
4
)
2
(KLuW) WG lasers and their characterization of noise spectra depending on cavity parameters.