Abstract

Ultrashort-pulsed laser sources with repetition rates over 1 GHz are important for applications in telecommunications, frequency metrology and in fundamental physics. Here we present an approach to build-up compact ultrafast single-mode waveguide lasers with gigahertz repetition rate using graphene saturable absorber mirror (GSAM) as the output coupler [1, 2]. In particular, due to very efficient coupling of pump light into the femtosecond laser inscribed waveguide [3] and wavelength insensitive properties of graphene this approach demonstrates the possibility to achieve simultaneous generation of <20 picosecond pulses centered at 1061 and 1064 nm with 9.8 GHz repetition rate. Precise control of the intracavity dispersion and losses through the length of air-gap interferometer formed between the active medium and the GSAM allowed us to demonstrate the possibility of switching between single and dual-wavelength lasing and to adjust the stability of self-starting mode-locking at particular wavelength. However due to a constant trade-off between losses and dispersion compensation in the current scheme the CW mode-locking can be achieved only in a single-wavelength regime. We also demonstrated applicability of the developed laser as a tunable master-oscillator for fiber-based amplified laser systems and achieved 530 mW output power at 1061 nm using Yb-doped fiber amplifier. Our study open up new aspects of passive mode-locking in waveguide Nd:YAG lasers and demonstrates the compatebility of the developed device with the widely used fiber schemes.

© 2019 IEEE