Absorber-Free Mode-Locking of a Hybrid Integrated Diode Laser at Sub-GHz Repetition Rate
Anzal Memon,
Albert van Rees,
Jesse Mak,
Youwen Fan,
Peter J. M. van der Slot,
Hubertus M. J. Bastiaens,
Klaus-Jochen Boller
Affiliations
Anzal Memon
Laser Physics and Nonlinear Optics, Mesa+ Institute for Nanotechnology, Department for Science and Technology, Applied Nanophotonics, University of Twente, 7522 NB Enschede, The Netherlands
Albert van Rees
Laser Physics and Nonlinear Optics, Mesa+ Institute for Nanotechnology, Department for Science and Technology, Applied Nanophotonics, University of Twente, 7522 NB Enschede, The Netherlands
Jesse Mak
Laser Physics and Nonlinear Optics, Mesa+ Institute for Nanotechnology, Department for Science and Technology, Applied Nanophotonics, University of Twente, 7522 NB Enschede, The Netherlands
Youwen Fan
Laser Physics and Nonlinear Optics, Mesa+ Institute for Nanotechnology, Department for Science and Technology, Applied Nanophotonics, University of Twente, 7522 NB Enschede, The Netherlands
Peter J. M. van der Slot
Laser Physics and Nonlinear Optics, Mesa+ Institute for Nanotechnology, Department for Science and Technology, Applied Nanophotonics, University of Twente, 7522 NB Enschede, The Netherlands
Hubertus M. J. Bastiaens
Laser Physics and Nonlinear Optics, Mesa+ Institute for Nanotechnology, Department for Science and Technology, Applied Nanophotonics, University of Twente, 7522 NB Enschede, The Netherlands
Klaus-Jochen Boller
Laser Physics and Nonlinear Optics, Mesa+ Institute for Nanotechnology, Department for Science and Technology, Applied Nanophotonics, University of Twente, 7522 NB Enschede, The Netherlands
We demonstrate absorber-free passive and hybrid mode-locking at sub-GHz repetition rates, using a hybrid integrated extended cavity diode laser operating near 1550 nm. The laser is based on InP as a gain medium and a Si3N4 waveguide feedback circuit. Absorber-free Fourier domain mode-locking with ≈15 comb lines at around 0.2 mW total power is achieved with repetition rates around 500 MHz, using three highly frequency-selective micro-ring resonators that extend the on-chip cavity length to 0.6 m. To stabilize the repetition rate, hybrid mode-locking is demonstrated by weak RF modulation of the diode current. The RF injection reduces the Lorentzian linewidth component from 8.9 kHz to a detection-limited value of around 300 mHz. To measure the locking range of the repetition rate, the injected RF frequency is tuned with regard to the passive mode-locking frequency and the injected RF power is varied. The locking range increases approximately as a square-root function of the injected RF power. At 1 mW injection, a wide locking range of about 80 MHz is obtained. We also observe the laser maintaining stable mode-locking when the DC diode pump current is increased from 40 mA to 190 mA, provided that the cavity length is maintained constant with thermo-refractive tuning.
