Absorber-Free Mode-Locking of a Hybrid Integrated Diode Laser at Sub-GHz Repetition Rate

Anzal Memon, Albert van Rees, J. Mak, Youwen Fan, P.J.M. van der Slot, H.M.J. Bastiaens, K.-J. Boller

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Abstract

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.
Original languageEnglish
Article number1002
Number of pages16
JournalPhotonics
Volume11
Issue number11
DOIs
Publication statusPublished - 21 Oct 2024

Keywords

  • mode-locking
  • absorber-free
  • hybrid laser
  • Passive Mode-Locking
  • Hybrid Mode-locking
  • Frequency combs
  • sub-GHz repetition rate

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