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  • Received: Jun. 10, 2020

    Accepted: Sep. 14, 2020

    Posted: Sep. 18, 2020

    Published Online: Dec. 1, 2020

    The Author Email: Siming Chen (

    DOI: 10.1364/PRJ.399957

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    Shujie Pan, Jianou Huang, Zichuan Zhou, Zhixin Liu, Lalitha Ponnampalam, Zizhuo Liu, Mingchu Tang, Mu-Chieh Lo, Zizheng Cao, Kenichi Nishi, Keizo Takemasa, Mitsuru Sugawara, Richard Penty, Ian White, Alwyn Seeds, Huiyun Liu, Siming Chen. Quantum dot mode-locked frequency comb with ultra-stable 25.5 GHz spacing between 20°C and 120°C[J]. Photonics Research, 2020, 8(12): 12001937

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Photonics Research, Vol. 8, Issue 12, 12001937 (2020)

Quantum dot mode-locked frequency comb with ultra-stable 25.5 GHz spacing between 20°C and 120°C 

Shujie Pan1,†, Jianou Huang2,†, Zichuan Zhou1, Zhixin Liu1, Lalitha Ponnampalam1, Zizhuo Liu1, Mingchu Tang1, Mu-Chieh Lo1, Zizheng Cao2,5, Kenichi Nishi3, Keizo Takemasa3, Mitsuru Sugawara3, Richard Penty4, Ian White4, Alwyn Seeds1, Huiyun Liu1, and Siming Chen1,*

Author Affiliations

  • 1Department of Electronic and Electrical Engineering, University College London, Torrington Place, London, WC1E 7JE, United Kingdom
  • 2Institute of Photonic Integration, Eindhoven University of Technology, Eindhoven 5600 MB, The Netherlands
  • 3QD Laser, Inc., Kawasaki 210-0855, Japan
  • 4Centre for Photonics Systems, Department of Engineering, University of Cambridge, Cambridge CB3 0FA, United Kingdom
  • 5e-mail:


Semiconductor mode-locked lasers (MLLs) are promising frequency comb sources for dense wavelength-division-multiplexing (DWDM) data communications. Practical data communication requires a frequency-stable comb source in a temperature-varying environment and a minimum tone spacing of 25 GHz to support high-speed DWDM transmissions. To the best of our knowledge, however, to date, there have been no demonstrations of comb sources that simultaneously offer a high repetition rate and stable mode spacing over an ultrawide temperature range. Here, we report a frequency comb source based on a quantum dot (QD) MLL that generates a frequency comb with stable mode spacing over an ultrabroad temperature range of 20–120°C. The two-section passively mode-locked InAs QD MLL comb source produces an ultra-stable fundamental repetition rate of 25.5 GHz (corresponding to a 25.5 GHz spacing between adjacent tones in the frequency domain) with a variation of 0.07 GHz in the tone spacing over the tested temperature range. By keeping the saturable absorber reversely biased at -2 V, stable mode-locking over the whole temperature range can be achieved by tuning the current of the gain section only, providing easy control of the device. At an elevated temperature of 100°C, the device shows a 6 dB comb bandwidth of 4.81 nm and 31 tones with >36 dB optical signal-to-noise ratio. The corresponding relative intensity noise, averaged between 0.5 GHz and 10 GHz, is -146 dBc/Hz. Our results show the viability of the InAs QD MLLs as ultra-stable, uncooled frequency comb sources for low-cost, large-bandwidth, and low-energy-consumption optical data communications.

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