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  • Received: Dec. 30, 2019

    Accepted: Mar. 24, 2020

    Posted: Mar. 24, 2020

    Published Online: May. 18, 2020

    The Author Email: Feng Li (

    DOI: 10.1364/PRJ.386900

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    Dongmei Huang, Feng Li, Chao Shang, Zihao Cheng, S. T. Chu, P. K. A. Wai. Frequency comb swept laser with a high-Q microring filter[J]. Photonics Research, 2020, 8(6): 06000904

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Photonics Research, Vol. 8, Issue 6, 06000904 (2020)

Frequency comb swept laser with a high-Q microring filter

Dongmei Huang1,2, Feng Li1,2,*, Chao Shang2,3, Zihao Cheng1,2, S. T. Chu4, and P. K. A. Wai1,2

Author Affiliations

  • 1Photonics Research Centre, Department of Electronic and Information Engineering, The Hong Kong Polytechnic University, Hong Kong SAR, China
  • 2The Hong Kong Polytechnic University Shenzhen Research Institute, Shenzhen 518057, China
  • 3Photonics Research Centre, Department of Electrical Engineering, The Hong Kong Polytechnic University, Hong Kong SAR, China
  • 4Department of Physics and Materials Science, City University of Hong Kong, Hong Kong SAR, China


Frequency comb swept lasers are the enabling technology of circular interferometric imaging, which was proposed to break the bottleneck of data acquisition and processing in optical coherence tomography (OCT) at video rate. In this paper, we propose and demonstrate a highly coherent frequency comb swept laser by using a high-quality (high-Q) microring comb filter to discretize a Fourier-domain mode-locked (FDML) laser. The microring filter has a Q factor of 2×106 and a linewidth of 90 MHz. To demonstrate the improvement in performance, a Fabry–Pérot comb filter with a Q factor of 6.2×104 and a linewidth of 3.1 GHz is also used in the experiment for comparison. Both comb filters have free spectral ranges (FSRs) of 50 GHz for consistence. Stable and clearly discretized temporal waveforms and frequency comb spectra with 50 GHz FSR are observed. Adoption of the high-Q microring filter narrows the instantaneous linewidth of the FDML laser down to 1.5 GHz. The OCT system with the frequency comb swept laser source with a microring filter demonstrates an ultralong imaging range, which has a 6, 10, and 15 dB sensitivity roll-off length of 53, 73, and over 100 mm, respectively.

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