Description: photograph Professor Hon Ki TSANG
Department of Electronic Engineering

BA, Ph.D.(Cambridge), Fellow IEEE, Fellow OSA, C.Eng., MIET, MHKIE,

Telephone: +852 39438276

Hon Ki Tsang is a Professor at the Chinese University of Hong Kong. He served as Chairman of the Department of Electronic Engineering from 2010-2016. He is currently Director of the Center for Advanced Research in Photonics and Associate Dean (Research) of the Faculty of Engineering. He is the current Editor-in-Chief of IEEE Journal of Quantum Electronics. He is a Fellow of IEEE and a Fellow of Optica (Optica was formerly the Optical Society (OSA)).

Description: photograph

Research Interests

Hon Tsang obtained a PhD from Cambridge University on III-V semiconductor waveguides devices and their nonlinear optical properties in 1991. He joined CUHK in 1993 and shortly thereafter branched out into the then emerging field of silicon photonics. From its small beginnings attracting interest from only a handful of groups, silicon photonics has grown in the last 20 years to become a mainstream technology for high speed energy efficient communications. It is emerging as a key technology for optical interconnects in data centers, with large volume silicon photonic products being manufactured by companies such as Intel.

Despite the commercial silicon photonics transceiver products now being widely available, silicon photonics still remains a fruitful topic for research because there remains many important potential future applications as energy efficient on-chip optical interconnects in high performance computers, low cost lab-on-a-chip gas sensors and integrated biosensors, and integrated quantum photonic devices for quantum computing and quantum communications. Hon Tsang has made fundamental contributions on the understanding of nonlinear properties of guided wave optics in silicon waveguides, having carried out some of the first studies of optical nonlinearities in silicon optical waveguides. As an R&D director in Bookham Technology plc, in the early 2000s he led the development team for the silicon waveguide variable optical attenuator arrays which were deployed commercially in telecommunication networks. Those early silicon photonic products enabled dynamic balancing of optical power levels during the reconfiguration of Wavelength Division Multiplexed (WDM) networks.

Hon Tsang’s research on the inter-relationships between two photon absorption, free carrier absorption and nonlinear refraction, led to the experimental realization of high net gain optical amplifiers based on stimulated Raman scattering in silicon waveguides. These papers are increasingly relevant in the design of silicon nanophotonic integrated circuits because the tiny cross-sectional areas of these silicon waveguides enable nonlinear optical effects such as two photon absorption or self-phase modulation to manifest at optical powers as low as a few milliwatts. Hon Tsang’s current research topics include:

· Subwavelength gratings for steering, coupling, switching, filtering light in the spatial, spectral and polarization domains

· Silicon photonics for energy efficient terabit/s optical communications

· Integrated quantum photonics for quantum imaging

· Hybrid integration of 2D materials (such as graphene, MoS₂, WS₂ WSe₂ , hBN etc) for photodetectors, modulators and nonlinear photonics

· Integrated photonics for 3D imaging and optical coherence tomography

Ongoing Research Grants as Principal Investigator

Title	Funding Agency	Start	End	Amount
Hybrid integrated photodetectors for silicon nitride waveguide based on-chip optical interconnects using 2-D materials and Van der Waals heterostructures	RGC GRF	01/01/2019	31/12/2021	$495,086
Ultra-high Q Silicon Micro-resonators for Integrated Quantum Photonics	RGC GRF	01/01/2018	31/03/2021	$875,000
Multimode Waveguide Grating Couplers	RGC GRF	01/01/2021	31/12/2023	$845,055
Integrated Spectrometer for Dynamic Optical Coherence Tomography	ITF	01/01/2021	31/12/2023	$4,998,739
Resonance-Enhanced Waveguide Grating Couplers for Wideband High Capacity CWDM Transceivers	RGC GRF	01/01/2022	31/12/2024	$838,393

Description of RGC GRF grants are available from RGC GRF online search

Research Opportunities

Please email Prof Tsang if you are interested in joining his group. We have openings for summer research interns and PhD students and postdocs supported by the ITF Research Talent Hub scheme. Candidates with good publication records satisfying the talent hub requirements may email Prof. Tsang to inquire about new vacancies before applying,

Prof. Tsang has research grants funding which can support candidates interested in pursuing a PhD or MPhil degree in photonics. Please submit your formal applications to the Electronic Engineering graduate division and CUHK before 1 December of each year. Financial support of MPhil or PhD students via postgraduate studentship (PGS) of $216300 per year (2020-21 rates) are available. Potential students may also consider applying for RGC PhD fellowship which has a higher level of financial support (note deadline of application to RGC is in December of each year).

Current Research Team

Postdoctoral Researchers: Dr.Yaojing Zhang, Dr.Yi Wang ; Dr. Zunyue Zhang; Dr Hongnan XU

PhD Students: Dan Yi, David Weng U Chan, Gaolei Hu, Jiapeng Luan, Keyi Zhong, Xuetong Zhou, Yue Qin, Shuqi Xiao

Recent Alumni: Dr.Rakesh R. KUMAR, Dr Yeyu Yong, Dr Wen Zhou, Dr Xinru Wu

Publications

Our group has published over 200 journal papers. The publications are listed on Researchgate. A potentially more up to date list of journal and conference publications may be found from the online publications databases such as: Scopus ID, ORCID ID: or Researcher ID. The list below is a selection of journal papers published between 2017 and September 2021 and the authors in bold are students/postdocs supervised by Prof. Tsang.

1. D. Yi, Y. Wang, and H. K. Tsang, “Multi-functional Photonic Processors using Coherent Network of Micro-ring Resonators” APL Photonics 6, article 100801, 2021.

2. Y. Zhang, G. Hu, K. Zhong, W.Zhou and H.K. Tsang, "Investigation of low-power comb generation in silicon microresonators from dual pumps," Journal of Optics (2021).

3. Y. Xue, Y.Han, Y.Tong, Z. Yan, Y. Wang, Z. Zhang, H.K.Tsang and K. M.Lau, "High-performance III-V photodetectors on a monolithic InP/SOI platform, " Optica vol. 8 pp.1204-09 (2021)

4. Z. Zhang, Y. Li, Y.Wang,Z.Yu,X. Sun and H.K.Tsang, "Compact High Resolution Speckle Spectrometer by Using Linear Coherent Integrated Network on Silicon Nitride Platform at 776 nm," Lasers and Photonics Reviews , article 2100039 (2021)

5. B. Sun, G.Zhou, Y.Wang, X.Xu, L.Tao,N.Zhao, H.KTsang, X.Wang, Z.Chen, J.B. Xu, "Ultra-Narrowband Photodetector with High Responsivity Enabled by Integrating Monolayer J-Aggregate Organic Crystal with Graphene," Advanced Optical Materials vol. 9 article 2100158 (2021).

6. Z. Zhang, Y. Wang and H. K. Tsang, "Tandem Configuration of Microrings and Arrayed Waveguide Gratings for a High-Resolution and Broadband Stationary Optical Spectrometer at 860 nm," ACS Photonics vol. 8 pp. 1251-1257 (2021).

7. Y. Xue, Yi Wang, W. Luo, J. Huang, L. Lin, H. K.Tsang and K.M. Lau, "Telecom InP-based quantum dash photodetectors grown on Si" Applied Physics Letters 118, article 141101 (2021)

8. Z. Zhang, Y. Tong, Y. Wang and H. K. Tsang, "Nonparaxial Mode-size Converter Using an Ultracompact Metamaterial Mikaelian Lens," Journal of Lightwave Technology 39, 2077-2083,(2021), doi: 10.1109/JLT.2020.3047118

9. Y. Wang, Z. Yu, Z. Zhang, X. Sun, and H.K. Tsang, "Fabrication-Tolerant and Low-Loss Hybrid Plasmonic Slot Waveguide Mode Converter," Journal of Lightwave Technology 39, 2106-2112, (2021), doi: 10.1109/JLT.2020.3045742.

10. Yaojing Zhang, Keyi Zhong and H.K. Tsang, “Raman Lasing in Multimode Silicon Racetrack Resonators,” Lasers & Photonics Reviews 15, 2000336 (2021).

11. Dan Yi, Wen Zhou, Yaojing Zhang, and H.K. Tsang, "Inverse design of multi-band and wideband waveguide crossings," Opt. Lett. 46, 884-887 (2021)

12. Dan Yi, Yaojing Zhang, and H.K. Tsang, "Optimal Bezier curve transition for low-loss ultra-compact S-bends," Opt. Lett. 46, 876-879 (2021).

13. D. Yi, Y. Zhang, X. Wu and H. K. Tsang, "Integrated Multimode Waveguide with Photonic Lantern for Speckle Spectroscopy," IEEE Journal of Quantum Electronics, vol. 57, no. 1, 0600108, (2021).

14. Rakesh Ranjan Kumar and H.K. Tsang, "High-extinction CROW filters for scalable quantum photonics," Opt. Lett. 46, 134-137 (2021)

15. Yaojing Zhang, Keyi Zhong, Gaolei Hu, Dan Yi, Rakesh Ranjan Kumar, and H.K. Tsang, "Sub-milliwatt optical frequency combs in dual-pumped high-Q multimode silicon resonators" Appl. Phys. Lett. 117, 221103 (2020).

16. Yi Wang, Zejie Yu, Zunyue Zhang, Beilei Sun, Yeyu Tong, Jian-Bin Xu, Xiankai Sun, and H.K. Tsang "Bound-States-in-Continuum Hybrid Integration of 2D Platinum Diselenide on Silicon Nitride for High-Speed Photodetectors" ACS Photonics 7 , 2643–2649, (2020).

17. Yeyu Tong, Guan-Hong Chen, Yi Wang, Zunyue Zhang, David Weng U Chan, Chi-Wai Chow and H.K. Tsang, "1.12-Tbit/s PAM-4 Enabled by a Silicon Photonic Transmitter Bridged With a 7-Channel MCF," IEEE Photonics Technology Letters, 32, 987-990, (2020).

18. Z. Yu, Y. Tong, H. K. Tsang, and X. Sun, "High-dimensional communication on etchless lithium niobate platform with photonic bound states in the continuum," Nature Communications 11, Article number: 2602 (2020).

19. Y.Tong, W. Zhou, X. Wu and H.K.Tsang, “Efficient Mode Multiplexer for Few-Mode Fibers Using Integrated Silicon-on-Insulator Waveguide Grating Coupler” IEEE Journal of Quantum Electronics 56, 8400107 (2020).

20. R.R. Kumar, Y.Wang, Y. Zhang, and H.K. Tsang, “ Quantum States of Higher Order Whispering Gallery Modes in a Silicon Micro-disk Resonator” Journal of the Optical Society of America B (2020).

21. Y. Wang, Z. Yu, Y. Tong, B. Sun, Z. Zhang, J.-B. Xu, X. Sun, and H. K. Tsang, "High-speed infrared two-dimensional platinum diselenide photodetectors," Applied Physics Letters 116 article 211101(2020).

22. Z. Zhang, Y. Wang, and H. K. Tsang, "Ultracompact 40-Channel Arrayed Waveguide Grating on Silicon Nitride Platform at 860 nm," IEEE Journal of Quantum Electronics 56, 8400308 (2020).

23. Y. Tong, Z. Hu, X. Wu, S. Liu, L. Chang, A. Netherton, C.-K. Chan, J. E. Bowers, and H. K. Tsang, "An Experimental Demonstration of 160-Gbit/s PAM-4 Using a Silicon Micro-Ring Modulator," IEEE Photonics Technology Letters 32, 125–128 (2020).

24. R. R. Kumar, X. Wu, and H.K. Tsang, "Compact High-Extinction Tunable CROW filters for Integrated Quantum Photonic Circuits," Optics Letters 45, 1289-1292, (2020).

25. Y. Xue, Y. Han, Y. Wang, Z. Zhang, H.K. Tsang, and K. M. Lau, "Bufferless III-V photodetectors directly grown on (001) silicon-on-insulators," Optics Letters 45 1754-1757 (2020).

26. W. Zhou, Y. Tong, X. Sun, and H. K. Tsang, "Ultra-Broadband Hyperuniform Disordered Silicon Photonic Polarizers," IEEE Journal of Selected Topics in Quantum Electronics 26, 8200109 (2020).

27. Y. Zhang, Y. Yao, D. Yi, and H. K. Tsang, "Radiation pressure and electrostriction induced enhancement for Kerr-like nonlinearities in a nanoscale silicon pedestal waveguide," Journal of Optics 22, article 055502 (2020).

28. Y. Zhang, L. Tao, D. Yi, J.-B. Xu, and H. K. Tsang, "Enhanced thermo-optic nonlinearities in a MoS₂-on-silicon microring resonator," Applied Physics Express 13, article 002004 (2020).

29. Y. Zhang, L. Tao, D. Yi, J.-B. Xu, and H. K. Tsang, "Enhanced four-wave mixing with MoS₂ on a silicon waveguide," Journal of Optics 22, article 025503 (2020).

30. Y. Wan, S. Zhang, J. C. Norman, M. J. Kennedy, W. He, Y. Tong, C. Shang, J.-J. He, H. K. Tsang, A. C. Gossard, and J. E. Bowers, "Directly Modulated Single-Mode Tunable Quantum Dot Lasers at 1.3 mm," Laser and Photonics Reviews 14, article 1900348 (2020).

31. Y. Wan, J. C. Norman, Y. Tong, M. J. Kennedy, W. He, J. Selvidge, C. Shang, M. Dumont, A. Malik, H. K. Tsang, A. C. Gossard, and J. E. Bowers, "1.3 mm Quantum Dot-Distributed Feedback Lasers Directly Grown on (001) Si," Laser and Photonics Reviews 14, article 2000037 (2020).

32. X. Ding, B.P.Yan, W. Karlen, Y.T. Zhang, H.K. Tsang, "Pulse transit time based respiratory rate estimation with singular spectrum analysis," Medical & Biological Engineering & Computing 58 (2), 257-266, 2020

33. Y. Jiao, J. van der Tol, V. Pogoretskii, J. van Engelen, A. A. Kashi, S. Reniers, Y. Wang, X. Zhao, W. Yao, T. Liu, F. Pagliano, A. Fiore, X. Zhang, Z. Cao, R. R. Kumar, H. K. Tsang, R. van Veldhoven, T. de Vries, E.-J. Geluk, J. Bolk, H. Ambrosius, M. Smit, and K. Williams, "Indium Phosphide Membrane Nanophotonic Integrated Circuits on Silicon," Physica Status Solidi (A) Applications and Materials Science 217, article 1900606 (2020).

34. Z. Yu, X. Xi, J. Ma, H. K. Tsang, C.-L. Zou, and X. Sun, "Photonic integrated circuits with bound states in the continuum," Optica 6, pp. 1342-1348 (2019).

35. Y. Tong, Q. Zhang, X. Wu, C. Shu, and H. K. Tsang, "112 Gb/s 16-QAM OFDM for 80-km Data Center Interconnects Using Silicon Photonic Integrated Circuits and Kramers–Kronig Detection," Journal of Lightwave Technology 37, 3532-3538 (2019).

36. A. Jain, N. Hosseinzadeh, X. Wu, H. K. Tsang, R. Helkey, J. E. Bowers, and J. F. Buckwalter, "A High Spur-Free Dynamic Range Silicon DC Kerr Ring Modulator for RF Applications," Journal of Lightwave Technology 37, 3261–3272 (2019).

37. W. Zhou, Z. Cheng, X. Chen, K. Xu, X. Sun, and H. Tsang, "Subwavelength Engineering in Silicon Photonic Devices," IEEE Journal of Selected Topics in Quantum Electronics 25, article 2900113 (2019).

38. Y. Tong, C.-W. Chow, G.-H. Chen, C.-W. Peng, C.-H. Yeh, and H. K. Tsang, "Integrated Silicon Photonics Remote Radio Frontend (RRF) for Single-Sideband (SSB) Millimeter-Wave Radio-Over-Fiber (ROF) Systems," IEEE Photonics Journal 11, 7202108 (2019).

39. H.Wu C. Li, L.Song, H.K. Tsang, J.E. Bowers and D. Dai, "Ultra-Sharp Multimode Waveguide Bends with Subwavelength Gratings," Laser and Photonics Reviews 13, article 1800119 (2019).

40. B. Zhu, M. Chen, Q. Zhu, G. Zhou, W. Zhou, N. Zhao, and H. K. Tsang, "Integrated Plasmonic Infrared Photodetector Based on Colloidal HgTe Quantum Dots," Advanced Materials Technologies 4, 1900354 (2019).

41. Z. Yu, Y. Wang, B. Sun, Y. Tong, J.-B. Xu, H. K. Tsang, and X. Sun, "Hybrid 2D-Material Photonics with Bound States in the Continuum," Advanced Optical Materials 7, article 1901306 (2019).

42. W. Zhou, and H. K. Tsang, "Dual-wavelength-band subwavelength grating coupler operating in the near infrared and extended shortwave infrared," Optics Letters 44 3621-3624 (2019).

43. W. Zhou, Y. Tong, X. Sun, and H. K. Tsang, "Hyperuniform disordered photonic bandgap polarizers," Journal of Applied Physics 126 article 113106 (2019).

44. S. Liu, X. Wu, D. Jung, J. C. Norman, M. J. Kennedy, H. K. Tsang, A. C. Gossard, and J. E. Bowers, "High-channel-count 20 GHz passively mode-locked quantum dot laser directly grown on Si with 4.1 Tbit/s transmission capacity," Optica 6, 128-134 (2019).

45. R. R. Kumar, M. Raevskaia, V. Pogoretskii, Y. Jiao, and H. K. Tsang, "Entangled photon pair generation from an InP membrane micro-ring resonator," Applied Physics Letters 114 021104 (2019).

46. Z. Hu, Y. Shao, X. Ouyang, Y. Tong, J. Zhao, H. K. Tsang, P. D. Townsend, and C.-K. Chan, "Experimental demonstration of 111.1-Gb/s net information rate using IM/DD probabilistically shaped orthogonal chirp-division multiplexing with a 10-GHz-class modulator," Optics Express 27 ,33789-33798 (2019).

47. Y. Gao, G. Zhou, H. K. Tsang, and C. Shu, "High-speed van der Waals heterostructure tunneling photodiodes integrated on silicon nitride waveguides," Optica 6, 514-517 (2019).

48. G. Chen, C.W. Chow, C.H. Yeh, C.W. Peng, P.C. Guo, J.F. Tsai,M.W. Cheng, Y. Tong and H. K. Tsang, "Mode-Division-Multiplexing (MDM) of 9.4-Tbit/s OFDM Signals on Silicon-on-Insulator (SOI) Platform," IEEE Access 7, 129104-129111 (2019).

49. R. R. Kumar, M. Raevskaia, V. Pogoretskii, Y. Jiao, and H. K. Tsang, "InP membrane micro-ring resonator for generating heralded single photons," Journal of Optics 21, 115201 (2019).

50. Y. Gao, H. K. Tsang, and C. Shu, "A silicon nitride waveguide-integrated chemical vapor deposited graphene photodetector with 38 GHz bandwidth," Nanoscale 10, 21851-21856 (2018).

51. Y. Tong, Z. Hu, X. Wu, J. Liu, C.-K. Chan, C. Shu, and H. K. Tsang, "Negative Frequency-Chirped 112-Gb/s PAM-4 Using an Integrated Germanium Franz-Keldysh Modulator," IEEE Photonics Technology Letters 30, 1443-1446 (2018).

52. Y.Yin, J. Li, H.K. Tsang and D. Dai, "Silicon-graphene photonic devices," Journal of Semiconductors 39, 061009, (2018).

53. J. Liu, X. Wu, C. Huang, H. K. Tsang, and C. Shu, "Compensation of Dispersion-Induced Power Fading in Analog Photonic Links by Gain-Transparent SBS," IEEE Photonics Technology Letters 30, 688–691 (2018).

54. Y. Gao, G. Zhou, N. Zhao, H. K. Tsang and C. Shu, "High-performance chemical vapor deposited graphene-on-silicon nitride waveguide photodetectors," Optics Letters 43, 1399–1402 (2018).

55. X. Wu, C. Huang, K. Xu, W. Zhou, C. Shu, and H. K. Tsang, "3 × 104 Gb/s Single-l Interconnect of Mode-Division Multiplexed Network With a Multicore Fiber," Journal of Lightwave Technology 36, 318–324 (2018).

56. D. Dai, C. Li, S Wang, H. Wu, Y.Shi, Z. Wu, S. Gao, T. Dai,H. Yu and H.K. Tsang, "10-Channel Mode (de)multiplexer with Dual Polarizations," Laser and Photonics Reviews 12, 1700109 (2018).

57. W. Zhou, Z. Cheng, X. Sun, and H. K. Tsang, "Tailorable dual-wavelength-band coupling in a transverse-electric-mode focusing subwavelength grating coupler," Optics Letters 43, 2985-2988 (2018).

58. W. Zhou, Z. Cheng, X. Wu, X. Sun, and H. K. Tsang, "Fully suspended slot waveguide platform," Journal of Applied Physics 123 063103 (2018)

59. T.-H. Xiao, Z. Zhao, W. Zhou, C.-Y. Chang, S. Y. Set, M. Takenaka, H. K. Tsang, Z. Cheng, and K. Goda, "Mid-infrared high-Q germanium microring resonator," Optics Letters 43, 2885-2888 (2018).

60. T.-H. Xiao, Z. Zhao, W. Zhou, M. Takenaka, H. K. Tsang, Z. Cheng, and K. Goda, "High-Q germanium optical nanocavity," Photonics Research 6 925-928 (2018).

61. Y. Tong, W. Zhou, and H. K. Tsang, "Efficient perfectly vertical grating coupler for multi-core fibers fabricated with 193 nm DUV lithography," Optics Letters 43 5709-5712 (2018).

62. Y. Tong, Q. Zhang, X. Wu, C.-W. Chow, C. Shu, and H. K. Tsang, "Integrated germanium-on-silicon Franz–Keldysh vector modulator used with a Kramers–Kronig receiver," Optics Letters 43, 4333-4336, (2018).

63. Y. Gao, L. Tao, H. K. Tsang, and C. Shu, "Graphene-on-silicon nitride waveguide photodetector with interdigital contacts," Applied Physics Letters 112 211107 (2018).

64. T. C. Tzu,Y. Hsu, C. Y. Chuang, X. Wu, C. W. Chow, J. Chen, C. H. Yeh and H. K. Tsang, "Equalization of PAM-4 Signal Generated by Silicon Microring Modulator for 64-Gbit/s Transmission," Journal of Lightwave Technology 35, 4943-4948 (2017).

65. X. Wu, K. Xu, W. Zhou, C. W. Chow, and H. K. Tsang, "Scalable Ultra-Wideband Pulse Generation Based on Silicon Photonic Integrated Circuits," IEEE Photonics Technology Letters 29, 1896–1899 (2017).

66. Y. Zhang, L. Wang, Z. Cheng, and H. K. Tsang, "Forward stimulated Brillouin scattering in silicon microring resonators," Applied Physics Letters 111, 041104 (2017).

67. Y. Gao, W. Zhou, X. Sun, H. K. Tsang, and C. Shu, "Cavity-enhanced thermo-optic bistability and hysteresis in a graphene-on-Si_3N_4 ring resonator," Optics Letters 42, 1950-1953 (2017).

68. W. Zhou, Z. Cheng, X. Wu, B. Zhu, X. Sun, and H. K. Tsang, "Fully suspended slot waveguides for high refractive index sensitivity," Optics Letters 42, 1245–1248 (2017).

69. T.-H. Xiao, Z. Zhao, W. Zhou, M. Takenaka, H. K. Tsang, Z. Cheng, and K. Goda, "Mid-infrared germanium photonic crystal cavity," Optics Letters 42, 2882–2885 (2017).

70. X. Wu, C. Huang, K. Xu, C. Shu, and H. K. Tsang, "Mode-Division Multiplexing for Silicon Photonic Network-on-Chip," Journal of Lightwave Technology 35, 3223–3228 (2017).

71. S. Wang, X. Feng, S. Gao, Y. Shi, T. Dai, H. Yu, H.-K. Tsang, and D. Dai, "On-chip reconfigurable optical add-drop multiplexer for hybrid wavelength/mode-division-multiplexing systems," Optics Letters 42, 2802–2805 (2017).

72. J. Kang, Z. Cheng, W. Zhou, T.-H. Xiao, K.-L. Gopalakrisna, M. Takenaka, H. K. Tsang, and K. Goda, "Focusing subwavelength grating coupler for mid-infrared suspended membrane germanium waveguides," Optics Letters 42, 2094–2097 (2017).

73. Z. Chen, X. Li, J. Wang, L. Tao, M. Long, S.-J. Liang, L. K. Ang, C. Shu, H. K. Tsang, and J.-B. Xu, "Synergistic Effects of Plasmonics and Electron Trapping in Graphene Short-Wave Infrared Photodetectors with Ultrahigh Responsivity," ACS Nano 11, 430–437 (2017).

74. X. Ding, B.P.Yan Y.T. Zhang, and J. Liu, N. Zhao and H. K. Tsang,, "Pulse Transit Time Based Continuous Cuffless Blood Pressure Estimation: A New Extension and A Comprehensive Evaluation," Scientific Reports 7, 11554 (2017).