Abstract

We describe and experimentally demonstrate a method for active control of resonant modulators and filters in an integrated photonics platform. Variations in resonance frequency due to manufacturing processes and thermal fluctuations are corrected by way of balanced homodyne locking. The method is compact, insensitive to intensity fluctuations, minimally disturbs the micro-resonator, and does not require an arbitrary reference to lock. We demonstrate long-term stable locking of an integrated filter to a laser swept over 1.25 THz. In addition, we show locking of a modulator with low bit error rate while the chip temperature is varied from 5 to 60° C.

© 2014 Optical Society of America

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  1. M. R. Watts, W. A. Zortman, D. C. Trotter, R. W. Young, A. L. Lentine, “Vertical junction silicon microdisk modulators and switches,” Opt. Express 19(22), 21989–22003 (2011).
    [CrossRef] [PubMed]
  2. W. Zortman, A. Lentine, D. Trotter, and M. Watts, “Integrated CMOS comaptible low power 10Gbps silicon photonic heater modulator,” in Optical Fiber Communication Conference, OSA Technical Digest (Optical Society of America, 2012), paper OW4I.5.
    [CrossRef]
  3. M. Lipson, “Compact electro-optic modulators on a silicon chip,” IEEE J. Sel. Top. Quantum Electron. 12(6), 1520–1526 (2006).
    [CrossRef]
  4. J. S. Levy, A. Gondarenko, M. A. Foster, A. C. Turner-Foster, A. L. Gaeta, M. Lipson, “CMOS-compatible multiple-wavelength oscillator for on-chip optical interconnects,” Nat. Photonics 4(1), 37–40 (2010).
    [CrossRef]
  5. A. Schliesser, P. Del’Haye, N. Nooshi, K. J. Vahala, T. J. Kippenberg, “Radiation pressure cooling of a micromechanical oscillator using dynamical backaction,” Phys. Rev. Lett. 97(24), 243905 (2006).
    [CrossRef] [PubMed]
  6. G. Cocorullo, F. G. Della Corte, I. Rendina, “Temperature dependence of the thermo-optic coefficient in crystalline silicon between room temperature and 550 K at the wavelength of 1523 nm,” Appl. Phys. Lett. 74(22), 3338 (1999).
    [CrossRef]
  7. V. R. Almeida, M. Lipson, “Optical bistability on a silicon chip,” Opt. Lett. 29(20), 2387–2389 (2004).
    [CrossRef] [PubMed]
  8. W. A. Zortman, D. C. Trotter, M. R. Watts, “Silicon photonics manufacturing,” Opt. Express 18(23), 23598–23607 (2010).
    [CrossRef] [PubMed]
  9. A. V. Krishnamoorthy, Xuezhe Zheng, Guoliang Li, T. Jin Yao, A. Pinguet, H. Mekis, I. Thacker, Shubin, K. Ying Luo, Raj, J. E. Cunningham, “Exploiting CMOS manufacturing to reduce tuning requirements for resonant optical devices,” IEEE Photonics J. 3(3), 567–579 (2011).
    [CrossRef]
  10. V. Raghunathan, W. N. Ye, J. Hu, T. Izuhara, J. Michel, L. Kimerling, “Athermal operation of Silicon waveguides: spectral, second order and footprint dependencies,” Opt. Express 18(17), 17631–17639 (2010).
    [CrossRef] [PubMed]
  11. H. L. R. Lira, S. Manipatruni, M. Lipson, “Broadband hitless silicon electro-optic switch for on-chip optical networks,” Opt. Express 17(25), 22271–22280 (2009).
    [CrossRef] [PubMed]
  12. J. E. Cunningham, I. Shubin, X. Zheng, T. Pinguet, A. Mekis, Y. Luo, H. Thacker, G. Li, J. Yao, K. Raj, A. V. Krishnamoorthy, “Highly-efficient thermally-tuned resonant optical filters,” Opt. Express 18(18), 19055–19063 (2010).
    [CrossRef] [PubMed]
  13. G. Li, X. Zheng, J. Yao, H. Thacker, I. Shubin, Y. Luo, K. Raj, J. E. Cunningham, A. V. Krishnamoorthy, “25Gb/s 1V-driving CMOS ring modulator with integrated thermal tuning,” Opt. Express 19(21), 20435–20443 (2011).
    [CrossRef] [PubMed]
  14. M. R. Watts, “Adiabatic microring resonators,” Opt. Lett. 35(19), 3231–3233 (2010).
    [CrossRef] [PubMed]
  15. K. Padmaraju, J. Chan, L. Chen, M. Lipson, K. Bergman, “Thermal stabilization of a microring modulator using feedback control,” Opt. Express 20(27), 27999–28008 (2012).
    [CrossRef] [PubMed]
  16. E. Timurdogan, A. Biberman, D. C. Trotter, C. Sun, M. Moresco, V. Stojanovic, and M. R. Watts, “Automated wavelength recovery for microring resonators,” in Conference on Lasers and Electro-Optics 2012, OSA Technical Digest (Optical Society of America, 2012), paper CM2M.1.
    [CrossRef]
  17. C. T. DeRose, M. R. Watts, D. C. Trotter, D. L. Luck, G. N. Nielson, and R. W. Young, “Silicon microring modulator with integrated heater and temperature sensor for thermal control,” in Conference on Lasers and Electro-Optics 2010, OSA Technical Digest (Optical Society of America, 2010), paper CThJ3.
    [CrossRef]
  18. W. Zortman, A. Lentine, D. Trotter, M. Watts, “Bit-error-rate monitoring for active wavelength control of resonant modulators,” IEEE Micro 33, 42–52 (2012).
    [CrossRef]
  19. K. Padmaraju, D. F. Logan, T. Shiraishi, J. J. Ackert, A. P. Knights, K. Bergman, “Wavelength locking and thermally stabilizing microring resonators using dithering signals,” J. Lightwave Technol. 32(3), 505–512 (2014).
    [CrossRef]
  20. J. Chambers, “High frequency Pound-Drever-Hall optical ring resonator sensing,” Master’s thesis, Texas A&M University (2007).
  21. C. Qiu, J. Shu, Z. Li, X. Zhang, Q. Xu, “Wavelength tracking with thermally controlled silicon resonators,” Opt. Express 19(6), 5143–5148 (2011).
    [CrossRef] [PubMed]
  22. J. A. Cox, D. C. Trotter, A. L. Starbuck, “Integrated control of silicon-photonic micro-resonator wavelength via balanced homodyne locking,” in Optical Interconnects Conference 2013 (IEEE, 2013), pp. 52–53.
    [CrossRef]
  23. M. Heurs, I. R. Petersen, M. R. James, E. H. Huntington, “Homodyne locking of a squeezer,” Opt. Lett. 34(16), 2465–2467 (2009).
    [CrossRef] [PubMed]
  24. C. T. DeRose, D. C. Trotter, W. A. Zortman, A. L. Starbuck, M. Fisher, M. R. Watts, P. S. Davids, “Ultra compact 45 GHz CMOS compatible Germanium waveguide photodiode with low dark current,” Opt. Express 19(25), 24897–24904 (2011).
    [CrossRef] [PubMed]
  25. M. R. Watts, J. Sun, C. DeRose, D. C. Trotter, R. W. Young, G. N. Nielson, “Adiabatic thermo-optic Mach-Zehnder switch,” Opt. Lett. 38(5), 733–735 (2013).
    [CrossRef] [PubMed]
  26. W. A. Zortman, A. L. Lentine, D. C. Trotter, M. R. Watts, “Low-voltage differentially-signaled modulators,” Opt. Express 19(27), 26017–26026 (2011).
    [CrossRef] [PubMed]

2014 (1)

2013 (1)

2012 (2)

K. Padmaraju, J. Chan, L. Chen, M. Lipson, K. Bergman, “Thermal stabilization of a microring modulator using feedback control,” Opt. Express 20(27), 27999–28008 (2012).
[CrossRef] [PubMed]

W. Zortman, A. Lentine, D. Trotter, M. Watts, “Bit-error-rate monitoring for active wavelength control of resonant modulators,” IEEE Micro 33, 42–52 (2012).
[CrossRef]

2011 (6)

2010 (5)

2009 (2)

2006 (2)

A. Schliesser, P. Del’Haye, N. Nooshi, K. J. Vahala, T. J. Kippenberg, “Radiation pressure cooling of a micromechanical oscillator using dynamical backaction,” Phys. Rev. Lett. 97(24), 243905 (2006).
[CrossRef] [PubMed]

M. Lipson, “Compact electro-optic modulators on a silicon chip,” IEEE J. Sel. Top. Quantum Electron. 12(6), 1520–1526 (2006).
[CrossRef]

2004 (1)

1999 (1)

G. Cocorullo, F. G. Della Corte, I. Rendina, “Temperature dependence of the thermo-optic coefficient in crystalline silicon between room temperature and 550 K at the wavelength of 1523 nm,” Appl. Phys. Lett. 74(22), 3338 (1999).
[CrossRef]

Ackert, J. J.

Almeida, V. R.

Bergman, K.

Chan, J.

Chen, L.

Cocorullo, G.

G. Cocorullo, F. G. Della Corte, I. Rendina, “Temperature dependence of the thermo-optic coefficient in crystalline silicon between room temperature and 550 K at the wavelength of 1523 nm,” Appl. Phys. Lett. 74(22), 3338 (1999).
[CrossRef]

Cox, J. A.

J. A. Cox, D. C. Trotter, A. L. Starbuck, “Integrated control of silicon-photonic micro-resonator wavelength via balanced homodyne locking,” in Optical Interconnects Conference 2013 (IEEE, 2013), pp. 52–53.
[CrossRef]

Cunningham, J. E.

Davids, P. S.

Del’Haye, P.

A. Schliesser, P. Del’Haye, N. Nooshi, K. J. Vahala, T. J. Kippenberg, “Radiation pressure cooling of a micromechanical oscillator using dynamical backaction,” Phys. Rev. Lett. 97(24), 243905 (2006).
[CrossRef] [PubMed]

Della Corte, F. G.

G. Cocorullo, F. G. Della Corte, I. Rendina, “Temperature dependence of the thermo-optic coefficient in crystalline silicon between room temperature and 550 K at the wavelength of 1523 nm,” Appl. Phys. Lett. 74(22), 3338 (1999).
[CrossRef]

DeRose, C.

DeRose, C. T.

Fisher, M.

Foster, M. A.

J. S. Levy, A. Gondarenko, M. A. Foster, A. C. Turner-Foster, A. L. Gaeta, M. Lipson, “CMOS-compatible multiple-wavelength oscillator for on-chip optical interconnects,” Nat. Photonics 4(1), 37–40 (2010).
[CrossRef]

Gaeta, A. L.

J. S. Levy, A. Gondarenko, M. A. Foster, A. C. Turner-Foster, A. L. Gaeta, M. Lipson, “CMOS-compatible multiple-wavelength oscillator for on-chip optical interconnects,” Nat. Photonics 4(1), 37–40 (2010).
[CrossRef]

Gondarenko, A.

J. S. Levy, A. Gondarenko, M. A. Foster, A. C. Turner-Foster, A. L. Gaeta, M. Lipson, “CMOS-compatible multiple-wavelength oscillator for on-chip optical interconnects,” Nat. Photonics 4(1), 37–40 (2010).
[CrossRef]

Guoliang Li,

A. V. Krishnamoorthy, Xuezhe Zheng, Guoliang Li, T. Jin Yao, A. Pinguet, H. Mekis, I. Thacker, Shubin, K. Ying Luo, Raj, J. E. Cunningham, “Exploiting CMOS manufacturing to reduce tuning requirements for resonant optical devices,” IEEE Photonics J. 3(3), 567–579 (2011).
[CrossRef]

Heurs, M.

Hu, J.

Huntington, E. H.

Izuhara, T.

James, M. R.

Jin Yao, T.

A. V. Krishnamoorthy, Xuezhe Zheng, Guoliang Li, T. Jin Yao, A. Pinguet, H. Mekis, I. Thacker, Shubin, K. Ying Luo, Raj, J. E. Cunningham, “Exploiting CMOS manufacturing to reduce tuning requirements for resonant optical devices,” IEEE Photonics J. 3(3), 567–579 (2011).
[CrossRef]

Kimerling, L.

Kippenberg, T. J.

A. Schliesser, P. Del’Haye, N. Nooshi, K. J. Vahala, T. J. Kippenberg, “Radiation pressure cooling of a micromechanical oscillator using dynamical backaction,” Phys. Rev. Lett. 97(24), 243905 (2006).
[CrossRef] [PubMed]

Knights, A. P.

Krishnamoorthy, A. V.

Lentine, A.

W. Zortman, A. Lentine, D. Trotter, M. Watts, “Bit-error-rate monitoring for active wavelength control of resonant modulators,” IEEE Micro 33, 42–52 (2012).
[CrossRef]

Lentine, A. L.

Levy, J. S.

J. S. Levy, A. Gondarenko, M. A. Foster, A. C. Turner-Foster, A. L. Gaeta, M. Lipson, “CMOS-compatible multiple-wavelength oscillator for on-chip optical interconnects,” Nat. Photonics 4(1), 37–40 (2010).
[CrossRef]

Li, G.

Li, Z.

Lipson, M.

Lira, H. L. R.

Logan, D. F.

Luo, Y.

Manipatruni, S.

Mekis, A.

Mekis, H.

A. V. Krishnamoorthy, Xuezhe Zheng, Guoliang Li, T. Jin Yao, A. Pinguet, H. Mekis, I. Thacker, Shubin, K. Ying Luo, Raj, J. E. Cunningham, “Exploiting CMOS manufacturing to reduce tuning requirements for resonant optical devices,” IEEE Photonics J. 3(3), 567–579 (2011).
[CrossRef]

Michel, J.

Nielson, G. N.

Nooshi, N.

A. Schliesser, P. Del’Haye, N. Nooshi, K. J. Vahala, T. J. Kippenberg, “Radiation pressure cooling of a micromechanical oscillator using dynamical backaction,” Phys. Rev. Lett. 97(24), 243905 (2006).
[CrossRef] [PubMed]

Padmaraju, K.

Petersen, I. R.

Pinguet, A.

A. V. Krishnamoorthy, Xuezhe Zheng, Guoliang Li, T. Jin Yao, A. Pinguet, H. Mekis, I. Thacker, Shubin, K. Ying Luo, Raj, J. E. Cunningham, “Exploiting CMOS manufacturing to reduce tuning requirements for resonant optical devices,” IEEE Photonics J. 3(3), 567–579 (2011).
[CrossRef]

Pinguet, T.

Qiu, C.

Raghunathan, V.

Raj,

A. V. Krishnamoorthy, Xuezhe Zheng, Guoliang Li, T. Jin Yao, A. Pinguet, H. Mekis, I. Thacker, Shubin, K. Ying Luo, Raj, J. E. Cunningham, “Exploiting CMOS manufacturing to reduce tuning requirements for resonant optical devices,” IEEE Photonics J. 3(3), 567–579 (2011).
[CrossRef]

Raj, K.

Rendina, I.

G. Cocorullo, F. G. Della Corte, I. Rendina, “Temperature dependence of the thermo-optic coefficient in crystalline silicon between room temperature and 550 K at the wavelength of 1523 nm,” Appl. Phys. Lett. 74(22), 3338 (1999).
[CrossRef]

Schliesser, A.

A. Schliesser, P. Del’Haye, N. Nooshi, K. J. Vahala, T. J. Kippenberg, “Radiation pressure cooling of a micromechanical oscillator using dynamical backaction,” Phys. Rev. Lett. 97(24), 243905 (2006).
[CrossRef] [PubMed]

Shiraishi, T.

Shu, J.

Shubin,

A. V. Krishnamoorthy, Xuezhe Zheng, Guoliang Li, T. Jin Yao, A. Pinguet, H. Mekis, I. Thacker, Shubin, K. Ying Luo, Raj, J. E. Cunningham, “Exploiting CMOS manufacturing to reduce tuning requirements for resonant optical devices,” IEEE Photonics J. 3(3), 567–579 (2011).
[CrossRef]

Shubin, I.

Starbuck, A. L.

C. T. DeRose, D. C. Trotter, W. A. Zortman, A. L. Starbuck, M. Fisher, M. R. Watts, P. S. Davids, “Ultra compact 45 GHz CMOS compatible Germanium waveguide photodiode with low dark current,” Opt. Express 19(25), 24897–24904 (2011).
[CrossRef] [PubMed]

J. A. Cox, D. C. Trotter, A. L. Starbuck, “Integrated control of silicon-photonic micro-resonator wavelength via balanced homodyne locking,” in Optical Interconnects Conference 2013 (IEEE, 2013), pp. 52–53.
[CrossRef]

Sun, J.

Thacker, H.

Thacker, I.

A. V. Krishnamoorthy, Xuezhe Zheng, Guoliang Li, T. Jin Yao, A. Pinguet, H. Mekis, I. Thacker, Shubin, K. Ying Luo, Raj, J. E. Cunningham, “Exploiting CMOS manufacturing to reduce tuning requirements for resonant optical devices,” IEEE Photonics J. 3(3), 567–579 (2011).
[CrossRef]

Trotter, D.

W. Zortman, A. Lentine, D. Trotter, M. Watts, “Bit-error-rate monitoring for active wavelength control of resonant modulators,” IEEE Micro 33, 42–52 (2012).
[CrossRef]

Trotter, D. C.

Turner-Foster, A. C.

J. S. Levy, A. Gondarenko, M. A. Foster, A. C. Turner-Foster, A. L. Gaeta, M. Lipson, “CMOS-compatible multiple-wavelength oscillator for on-chip optical interconnects,” Nat. Photonics 4(1), 37–40 (2010).
[CrossRef]

Vahala, K. J.

A. Schliesser, P. Del’Haye, N. Nooshi, K. J. Vahala, T. J. Kippenberg, “Radiation pressure cooling of a micromechanical oscillator using dynamical backaction,” Phys. Rev. Lett. 97(24), 243905 (2006).
[CrossRef] [PubMed]

Watts, M.

W. Zortman, A. Lentine, D. Trotter, M. Watts, “Bit-error-rate monitoring for active wavelength control of resonant modulators,” IEEE Micro 33, 42–52 (2012).
[CrossRef]

Watts, M. R.

Xu, Q.

Xuezhe Zheng,

A. V. Krishnamoorthy, Xuezhe Zheng, Guoliang Li, T. Jin Yao, A. Pinguet, H. Mekis, I. Thacker, Shubin, K. Ying Luo, Raj, J. E. Cunningham, “Exploiting CMOS manufacturing to reduce tuning requirements for resonant optical devices,” IEEE Photonics J. 3(3), 567–579 (2011).
[CrossRef]

Yao, J.

Ye, W. N.

Ying Luo, K.

A. V. Krishnamoorthy, Xuezhe Zheng, Guoliang Li, T. Jin Yao, A. Pinguet, H. Mekis, I. Thacker, Shubin, K. Ying Luo, Raj, J. E. Cunningham, “Exploiting CMOS manufacturing to reduce tuning requirements for resonant optical devices,” IEEE Photonics J. 3(3), 567–579 (2011).
[CrossRef]

Young, R. W.

Zhang, X.

Zheng, X.

Zortman, W.

W. Zortman, A. Lentine, D. Trotter, M. Watts, “Bit-error-rate monitoring for active wavelength control of resonant modulators,” IEEE Micro 33, 42–52 (2012).
[CrossRef]

Zortman, W. A.

Appl. Phys. Lett. (1)

G. Cocorullo, F. G. Della Corte, I. Rendina, “Temperature dependence of the thermo-optic coefficient in crystalline silicon between room temperature and 550 K at the wavelength of 1523 nm,” Appl. Phys. Lett. 74(22), 3338 (1999).
[CrossRef]

IEEE J. Sel. Top. Quantum Electron. (1)

M. Lipson, “Compact electro-optic modulators on a silicon chip,” IEEE J. Sel. Top. Quantum Electron. 12(6), 1520–1526 (2006).
[CrossRef]

IEEE Micro (1)

W. Zortman, A. Lentine, D. Trotter, M. Watts, “Bit-error-rate monitoring for active wavelength control of resonant modulators,” IEEE Micro 33, 42–52 (2012).
[CrossRef]

IEEE Photonics J. (1)

A. V. Krishnamoorthy, Xuezhe Zheng, Guoliang Li, T. Jin Yao, A. Pinguet, H. Mekis, I. Thacker, Shubin, K. Ying Luo, Raj, J. E. Cunningham, “Exploiting CMOS manufacturing to reduce tuning requirements for resonant optical devices,” IEEE Photonics J. 3(3), 567–579 (2011).
[CrossRef]

J. Lightwave Technol. (1)

Nat. Photonics (1)

J. S. Levy, A. Gondarenko, M. A. Foster, A. C. Turner-Foster, A. L. Gaeta, M. Lipson, “CMOS-compatible multiple-wavelength oscillator for on-chip optical interconnects,” Nat. Photonics 4(1), 37–40 (2010).
[CrossRef]

Opt. Express (10)

W. A. Zortman, D. C. Trotter, M. R. Watts, “Silicon photonics manufacturing,” Opt. Express 18(23), 23598–23607 (2010).
[CrossRef] [PubMed]

C. Qiu, J. Shu, Z. Li, X. Zhang, Q. Xu, “Wavelength tracking with thermally controlled silicon resonators,” Opt. Express 19(6), 5143–5148 (2011).
[CrossRef] [PubMed]

G. Li, X. Zheng, J. Yao, H. Thacker, I. Shubin, Y. Luo, K. Raj, J. E. Cunningham, A. V. Krishnamoorthy, “25Gb/s 1V-driving CMOS ring modulator with integrated thermal tuning,” Opt. Express 19(21), 20435–20443 (2011).
[CrossRef] [PubMed]

M. R. Watts, W. A. Zortman, D. C. Trotter, R. W. Young, A. L. Lentine, “Vertical junction silicon microdisk modulators and switches,” Opt. Express 19(22), 21989–22003 (2011).
[CrossRef] [PubMed]

C. T. DeRose, D. C. Trotter, W. A. Zortman, A. L. Starbuck, M. Fisher, M. R. Watts, P. S. Davids, “Ultra compact 45 GHz CMOS compatible Germanium waveguide photodiode with low dark current,” Opt. Express 19(25), 24897–24904 (2011).
[CrossRef] [PubMed]

W. A. Zortman, A. L. Lentine, D. C. Trotter, M. R. Watts, “Low-voltage differentially-signaled modulators,” Opt. Express 19(27), 26017–26026 (2011).
[CrossRef] [PubMed]

K. Padmaraju, J. Chan, L. Chen, M. Lipson, K. Bergman, “Thermal stabilization of a microring modulator using feedback control,” Opt. Express 20(27), 27999–28008 (2012).
[CrossRef] [PubMed]

H. L. R. Lira, S. Manipatruni, M. Lipson, “Broadband hitless silicon electro-optic switch for on-chip optical networks,” Opt. Express 17(25), 22271–22280 (2009).
[CrossRef] [PubMed]

V. Raghunathan, W. N. Ye, J. Hu, T. Izuhara, J. Michel, L. Kimerling, “Athermal operation of Silicon waveguides: spectral, second order and footprint dependencies,” Opt. Express 18(17), 17631–17639 (2010).
[CrossRef] [PubMed]

J. E. Cunningham, I. Shubin, X. Zheng, T. Pinguet, A. Mekis, Y. Luo, H. Thacker, G. Li, J. Yao, K. Raj, A. V. Krishnamoorthy, “Highly-efficient thermally-tuned resonant optical filters,” Opt. Express 18(18), 19055–19063 (2010).
[CrossRef] [PubMed]

Opt. Lett. (4)

Phys. Rev. Lett. (1)

A. Schliesser, P. Del’Haye, N. Nooshi, K. J. Vahala, T. J. Kippenberg, “Radiation pressure cooling of a micromechanical oscillator using dynamical backaction,” Phys. Rev. Lett. 97(24), 243905 (2006).
[CrossRef] [PubMed]

Other (5)

J. Chambers, “High frequency Pound-Drever-Hall optical ring resonator sensing,” Master’s thesis, Texas A&M University (2007).

J. A. Cox, D. C. Trotter, A. L. Starbuck, “Integrated control of silicon-photonic micro-resonator wavelength via balanced homodyne locking,” in Optical Interconnects Conference 2013 (IEEE, 2013), pp. 52–53.
[CrossRef]

E. Timurdogan, A. Biberman, D. C. Trotter, C. Sun, M. Moresco, V. Stojanovic, and M. R. Watts, “Automated wavelength recovery for microring resonators,” in Conference on Lasers and Electro-Optics 2012, OSA Technical Digest (Optical Society of America, 2012), paper CM2M.1.
[CrossRef]

C. T. DeRose, M. R. Watts, D. C. Trotter, D. L. Luck, G. N. Nielson, and R. W. Young, “Silicon microring modulator with integrated heater and temperature sensor for thermal control,” in Conference on Lasers and Electro-Optics 2010, OSA Technical Digest (Optical Society of America, 2010), paper CThJ3.
[CrossRef]

W. Zortman, A. Lentine, D. Trotter, and M. Watts, “Integrated CMOS comaptible low power 10Gbps silicon photonic heater modulator,” in Optical Fiber Communication Conference, OSA Technical Digest (Optical Society of America, 2012), paper OW4I.5.
[CrossRef]

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Figures (9)

Fig. 1
Fig. 1

Signal diagram of the balanced homodyne locking (BHL) method. A Mach-Zehnder interferometer (MZI) is formed by splitting the waveguide input between the micro-resonator and a phase shifter, before recombining on a balanced photodetector with a 50% directional coupler (DC). The resulting error signal, e(t), drives the loop filter to tune the resonator. The locking point is adjusted by varying the phase shift.

Fig. 2
Fig. 2

The calculated transfer function for balanced homodyne locking (BHL) and the corresponding resonator drop port response are plotted above, for a critically coupled filter. (a)—(d) show the change in shape of the BHD transfer function for various relative phase shifts in the interferometer. (a) the ideal locking point for a filter is with no phase shift. (b) approximately ideal locking point for an on-off keyed modulator is at π/4. (c) no lock would be obtained for a π/2 phase shift. (d) the sign of the error signal can be inverted with a π phase shift.

Fig. 3
Fig. 3

An optical image of the filter locking system and corresponding experimental setup is shown above. A tunable laser provides the optical input to which the filter is locked. (ADC: analog to digital converter).

Fig. 4
Fig. 4

The measured response of the balanced homodyne transfer function, using integrated germanium photodetectors, is shown above for various settings of the phase shifter voltage. At zero volts, the transfer function exhibits approximately zero relative phase imbalance, which is ideal for locking a filter. However, at 5 volts, the filter will be locked to the side of the resonance (suitable for our modulator), while at 10 volts there is approximately π/2 phase shift, and no lock would be obtained. At 14 and 15 volts, π phase shift is achieved, inverting the transfer function.

Fig. 5
Fig. 5

Demonstration of the typical filter locking performance as the optical input wavelength is swept between 1532 and 1542 nm. Integrated germanium detectors were used for this test. The lock is enabled at 11 seconds, at which time the error signal (a) is driven to zero and the filter heater voltage (b) is driven so that the filter tracks the shifting wavelength. The relative optical power exiting the through port is shown in (c).

Fig. 6
Fig. 6

An optical image of the balanced homodyne modulator locking device is shown above. The modulator is driven with a bit error rate tester (BERT) while locked. A phase shifter is adjusted to set the optimal locking point. The modulator loop filter is also a simple integrator, as used to lock the filter.

Fig. 7
Fig. 7

An eye diagram is shown above for the modulator while locked to the laser line, with a pattern length of 223-1 bits and a data rate of 5 Gbit/s. (a) The driving electrical modulation signal from the pattern generator. (b) The received modulation signal after photodetection.

Fig. 8
Fig. 8

The bit error rate of the modulator is measured at 5 Gbit/s for a fixed wavelength input as the temperature of the chip is varied from 5 °C to 60 °C The phase shifter voltage is left fixed at 6.6 volts. The measurement is performed with three different pattern lengths, owing to the characteristics of this particular modulator. With a pattern length of 215 bits, no errors are observed until the temperature reached 60 °C. The coldest temperature measurable is limited by the performance of the thermo-electric cooler (TEC) and frost buildup on the chip. Integrated germanium photodetectors were used to lock the modulator wavelength to the signal wavelength.

Fig. 9
Fig. 9

The calculated (a) and measured (b) response for the balanced homodyne locking transfer function with the modulator is shown above. For (a), the transfer function is shown for 40—60° phase shifts. For (b), the transfer function for a modulator is measured for device temperatures of 5—60°C, with a corresponding heater voltage applied to hold the resonate wavelength constant. All transfer functions are normalized in order to compare the shapes. From comparison of (a) and (b), it can be seen that the phase shift varies by about 20 degrees, which can explain the increase in bit error rate observed at 60°C—since the modulator would be locked too far from resonance.

Equations (5)

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a 1 = a 0 i t e iϕ a 2 = a 0 1t A( β )
a 3 = 1ε a 1 +i ε a 2 a 4 =i ε a 1 + 1ε a 2
Y( β )=αG a m n 2 Z 0 [ | a 3 | 2 | a 4 | 2 ] =αG a m n 2 Z 0 a 0 2 [ 2 ε ε 2 t t 2 ( A( β ) e iϕ +A ( β ) * e iϕ ) +( 2εt2εt+1 ) | A( β ) | 2 +2εtt ]
A( β )= | κ | 4 κ 2 e i2πRβ e i4πRβ + | κ | 2 1
Y( β )=αG a 0 2 | κ | 4 a m n Z 0 t t 2 ( e iϕ κ 2 ¯ e i2πRβ e i4πRβ + | κ | 2 1 + e iϕ κ 2 e i2πRβ e i4πRβ + | κ | 2 1 )

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