Abstract

The high frequency operation of a low-voltage electrooptic modulator based on a strip-loaded BaTiO3 thin film waveguide structure has been demonstrated. The epitaxial BaTiO3 thin film on an MgO substrate forms a composite structure with a low effective dielectric constant of 20.8 at 40 GHz. A 3.9 V half-wave voltage with a 3.7 GHz 3-dB bandwidth and a 150 pm/V effective electrooptic coefficient is obtained for the 3.2mm-long modulator at 1.55 µm. Broadband modulation up to 40 GHz is measured with a calibrated detection system. Numerical simulations indicate that the BaTiO3 thin film modulator has the potential for a 3-dB operational bandwidth in excess of 40 GHz through optimized design.

© 2004 Optical Society of America

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References

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  1. M. Zgonik, P. Bernasconi, M. Duelli, R. Schlesser, P. Günter, M. H. Garrett, D. Rytz, Y. Zhu, and X. Wu, �??Dielectric, elastic, piezoelectric, electrooptic, and elasto-optic tensors of BaTiO3 crystals,�?? Phys. Rev. B 50, 5941-5949 (1994).
    [CrossRef]
  2. D.M. Gill, C.W. Conrad, G. Ford, B.W. Wessels, and S.T. Ho, �??Thin-film channel waveguide electro-optic modulator in epitaxial BaTiO3,�?? Appl. Phys. Lett. 71, 1783-1785 (1997).
    [CrossRef]
  3. A. Petraru, J. Schubert, M. Schmid, and C. Buchal, �??Ferroelectric BaTiO3 thin film optical waveguide modulators,�?? Appl. Phys. Lett. 81, 1375-1377 (2002).
    [CrossRef]
  4. P. Tang, D.J. Towner, A. L. Meier, and B. W. Wessels, �??Low-voltage, polarization-insensitive, electro-optic modulator based on a polydomain barium titanate thin film,�?? Appl. Phys. Lett. 85, 4615-4617 (2004).
    [CrossRef]
  5. T. Hamano, D. J. Towner, and B. W. Wessels, �??Relative dielectric constant of epitaxial BaTiO3 thin films in the GHz frequency range,�?? Appl. Phys. Lett. 83, 5274-5276 (2003).
    [CrossRef]
  6. P. Tang, D.J. Towner, A. L. Meier, and B.W. Wessels, �??Polarisation-insensitive Si3N4 strip-loaded BaTiO3 thin-film waveguide with low propagation losses,�?? Electron. Lett. 39, 1651-1652 (2003).
    [CrossRef]
  7. D. J. Towner, J. Ni, T.J. Marks, and B.W. Wessels, �??Effects of two-stage deposition on the structure and properties of heteroepitaxial BaTiO3 thin films,�?? J. Cryst. Growth 255, 107-113 (2003).
    [CrossRef]
  8. P. Tang, D. J. Towner, A. L. Meier, and B. W. Wessels, �??Low-loss electrooptic BaTiO3 thin film waveguide modulator,�?? IEEE Photon. Technol. Lett. 16, 1837-1839 (2004).
    [CrossRef]
  9. G. K. Gopalakrishnan, W. K. Burns, R. W. McElhanon, C. G. Bulmer, and A. S. Greenblatt, �??Performance and modeling of broadband LiNbO3 traveling wave optical intensity modulators,�?? J. Lightwave Technol. 12, 1807-1818 (1994).
    [CrossRef]
  10. D. M. Gill, and A. Chowdhury, �??Electro-optic polymer-based modulator design and perormance for 40 Gb/s system applications,�?? J. Lightwave Technol. 20, 2145-2153 (2002).
    [CrossRef]
  11. P. Tang, A. L. Meier, D. J. Towner, T. Hamano, and B. W. Wessels, �??BaTiO3 waveguide modulators with 360 pm/V effective electro-optic coefficient at 1.55 �?�m, �?? in Optical Amplifiers and TheirApplications/Integrated Photonics Research Topical Meetings (The Optical Society of America, Washington, DC, 2004), PD3-1.
  12. N. Dagli, �??Wide-bandwidth lasers and modulators for RF photonics,�?? IEEE Trans. Microwave Theory Tech. 47, 1151-1171 (1999).
    [CrossRef]
  13. K. C. Gupta, R. Garg, I. Bahl, and P. Bhartia, Microstrip Lines and Slotlines, (Norwood, MA: Artech House, 1996).
  14. K. Kubota, J. Noda, and O. Mikami, �??Traveling wave optical modulator using a directional coupler LiNbO3 waveguide,�?? IEEE J. Quantum Electron. 16, 754-760 (1980).
    [CrossRef]
  15. G. Gonzales, Microwave Transition Amplifiers, (Englewood Cliffs, NJ: Prentice, 1984).
  16. A. Chowdhury, and L. McCaughan, �??Figure of merit for near-velocity-matched traveling-wave modulators,�?? Opt. Lett. 26, 1317-1319 (2001).
    [CrossRef]

Appl. Phys. Lett. (4)

D.M. Gill, C.W. Conrad, G. Ford, B.W. Wessels, and S.T. Ho, �??Thin-film channel waveguide electro-optic modulator in epitaxial BaTiO3,�?? Appl. Phys. Lett. 71, 1783-1785 (1997).
[CrossRef]

A. Petraru, J. Schubert, M. Schmid, and C. Buchal, �??Ferroelectric BaTiO3 thin film optical waveguide modulators,�?? Appl. Phys. Lett. 81, 1375-1377 (2002).
[CrossRef]

P. Tang, D.J. Towner, A. L. Meier, and B. W. Wessels, �??Low-voltage, polarization-insensitive, electro-optic modulator based on a polydomain barium titanate thin film,�?? Appl. Phys. Lett. 85, 4615-4617 (2004).
[CrossRef]

T. Hamano, D. J. Towner, and B. W. Wessels, �??Relative dielectric constant of epitaxial BaTiO3 thin films in the GHz frequency range,�?? Appl. Phys. Lett. 83, 5274-5276 (2003).
[CrossRef]

Electron. Lett. (1)

P. Tang, D.J. Towner, A. L. Meier, and B.W. Wessels, �??Polarisation-insensitive Si3N4 strip-loaded BaTiO3 thin-film waveguide with low propagation losses,�?? Electron. Lett. 39, 1651-1652 (2003).
[CrossRef]

IEEE J. Quantum Electron. (1)

K. Kubota, J. Noda, and O. Mikami, �??Traveling wave optical modulator using a directional coupler LiNbO3 waveguide,�?? IEEE J. Quantum Electron. 16, 754-760 (1980).
[CrossRef]

IEEE Photon. Technol. Lett. (1)

P. Tang, D. J. Towner, A. L. Meier, and B. W. Wessels, �??Low-loss electrooptic BaTiO3 thin film waveguide modulator,�?? IEEE Photon. Technol. Lett. 16, 1837-1839 (2004).
[CrossRef]

IEEE Trans. Microwave Theory Tech. (1)

N. Dagli, �??Wide-bandwidth lasers and modulators for RF photonics,�?? IEEE Trans. Microwave Theory Tech. 47, 1151-1171 (1999).
[CrossRef]

J. Cryst. Growth (1)

D. J. Towner, J. Ni, T.J. Marks, and B.W. Wessels, �??Effects of two-stage deposition on the structure and properties of heteroepitaxial BaTiO3 thin films,�?? J. Cryst. Growth 255, 107-113 (2003).
[CrossRef]

J. Lightwave Technol. (2)

G. K. Gopalakrishnan, W. K. Burns, R. W. McElhanon, C. G. Bulmer, and A. S. Greenblatt, �??Performance and modeling of broadband LiNbO3 traveling wave optical intensity modulators,�?? J. Lightwave Technol. 12, 1807-1818 (1994).
[CrossRef]

D. M. Gill, and A. Chowdhury, �??Electro-optic polymer-based modulator design and perormance for 40 Gb/s system applications,�?? J. Lightwave Technol. 20, 2145-2153 (2002).
[CrossRef]

Opt. Lett. (1)

Phys. Rev. B (1)

M. Zgonik, P. Bernasconi, M. Duelli, R. Schlesser, P. Günter, M. H. Garrett, D. Rytz, Y. Zhu, and X. Wu, �??Dielectric, elastic, piezoelectric, electrooptic, and elasto-optic tensors of BaTiO3 crystals,�?? Phys. Rev. B 50, 5941-5949 (1994).
[CrossRef]

Other (3)

G. Gonzales, Microwave Transition Amplifiers, (Englewood Cliffs, NJ: Prentice, 1984).

P. Tang, A. L. Meier, D. J. Towner, T. Hamano, and B. W. Wessels, �??BaTiO3 waveguide modulators with 360 pm/V effective electro-optic coefficient at 1.55 �?�m, �?? in Optical Amplifiers and TheirApplications/Integrated Photonics Research Topical Meetings (The Optical Society of America, Washington, DC, 2004), PD3-1.

K. C. Gupta, R. Garg, I. Bahl, and P. Bhartia, Microstrip Lines and Slotlines, (Norwood, MA: Artech House, 1996).

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Figures (5)

Fig. 1.
Fig. 1.

(a) Schematic cross-section of the electrooptic waveguide modulator. (b) Low frequency electrooptic modulator performance at 1561 nm wavelength. Applied 1 kHz triangle-driving voltages with 2 V DC bias on 3.2 mm long electrode (bottom trace, 4 V/div) and modulation output signal (top trace, 0.2 V/div).

Fig. 2.
Fig. 2.

Schematic diagram of the modulator characterization setup.

Fig.3.
Fig.3.

Microwave power loss characterization of the electrodes. (a) Reflected loss (S11); (b) transmitted loss (S21); (c) fitted loss assuming a linear and square root frequency dependence; (d) dielectric and radiation losses assuming a linear frequency dependence; (e) conductor loss assuming a square root frequency dependence.

Fig. 4.
Fig. 4.

(a) Measured 35 ps time delay for a 3.2 mm long electrodes. (b) Calculated effective microwave index as a function of frequency through measured electrical S-parameters.

Fig. 5.
Fig. 5.

Frequency response of the modulator. (a) Measured response from the calibrated detection system; (b) predicted response for Zm=30 Ω, Nm=3.3 at 40 GHz, αc=1.0 1 dB·cm -1·GHz -0.5 and αd=0.3 dB·cm -1·GHz -1 ; (c) calculated response for Zm=45 Ω, Nm=3.3 at 40 GHz, αc=0.5 dB·cm -1·GHz -0.5 and αd=0.3 dB·cm -1·GHz -1.

Equations (4)

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α ( f ) = α c · L · f + α d · L · f
N m = c · τ L
ε B a T i O 3 / m g O = 2 · N m 2 1
F = ( 1 . 484 n eff 3 r eff Γ α c λ G )

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