Abstract

The effect of design and fabrication parameters on the dependence on polarization of the splitting ratio in directional couplers produced by Ti diffusion in LiNbO3 has been investigated experimentally at a wavelength of 1.54 µm. The parametric study was carried out at a diffusion temperature of 1025 °C, which was found to suppress outdiffusion effects. The directional couplers were produced by use of various combinations of waveguide separation, Ti film thickness, and diffusion time. Of particular interest was the identification of parameter sets for which the sum of TE and TM splitting ratios equals unity, as required for electro-optic and acousto-optic tunable filter designs with relaxed beam-splitter requirements. Directional couplers that closely match this criterion were obtained by diffusion of 3.5-mm-long, 7-µm-wide Ti strips separated by 11 µm for 11 h. It was found that a bending angle of 0.6° for input and output waveguides produces lower transmission loss for both polarizations than a 1.0° bend angle (>1-dB loss reduction).

© 2002 Optical Society of America

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References

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    [CrossRef] [PubMed]
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    [CrossRef] [PubMed]
  3. R. C. Alferness, L. H. Buhl, “Polarization independent optical filter using interwaveguide TE ↔ TM conversion,” Appl. Phys. Lett. 39, 131–134 (1981).
    [CrossRef]
  4. A. Neyer, “Low-crosstalk passive polarization splitters using Ti:LiNbO3 waveguide crossings,” Appl. Phys. Lett. 55, 927–929 (1989).
    [CrossRef]
  5. F. Wehrmann, C. Harizi, H. Herrmann, U. Rust, W. Sohler, S. Westonhofer, “Integrated optical, wavelength selective, acoustically tunable 2 × 2 switches (add–drop multiplexers) in LiNbO3,” IEEE J. Sel. Top. Quantum Electron. 2, 263–269 (1996).
    [CrossRef]
  6. T. Pohlmann, A. Neyer, E. Voges, “Polarization independent Ti:LiNbO3 switches and filters,” IEEE J. Quantum Electron. 27, 602–607 (1991).
    [CrossRef]
  7. J. E. Baran, D. A. Smith, “Adiabatic 2 × 2 polarization splitter on LiNbO3,” IEEE Photon. Technol. Lett. 4, 39–40 (1992).
    [CrossRef]
  8. W. Warzanskyi, F. Hesimann, R. C. Alferness, “Polarization-independent electrooptically tunable narrow-band wavelength filter,” Appl. Phys. Lett. 53, 13–15 (1998).
    [CrossRef]
  9. N. Kuzuta, K. Takakura, “Polarisation insensitive LiNbO3 optical devices with power splitting and switching functions,” Electron. Lett. 27, 157–158 (1991).
    [CrossRef]
  10. H. F. Taylor, O. Eknoyan, “Guided wave acousto-optic and electro-optic tunable filter designs with relaxed beam-splitter requirements,” Appl. Opt. 39, 124–128 (2000).
    [CrossRef]

2000 (1)

1998 (1)

W. Warzanskyi, F. Hesimann, R. C. Alferness, “Polarization-independent electrooptically tunable narrow-band wavelength filter,” Appl. Phys. Lett. 53, 13–15 (1998).
[CrossRef]

1996 (1)

F. Wehrmann, C. Harizi, H. Herrmann, U. Rust, W. Sohler, S. Westonhofer, “Integrated optical, wavelength selective, acoustically tunable 2 × 2 switches (add–drop multiplexers) in LiNbO3,” IEEE J. Sel. Top. Quantum Electron. 2, 263–269 (1996).
[CrossRef]

1992 (1)

J. E. Baran, D. A. Smith, “Adiabatic 2 × 2 polarization splitter on LiNbO3,” IEEE Photon. Technol. Lett. 4, 39–40 (1992).
[CrossRef]

1991 (2)

T. Pohlmann, A. Neyer, E. Voges, “Polarization independent Ti:LiNbO3 switches and filters,” IEEE J. Quantum Electron. 27, 602–607 (1991).
[CrossRef]

N. Kuzuta, K. Takakura, “Polarisation insensitive LiNbO3 optical devices with power splitting and switching functions,” Electron. Lett. 27, 157–158 (1991).
[CrossRef]

1989 (1)

A. Neyer, “Low-crosstalk passive polarization splitters using Ti:LiNbO3 waveguide crossings,” Appl. Phys. Lett. 55, 927–929 (1989).
[CrossRef]

1981 (1)

R. C. Alferness, L. H. Buhl, “Polarization independent optical filter using interwaveguide TE ↔ TM conversion,” Appl. Phys. Lett. 39, 131–134 (1981).
[CrossRef]

1979 (1)

1976 (1)

Alferness, R. C.

W. Warzanskyi, F. Hesimann, R. C. Alferness, “Polarization-independent electrooptically tunable narrow-band wavelength filter,” Appl. Phys. Lett. 53, 13–15 (1998).
[CrossRef]

R. C. Alferness, L. H. Buhl, “Polarization independent optical filter using interwaveguide TE ↔ TM conversion,” Appl. Phys. Lett. 39, 131–134 (1981).
[CrossRef]

R. C. Alferness, R. V. Schmidt, E. H. Turner, “Characteristics of Ti-diffused lithium niobate optical directional couplers,” Appl. Opt. 18, 4012–4016 (1979).
[CrossRef] [PubMed]

Baran, J. E.

J. E. Baran, D. A. Smith, “Adiabatic 2 × 2 polarization splitter on LiNbO3,” IEEE Photon. Technol. Lett. 4, 39–40 (1992).
[CrossRef]

Buhl, L. H.

R. C. Alferness, L. H. Buhl, “Polarization independent optical filter using interwaveguide TE ↔ TM conversion,” Appl. Phys. Lett. 39, 131–134 (1981).
[CrossRef]

Eknoyan, O.

Giallorenzi, T. G.

Harizi, C.

F. Wehrmann, C. Harizi, H. Herrmann, U. Rust, W. Sohler, S. Westonhofer, “Integrated optical, wavelength selective, acoustically tunable 2 × 2 switches (add–drop multiplexers) in LiNbO3,” IEEE J. Sel. Top. Quantum Electron. 2, 263–269 (1996).
[CrossRef]

Herrmann, H.

F. Wehrmann, C. Harizi, H. Herrmann, U. Rust, W. Sohler, S. Westonhofer, “Integrated optical, wavelength selective, acoustically tunable 2 × 2 switches (add–drop multiplexers) in LiNbO3,” IEEE J. Sel. Top. Quantum Electron. 2, 263–269 (1996).
[CrossRef]

Hesimann, F.

W. Warzanskyi, F. Hesimann, R. C. Alferness, “Polarization-independent electrooptically tunable narrow-band wavelength filter,” Appl. Phys. Lett. 53, 13–15 (1998).
[CrossRef]

Kuzuta, N.

N. Kuzuta, K. Takakura, “Polarisation insensitive LiNbO3 optical devices with power splitting and switching functions,” Electron. Lett. 27, 157–158 (1991).
[CrossRef]

Neyer, A.

T. Pohlmann, A. Neyer, E. Voges, “Polarization independent Ti:LiNbO3 switches and filters,” IEEE J. Quantum Electron. 27, 602–607 (1991).
[CrossRef]

A. Neyer, “Low-crosstalk passive polarization splitters using Ti:LiNbO3 waveguide crossings,” Appl. Phys. Lett. 55, 927–929 (1989).
[CrossRef]

Pohlmann, T.

T. Pohlmann, A. Neyer, E. Voges, “Polarization independent Ti:LiNbO3 switches and filters,” IEEE J. Quantum Electron. 27, 602–607 (1991).
[CrossRef]

Rust, U.

F. Wehrmann, C. Harizi, H. Herrmann, U. Rust, W. Sohler, S. Westonhofer, “Integrated optical, wavelength selective, acoustically tunable 2 × 2 switches (add–drop multiplexers) in LiNbO3,” IEEE J. Sel. Top. Quantum Electron. 2, 263–269 (1996).
[CrossRef]

Schmidt, R. V.

Smith, D. A.

J. E. Baran, D. A. Smith, “Adiabatic 2 × 2 polarization splitter on LiNbO3,” IEEE Photon. Technol. Lett. 4, 39–40 (1992).
[CrossRef]

Sohler, W.

F. Wehrmann, C. Harizi, H. Herrmann, U. Rust, W. Sohler, S. Westonhofer, “Integrated optical, wavelength selective, acoustically tunable 2 × 2 switches (add–drop multiplexers) in LiNbO3,” IEEE J. Sel. Top. Quantum Electron. 2, 263–269 (1996).
[CrossRef]

Steinberg, R. A.

Takakura, K.

N. Kuzuta, K. Takakura, “Polarisation insensitive LiNbO3 optical devices with power splitting and switching functions,” Electron. Lett. 27, 157–158 (1991).
[CrossRef]

Taylor, H. F.

Turner, E. H.

Voges, E.

T. Pohlmann, A. Neyer, E. Voges, “Polarization independent Ti:LiNbO3 switches and filters,” IEEE J. Quantum Electron. 27, 602–607 (1991).
[CrossRef]

Warzanskyi, W.

W. Warzanskyi, F. Hesimann, R. C. Alferness, “Polarization-independent electrooptically tunable narrow-band wavelength filter,” Appl. Phys. Lett. 53, 13–15 (1998).
[CrossRef]

Wehrmann, F.

F. Wehrmann, C. Harizi, H. Herrmann, U. Rust, W. Sohler, S. Westonhofer, “Integrated optical, wavelength selective, acoustically tunable 2 × 2 switches (add–drop multiplexers) in LiNbO3,” IEEE J. Sel. Top. Quantum Electron. 2, 263–269 (1996).
[CrossRef]

Westonhofer, S.

F. Wehrmann, C. Harizi, H. Herrmann, U. Rust, W. Sohler, S. Westonhofer, “Integrated optical, wavelength selective, acoustically tunable 2 × 2 switches (add–drop multiplexers) in LiNbO3,” IEEE J. Sel. Top. Quantum Electron. 2, 263–269 (1996).
[CrossRef]

Appl. Opt. (3)

Appl. Phys. Lett. (3)

R. C. Alferness, L. H. Buhl, “Polarization independent optical filter using interwaveguide TE ↔ TM conversion,” Appl. Phys. Lett. 39, 131–134 (1981).
[CrossRef]

A. Neyer, “Low-crosstalk passive polarization splitters using Ti:LiNbO3 waveguide crossings,” Appl. Phys. Lett. 55, 927–929 (1989).
[CrossRef]

W. Warzanskyi, F. Hesimann, R. C. Alferness, “Polarization-independent electrooptically tunable narrow-band wavelength filter,” Appl. Phys. Lett. 53, 13–15 (1998).
[CrossRef]

Electron. Lett. (1)

N. Kuzuta, K. Takakura, “Polarisation insensitive LiNbO3 optical devices with power splitting and switching functions,” Electron. Lett. 27, 157–158 (1991).
[CrossRef]

IEEE J. Quantum Electron. (1)

T. Pohlmann, A. Neyer, E. Voges, “Polarization independent Ti:LiNbO3 switches and filters,” IEEE J. Quantum Electron. 27, 602–607 (1991).
[CrossRef]

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

F. Wehrmann, C. Harizi, H. Herrmann, U. Rust, W. Sohler, S. Westonhofer, “Integrated optical, wavelength selective, acoustically tunable 2 × 2 switches (add–drop multiplexers) in LiNbO3,” IEEE J. Sel. Top. Quantum Electron. 2, 263–269 (1996).
[CrossRef]

IEEE Photon. Technol. Lett. (1)

J. E. Baran, D. A. Smith, “Adiabatic 2 × 2 polarization splitter on LiNbO3,” IEEE Photon. Technol. Lett. 4, 39–40 (1992).
[CrossRef]

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Figures (4)

Fig. 1
Fig. 1

Four-port directional-coupler beam splitter.

Fig. 2
Fig. 2

Optical setup for characterizing the dependence of the transmittance of the directional coupler on the polarization.

Fig. 3
Fig. 3

Dependence of the power transfer on separation gap d with diffusion time as a parameter: (a) TE input polarization, (b) TM input polarization. Devices are produced by diffusion of 1055-Å-thick, 7-µm-wide Ti strips at 1025 °C with a bending angle of 0.6° for input and output waveguides. W/G, waveguide.

Fig. 4
Fig. 4

Sum of power-transfer coefficients as a function of separation gap d with diffusion time as a parameter for same devices as in Fig. 3. W/G, waveguide.

Tables (3)

Tables Icon

Table 1 Variation of FWHM with Additional Diffusion Time at 1025 °C in an 8-µm Channel Waveguide Produced from 1080-Å-Thick Ti Film

Tables Icon

Table 2 Variation of Insertion Loss with Additional Diffusion Time at 1025 °C in an 8-µm Channel Waveguide Produced from 1105-Å-Thick Ti Film

Tables Icon

Table 3 Variation of Transmission Loss with Bending Angle for Directional Couplers of Various Separation Gap Widths Produced from 1080-Å Ti Film Diffused at 1025 °C for 9 h Relative to a Straight Channel Waveguide

Equations (2)

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fTE+fTM=1.
fP=P2PP1P+P2P,

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