Abstract

We demonstrate experimentally an optical sensor based on a monolithically integrated Mach-Zehnder interferometer comprising a liquid-core waveguide in one of the optical paths. The device is fabricated with a technique for self-forming microchannels in silica-on-silicon using standard photolithography and deposition processes. Refractometry with a resolution of better than 4×10-6 is demonstrated using the thermo-optic effect of the liquid medium to vary its refractive index. The polarization dependence of the device response is analyzed.

© 2008 Optical Society of America

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  1. C. Monat, P. Domachuk, and B. J. Eggleton, "Integrated optofluidics: A new river of light," Nature Photon. 1, 106-114 (2007).
    [CrossRef]
  2. B. Maisenhölder, H. P. Zappe, M. Moser, P. Riel, R. E. Kunz, and J. Edlinger, "Monolithically integrated optical interferometer for refractometry," Electron. Lett. 33, 986-988 (1997).
    [CrossRef]
  3. Th. Schubert, N. Haase, H. Kück, and R. Gottfried-Gottfried, "Refractive-index measurements using an integrated Mach-Zehnder interferometer," Sens. Actuators A 60, 108-112 (1997).
    [CrossRef]
  4. C. A. Barrios, K. B. Gylafson, B. Sánchez, A. Griol, H. Sohlström, M. Holgado, and R. Casquel, "Slot-waveguide biochemical sensor," Opt. Lett. 32, 3080-3082 (2007).
    [CrossRef] [PubMed]
  5. D. Yin, H. Schmidt, J. P. Barber, E. J. Lunt, and A. R. Hawkins, "Optical characterization of arch-shaped ARROW waveguides with liquid cores," Opt. Express 13, 10564-10570 (2005), http://www.opticsinfobase.org/abstract.cfm?URI=oe-13-26-10564.
    [CrossRef] [PubMed]
  6. R. Bernini, G. Testa, L. Zeni, and P. M. Sarro, "Integrated optofluidic Mach-Zehnder interferometer based on liquid core waveguides," Appl. Phys. Lett. 93, 011106 (2008).
    [CrossRef]
  7. P. Dumais, C. L. Callender, C. J. Ledderhof, and J. P. Noad, "Monolithic integration of microfluidic channels, liquid-core waveguides, and silica waveguides on silicon," Appl. Opt. 45, 9182-9190 (2006).
    [CrossRef] [PubMed]
  8. P. Dumais, C. L. Callender, C. J. Ledderhof, and J. P. Noad, "Microchannel-based refractive index sensors monolithically integrated with silica waveguides: structures and sensitivities," IEEE Sensors 8, 457-464 (2008).
    [CrossRef]
  9. P. Dumais, C. L. Callender, C. J. Ledderhof, and J. P. Noad, "Temperature sensors and refractometers using liquid-core waveguide structures monolithically integrated in silica-on-silicon," Proc. SPIE 7099, 70991Y (2008).
    [CrossRef]
  10. M.-S. Kwon and S.-Y. Shin, "Refractive index sensitivity measurement of a long-period-waveguide grating," IEEE Photon. Technol. Lett. 17,1923-1925 (2005).
    [CrossRef]
  11. H. P. Schriemer and M. Cada, " Modal birefringence and power density distribution in strained buried-core square waveguides," IEEE J. Quantum Electron. 40, 1131- 1139 (2004).
    [CrossRef]
  12. C. Blanchetière, C. L. Callender, C. J. Ledderhof, P. Dumais, and J. P. Noad, "Optimization of planar silica-on-silicon photonic devices through cladding material properties," Proc. SPIE 6796, 67961D (2007).
    [CrossRef]

2008 (3)

P. Dumais, C. L. Callender, C. J. Ledderhof, and J. P. Noad, "Microchannel-based refractive index sensors monolithically integrated with silica waveguides: structures and sensitivities," IEEE Sensors 8, 457-464 (2008).
[CrossRef]

P. Dumais, C. L. Callender, C. J. Ledderhof, and J. P. Noad, "Temperature sensors and refractometers using liquid-core waveguide structures monolithically integrated in silica-on-silicon," Proc. SPIE 7099, 70991Y (2008).
[CrossRef]

R. Bernini, G. Testa, L. Zeni, and P. M. Sarro, "Integrated optofluidic Mach-Zehnder interferometer based on liquid core waveguides," Appl. Phys. Lett. 93, 011106 (2008).
[CrossRef]

2007 (3)

C. Blanchetière, C. L. Callender, C. J. Ledderhof, P. Dumais, and J. P. Noad, "Optimization of planar silica-on-silicon photonic devices through cladding material properties," Proc. SPIE 6796, 67961D (2007).
[CrossRef]

C. Monat, P. Domachuk, and B. J. Eggleton, "Integrated optofluidics: A new river of light," Nature Photon. 1, 106-114 (2007).
[CrossRef]

C. A. Barrios, K. B. Gylafson, B. Sánchez, A. Griol, H. Sohlström, M. Holgado, and R. Casquel, "Slot-waveguide biochemical sensor," Opt. Lett. 32, 3080-3082 (2007).
[CrossRef] [PubMed]

2006 (1)

2005 (2)

2004 (1)

H. P. Schriemer and M. Cada, " Modal birefringence and power density distribution in strained buried-core square waveguides," IEEE J. Quantum Electron. 40, 1131- 1139 (2004).
[CrossRef]

1997 (2)

B. Maisenhölder, H. P. Zappe, M. Moser, P. Riel, R. E. Kunz, and J. Edlinger, "Monolithically integrated optical interferometer for refractometry," Electron. Lett. 33, 986-988 (1997).
[CrossRef]

Th. Schubert, N. Haase, H. Kück, and R. Gottfried-Gottfried, "Refractive-index measurements using an integrated Mach-Zehnder interferometer," Sens. Actuators A 60, 108-112 (1997).
[CrossRef]

Barber, J. P.

Barrios, C. A.

Bernini, R.

R. Bernini, G. Testa, L. Zeni, and P. M. Sarro, "Integrated optofluidic Mach-Zehnder interferometer based on liquid core waveguides," Appl. Phys. Lett. 93, 011106 (2008).
[CrossRef]

Blanchetière, C.

C. Blanchetière, C. L. Callender, C. J. Ledderhof, P. Dumais, and J. P. Noad, "Optimization of planar silica-on-silicon photonic devices through cladding material properties," Proc. SPIE 6796, 67961D (2007).
[CrossRef]

Cada, M.

H. P. Schriemer and M. Cada, " Modal birefringence and power density distribution in strained buried-core square waveguides," IEEE J. Quantum Electron. 40, 1131- 1139 (2004).
[CrossRef]

Callender, C. L.

P. Dumais, C. L. Callender, C. J. Ledderhof, and J. P. Noad, "Temperature sensors and refractometers using liquid-core waveguide structures monolithically integrated in silica-on-silicon," Proc. SPIE 7099, 70991Y (2008).
[CrossRef]

P. Dumais, C. L. Callender, C. J. Ledderhof, and J. P. Noad, "Microchannel-based refractive index sensors monolithically integrated with silica waveguides: structures and sensitivities," IEEE Sensors 8, 457-464 (2008).
[CrossRef]

C. Blanchetière, C. L. Callender, C. J. Ledderhof, P. Dumais, and J. P. Noad, "Optimization of planar silica-on-silicon photonic devices through cladding material properties," Proc. SPIE 6796, 67961D (2007).
[CrossRef]

P. Dumais, C. L. Callender, C. J. Ledderhof, and J. P. Noad, "Monolithic integration of microfluidic channels, liquid-core waveguides, and silica waveguides on silicon," Appl. Opt. 45, 9182-9190 (2006).
[CrossRef] [PubMed]

Casquel, R.

Domachuk, P.

C. Monat, P. Domachuk, and B. J. Eggleton, "Integrated optofluidics: A new river of light," Nature Photon. 1, 106-114 (2007).
[CrossRef]

Dumais, P.

P. Dumais, C. L. Callender, C. J. Ledderhof, and J. P. Noad, "Microchannel-based refractive index sensors monolithically integrated with silica waveguides: structures and sensitivities," IEEE Sensors 8, 457-464 (2008).
[CrossRef]

P. Dumais, C. L. Callender, C. J. Ledderhof, and J. P. Noad, "Temperature sensors and refractometers using liquid-core waveguide structures monolithically integrated in silica-on-silicon," Proc. SPIE 7099, 70991Y (2008).
[CrossRef]

C. Blanchetière, C. L. Callender, C. J. Ledderhof, P. Dumais, and J. P. Noad, "Optimization of planar silica-on-silicon photonic devices through cladding material properties," Proc. SPIE 6796, 67961D (2007).
[CrossRef]

P. Dumais, C. L. Callender, C. J. Ledderhof, and J. P. Noad, "Monolithic integration of microfluidic channels, liquid-core waveguides, and silica waveguides on silicon," Appl. Opt. 45, 9182-9190 (2006).
[CrossRef] [PubMed]

Edlinger, J.

B. Maisenhölder, H. P. Zappe, M. Moser, P. Riel, R. E. Kunz, and J. Edlinger, "Monolithically integrated optical interferometer for refractometry," Electron. Lett. 33, 986-988 (1997).
[CrossRef]

Eggleton, B. J.

C. Monat, P. Domachuk, and B. J. Eggleton, "Integrated optofluidics: A new river of light," Nature Photon. 1, 106-114 (2007).
[CrossRef]

Gottfried-Gottfried, R.

Th. Schubert, N. Haase, H. Kück, and R. Gottfried-Gottfried, "Refractive-index measurements using an integrated Mach-Zehnder interferometer," Sens. Actuators A 60, 108-112 (1997).
[CrossRef]

Griol, A.

Gylafson, K. B.

Haase, N.

Th. Schubert, N. Haase, H. Kück, and R. Gottfried-Gottfried, "Refractive-index measurements using an integrated Mach-Zehnder interferometer," Sens. Actuators A 60, 108-112 (1997).
[CrossRef]

Hawkins, A. R.

Holgado, M.

Kück, H.

Th. Schubert, N. Haase, H. Kück, and R. Gottfried-Gottfried, "Refractive-index measurements using an integrated Mach-Zehnder interferometer," Sens. Actuators A 60, 108-112 (1997).
[CrossRef]

Kunz, R. E.

B. Maisenhölder, H. P. Zappe, M. Moser, P. Riel, R. E. Kunz, and J. Edlinger, "Monolithically integrated optical interferometer for refractometry," Electron. Lett. 33, 986-988 (1997).
[CrossRef]

Kwon, M.-S.

M.-S. Kwon and S.-Y. Shin, "Refractive index sensitivity measurement of a long-period-waveguide grating," IEEE Photon. Technol. Lett. 17,1923-1925 (2005).
[CrossRef]

Ledderhof, C. J.

P. Dumais, C. L. Callender, C. J. Ledderhof, and J. P. Noad, "Temperature sensors and refractometers using liquid-core waveguide structures monolithically integrated in silica-on-silicon," Proc. SPIE 7099, 70991Y (2008).
[CrossRef]

P. Dumais, C. L. Callender, C. J. Ledderhof, and J. P. Noad, "Microchannel-based refractive index sensors monolithically integrated with silica waveguides: structures and sensitivities," IEEE Sensors 8, 457-464 (2008).
[CrossRef]

C. Blanchetière, C. L. Callender, C. J. Ledderhof, P. Dumais, and J. P. Noad, "Optimization of planar silica-on-silicon photonic devices through cladding material properties," Proc. SPIE 6796, 67961D (2007).
[CrossRef]

P. Dumais, C. L. Callender, C. J. Ledderhof, and J. P. Noad, "Monolithic integration of microfluidic channels, liquid-core waveguides, and silica waveguides on silicon," Appl. Opt. 45, 9182-9190 (2006).
[CrossRef] [PubMed]

Lunt, E. J.

Maisenhölder, B.

B. Maisenhölder, H. P. Zappe, M. Moser, P. Riel, R. E. Kunz, and J. Edlinger, "Monolithically integrated optical interferometer for refractometry," Electron. Lett. 33, 986-988 (1997).
[CrossRef]

Monat, C.

C. Monat, P. Domachuk, and B. J. Eggleton, "Integrated optofluidics: A new river of light," Nature Photon. 1, 106-114 (2007).
[CrossRef]

Moser, M.

B. Maisenhölder, H. P. Zappe, M. Moser, P. Riel, R. E. Kunz, and J. Edlinger, "Monolithically integrated optical interferometer for refractometry," Electron. Lett. 33, 986-988 (1997).
[CrossRef]

Noad, J. P.

P. Dumais, C. L. Callender, C. J. Ledderhof, and J. P. Noad, "Microchannel-based refractive index sensors monolithically integrated with silica waveguides: structures and sensitivities," IEEE Sensors 8, 457-464 (2008).
[CrossRef]

P. Dumais, C. L. Callender, C. J. Ledderhof, and J. P. Noad, "Temperature sensors and refractometers using liquid-core waveguide structures monolithically integrated in silica-on-silicon," Proc. SPIE 7099, 70991Y (2008).
[CrossRef]

C. Blanchetière, C. L. Callender, C. J. Ledderhof, P. Dumais, and J. P. Noad, "Optimization of planar silica-on-silicon photonic devices through cladding material properties," Proc. SPIE 6796, 67961D (2007).
[CrossRef]

P. Dumais, C. L. Callender, C. J. Ledderhof, and J. P. Noad, "Monolithic integration of microfluidic channels, liquid-core waveguides, and silica waveguides on silicon," Appl. Opt. 45, 9182-9190 (2006).
[CrossRef] [PubMed]

Riel, P.

B. Maisenhölder, H. P. Zappe, M. Moser, P. Riel, R. E. Kunz, and J. Edlinger, "Monolithically integrated optical interferometer for refractometry," Electron. Lett. 33, 986-988 (1997).
[CrossRef]

Sánchez, B.

Sarro, P. M.

R. Bernini, G. Testa, L. Zeni, and P. M. Sarro, "Integrated optofluidic Mach-Zehnder interferometer based on liquid core waveguides," Appl. Phys. Lett. 93, 011106 (2008).
[CrossRef]

Schmidt, H.

Schriemer, H. P.

H. P. Schriemer and M. Cada, " Modal birefringence and power density distribution in strained buried-core square waveguides," IEEE J. Quantum Electron. 40, 1131- 1139 (2004).
[CrossRef]

Schubert, Th.

Th. Schubert, N. Haase, H. Kück, and R. Gottfried-Gottfried, "Refractive-index measurements using an integrated Mach-Zehnder interferometer," Sens. Actuators A 60, 108-112 (1997).
[CrossRef]

Shin, S.-Y.

M.-S. Kwon and S.-Y. Shin, "Refractive index sensitivity measurement of a long-period-waveguide grating," IEEE Photon. Technol. Lett. 17,1923-1925 (2005).
[CrossRef]

Sohlström, H.

Testa, G.

R. Bernini, G. Testa, L. Zeni, and P. M. Sarro, "Integrated optofluidic Mach-Zehnder interferometer based on liquid core waveguides," Appl. Phys. Lett. 93, 011106 (2008).
[CrossRef]

Yin, D.

Zappe, H. P.

B. Maisenhölder, H. P. Zappe, M. Moser, P. Riel, R. E. Kunz, and J. Edlinger, "Monolithically integrated optical interferometer for refractometry," Electron. Lett. 33, 986-988 (1997).
[CrossRef]

Zeni, L.

R. Bernini, G. Testa, L. Zeni, and P. M. Sarro, "Integrated optofluidic Mach-Zehnder interferometer based on liquid core waveguides," Appl. Phys. Lett. 93, 011106 (2008).
[CrossRef]

Appl. Opt. (1)

Appl. Phys. Lett. (1)

R. Bernini, G. Testa, L. Zeni, and P. M. Sarro, "Integrated optofluidic Mach-Zehnder interferometer based on liquid core waveguides," Appl. Phys. Lett. 93, 011106 (2008).
[CrossRef]

Electron. Lett. (1)

B. Maisenhölder, H. P. Zappe, M. Moser, P. Riel, R. E. Kunz, and J. Edlinger, "Monolithically integrated optical interferometer for refractometry," Electron. Lett. 33, 986-988 (1997).
[CrossRef]

IEEE J. Quantum Electron. (1)

H. P. Schriemer and M. Cada, " Modal birefringence and power density distribution in strained buried-core square waveguides," IEEE J. Quantum Electron. 40, 1131- 1139 (2004).
[CrossRef]

IEEE Photon. Technol. Lett. (1)

M.-S. Kwon and S.-Y. Shin, "Refractive index sensitivity measurement of a long-period-waveguide grating," IEEE Photon. Technol. Lett. 17,1923-1925 (2005).
[CrossRef]

IEEE Sensors (1)

P. Dumais, C. L. Callender, C. J. Ledderhof, and J. P. Noad, "Microchannel-based refractive index sensors monolithically integrated with silica waveguides: structures and sensitivities," IEEE Sensors 8, 457-464 (2008).
[CrossRef]

Nature Photon. (1)

C. Monat, P. Domachuk, and B. J. Eggleton, "Integrated optofluidics: A new river of light," Nature Photon. 1, 106-114 (2007).
[CrossRef]

Opt. Express (1)

Opt. Lett. (1)

Proc. SPIE (2)

P. Dumais, C. L. Callender, C. J. Ledderhof, and J. P. Noad, "Temperature sensors and refractometers using liquid-core waveguide structures monolithically integrated in silica-on-silicon," Proc. SPIE 7099, 70991Y (2008).
[CrossRef]

C. Blanchetière, C. L. Callender, C. J. Ledderhof, P. Dumais, and J. P. Noad, "Optimization of planar silica-on-silicon photonic devices through cladding material properties," Proc. SPIE 6796, 67961D (2007).
[CrossRef]

Sens. Actuators A (1)

Th. Schubert, N. Haase, H. Kück, and R. Gottfried-Gottfried, "Refractive-index measurements using an integrated Mach-Zehnder interferometer," Sens. Actuators A 60, 108-112 (1997).
[CrossRef]

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Figures (6)

Fig. 1.
Fig. 1.

Top views of the Mach-Zehnder device: (a) Schematic mask layout for silica ridges, (b) optical micrographs of the fully fabricated liquid-core input and output junctions, (c) a representative micrograph of the device cross-section showing both microchannel and solid-core waveguide mesas. In the actual device, the two mesas are 50 µm apart. The position and size of the solid-core waveguide is outlined with a drawn square.

Fig. 2.
Fig. 2.

Output spectra of the LCMZI for both polarization states at temperatures of (a) 25.0 °C and (b) 35.0 °C.

Fig. 3.
Fig. 3.

(a) Frequency spacing as a function of temperature and the refractive index of the medium (top scale), for a fixed central frequency (1540 nm wavelength), and (b) the corresponding difference in group indexes between the liquid-core and solid-core waveguides, as calculated from Eq. (5).

Fig. 4.
Fig. 4.

Synthesis of the measured spectral response of the device for 190 temperature points between 34.3 °C and 35.5 °C, TM polarization. The circled numbers label the trace endpoints to establish the correspondence between (a) and (b). (a) Center wavelengths (i. e. the average wavelength of two consecutive minima) as a function of temperature. Top scale: calculated refractive index of the liquid medium at 1540 nm wavelength, from manufacturer data. (b) Fringe spacings as a function of center wavelength, for the same data set.

Fig. 5.
Fig. 5.

Wavelength of one of the transmission minima as a function of temperature, showing the device resolution near 28.7 °C.

Fig. 6.
Fig. 6.

Schematized cross-sections of the two waveguides in the MZI (silicon substrate not shown). (a) solid-core waveguide (b) liquid-core waveguide. The liquid core is represented by a black ellipse.

Equations (7)

Equations on this page are rendered with MathJax. Learn more.

Δ φ ( ν ) = Δ φ 0 + 2 π c 0 ν · Δ n eff ( ν ) · L LC
Δ n eff ( ν 0 + Δ ν ) = Δ n eff ( ν 0 ) + d d ν ( Δ n eff ) Δ ν
Δ n eff ( ν 0 ) ν 0 ( Δ n eff ( ν 0 ) + d d ν ( Δ n eff ) Δ ν ) ( ν 0 + Δ ν ) = c 0 L LC
Δ n g ( ν ) Δ n eff ( ν ) + ν d d ν Δ n eff ( ν )
Δ ν c 0 L LC Δ n g ( ν )
B X ( n eff TM n eff TE ) X
Δ B B LC B SC

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