Abstract

We studied a refractive index sensor that consists of two cascaded ring resonators and that works analogously to a Vernier-scale. We implemented it in silicon-on-insulator and experimentally determined its sensitivity to be as high as 2169nm/RIU in aqueous environment. We derived formulas describing the sensor’s operation, and introduced a fitting procedure that allows to accurately detect changes in the sensor response. We determined the detection limit of this first prototype to be 8.3 10−6RIU.

© 2010 Optical Society of America

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  1. X. Fan, I. M. White, S. I. Shopoua, H. Zhu, J. D. Suter, and Y. Sun, "Sensitive optical biosensors for unlabeled targets: A review," Anal. Chim. Acta 620, 8-26 (2008).
    [CrossRef] [PubMed]
  2. A. J. Qavi, A. L. Washburn, J.-Y. Byeon, and R. C. Bailey, "Label-free technologies for quantitative Multiparameter biological analysis," Anal. Bioanal. Chem. 394, 121-135 (2009).
    [CrossRef] [PubMed]
  3. I. M. White, and X. Fan, "On the performance quantification of resonant refractive index sensors," Opt. Express 16, 1020-1028 (2008).
    [CrossRef] [PubMed]
  4. M. Iqbal, M. A. Gleeson, B. Spaugh, F. Tybor, W. G. Gunn, M. Hochberg, T. Baehr-Jones, R. C. Bailey, and L. C. Gunn, "Label-free biosensor arrays based on silicon ring resonators and high-speed optical scanning instrumentation," IEEE J. Sel. Top. Quantum Electron. 16, 654-661 (2010).
    [CrossRef]
  5. D. X. Xu, A. Densmore, A. Delâge, P. Waldron, R. McKinnon, S. Janz, J. Lapointe, G. Lopinski, T. Mischki, E. Post, P. Cheben, and J. H. Schmid, "Folded cavity soi microring sensors for high sensitivity and real time measurement of biomolecular binding," Opt. Express 16, 15137-15148 (2008).
    [CrossRef] [PubMed]
  6. K. De Vos, J. Girones, T. Claes, Y. De Koninck, S. Popelka, E. Schacht, R. Baets, and P. Bienstman, "Multiplexed antibody detection with an array of silicon-on-insulator microring resonators," IEEE Photon. J. 1, 225-235 (2009).
    [CrossRef]
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2010

M. Iqbal, M. A. Gleeson, B. Spaugh, F. Tybor, W. G. Gunn, M. Hochberg, T. Baehr-Jones, R. C. Bailey, and L. C. Gunn, "Label-free biosensor arrays based on silicon ring resonators and high-speed optical scanning instrumentation," IEEE J. Sel. Top. Quantum Electron. 16, 654-661 (2010).
[CrossRef]

2009

A. J. Qavi, A. L. Washburn, J.-Y. Byeon, and R. C. Bailey, "Label-free technologies for quantitative Multiparameter biological analysis," Anal. Bioanal. Chem. 394, 121-135 (2009).
[CrossRef] [PubMed]

K. De Vos, J. Girones, T. Claes, Y. De Koninck, S. Popelka, E. Schacht, R. Baets, and P. Bienstman, "Multiplexed antibody detection with an array of silicon-on-insulator microring resonators," IEEE Photon. J. 1, 225-235 (2009).
[CrossRef]

2008

2007

Baehr-Jones, T.

M. Iqbal, M. A. Gleeson, B. Spaugh, F. Tybor, W. G. Gunn, M. Hochberg, T. Baehr-Jones, R. C. Bailey, and L. C. Gunn, "Label-free biosensor arrays based on silicon ring resonators and high-speed optical scanning instrumentation," IEEE J. Sel. Top. Quantum Electron. 16, 654-661 (2010).
[CrossRef]

Baets, R.

K. De Vos, J. Girones, T. Claes, Y. De Koninck, S. Popelka, E. Schacht, R. Baets, and P. Bienstman, "Multiplexed antibody detection with an array of silicon-on-insulator microring resonators," IEEE Photon. J. 1, 225-235 (2009).
[CrossRef]

Bailey, R. C.

M. Iqbal, M. A. Gleeson, B. Spaugh, F. Tybor, W. G. Gunn, M. Hochberg, T. Baehr-Jones, R. C. Bailey, and L. C. Gunn, "Label-free biosensor arrays based on silicon ring resonators and high-speed optical scanning instrumentation," IEEE J. Sel. Top. Quantum Electron. 16, 654-661 (2010).
[CrossRef]

A. J. Qavi, A. L. Washburn, J.-Y. Byeon, and R. C. Bailey, "Label-free technologies for quantitative Multiparameter biological analysis," Anal. Bioanal. Chem. 394, 121-135 (2009).
[CrossRef] [PubMed]

Bienstman, P.

K. De Vos, J. Girones, T. Claes, Y. De Koninck, S. Popelka, E. Schacht, R. Baets, and P. Bienstman, "Multiplexed antibody detection with an array of silicon-on-insulator microring resonators," IEEE Photon. J. 1, 225-235 (2009).
[CrossRef]

Byeon, J.-Y.

A. J. Qavi, A. L. Washburn, J.-Y. Byeon, and R. C. Bailey, "Label-free technologies for quantitative Multiparameter biological analysis," Anal. Bioanal. Chem. 394, 121-135 (2009).
[CrossRef] [PubMed]

Cheben, P.

Claes, T.

K. De Vos, J. Girones, T. Claes, Y. De Koninck, S. Popelka, E. Schacht, R. Baets, and P. Bienstman, "Multiplexed antibody detection with an array of silicon-on-insulator microring resonators," IEEE Photon. J. 1, 225-235 (2009).
[CrossRef]

De Koninck, Y.

K. De Vos, J. Girones, T. Claes, Y. De Koninck, S. Popelka, E. Schacht, R. Baets, and P. Bienstman, "Multiplexed antibody detection with an array of silicon-on-insulator microring resonators," IEEE Photon. J. 1, 225-235 (2009).
[CrossRef]

De Vos, K.

K. De Vos, J. Girones, T. Claes, Y. De Koninck, S. Popelka, E. Schacht, R. Baets, and P. Bienstman, "Multiplexed antibody detection with an array of silicon-on-insulator microring resonators," IEEE Photon. J. 1, 225-235 (2009).
[CrossRef]

Delâge, A.

Densmore, A.

Fan, X.

I. M. White, and X. Fan, "On the performance quantification of resonant refractive index sensors," Opt. Express 16, 1020-1028 (2008).
[CrossRef] [PubMed]

X. Fan, I. M. White, S. I. Shopoua, H. Zhu, J. D. Suter, and Y. Sun, "Sensitive optical biosensors for unlabeled targets: A review," Anal. Chim. Acta 620, 8-26 (2008).
[CrossRef] [PubMed]

Girones, J.

K. De Vos, J. Girones, T. Claes, Y. De Koninck, S. Popelka, E. Schacht, R. Baets, and P. Bienstman, "Multiplexed antibody detection with an array of silicon-on-insulator microring resonators," IEEE Photon. J. 1, 225-235 (2009).
[CrossRef]

Gleeson, M. A.

M. Iqbal, M. A. Gleeson, B. Spaugh, F. Tybor, W. G. Gunn, M. Hochberg, T. Baehr-Jones, R. C. Bailey, and L. C. Gunn, "Label-free biosensor arrays based on silicon ring resonators and high-speed optical scanning instrumentation," IEEE J. Sel. Top. Quantum Electron. 16, 654-661 (2010).
[CrossRef]

Gunn, L. C.

M. Iqbal, M. A. Gleeson, B. Spaugh, F. Tybor, W. G. Gunn, M. Hochberg, T. Baehr-Jones, R. C. Bailey, and L. C. Gunn, "Label-free biosensor arrays based on silicon ring resonators and high-speed optical scanning instrumentation," IEEE J. Sel. Top. Quantum Electron. 16, 654-661 (2010).
[CrossRef]

Gunn, W. G.

M. Iqbal, M. A. Gleeson, B. Spaugh, F. Tybor, W. G. Gunn, M. Hochberg, T. Baehr-Jones, R. C. Bailey, and L. C. Gunn, "Label-free biosensor arrays based on silicon ring resonators and high-speed optical scanning instrumentation," IEEE J. Sel. Top. Quantum Electron. 16, 654-661 (2010).
[CrossRef]

Hochberg, M.

M. Iqbal, M. A. Gleeson, B. Spaugh, F. Tybor, W. G. Gunn, M. Hochberg, T. Baehr-Jones, R. C. Bailey, and L. C. Gunn, "Label-free biosensor arrays based on silicon ring resonators and high-speed optical scanning instrumentation," IEEE J. Sel. Top. Quantum Electron. 16, 654-661 (2010).
[CrossRef]

Iqbal, M.

M. Iqbal, M. A. Gleeson, B. Spaugh, F. Tybor, W. G. Gunn, M. Hochberg, T. Baehr-Jones, R. C. Bailey, and L. C. Gunn, "Label-free biosensor arrays based on silicon ring resonators and high-speed optical scanning instrumentation," IEEE J. Sel. Top. Quantum Electron. 16, 654-661 (2010).
[CrossRef]

Janz, S.

Lapointe, J.

Lopinski, G.

McKinnon, R.

Mischki, T.

Popelka, S.

K. De Vos, J. Girones, T. Claes, Y. De Koninck, S. Popelka, E. Schacht, R. Baets, and P. Bienstman, "Multiplexed antibody detection with an array of silicon-on-insulator microring resonators," IEEE Photon. J. 1, 225-235 (2009).
[CrossRef]

Post, E.

Qavi, A. J.

A. J. Qavi, A. L. Washburn, J.-Y. Byeon, and R. C. Bailey, "Label-free technologies for quantitative Multiparameter biological analysis," Anal. Bioanal. Chem. 394, 121-135 (2009).
[CrossRef] [PubMed]

Schacht, E.

K. De Vos, J. Girones, T. Claes, Y. De Koninck, S. Popelka, E. Schacht, R. Baets, and P. Bienstman, "Multiplexed antibody detection with an array of silicon-on-insulator microring resonators," IEEE Photon. J. 1, 225-235 (2009).
[CrossRef]

Schmid, J. H.

Shopoua, S. I.

X. Fan, I. M. White, S. I. Shopoua, H. Zhu, J. D. Suter, and Y. Sun, "Sensitive optical biosensors for unlabeled targets: A review," Anal. Chim. Acta 620, 8-26 (2008).
[CrossRef] [PubMed]

Spaugh, B.

M. Iqbal, M. A. Gleeson, B. Spaugh, F. Tybor, W. G. Gunn, M. Hochberg, T. Baehr-Jones, R. C. Bailey, and L. C. Gunn, "Label-free biosensor arrays based on silicon ring resonators and high-speed optical scanning instrumentation," IEEE J. Sel. Top. Quantum Electron. 16, 654-661 (2010).
[CrossRef]

Sun, Y.

X. Fan, I. M. White, S. I. Shopoua, H. Zhu, J. D. Suter, and Y. Sun, "Sensitive optical biosensors for unlabeled targets: A review," Anal. Chim. Acta 620, 8-26 (2008).
[CrossRef] [PubMed]

Suter, J. D.

X. Fan, I. M. White, S. I. Shopoua, H. Zhu, J. D. Suter, and Y. Sun, "Sensitive optical biosensors for unlabeled targets: A review," Anal. Chim. Acta 620, 8-26 (2008).
[CrossRef] [PubMed]

Tybor, F.

M. Iqbal, M. A. Gleeson, B. Spaugh, F. Tybor, W. G. Gunn, M. Hochberg, T. Baehr-Jones, R. C. Bailey, and L. C. Gunn, "Label-free biosensor arrays based on silicon ring resonators and high-speed optical scanning instrumentation," IEEE J. Sel. Top. Quantum Electron. 16, 654-661 (2010).
[CrossRef]

Waldron, P.

Washburn, A. L.

A. J. Qavi, A. L. Washburn, J.-Y. Byeon, and R. C. Bailey, "Label-free technologies for quantitative Multiparameter biological analysis," Anal. Bioanal. Chem. 394, 121-135 (2009).
[CrossRef] [PubMed]

White, I. M.

X. Fan, I. M. White, S. I. Shopoua, H. Zhu, J. D. Suter, and Y. Sun, "Sensitive optical biosensors for unlabeled targets: A review," Anal. Chim. Acta 620, 8-26 (2008).
[CrossRef] [PubMed]

I. M. White, and X. Fan, "On the performance quantification of resonant refractive index sensors," Opt. Express 16, 1020-1028 (2008).
[CrossRef] [PubMed]

Xu, D. X.

Zhu, H.

X. Fan, I. M. White, S. I. Shopoua, H. Zhu, J. D. Suter, and Y. Sun, "Sensitive optical biosensors for unlabeled targets: A review," Anal. Chim. Acta 620, 8-26 (2008).
[CrossRef] [PubMed]

Anal. Bioanal. Chem.

A. J. Qavi, A. L. Washburn, J.-Y. Byeon, and R. C. Bailey, "Label-free technologies for quantitative Multiparameter biological analysis," Anal. Bioanal. Chem. 394, 121-135 (2009).
[CrossRef] [PubMed]

Anal. Chim. Acta

X. Fan, I. M. White, S. I. Shopoua, H. Zhu, J. D. Suter, and Y. Sun, "Sensitive optical biosensors for unlabeled targets: A review," Anal. Chim. Acta 620, 8-26 (2008).
[CrossRef] [PubMed]

IEEE J. Sel. Top. Quantum Electron.

M. Iqbal, M. A. Gleeson, B. Spaugh, F. Tybor, W. G. Gunn, M. Hochberg, T. Baehr-Jones, R. C. Bailey, and L. C. Gunn, "Label-free biosensor arrays based on silicon ring resonators and high-speed optical scanning instrumentation," IEEE J. Sel. Top. Quantum Electron. 16, 654-661 (2010).
[CrossRef]

IEEE Photon. J.

K. De Vos, J. Girones, T. Claes, Y. De Koninck, S. Popelka, E. Schacht, R. Baets, and P. Bienstman, "Multiplexed antibody detection with an array of silicon-on-insulator microring resonators," IEEE Photon. J. 1, 225-235 (2009).
[CrossRef]

Opt. Express

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Figures (9)

Fig. 1
Fig. 1

Illustration of the concept of the photonic sensor consisting of two cascaded ring resonators. Two ring resonators with different optical roundtrip lengths are cascaded. The complete chip is covered with a thick cladding, with only an opening for one of the two resonators. This sensor ring resonator will be exposed to refractive index changes in its environment, while the other resonator, the filter ring resonator, is shielded from these refractive index changes by the cladding.

Fig. 2
Fig. 2

Calculated transmission spectra that illustrate the operation of the cascade. The graphs on the left side illustrate a first regime that occurs when the free spectral range difference between the two resonators is large compared to the full-width at half-maximum of the resonance peaks of the individual resonators. The graphs on the right side illustrate a second regime that occurs when the free spectral range difference between the two resonators is small compared to the full-width at half-maximum of the resonance peaks of the individual resonators. Top: transmission spectra of the individual filter ring resonator (dashed line) and sensor ring resonator (normal line). Middle: transmission spectra of the cascade of these two resonators in the same wavelength range as the top image, illustrating only one clearly visible transmitted peak in the first regime (left), while in the second regime (right) an envelope signal is superposed on the constituent peaks. Bottom: transmission spectra of the cascade in a larger wavelength range.

Fig. 3
Fig. 3

Left: Optical microscope image of the device fabricated in silicon-on-insulator. Two ring resonators with 2.5mm physical roundtrip length are cascaded, and their footprint is reduced by folding the cavity. The complete chip was covered with 500nm silicon oxide, and an opening was etched to the second ring resonator. Right: Scanning electron microscope image of the second ring resonator with folded cavity.

Fig. 4
Fig. 4

Measured transmission spectrum of the device as deionized water is flowing over the sensor ring resonator. The height of the envelope peaks varies due to the wavelength-dependent coupling efficiency of the grating couplers.

Fig. 5
Fig. 5

Illustration of the fitting procedure. In grey a measured transmission spectrum of our device is shown. In a first step Eq. (2) is fitted to the highest constituent peaks, shown by the solid lines. Then the analytical maxima of these fits are determined, shown by the dots. In a second step, Eq. (3) is fitted to the envelope signal formed by these maxima, which is shown by the dashed line. The position of the analytical maximum of that last fit is taken as the central wavelength of the envelope peak.

Fig. 6
Fig. 6

Shift of the transmission spectrum of the sensor consisting of two cascaded ring resonators as a function of the bulk refractive index in its top cladding. The dots show the shift that was measured by changing the flow between deionized water and aqueous solutions of NaCl with different concentrations, and the solid line represents the linear fit to this experimental data, revealing a sensitivity of 2169nm/RIU. For comparison, the dashed line shows the calculated resonance wavelength shift of a single ring resonator.

Fig. 7
Fig. 7

Transmission spectra of the two individual ring resonators with different optical roundtrip. The resonator with the short optical roundtrip (solid line) has a larger free spectral range than the resonator with the long optical roundtrip (dashed line).

Fig. 8
Fig. 8

Top:transmission spectra of the filter ring resonator (solid line) and sensor ring resonator (dashed line). Bottom: transmission spectrum of the cascade of the two ring resonators, showing three different constituent peaks of which the maxima form an envelope signal. This is a special case, where two resonance peaks coincide.

Fig. 9
Fig. 9

Transmission spectra of the individual filter ring resonator (solid line) and sensor ring resonator (dashed line) for the case where two resonances of the respective resonators coincide at λ0. Left: the free spectral range of the filter resonator is larger than the free spectral range of the sensor resonator. Right: the free spectral range of the filter resonator is smaller than the free spectral range of the sensor resonator.

Equations (33)

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fsr sensor fsr filter | fsr sensor fsr filter |
T constituent ( λ ) = t max , filter fwhm filter 2 4 fwhm filter 2 4 + ( λ λ 0 Δ λ 2 ) 2 t max , sensor fwhm sensor 2 4 fwhm sensor 2 4 + ( λ λ 0 + Δ λ 2 ) 2
T envelope ( λ ) = ( t max , filter t max , sensor ( FWHM 2 ) 2 ( FWHM 2 ) 2 + ( λ λ central ) 2 ) 2
FWHM = 2 fwhm min ( fsr sensor , fsr filter ) | fsr filter fsr sensor |
λ central n env = fsr filter fsr filter fsr sensor n eff , sensor n env λ n g , sensor
λ short , k = λ 0 + k fsr short
λ long , k = λ 0 + k fsr long
λ short , K = λ long , K + 1
K fsr short = ( K + 1 ) fsr long
K = fsr long fsr short fsr long
period = λ short , K λ 0
period = fsr long fsr short fsr short fsr long
= fsr filter fsr sensor | fsr sensor fsr filter |
T drop ( λ ) = t max fwhm 2 4 fwhm 2 4 + ( λ λ res ) 2
T constituent ( λ ) = t max , filter fwhm filter 2 4 fwhm filter 2 4 + ( λ λ 0 Δ λ 2 ) 2 t max , sensor fwhm sensor 2 4 fwhm sensor 2 4 + ( λ λ 0 + Δ λ 2 ) 2
T constituent ( λ ) = t max , filter t max , sensor fwhm 2 4 fwhm 2 4 + ( λ λ 0 Δ λ 2 ) 2 t max , filter t max , sensor fwhm 2 4 fwhm 2 4 + ( λ λ 0 + Δ λ 2 ) 2
T constituent ( λ ) λ = 0
λ 0 , λ 0 + Δ λ 2 fwhm 2 2 , λ 0 Δ λ 2 fwhm 2 2
T max = ( t max , filter t max , sensor fwhm 2 Δ λ ) 2
T max = ( t max , filter t max , sensor fwhm 2 fwhm 2 + Δ λ 2 ) 2
T max = ( t max , filter t max , sensor fwhm 2 fwhm 2 + Δ λ 2 ) 2
Δ λ k = | k ( fsr sensor fsr filter ) |
λ k = λ 0 + k ( min ( fsr sensor , fsr filter ) + | fsr sensor fsr filter | 2 )
Δ λ k = | fsr sensor fsr filter | min ( fsr sensor , fsr filter ) + | fsr sensor fsr filter | 2 | λ k λ 0 |
Δ λ k | fsr sensor fsr filter | min ( fsr sensor , fsr filter ) | λ k λ 0 |
T max ( k ) = ( t max , filter t max , sensor ( FWHM 2 ) 2 ( FWHM 2 ) 2 + ( λ k λ 0 ) 2 ) 2
FWHM = 2 fwhm min ( fsr sensor , fsr filter ) | fsr filter fsr sensor |
T envelope ( λ ) = ( t max , filter t max , sensor ( FWHM 2 ) 2 ( FWHM 2 ) 2 + ( λ λ central ) 2 ) 2
FWHM = 2 fwhm min ( fsr sensor , fsr filter ) | fsr filter fsr sensor |
λ res n env = n eff , sensor n env λ n g , sensor
λ central n env = λ central λ res λ res n env
= fsr filter fsr filter fsr sensor n eff , sensor n env λ n g , sensor
λ resonance n env = n eff , sensor n env λ n g , sensor

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