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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 18, Iss. 7 — Mar. 29, 2010
  • pp: 7421–7426
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Performance investigation of an integrated Young interferometer sensor using a novel prism-chamber assembly

Zhi-mei Qi, Shukai Zhao, Fang Chen, Ruipeng Liu, and Shanhong Xia  »View Author Affiliations


Optics Express, Vol. 18, Issue 7, pp. 7421-7426 (2010)
http://dx.doi.org/10.1364/OE.18.007421


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Abstract

A novel prism-chamber assembly was prepared for application in optical waveguide based chemical and biological sensors, making the sensor easily and reproducibly operate. By using the prism-chamber assembly, the performance of a composite waveguide based integrated Young interferometer sensor was investigated. The temporal interference pattern detected with a single-slit photodetector heavily relies on the slit width, and regular high-contrast patterns can be obtained under the condition that the slit width is smaller than the spatial periodicity of the sensor. Increasing the temperature of water in the chamber leads to a quasi-linear variation in the phase difference with Δϕ/ΔT ≈−9.1°/°C. Significant dependence of the sensor’s sensitivity on the polarization state of the guided mode was also observed. The sensor is stable and reliable, capable of real-time detection of very slow bioreactions at the interface.

© 2010 OSA

1. Introduction

Chemical and biological sensors based on integrated optical (IO) Young interferometry have attracted considerable attention in the past decade because of their high sensitivity, label-free detection capability and large dynamic range [1

1. Y. Ren, P. Mormile, L. Petti, and G. H. Cross, “Optical waveguide humidity sensor with symmetric multilayer configuration,” Sens. Actuators B Chem. 75(1-2), 76–82 (2001). [CrossRef]

11

11. Z. Qi, S. Zhao, F. Chen, and S. Xia, “Integrated Young interferometer sensor with a channel-planar composite waveguide sensing arm,” Opt. Lett. 34(14), 2213–2215 (2009). [CrossRef] [PubMed]

]. Several types of IO Young interferometer sensors have been developed based on either slab or stripe waveguides. There are two slab Young interferometer sensors, one consists of two planar core layers separated by a low-index buffer layer, which is now commercially available [1

1. Y. Ren, P. Mormile, L. Petti, and G. H. Cross, “Optical waveguide humidity sensor with symmetric multilayer configuration,” Sens. Actuators B Chem. 75(1-2), 76–82 (2001). [CrossRef]

4

4. G. H. Cross, Y. Ren, and N. J. Freeman, “Young’s fringes from vertically integrated slab waveguides: Applications to humidity sensing,” J. Appl. Phys. 86(11), 6483–6488 (1999). [CrossRef]

]; the other uses double slits to yield two light beams that were simultaneously coupled with an integrated grating into a single planar waveguide for sensing and reference [5

5. K. Schmitt, B. Schirmer, C. Hoffmann, A. Brandenburg, and P. Meyrueis, “Interferometric biosensor based on planar optical waveguide sensor chips for label-free detection of surface bound bioreactions,” Biosens. Bioelectron. 22(11), 2591–2597 (2007). [CrossRef]

,6

6. D. Hradetzky, C. Mueller, and H. Reinecke, “Interferometric label-free biomolecular detection system,” J. Opt. A, Pure Appl. Opt. 8(7), S360–S364 (2006). [CrossRef]

]. The stripe Young interferometer sensors generally contain a sensing and a reference arm that are connected with a 3dB Y-branch power splitter (an exception is shown in Refs. 9

9. A. Ymeti, J. S. Kanger, J. Greve, P. V. Lambeck, R. Wijn, and R. G. Heideman, “Realization of a multichannel integrated Young interferometer chemical sensor,” Appl. Opt. 42(28), 5649–5660 (2003). [CrossRef] [PubMed]

, 10

10. A. Ymeti, J. Greve, P. V. Lambeck, T. Wink, S. W. van Hövell, T. A. Beumer, R. R. Wijn, R. G. Heideman, V. Subramaniam, and J. S. Kanger, “Fast, ultrasensitive virus detection using a Young interferometer sensor,” Nano Lett. 7(2), 394–397 (2007). [CrossRef] [PubMed]

) [7

7. E. Brynda, M. Houska, A. Brandenburg, and A. Wikerstål, “Optical biosensors for real-time measurement of analytes in blood plasma,” Biosens. Bioelectron. 17(8), 665–675 (2002). [CrossRef] [PubMed]

10

10. A. Ymeti, J. Greve, P. V. Lambeck, T. Wink, S. W. van Hövell, T. A. Beumer, R. R. Wijn, R. G. Heideman, V. Subramaniam, and J. S. Kanger, “Fast, ultrasensitive virus detection using a Young interferometer sensor,” Nano Lett. 7(2), 394–397 (2007). [CrossRef] [PubMed]

]. For these existing IO Young devices, the butt-coupling method was commonly used and the measurand-induced phase variation was generally determined by means of Fourier analysis of the spatial interference pattern detected with a linear charge-coupled device (CCD) detector.

We recently developed a simple IO Young interferometer sensor that is different from the conventional devices in four aspects [11

11. Z. Qi, S. Zhao, F. Chen, and S. Xia, “Integrated Young interferometer sensor with a channel-planar composite waveguide sensing arm,” Opt. Lett. 34(14), 2213–2215 (2009). [CrossRef] [PubMed]

]: (1) the sensor chip is a glass sheet with several pairs of single-mode straight channel waveguides but without having a Y-branch power splitter, such a simple structure makes the sensor chip readily prepared for a single use; (2) the sensing arm is a channel-planar composite waveguide that offers the sensor a high sensitivity and enables the uncovered channel waveguide to be used as the reference arm; (3) the prism-coupling method was used, to provide the sensor with a high-contrast dotted-line interference pattern in the lateral direction; (4) by using a simple single-slit photodetector instead of the expensive CCD detector, the induced variation in the phase difference of the sensor was detected in real time.

2. The waveguide chip and the prism-chamber assembly

To facilitate operation of the IO Young interferometer sensor and to improve the sensor performance, the prism-chamber assembly was designed and prepared. Figure 2(a)
Fig. 2 (a) the front view of the prism-chamber assembly in the close state; (b) the side view in the open state; (c) Photograph of an actual prism-chamber assembly (1. back board, 2. waveguide chip, 3. prism coupler, 4. prism holder, 5. springs, 6. front board, 7. slide screws, 8. fluid chamber, 9. inlet and outlet, 10. locking screw, 11. strut, 12, rotation axis, 13. silicone gasket, 14. temperature sensor)
shows the front view of the prism-chamber assembly in the close state; Fig. 2(b) illustrates the side view of the assembly in the open state. Figure 2(c) shows a photopicture of a real prism-chamber assembly being used. The prism-chamber assembly consists of an aluminum back board for holding the waveguide chip, a PMMA front board in which two fluid chambers with the respective inlets and outlets were made (each chamber 300 μL), the silicone gasket, the prism in- and out-couplers that were mounted on their holders. The prism holders were flexibly linked to the front board with the slide screws. The back and front boards are interconnected at their bottom sides with the axis of rotation. When using the prism-chamber assembly, just place the waveguide chip on the given area of the back board and then tightly sandwich the chip between the back and front boards with the locking screw. The two spring between each prism holder and the front board lead to a constant-pressure attachment of the prism coupler to the waveguide chip. With a peristaltic pump the sample solution is injected in the chamber at a given rate. The silicone gasket offers the chamber a good sealing. A miniaturized thermal sensor was installed in the chamber to detect the solution temperature. A linearly polarized laser beam of 633 nm wavelength was irradiated upon the prism in-coupler at a given angle, to simultaneously excite the fundamental transverse electric (TE) or magnetic (TM) modes in a pair of channel waveguides. A single-slit photodetector was fixed at a distance of D = 95 mm from the prism out-coupler, and the sensor system was investigated. With λ = 633 nm, D = 95 mm and d = 75 μm the spatial interference pattern of the sensor was simulated, as shown in Fig. 1(e). The spatial periodicity was calculated as λD/d = 0.8 mm.

3. Influence of the slit width on the fringe contrast of the sensor

γ=λDπda|sin(πdaλD)|=|sinc(πdaλD)|
(1)

4. Response of the sensor to temperature

For chemical and biological sensing application, the IO Young interferometer is required to be insensitive to the ambient temperature around the device. Here the response of the sensor to temperature of water in the chamber was investigated. To avoid an abrupt refractive-index change, the water was pumped into the chamber prior to heating. The water temperature in the chamber was monitored in real time by mounting a small thermo-couple probe in the chamber. In the meantime, the induced phase-difference change was detected with the = 0.2 mm slit. Figure 4(a)
Fig. 4 (a) Time variation of the water temperature and the response of the IO Young interferometer to water temperature; (b) Δϕ, Δϕ/ and Δϕ − Δϕ/ versus water temperature (Δϕ is the measured phase-difference change, Δϕ/ is that calculated due to the thermo-optical effect of water.)
shows a reversible response to water temperature. In Fig. 4(a) the water temperature increases from 28.6°C to 50°C, leading to a phase-difference change of Δϕ = −194.7°. The thermo-optical coefficient of water is −0.000091/°C, thus a temperature change of ΔT = 21.4°C would lead to a refractive-index variation of Δn = −0.00195, which corresponds to a phase-difference change of Δϕ/ = −131.5° according to the refractive-index sensitivity measured with the same waveguide chip. The difference between Δϕ and Δϕ/ is −63.2°, which results from the difference in the thermo-optical effect between the sensing and reference arms of the chip. Figure 4(b) shows Δϕ, Δϕ/ and Δϕ − Δϕ/ versus T. With the quasi-linear dependences of Δϕ/ and Δϕ − Δϕ/ on T the slopes were determined as d(Δϕ/)/dT = −6.14°/°C and d(Δϕ−Δϕ/)/dT = −3.26°/°C. The phase-difference changes contributed from the thermo-optical effect of water and that of the chip have the same signs but different values. The former is almost 2 times as large as the latter. Owing to the same signs of the two contributions, the temperature influence on the sensor’s sensitivities cannot be ignored. For accurate measurement, the temperature of the solution sample should be controlled to be equal to the ambient temperature. If the measurement needs to be performed at an elevated temperature, then the temperature influence on the measured result should be removed using the T−Δϕ calibration curve shown in Fig. 4(b).

Figure 5(a)
Fig. 5 (a) Response to β-casein adsorption of the IO Young interferometer with the TE mode (b) Response to refractive index of liquid of the same sensor with the TM mode.
shows response of the sensor to β-casein adsorption from the aqueous protein solution (3 μM). It is seen from this result that a small change of Δϕ = 2° per minute can be detected. A combination of Fig. 4(a) and Fig. 5(a) indicates that with the prism-chamber assembly the sensor is stable and reliable, capable of real-time detection of very slow physical and chemical processes at the waveguide surface.

5. Polarization dependence of sensitivity of the sensor

The above measurements were fulfilled with the TE mode. Compared with the TE mode, the TM mode makes the same waveguide chip much less sensitive to refractive index of liquid and thickness of the adlayer. This is so because a small thickness of the tapered layer of TiO2 on the sensing arm makes the evanescent field with the TM mode much weaker than that with the TE mode. Figure 5(b) shows the sensor response to liquid index with the TM mode. Δϕ induced by the water−salt solution exchange is smaller than 180°. In contrast, with the TE mode Δϕ was measured to be 24 × 180° [11

11. Z. Qi, S. Zhao, F. Chen, and S. Xia, “Integrated Young interferometer sensor with a channel-planar composite waveguide sensing arm,” Opt. Lett. 34(14), 2213–2215 (2009). [CrossRef] [PubMed]

]. Therefore, the refractive-index sensitivity with the TE mode is 24 times greater than that with the TM mode. In this work, the thickness of the tapered film of TiO2 was controlled to be below 30 nm. Simulation based on a five-layer planar waveguide model indicates that for a high sensitivity with the TM mode, the thickness of the tapered layer of TiO2 should be increased in the range of 40 to 60 nm. In this case, the sensor could not work with the TE mode because of a tremendous scattering loss near the cut-off position in the first TiO2 taper [12

12. Z. Qi, N. Matsuda, K. Itoh, and D. Qing, “Characterization of an optical waveguide with a composite structure,” J. Lightwave Technol. 20(8), 1598–1603 (2002). [CrossRef]

].

6. Conclusions

The IO Young interferometer sensor with a prism-chamber assembly and a single-slit photodetector was characterized. The fringe contrast depends on the ratio of the slit width to the spatial periodicity of the sensor, the regular high-contrast interference pattern can be readily detected as the slit width is smaller than the spatial periodicity. The thermo-optical effect of water together with that of the sensor chip makes the temperature influence on the sensor’s sensitivity unnegligible. Depending on the thickness of the tapered layer of TiO2, the sensitivity with the TE mode is different from that with the TM mode. The prism-chamber assembly offers the sensor a good stability, and the sensor allows for continuous measurement over several hours.

Acknowledgement

This work was supported by the National Basic Research Programme of China (No. 2009CB320300) and the BaiRenJiHua Program of the Chinese Academy of Sciences.

References and links

1.

Y. Ren, P. Mormile, L. Petti, and G. H. Cross, “Optical waveguide humidity sensor with symmetric multilayer configuration,” Sens. Actuators B Chem. 75(1-2), 76–82 (2001). [CrossRef]

2.

S. Ricard-Blum, L. L. Peel, F. Ruggiero, and N. J. Freeman, “Dual polarization interferometry characterization of carbohydrate-protein interactions,” Anal. Biochem. 352(2), 252–259 (2006). [CrossRef] [PubMed]

3.

P. D. Coffey, M. J. Swann, T. A. Waigh, F. Schedin, and J. R. Lu, “Multiple path length dual polarization interferometry,” Opt. Express 17(13), 10959–10969 (2009). [CrossRef] [PubMed]

4.

G. H. Cross, Y. Ren, and N. J. Freeman, “Young’s fringes from vertically integrated slab waveguides: Applications to humidity sensing,” J. Appl. Phys. 86(11), 6483–6488 (1999). [CrossRef]

5.

K. Schmitt, B. Schirmer, C. Hoffmann, A. Brandenburg, and P. Meyrueis, “Interferometric biosensor based on planar optical waveguide sensor chips for label-free detection of surface bound bioreactions,” Biosens. Bioelectron. 22(11), 2591–2597 (2007). [CrossRef]

6.

D. Hradetzky, C. Mueller, and H. Reinecke, “Interferometric label-free biomolecular detection system,” J. Opt. A, Pure Appl. Opt. 8(7), S360–S364 (2006). [CrossRef]

7.

E. Brynda, M. Houska, A. Brandenburg, and A. Wikerstål, “Optical biosensors for real-time measurement of analytes in blood plasma,” Biosens. Bioelectron. 17(8), 665–675 (2002). [CrossRef] [PubMed]

8.

A. Brandenburg and R. Henninger, “Integrated optical Young interferometer,” Appl. Opt. 33(25), 5941–5947 (1994). [CrossRef] [PubMed]

9.

A. Ymeti, J. S. Kanger, J. Greve, P. V. Lambeck, R. Wijn, and R. G. Heideman, “Realization of a multichannel integrated Young interferometer chemical sensor,” Appl. Opt. 42(28), 5649–5660 (2003). [CrossRef] [PubMed]

10.

A. Ymeti, J. Greve, P. V. Lambeck, T. Wink, S. W. van Hövell, T. A. Beumer, R. R. Wijn, R. G. Heideman, V. Subramaniam, and J. S. Kanger, “Fast, ultrasensitive virus detection using a Young interferometer sensor,” Nano Lett. 7(2), 394–397 (2007). [CrossRef] [PubMed]

11.

Z. Qi, S. Zhao, F. Chen, and S. Xia, “Integrated Young interferometer sensor with a channel-planar composite waveguide sensing arm,” Opt. Lett. 34(14), 2213–2215 (2009). [CrossRef] [PubMed]

12.

Z. Qi, N. Matsuda, K. Itoh, and D. Qing, “Characterization of an optical waveguide with a composite structure,” J. Lightwave Technol. 20(8), 1598–1603 (2002). [CrossRef]

OCIS Codes
(120.3180) Instrumentation, measurement, and metrology : Interferometry
(130.6010) Integrated optics : Sensors
(230.7380) Optical devices : Waveguides, channeled

ToC Category:
Sensors

History
Original Manuscript: January 19, 2010
Revised Manuscript: March 9, 2010
Manuscript Accepted: March 10, 2010
Published: March 25, 2010

Virtual Issues
Vol. 5, Iss. 7 Virtual Journal for Biomedical Optics

Citation
Zhi-mei Qi, Shukai Zhao, Fang Chen, Ruipeng Liu, and Shanhong Xia, "Performance investigation of an integrated Young interferometer sensor using a novel prism-chamber assembly," Opt. Express 18, 7421-7426 (2010)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-18-7-7421


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References

  1. Y. Ren, P. Mormile, L. Petti, and G. H. Cross, “Optical waveguide humidity sensor with symmetric multilayer configuration,” Sens. Actuators B Chem. 75(1-2), 76–82 (2001). [CrossRef]
  2. S. Ricard-Blum, L. L. Peel, F. Ruggiero, and N. J. Freeman, “Dual polarization interferometry characterization of carbohydrate-protein interactions,” Anal. Biochem. 352(2), 252–259 (2006). [CrossRef] [PubMed]
  3. P. D. Coffey, M. J. Swann, T. A. Waigh, F. Schedin, and J. R. Lu, “Multiple path length dual polarization interferometry,” Opt. Express 17(13), 10959–10969 (2009). [CrossRef] [PubMed]
  4. G. H. Cross, Y. Ren, and N. J. Freeman, “Young’s fringes from vertically integrated slab waveguides: Applications to humidity sensing,” J. Appl. Phys. 86(11), 6483–6488 (1999). [CrossRef]
  5. K. Schmitt, B. Schirmer, C. Hoffmann, A. Brandenburg, and P. Meyrueis, “Interferometric biosensor based on planar optical waveguide sensor chips for label-free detection of surface bound bioreactions,” Biosens. Bioelectron. 22(11), 2591–2597 (2007). [CrossRef]
  6. D. Hradetzky, C. Mueller, and H. Reinecke, “Interferometric label-free biomolecular detection system,” J. Opt. A, Pure Appl. Opt. 8(7), S360–S364 (2006). [CrossRef]
  7. E. Brynda, M. Houska, A. Brandenburg, and A. Wikerstål, “Optical biosensors for real-time measurement of analytes in blood plasma,” Biosens. Bioelectron. 17(8), 665–675 (2002). [CrossRef] [PubMed]
  8. A. Brandenburg and R. Henninger, “Integrated optical Young interferometer,” Appl. Opt. 33(25), 5941–5947 (1994). [CrossRef] [PubMed]
  9. A. Ymeti, J. S. Kanger, J. Greve, P. V. Lambeck, R. Wijn, and R. G. Heideman, “Realization of a multichannel integrated Young interferometer chemical sensor,” Appl. Opt. 42(28), 5649–5660 (2003). [CrossRef] [PubMed]
  10. A. Ymeti, J. Greve, P. V. Lambeck, T. Wink, S. W. van Hövell, T. A. Beumer, R. R. Wijn, R. G. Heideman, V. Subramaniam, and J. S. Kanger, “Fast, ultrasensitive virus detection using a Young interferometer sensor,” Nano Lett. 7(2), 394–397 (2007). [CrossRef] [PubMed]
  11. Z. Qi, S. Zhao, F. Chen, and S. Xia, “Integrated Young interferometer sensor with a channel-planar composite waveguide sensing arm,” Opt. Lett. 34(14), 2213–2215 (2009). [CrossRef] [PubMed]
  12. Z. Qi, N. Matsuda, K. Itoh, and D. Qing, “Characterization of an optical waveguide with a composite structure,” J. Lightwave Technol. 20(8), 1598–1603 (2002). [CrossRef]

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