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Virtual Journal for Biomedical Optics

| EXPLORING THE INTERFACE OF LIGHT AND BIOMEDICINE

  • Editors: Andrew Dunn and Anthony Durkin
  • Vol. 6, Iss. 3 — Mar. 18, 2011
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Microstructured-core photonic-crystal fiber for ultra-sensitive refractive index sensing

Bing Sun, Ming-Yang Chen, Yong-Kang Zhang, Ji-chang Yang, Jian-quan Yao, and Hai-Xia Cui  »View Author Affiliations


Optics Express, Vol. 19, Issue 5, pp. 4091-4100 (2011)
http://dx.doi.org/10.1364/OE.19.004091


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Abstract

We propose a novel photonic crystal fiber refractive index sensor which is based on the selectively resonant coupling between a conventional solid core and a microstructured core. The introduced microstructured core is realized by filling the air-holes in the core with low index analyte. We show that a detection limit (DL) of 2.02 × 10−6 refractive index unit (RIU) and a sensitivity of 8500 nm/RIU can be achieved for analyte with refractive index of 1.33.

© 2011 OSA

1. Introduction

In recent years, optical fiber refractive index sensors have achieved considerable attention especially in the context of label-free fiber-optic biosensor, in which biomolecules are unlabeled or unmodified [1

1. L. Rindorf, J. B. Jensen, M. Dufva, L. H. Pedersen, P. E. Høiby, and O. Bang, “Photonic crystal fiber long-period gratings for biochemical sensing,” Opt. Express 14(18), 8224–8231 (2006), http://www.opticsinfobase.org/abstract.cfm?id=97940&CFID=12293554&CFTOKEN=19235945. [CrossRef] [PubMed]

4

4. J. R. Ott, M. Heuck, C. Agger, P. D. Rasmussen, and O. Bang, “Label-free and selective nonlinear fiber-optical biosensing,” Opt. Express 16(25), 20834–20847 (2008), http://www.opticsinfobase.org/abstract.cfm?URI=oe-16-25-20834. [CrossRef] [PubMed]

]. For example, Rindorf et al. demonstrated a sensitivity of 1.4 nm shift of a long-period grating resonance per nm biolayer (1.4 nm/nm) [1

1. L. Rindorf, J. B. Jensen, M. Dufva, L. H. Pedersen, P. E. Høiby, and O. Bang, “Photonic crystal fiber long-period gratings for biochemical sensing,” Opt. Express 14(18), 8224–8231 (2006), http://www.opticsinfobase.org/abstract.cfm?id=97940&CFID=12293554&CFTOKEN=19235945. [CrossRef] [PubMed]

], and Ott et al. [4

4. J. R. Ott, M. Heuck, C. Agger, P. D. Rasmussen, and O. Bang, “Label-free and selective nonlinear fiber-optical biosensing,” Opt. Express 16(25), 20834–20847 (2008), http://www.opticsinfobase.org/abstract.cfm?URI=oe-16-25-20834. [CrossRef] [PubMed]

] reported a biosensor using the inherent nonlinearity of the photonic crystal fiber (PCF) for FWM-based label-free biosensing, which predicted a sensitivity of 10.4 nm/nm.

PCFs can provide a flexible platform for optical sensing of a wide range of analyte refractive index in a variety of configurations. PCF index sensors can be based on a Bragg or long period grating (LPG) [1

1. L. Rindorf, J. B. Jensen, M. Dufva, L. H. Pedersen, P. E. Høiby, and O. Bang, “Photonic crystal fiber long-period gratings for biochemical sensing,” Opt. Express 14(18), 8224–8231 (2006), http://www.opticsinfobase.org/abstract.cfm?id=97940&CFID=12293554&CFTOKEN=19235945. [CrossRef] [PubMed]

,3

3. L. Rindorf and O. Bang, “Sensitivity of photonic crystal fiber grating sensors: biosensing, refractive index strain, and temperature sensing,” J. Opt. Soc. Am. B 25(3), 310–324 (2008). [CrossRef]

,5

5. L. Rindorf and O. Bang, “Highly sensitive refractometer with a photonic-crystal-fiber long-period grating,” Opt. Lett. 33(6), 563–565 (2008). [CrossRef] [PubMed]

], surface plasmon resonances [6

6. A. Hassani and M. Skorobogatiy, “Design of the microstructured optical fiber-based surface plasmon resonance sensors with enhanced microfluidics,” Opt. Express 14(24), 11616–11621 (2006), http://www.opticsinfobase.org/abstract.cfm?URI=oe-14-24-11616. [CrossRef] [PubMed]

,7

7. B. Gauvreau, A. Hassani, M. Fassi Fehri, A. Kabashin, and M. A. Skorobogatiy, “Photonic bandgap fiber-based Surface Plasmon Resonance sensors,” Opt. Express 15(18), 11413–11426 (2007), http://www.opticsinfobase.org/abstract.cfm?&id=141029. [CrossRef] [PubMed]

], photonic bandgap properties of the PCF [8

8. N. M. Litchinitser and E. Poliakov, “Antiresonant guiding microstructured optical fibers for sensing applications,” Appl. Phys. B 81(2-3), 347–351 (2005). [CrossRef]

,9

9. D. Noordegraaf, L. Scolari, J. Laegsgaard, T. Tanggaard Alkeskjold, G. Tartarini, E. Borelli, P. Bassi, J. Li, and S.-T. Wu, “Avoided-crossing-based liquid-crystal photonic-bandgap notch filter,” Opt. Lett. 33(9), 986–988 (2008). [CrossRef] [PubMed]

], or resonant coupling [10

10. Z. Wang, T. Taru, T. A. Birks, J. C. Knight, Y. Liu, and J. Du, “Coupling in dual-core photonic bandgap fibers: theory and experiment,” Opt. Express 15(8), 4795–4803 (2007), http://www.opticsinfobase.org/abstract.cfm?URI=oe-15-8-4795. [CrossRef] [PubMed]

15

15. D. K. Wu, B. T. Kuhlmey, and B. J. Eggleton, “Ultrasensitive photonic crystal fiber refractive index sensor,” Opt. Lett. 34(3), 322–324 (2009). [CrossRef] [PubMed]

], nonlinear process of modulational instability [4

4. J. R. Ott, M. Heuck, C. Agger, P. D. Rasmussen, and O. Bang, “Label-free and selective nonlinear fiber-optical biosensing,” Opt. Express 16(25), 20834–20847 (2008), http://www.opticsinfobase.org/abstract.cfm?URI=oe-16-25-20834. [CrossRef] [PubMed]

]. Recently, Hassani and Skorobogatiy [6

6. A. Hassani and M. Skorobogatiy, “Design of the microstructured optical fiber-based surface plasmon resonance sensors with enhanced microfluidics,” Opt. Express 14(24), 11616–11621 (2006), http://www.opticsinfobase.org/abstract.cfm?URI=oe-14-24-11616. [CrossRef] [PubMed]

] have investigated a microstructure optical fiber sensor based on surface plasmon resonance, the detection limit of the sensor for measuring changes in the aqueous analyte was found to be 5 × 10−5 RIU, assuming a 1% amplitude change detection limit in the shift of a plasmonic peak. Huy et al. have shown that a fiber sensing system based on photowriting fiber Bragg gratings in a six-hole microstructured optical fiber can achieve a detection limit of 4 × 10−3 RIU for analyte refractive index close to 1.33 [16

16. M. C. Phan Huy, G. Laffont, V. Dewynter, P. Ferdinand, L. Labonté, D. Pagnoux, P. Roy, W. Blanc, and B. Dussardier, “Tilted Fiber Bragg Grating photowritten in microstructured optical fiber for improved refractive index measurement,” Opt. Express 14(22), 10359–10370 (2006), http://www.opticsinfobase.org/abstract.cfm?URI=OE-14-22-10359. [CrossRef] [PubMed]

]. In addition, by using a three-hole fiber a resolution of 3 × 10−5 RIU for analyte refractive index as low as 1.33 can be achieved [17

17. M. C. Phan Huy, G. Laffont, V. Dewynter, P. Ferdinand, P. Roy, J. L. Auguste, D. Pagnoux, W. Blanc, and B. Dussardier, “Three-hole microstructured optical fiber for efficient fiber Bragg grating refractometer,” Opt. Lett. 32(16), 2390–2392 (2007). [CrossRef] [PubMed]

]. Photonic crystal fiber grating sensors with a high sensitivity of 1500 nm/RIU and low detectable index change (2 × 10−5) have been demonstrated by Rindorf and Bang [5

5. L. Rindorf and O. Bang, “Highly sensitive refractometer with a photonic-crystal-fiber long-period grating,” Opt. Lett. 33(6), 563–565 (2008). [CrossRef] [PubMed]

].

Sensors based on dual-core PCFs configuration have been shown to be capable of achieving enhanced sensitivity for refractive index sensing [13

13. G. E. Town, W. Yuan, R. McCosker, and O. Bang, “Microstructured optical fiber refractive index sensor,” Opt. Lett. 35(6), 856–858 (2010). [CrossRef] [PubMed]

15

15. D. K. Wu, B. T. Kuhlmey, and B. J. Eggleton, “Ultrasensitive photonic crystal fiber refractive index sensor,” Opt. Lett. 34(3), 322–324 (2009). [CrossRef] [PubMed]

]. In particular, a dual-core microstructured optical fiber realized by using the exponential dependence of intercore coupling on analyte refractive index, has the potential for use over a wide range of analyte refractive index with high sensitivity [13

13. G. E. Town, W. Yuan, R. McCosker, and O. Bang, “Microstructured optical fiber refractive index sensor,” Opt. Lett. 35(6), 856–858 (2010). [CrossRef] [PubMed]

]. For example, for analyte with refractive index around 1.44, the sensitivity of the device is 167,911%/RIU. Very recently, a refractive index sensor based on a twin-core coupler in an all-solid photonic bandgap guiding optical fiber shows a highly sensitivity of 70,000 nm/RIU [14

14. W. Yuan, G. E. Town, and O. Bang, “Refractive index sensing in an all-solid twin-core photonic bandgap fiber,” IEEE Sens. J. 10(7), 1192–1199 (2010). [CrossRef]

]. By operating in the bandgap guiding regime the proposed sensor is capable of measuring refractive indices around that of water. A microfluidic refractive index sensor based on a directional coupler architecture using solid core photonic crystal fibers, has been demonstrated experimentally by Wu et al. [15

15. D. K. Wu, B. T. Kuhlmey, and B. J. Eggleton, “Ultrasensitive photonic crystal fiber refractive index sensor,” Opt. Lett. 34(3), 322–324 (2009). [CrossRef] [PubMed]

]. The sensor can achieve very high sensitivity by coupling the core mode to a mode in the adjacent fluid-filled waveguide. A detection limit of 4.6 × 10−7 refractive index units with a sensitivity of 30,100 nm/RIU can be achieved. However, the device is restricted to measuring analyte index higher than the silica host. It has now been shown that coating the holes and using flourinated polymer microstructured optical fibers can extend the regime of operation to low indices, such as water [18

18. B. T. Kuhlmey, S. Coen, and S. Mahmoodian, “Coated photonic bandgap fibres for low-index sensing applications: cutoff analysis,” Opt. Express 17(18), 16306–16321 (2009), http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-17-18-16306. [CrossRef] [PubMed]

].

In this article, we present a novel PCF-based low-index sensor, the wavelength-selective resonant coupling in a dual-core directional geometry with an analyte-filled microstructured core can detect analyte with refractive index as low as 1.33. Numerical simulation demonstrates that a detection limit of 2.02 × 10−6 refractive index unit (RIU) and a sensitivity of 8500 nm/RIU can be achieved.

2. Numerical simulation

High sensitive detection for high-index fluid can be realized by exploiting selectively resonant coupling in dual-core PCFs. The inclusion of analyte in the center of core can effectively increase the overlap between the evanescent field and the analyte, which increases the detection sensitivity of the device [15

15. D. K. Wu, B. T. Kuhlmey, and B. J. Eggleton, “Ultrasensitive photonic crystal fiber refractive index sensor,” Opt. Lett. 34(3), 322–324 (2009). [CrossRef] [PubMed]

]. In this section, we will focus on the detection of analyte with refractive index na = 1.33. However, for a dual-core PCF composed of a conventional solid core and an analyte-filled channel as shown in Fig. 1
Fig. 1 Schematic of a dual-core PCF with an analyte channel waveguide.
, the inclusion of low-index material in the core reduces effective fundamental index of the core, which makes the index-matched coupling between the fundamental modes in the two cores impossible. The remedy is to increase the effective fundamental index of the analyte-filled core by increasing its core area. This can be realized by eliminating several air-holes to form a large core and then introducing a large analyte-filled channel in the center. There are some disadvantages in this method which we will discuss further in Sec. 3.3. Another method is the introduction of analyte-filled microstructured core. Microstructured core optical fibers have been investigated by several groups [19

19. M. Yan, P. Shum, and X. Yu, “Heterostructured photonic crystal fiber,” IEEE Photon. Technol. Lett. 17(7), 1438–1440 (2005). [CrossRef]

22

22. K. Nielsen, H. K. Rasmussen, P. U. Jepsen, and O. Bang, “Broadband terahertz fiber directional coupler,” Opt. Lett. 35(17), 2879–2881 (2010). [CrossRef] [PubMed]

]. The microstructured core, which is composed of air-holes or all-solid configuration, forms an effectively step-index core. Recently, a directional coupler fiber has been reported in the THz regime and demonstrated a 3 dB coupler with a broad bandwidth of 0.6 THz centered at 1.4 THz [22

22. K. Nielsen, H. K. Rasmussen, P. U. Jepsen, and O. Bang, “Broadband terahertz fiber directional coupler,” Opt. Lett. 35(17), 2879–2881 (2010). [CrossRef] [PubMed]

]. The broadband coupling is achieved by microstructuring the cores of a dual-core PCF.

The cross-section of an analyte-filled microstructure configuration, which is composed of seven analyte channels embedded in a silica background, is shown in Fig. 2(a)
Fig. 2 (a) Cross-section of an analyte-filled microstructured core optical fiber. The dark area denotes pure silica, the black areas denote analyte-filled channels and the white areas represent air holes. (b) Mode field profile of the microstructured core optical fiber.
. The refractive index of the analyte is set as na. The centers of all air holes and channels are arrayed in a regular triangular lattice and the center-to-center distance of the two nearest air-holes is set as Λ. We set the diameter of the cladding holes as d and the diameter of the channels as da in this article. Figure 2(b) shows the z-component of the Poynting vector with the configuration parameters chosen as d/Λ = da/Λ = 0.4, Λ/λ = 1.661 and na = 1.33. We can see that the fundamental mode field is similar to that of a conventional PCF except that the field distribution is more complex.

We solve the modes of the individual cores in the proposed fiber by semi-vectorial beam propagation method [23

23. W. P. Huang and C. L. Xu, “Simulation of three-dimensional optical waveguides by a full- vector beam propagation method,” IEEE J. Quantum Electron. 29(10), 2639–2649 (1993). [CrossRef]

]. Figure 3
Fig. 3 Effective indexes curves of core A and core B for the vertical polarization with d/Λ = da/Λ = 0.4, and na = 1.33. The inset shows the cross-section of the proposed fiber.
plots the effective indices of the fundamental modes in the two cores of the dual-core PCF with d/Λ = da/Λ = 0.4. The inset shows the proposed structure with a conventional solid core (core A) and a microstructured core (core B). Owing to the fact that index-matching is reached at the frequency where Λ/λ = 1.661, we expect the effective coupling can appear at this point. Therefore, if the index-matched coupling happens at the wavelength of 1.55 μm, the pitch Λ should be 2.575 μm.

It’s found the coupling characteristics of the dual-core fiber are slightly dependent on polarization state of the input signal. In this case, the resonant wavelength difference between the horizontally polarized (x-polarized) and the vertically polarized (y-polarized) modes is 1.5 nm. The coupling length difference for the two different polarizations is less than 0.2 mm. We will only consider the coupling characteristics of vertically polarized state. The horizontally polarized mode can be eliminated by inserting a polarizer before the OSA [15

15. D. K. Wu, B. T. Kuhlmey, and B. J. Eggleton, “Ultrasensitive photonic crystal fiber refractive index sensor,” Opt. Lett. 34(3), 322–324 (2009). [CrossRef] [PubMed]

]. The coupling length of the structure at the wavelength of 1550 nm is Lc = 2.25 mm. We plot in Fig. 4
Fig. 4 The field distributions of the y-polarized mode in the proposed dual-core sensor at propagation distance (a) z = 0 mm, (b) z = 0.75 mm, (c) z = 1.50 mm, and (d) z = 2.25 mm.
the evolution of the field distribution at different propagating distance, where the y-polarized mode at the resonant wavelength is injected into core A. We can clearly observe that at the distance of z = Lc, all the power injected from core A is transferred to core B and the transition is a smooth one. Obviously, the deviation of the wavelength from the resonant wavelength will lead to the rapid reduction of the power transferring between the two cores.

Typically, a refractive index sensor has a resonant feature whose resonant wavelength λr depends on the refractive index of the analyte na. The sensitivity of the sensor is defined asS=λr/na and the detection limit is formulated asδnL3/4.5*λFWHM/(S*SNR0.25), where λFWHM is the full width at half maximum of the resonance, and SNR is in linear units (e.g., 50 dB gives 10(50/10)) [24

24. I. M. White and X. D. Fan, “On the performance quantification of resonant refractive index sensors,” Opt. Express 16(2), 1020–1028 (2008), http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-16-2-1020. [CrossRef] [PubMed]

]. The evolution of the normalized power transmission at the output port of core B as a function of the operating wavelength after a propagation length of Lc, is plotted in Fig. 5
Fig. 5 Normalized transmission spectral of core B.
. The blueshift of the resonant wavelength between na = 1.33 and na = 1.3304 is 3.4 nm, which corresponds to a sensitivity of S = 8.5 × 103 nm/RIU. The spectral width λFWHM of the resonance at na = 1.33 is only 0.46 nm. Assuming a signal-to-noise ratio of 50 dB, we can get a detection limit of 2.02 × 10−6 RIU.

The detection limit and sensitivity as a function of analyte index for the fiber with L = 2.25 mm has been investigated. The results are shown in Fig. 6
Fig. 6 Variation of detection limit and sensitivity as a function of analyte index for the fiber with L = 2.25 mm.
. It should be noted that the sensitivity is only slightly changed with the analyte index, whereas the detection limit gets worse when the analyte index is deviated from the optimum value. By requiring the detection limit should be lower than 5 × 10−5 RIU, then we can get the dynamic range is Δn = 0.012 ranging from 1.324 to 1.336.

The fiber sensor proposed here can be fabricated by two steps. Firstly, a PCF with the core of which realized by the omission of one air-hole is fabricated by the stacking-and-draw procedure. Secondly, the seven air-holes are selectively filled with the anaylte by the similar technique proposed previously [15

15. D. K. Wu, B. T. Kuhlmey, and B. J. Eggleton, “Ultrasensitive photonic crystal fiber refractive index sensor,” Opt. Lett. 34(3), 322–324 (2009). [CrossRef] [PubMed]

].

3. Discussion

3.1 Tolerance and temperature stability analysis

One important issue about PCF coupler is the tolerance of the structure parameters. As shown in Fig. 7
Fig. 7 Variation of sensitivity and detect limit as a function of deviation of fiber length from the optimum length.
, the deviation of the fiber length from the optimum value will lead to a linear increase of the detection limit while the sensitivity is only slightly changed. As shown in Sec. 2, the detection limit for the fiber with fiber length L = 2.25 mm for the detection of analyte with dynamic range Δn = 0.012 is 5 × 10−5 RIU. We can see that the fiber with ± 7% variation in fiber length with respect to the optimum value can still have detection limit lower than 5 × 10−5 RIU. Therefore, the fiber can allow relatively large tolerance of the fiber length deviation.

It’s also possible the sensitivity and the detection limit will be influenced by the environmental temperature. For the fiber with L = 2.25 mm, the sensitivity of which is around 8500 nm/RIU for analyte with refractive index around 1.33, that is, the shift of 1 nm in resonant wavelength corresponding to 1/8500 RIU variation. The detection limit of this sensor is 5 × 10−5 RIU for the dynamic range Δn = 0.012. Therefore, if the resonant wavelength shift induced by temperature variation is within ± 0.2 nm, then the shift implies refractive index change is less than ± 2.5 × 10−5, which is well below the detection limit and will not be detected. We have calculated the shift of resonant wavelength as a function of temperature variation. The thermo-optic coefficient of fused silica is set to be 1 × 10−5/°C [25

25. J. Ju, Z. Wang, W. Jin, and M. S. Demokan, “Temperature sensitivity of a two-mode photonic crystal fiber interferometer sensor,” IEEE Photon. Technol. Lett. 18(20), 2168–2170 (2006). [CrossRef]

]. Figure 8
Fig. 8 Resonant wavelength shift Δλr as a function of temperature variation ΔT.
shows the shift value of the resonant wavelength as a function of temperature variation. Based on the figure, we can get the temperature variation should be in the range of ± 2 °C, such that the resonant wavelength shift induced by the temperature variation will be within ± 0.2 nm.

3.2 sensitivities and detect limits for different analytes

In this section, we will discuss how the sensitivity and detect limit change as different analytes are selected. Figure 9
Fig. 9 Effective indexes of the fundamental modes of the two cores, as a function of the operating wavelength λr, at different analyte indices.
shows the calculated effective fundamental indices of the two cores as functions of normalized frequency. It is evident that the index curves of the two cores will meet at different wavelengths for different analyte refractive indices. Figure 10
Fig. 10 Variation of resonant wavelength and coupling length in the proposed fiber as a function of analyte refractive index.
shows resonant wavelengths and coupling lengths as a function of analyte refractive index. As seen from Fig. 10, the change in coupling length can be approximated simulated by an exponential function. Although the high sensitivity and low detect limit detection of analyte is limited to a dynamic range of refractive index, the fiber with the same configuration can be used for the detection of analyte with a wide refractive index range by the appropriate selection of fiber length.

Table 1

Table 1. Numerical Results of the Proposed Fiber for the Detection of Different Analyte Refractive Indexes

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depicts the corresponding resonant wavelength λr, sensitivity S, spectral width λFWHM, and detect limit DL of the proposed sensor for the detection of analyte with refractive index around 1.33, 1.35 and 1.42, respectively. As shown in Table 1, the sensors designed for analyte with high refractive index show better performance. This can be attributed to the fact that a high analyte refractive index (or low index difference between the analyte and the background material) leads to strong overlapping between the optical field of the fundamental mode of core B and the analyte channels. Furthermore, a narrower spectral feature width λFWHM leads to lower detection limit. It’s also expected that if the background material of the PCF has lower refractive index, better detection limit can be achieved.

3.3 Analysis of single channel fiber sensor

As we have stated in Sec. 2, it’s also possible to realize wavelength dependent coupling by introducing a large analyte-filled hole in a core. In this section, we will discuss and compare the transmission properties of these two types of fiber sensors. We define the microstructured core dual-core fiber as Fiber І. And the dual-core fiber composed of a small core and a large analyte-filled hole core is named as Fiber ІІ, the configuration of which is shown in Fig. 11
Fig. 11 Cross-section of a dual-core PCF with an enlarged analyte-filled hole.
. Firstly, we will compare the sensitivity of the two fibers. The analyte index is assumed to be 1.40, using the same configuration as shown in Fig. 3, we can get the resonant wavelength λr to be 902.9 nm for Fiber I. By using the same configuration except that the microstructured core is replaced by a single large anaylte-hole, Fiber ІІ can be constructed. By requiring that index-matched coupling will also be meet at the wavelength of 902.9 nm for Fiber ІІ, we get the diameter of the large hole to be w = 3.622 μm. The numerical results are shown in Table 2

Table 2. Comparison of Two Different Couplers

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. We can see that although they have the same sensitivity, the spectral width of Fiber І is much narrower than that of Fiber ІІ. As a result, Fiber І has considerably better detect limit than Fiber ІІ. This can be explained based on the effective index difference between the fundamental modes of the two cores. As shown in Fig. 12
Fig. 12 The effective index curves of the fundamental modes for Fiber І and Fiber ІІ.
, both of the fibers have the same index curve for core A, whereas the different core B leads to different index curves. The index curves of the core B for the two fibers meet only at the resonant wavelength. There is always a small index difference between the effective fundamental index of core A and core B for Fiber ІІ. In contrast, as the wavelength is away from the resonant wavelength, the effective fundamental index of core B for Fiber I shows quite large index difference with that of core A, which leads to lower coupling efficiency and therefore, shorter spectral width.

4. Conclusion

In conclusion, we proposed in this article the design of an ultra-sensitive microstructured optical fiber refractive index sensor, which can be used for the detection of analyte with refractive index lower than that of the background index of the microstructured optical fiber. It’s also found that the detection limit reduces when the refractive index of the analyte is close to that of the background material of the PCF, which means that lower detection limits can be achieved for low analyte refractive index if the PCF is composed of lower index material.

Acknowledgments

This work is supported by the National Natural Science Foundation of China (NNSFC) (Grant No. 10904051), National Basic Research Program of China (Grant No. 2010CB327801), and the China Postdoctoral Science Foundation (Grant No. 20080441070 and 200902505).

References and links

1.

L. Rindorf, J. B. Jensen, M. Dufva, L. H. Pedersen, P. E. Høiby, and O. Bang, “Photonic crystal fiber long-period gratings for biochemical sensing,” Opt. Express 14(18), 8224–8231 (2006), http://www.opticsinfobase.org/abstract.cfm?id=97940&CFID=12293554&CFTOKEN=19235945. [CrossRef] [PubMed]

2.

L. Rindorf, P. E. Høiby, J. B. Jensen, L. H. Pedersen, O. Bang, and O. Geschke, “Towards biochips using microstructured optical fiber sensors,” Anal. Bioanal. Chem. 385(8), 1370–1375 (2006). [CrossRef] [PubMed]

3.

L. Rindorf and O. Bang, “Sensitivity of photonic crystal fiber grating sensors: biosensing, refractive index strain, and temperature sensing,” J. Opt. Soc. Am. B 25(3), 310–324 (2008). [CrossRef]

4.

J. R. Ott, M. Heuck, C. Agger, P. D. Rasmussen, and O. Bang, “Label-free and selective nonlinear fiber-optical biosensing,” Opt. Express 16(25), 20834–20847 (2008), http://www.opticsinfobase.org/abstract.cfm?URI=oe-16-25-20834. [CrossRef] [PubMed]

5.

L. Rindorf and O. Bang, “Highly sensitive refractometer with a photonic-crystal-fiber long-period grating,” Opt. Lett. 33(6), 563–565 (2008). [CrossRef] [PubMed]

6.

A. Hassani and M. Skorobogatiy, “Design of the microstructured optical fiber-based surface plasmon resonance sensors with enhanced microfluidics,” Opt. Express 14(24), 11616–11621 (2006), http://www.opticsinfobase.org/abstract.cfm?URI=oe-14-24-11616. [CrossRef] [PubMed]

7.

B. Gauvreau, A. Hassani, M. Fassi Fehri, A. Kabashin, and M. A. Skorobogatiy, “Photonic bandgap fiber-based Surface Plasmon Resonance sensors,” Opt. Express 15(18), 11413–11426 (2007), http://www.opticsinfobase.org/abstract.cfm?&id=141029. [CrossRef] [PubMed]

8.

N. M. Litchinitser and E. Poliakov, “Antiresonant guiding microstructured optical fibers for sensing applications,” Appl. Phys. B 81(2-3), 347–351 (2005). [CrossRef]

9.

D. Noordegraaf, L. Scolari, J. Laegsgaard, T. Tanggaard Alkeskjold, G. Tartarini, E. Borelli, P. Bassi, J. Li, and S.-T. Wu, “Avoided-crossing-based liquid-crystal photonic-bandgap notch filter,” Opt. Lett. 33(9), 986–988 (2008). [CrossRef] [PubMed]

10.

Z. Wang, T. Taru, T. A. Birks, J. C. Knight, Y. Liu, and J. Du, “Coupling in dual-core photonic bandgap fibers: theory and experiment,” Opt. Express 15(8), 4795–4803 (2007), http://www.opticsinfobase.org/abstract.cfm?URI=oe-15-8-4795. [CrossRef] [PubMed]

11.

J. Lægsgaard, “Directional coupling in twin-core photonic bandgap fibers,” Opt. Lett. 30(24), 3281–3283 (2005). [CrossRef]

12.

J. Laegsgaard, O. Bang, and A. Bjarklev, “Photonic crystal fiber design for broadband directional coupling,” Opt. Lett. 29(21), 2473–2475 (2004). [CrossRef] [PubMed]

13.

G. E. Town, W. Yuan, R. McCosker, and O. Bang, “Microstructured optical fiber refractive index sensor,” Opt. Lett. 35(6), 856–858 (2010). [CrossRef] [PubMed]

14.

W. Yuan, G. E. Town, and O. Bang, “Refractive index sensing in an all-solid twin-core photonic bandgap fiber,” IEEE Sens. J. 10(7), 1192–1199 (2010). [CrossRef]

15.

D. K. Wu, B. T. Kuhlmey, and B. J. Eggleton, “Ultrasensitive photonic crystal fiber refractive index sensor,” Opt. Lett. 34(3), 322–324 (2009). [CrossRef] [PubMed]

16.

M. C. Phan Huy, G. Laffont, V. Dewynter, P. Ferdinand, L. Labonté, D. Pagnoux, P. Roy, W. Blanc, and B. Dussardier, “Tilted Fiber Bragg Grating photowritten in microstructured optical fiber for improved refractive index measurement,” Opt. Express 14(22), 10359–10370 (2006), http://www.opticsinfobase.org/abstract.cfm?URI=OE-14-22-10359. [CrossRef] [PubMed]

17.

M. C. Phan Huy, G. Laffont, V. Dewynter, P. Ferdinand, P. Roy, J. L. Auguste, D. Pagnoux, W. Blanc, and B. Dussardier, “Three-hole microstructured optical fiber for efficient fiber Bragg grating refractometer,” Opt. Lett. 32(16), 2390–2392 (2007). [CrossRef] [PubMed]

18.

B. T. Kuhlmey, S. Coen, and S. Mahmoodian, “Coated photonic bandgap fibres for low-index sensing applications: cutoff analysis,” Opt. Express 17(18), 16306–16321 (2009), http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-17-18-16306. [CrossRef] [PubMed]

19.

M. Yan, P. Shum, and X. Yu, “Heterostructured photonic crystal fiber,” IEEE Photon. Technol. Lett. 17(7), 1438–1440 (2005). [CrossRef]

20.

C. M. B. Cordeiro, M. A. R. Franco, G. Chesini, E. C. S. Barretto, R. Lwin, C. H. Brito Cruz, and M. C. J. Large, “Microstructured-core optical fibre for evanescent sensing applications,” Opt. Express 14(26), 13056–13066 (2006), http://www.opticsinfobase.org/abstract.cfm?URI=OE-14-26-130. [CrossRef] [PubMed]

21.

M. Y. Chen, “Polarization and leakage properties of large-mode-area microstructured-core optical fibers,” Opt. Express 15(19), 12498–12507 (2007), http://www.opticsinfobase.org/abstract.cfm?URI=OE-15-19-12498. [CrossRef] [PubMed]

22.

K. Nielsen, H. K. Rasmussen, P. U. Jepsen, and O. Bang, “Broadband terahertz fiber directional coupler,” Opt. Lett. 35(17), 2879–2881 (2010). [CrossRef] [PubMed]

23.

W. P. Huang and C. L. Xu, “Simulation of three-dimensional optical waveguides by a full- vector beam propagation method,” IEEE J. Quantum Electron. 29(10), 2639–2649 (1993). [CrossRef]

24.

I. M. White and X. D. Fan, “On the performance quantification of resonant refractive index sensors,” Opt. Express 16(2), 1020–1028 (2008), http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-16-2-1020. [CrossRef] [PubMed]

25.

J. Ju, Z. Wang, W. Jin, and M. S. Demokan, “Temperature sensitivity of a two-mode photonic crystal fiber interferometer sensor,” IEEE Photon. Technol. Lett. 18(20), 2168–2170 (2006). [CrossRef]

OCIS Codes
(060.2370) Fiber optics and optical communications : Fiber optics sensors
(280.1415) Remote sensing and sensors : Biological sensing and sensors
(060.4005) Fiber optics and optical communications : Microstructured fibers
(060.5295) Fiber optics and optical communications : Photonic crystal fibers

ToC Category:
Fiber Optics and Optical Communications

History
Original Manuscript: October 28, 2010
Revised Manuscript: December 10, 2010
Manuscript Accepted: December 10, 2010
Published: February 16, 2011

Virtual Issues
Vol. 6, Iss. 3 Virtual Journal for Biomedical Optics

Citation
Bing Sun, Ming-Yang Chen, Yong-Kang Zhang, Ji-chang Yang, Jian-quan Yao, and Hai-Xia Cui, "Microstructured-core photonic-crystal fiber for ultra-sensitive refractive index sensing," Opt. Express 19, 4091-4100 (2011)
http://www.opticsinfobase.org/vjbo/abstract.cfm?URI=oe-19-5-4091


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References

  1. L. Rindorf, J. B. Jensen, M. Dufva, L. H. Pedersen, P. E. Høiby, and O. Bang, “Photonic crystal fiber long-period gratings for biochemical sensing,” Opt. Express 14(18), 8224–8231 (2006), http://www.opticsinfobase.org/abstract.cfm?id=97940&CFID=12293554&CFTOKEN=19235945 . [CrossRef] [PubMed]
  2. L. Rindorf, P. E. Høiby, J. B. Jensen, L. H. Pedersen, O. Bang, and O. Geschke, “Towards biochips using microstructured optical fiber sensors,” Anal. Bioanal. Chem. 385(8), 1370–1375 (2006). [CrossRef] [PubMed]
  3. L. Rindorf and O. Bang, “Sensitivity of photonic crystal fiber grating sensors: biosensing, refractive index strain, and temperature sensing,” J. Opt. Soc. Am. B 25(3), 310–324 (2008). [CrossRef]
  4. J. R. Ott, M. Heuck, C. Agger, P. D. Rasmussen, and O. Bang, “Label-free and selective nonlinear fiber-optical biosensing,” Opt. Express 16(25), 20834–20847 (2008), http://www.opticsinfobase.org/abstract.cfm?URI=oe-16-25-20834 . [CrossRef] [PubMed]
  5. L. Rindorf and O. Bang, “Highly sensitive refractometer with a photonic-crystal-fiber long-period grating,” Opt. Lett. 33(6), 563–565 (2008). [CrossRef] [PubMed]
  6. A. Hassani and M. Skorobogatiy, “Design of the microstructured optical fiber-based surface plasmon resonance sensors with enhanced microfluidics,” Opt. Express 14(24), 11616–11621 (2006), http://www.opticsinfobase.org/abstract.cfm?URI=oe-14-24-11616 . [CrossRef] [PubMed]
  7. B. Gauvreau, A. Hassani, M. Fassi Fehri, A. Kabashin, and M. A. Skorobogatiy, “Photonic bandgap fiber-based Surface Plasmon Resonance sensors,” Opt. Express 15(18), 11413–11426 (2007), http://www.opticsinfobase.org/abstract.cfm?&id=141029 . [CrossRef] [PubMed]
  8. N. M. Litchinitser and E. Poliakov, “Antiresonant guiding microstructured optical fibers for sensing applications,” Appl. Phys. B 81(2-3), 347–351 (2005). [CrossRef]
  9. D. Noordegraaf, L. Scolari, J. Laegsgaard, T. Tanggaard Alkeskjold, G. Tartarini, E. Borelli, P. Bassi, J. Li, and S.-T. Wu, “Avoided-crossing-based liquid-crystal photonic-bandgap notch filter,” Opt. Lett. 33(9), 986–988 (2008). [CrossRef] [PubMed]
  10. Z. Wang, T. Taru, T. A. Birks, J. C. Knight, Y. Liu, and J. Du, “Coupling in dual-core photonic bandgap fibers: theory and experiment,” Opt. Express 15(8), 4795–4803 (2007), http://www.opticsinfobase.org/abstract.cfm?URI=oe-15-8-4795 . [CrossRef] [PubMed]
  11. J. Lægsgaard, “Directional coupling in twin-core photonic bandgap fibers,” Opt. Lett. 30(24), 3281–3283 (2005). [CrossRef]
  12. J. Laegsgaard, O. Bang, and A. Bjarklev, “Photonic crystal fiber design for broadband directional coupling,” Opt. Lett. 29(21), 2473–2475 (2004). [CrossRef] [PubMed]
  13. G. E. Town, W. Yuan, R. McCosker, and O. Bang, “Microstructured optical fiber refractive index sensor,” Opt. Lett. 35(6), 856–858 (2010). [CrossRef] [PubMed]
  14. W. Yuan, G. E. Town, and O. Bang, “Refractive index sensing in an all-solid twin-core photonic bandgap fiber,” IEEE Sens. J. 10(7), 1192–1199 (2010). [CrossRef]
  15. D. K. Wu, B. T. Kuhlmey, and B. J. Eggleton, “Ultrasensitive photonic crystal fiber refractive index sensor,” Opt. Lett. 34(3), 322–324 (2009). [CrossRef] [PubMed]
  16. M. C. Phan Huy, G. Laffont, V. Dewynter, P. Ferdinand, L. Labonté, D. Pagnoux, P. Roy, W. Blanc, and B. Dussardier, “Tilted Fiber Bragg Grating photowritten in microstructured optical fiber for improved refractive index measurement,” Opt. Express 14(22), 10359–10370 (2006), http://www.opticsinfobase.org/abstract.cfm?URI=OE-14-22-10359 . [CrossRef] [PubMed]
  17. M. C. Phan Huy, G. Laffont, V. Dewynter, P. Ferdinand, P. Roy, J. L. Auguste, D. Pagnoux, W. Blanc, and B. Dussardier, “Three-hole microstructured optical fiber for efficient fiber Bragg grating refractometer,” Opt. Lett. 32(16), 2390–2392 (2007). [CrossRef] [PubMed]
  18. B. T. Kuhlmey, S. Coen, and S. Mahmoodian, “Coated photonic bandgap fibres for low-index sensing applications: cutoff analysis,” Opt. Express 17(18), 16306–16321 (2009), http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-17-18-16306 . [CrossRef] [PubMed]
  19. M. Yan, P. Shum, and X. Yu, “Heterostructured photonic crystal fiber,” IEEE Photon. Technol. Lett. 17(7), 1438–1440 (2005). [CrossRef]
  20. C. M. B. Cordeiro, M. A. R. Franco, G. Chesini, E. C. S. Barretto, R. Lwin, C. H. Brito Cruz, and M. C. J. Large, “Microstructured-core optical fibre for evanescent sensing applications,” Opt. Express 14(26), 13056–13066 (2006), http://www.opticsinfobase.org/abstract.cfm?URI=OE-14-26-130 . [CrossRef] [PubMed]
  21. M. Y. Chen, “Polarization and leakage properties of large-mode-area microstructured-core optical fibers,” Opt. Express 15(19), 12498–12507 (2007), http://www.opticsinfobase.org/abstract.cfm?URI=OE-15-19-12498 . [CrossRef] [PubMed]
  22. K. Nielsen, H. K. Rasmussen, P. U. Jepsen, and O. Bang, “Broadband terahertz fiber directional coupler,” Opt. Lett. 35(17), 2879–2881 (2010). [CrossRef] [PubMed]
  23. W. P. Huang and C. L. Xu, “Simulation of three-dimensional optical waveguides by a full- vector beam propagation method,” IEEE J. Quantum Electron. 29(10), 2639–2649 (1993). [CrossRef]
  24. I. M. White and X. D. Fan, “On the performance quantification of resonant refractive index sensors,” Opt. Express 16(2), 1020–1028 (2008), http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-16-2-1020 . [CrossRef] [PubMed]
  25. J. Ju, Z. Wang, W. Jin, and M. S. Demokan, “Temperature sensitivity of a two-mode photonic crystal fiber interferometer sensor,” IEEE Photon. Technol. Lett. 18(20), 2168–2170 (2006). [CrossRef]

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