OSA's Digital Library

Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 15, Iss. 26 — Dec. 24, 2007
  • pp: 17891–17901
« Show journal navigation

Enhancement of fluorescence-based sensing using microstructured optical fibres

V. Shahraam Afshar, Stephen C. Warren-Smith, and Tanya M. Monro  »View Author Affiliations


Optics Express, Vol. 15, Issue 26, pp. 17891-17901 (2007)
http://dx.doi.org/10.1364/OE.15.017891


View Full Text Article

Acrobat PDF (1687 KB)





Browse Journals / Lookup Meetings

Browse by Journal and Year


   


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools

Share
Citations

Abstract

We develop a generic model of excitation and fluorescence recapturing within filled microstructured optical fibres (MOFs) with arbitrary structure and demonstrate that the light-matter overlap alone does not determine the optimal fibre choice. Fibre designs with sub-wavelength features and high-index glasses exhibit localised regions of high intensity, and we show that these regions can lead to approximately two orders of magnitude enhancement of fluorescence recapturing. Here we show how this regime can be exploited for sensing and demonstrate experimentally in-fibre excitation and fluorescence recapturing within a filled, solid-core MOF.

© 2007 Optical Society of America

1. Introduction

Although different MOF-variants of fluorescence-based sensors have been reported [2

2. J. B. Jensen, P. E. Hoiby, G. Emiliyanov, O. Bang, L. H. Pedersen, and A. Bjarklev, “Selective Detection of Antibodies in Microstructured Polymer Optical Fibers,” Opt. Express 13, 5883–5889 (2005). [CrossRef] [PubMed]

, 3

3. S. O. Konorov, A. M. Zheltikov, and M. Scalora, “Photonic-Crystal Fiber as a Multifunctional Optical Sensor and Sample Collector,” Opt. Express 13, 3454–3459 (2005). [CrossRef] [PubMed]

, 4

4. L. Rindorf, P. E. Hoiby, J. B. Jensen, L. H. Pedersen, O. Bang, and O. Geschke, “Towards Biochips Using Microstructured Optical Fiber Sensors,” Anal. Bioanal. Chem. 385, 1370–1375 (2006). [CrossRef] [PubMed]

, 7

7. S. Smolka, M. Barth, and O. Benson, “Highly Efficient Fluorescence Sensing with Hollow Core Photonic Crystal Fibers,” Opt. Express 15, 12,783 (2007). [CrossRef]

, 10

10. G. Stewart, W. Jin, and B. Culshaw, “Prospects for Fibre-Optic Evanescent-Field Gas Sensors Using Absorption in the Near-Infrared,” Sens. Actuators B 3839, 42–47 (1997). [CrossRef]

], the benefits that can be obtained using MOFs are far from being realised, largely due to the lack of a formalism for predicting and thus optimizing the measurable fluorescence power. Although models of the efficiency of fluorescence-based optical fibre sensors have been developed for simple structures such as tapered or D-shaped fibres, they have limited applicability because; 1) it is assumed that the modes of the fibre are the same at both the absorption and fluorescence wavelengths and 2) they are based on ray-optics [1

1. G. Stewart and B. Culshaw, “Optical Waveguide Modelling and Design for Evanescent Field Chemical Sensors,” Opt. Quantum Electron. 26, s249 (1994). [CrossRef]

, 21

21. H. P. Kao, N. Yang, and J. S. Schoeniger, “Enhancement of Evanescent Fluorescence from Fiber-Optic Sensors by Thin-Film Sol-Gel Coating,” J. Opt. Soc. Am. A 15, 21632,170 (1998).

] or scalar electromagnetic fields (without including the effect of absorption loss) [8

8. W. Henry, “Evanescent Field Devices: A Comparison Between Tapered Optical Fibres and Polished or D-Fibres,” Opt. Quantum Electron. 26, s261–s272 (1994). [CrossRef]

]. These models do not work well for fluorescent dyes with significant excitation-fluorescence wavelength separation (such as quantum dots), MOFs with wavelength-scale features and high contrast refractive indices, or complex sensing geometries when the hole surface of MOFs are coated (functionalized) with chemical-biological materials.

Experimentally, chemical and biological sensing have been demonstrated using absorption spectroscopy in D-shaped fibres [10

10. G. Stewart, W. Jin, and B. Culshaw, “Prospects for Fibre-Optic Evanescent-Field Gas Sensors Using Absorption in the Near-Infrared,” Sens. Actuators B 3839, 42–47 (1997). [CrossRef]

] and MOFs [4

4. L. Rindorf, P. E. Hoiby, J. B. Jensen, L. H. Pedersen, O. Bang, and O. Geschke, “Towards Biochips Using Microstructured Optical Fiber Sensors,” Anal. Bioanal. Chem. 385, 1370–1375 (2006). [CrossRef] [PubMed]

, 5

5. C. M. B. Cordeiro, M. A. R. Franco, G. Chesini, E. C. S. Barretto, R. Lwin, C. H. B. Cruz, and M. C. J. Large, “Microstructured-Core Optical Fibre for Evanescent Sensing Applications,” Opt. Express 14, 13,056–13,066 (2006). [CrossRef]

] and captured fluorescence-based sensing in tapered fibres [26

26. R. E. Bailey, A. M. Smith, and S. Nie, “Quantum Dots in Biology and Medicine,” Physica E 25, 1–12 (2004). [CrossRef]

], liquid-filled hollow-core MOFs [19

19. Y. Huang, Y. Xu, and A. Yariv, “Fabrication of Functional Microstructured Optical Fibers Through a Selective-Filling Technique,” Appl. Phys. Lett. 85, 5182 (2004). [CrossRef]

, 7

7. S. Smolka, M. Barth, and O. Benson, “Highly Efficient Fluorescence Sensing with Hollow Core Photonic Crystal Fibers,” Opt. Express 15, 12,783 (2007). [CrossRef]

], side excited MOFs [2

2. J. B. Jensen, P. E. Hoiby, G. Emiliyanov, O. Bang, L. H. Pedersen, and A. Bjarklev, “Selective Detection of Antibodies in Microstructured Polymer Optical Fibers,” Opt. Express 13, 5883–5889 (2005). [CrossRef] [PubMed]

, 17

17. S. Smolka, M. Barth, and O. Benson, “Selectively Coated Photonic Crystal Fiber for Highly Sensitive Fluorescence Detection,” Appl. Phys. Lett. 90, 111,101 (2007). [CrossRef]

], and double-clad and multi-core (liquid filled) MOF [3

3. S. O. Konorov, A. M. Zheltikov, and M. Scalora, “Photonic-Crystal Fiber as a Multifunctional Optical Sensor and Sample Collector,” Opt. Express 13, 3454–3459 (2005). [CrossRef] [PubMed]

]. Here, we demonstrate experimentally both in-fibre excitation and fluorescence recapturing within a liquid-filled, solid-core, index-guiding MOF [Fig. 1(b)] through its core guided modes. The experimental methods based on selective hole filling of MOFs (c.f. Ref. [19

19. Y. Huang, Y. Xu, and A. Yariv, “Fabrication of Functional Microstructured Optical Fibers Through a Selective-Filling Technique,” Appl. Phys. Lett. 85, 5182 (2004). [CrossRef]

, 7

7. S. Smolka, M. Barth, and O. Benson, “Highly Efficient Fluorescence Sensing with Hollow Core Photonic Crystal Fibers,” Opt. Express 15, 12,783 (2007). [CrossRef]

] for example) or propagating modes of high index liquids (c.f. Ref. [3

3. S. O. Konorov, A. M. Zheltikov, and M. Scalora, “Photonic-Crystal Fiber as a Multifunctional Optical Sensor and Sample Collector,” Opt. Express 13, 3454–3459 (2005). [CrossRef] [PubMed]

] for example) may be limiting in some applications. Thus, the use of high-index glass (SF57 here) solid-core MOFs allows access to high light-matter overlaps without necessitating selective hole filling while relying on solid-core modes even when the MOF holes are filled with high index liquid.

2. Theory

To develop the model, we assume that the propagating modes of an absorbing MOF are the same as nonabsorbing ones except that their powers decay with an attenuation factor of γ as they propagate. The excitation electromagnetic power in the jth mode at excitation frequency ωE can then be expressed as: [27

27. A. W. Snyder and J. D. Love, Optical Waveguide Theory (Chapman and hall, 2–6 Boundary Row, London SE1 8HN, UK, 1995).

]

PEj(z)=aEj2NEjexp(γEjz);NEj=12Re{A(eEj×hEj*).ẑdA}
(1)
γEj=k(ε0μ0)12AnEnEieEj2dANEj,
(2)

where aEj is the expansion coefficient for mode j, e Ej(x,y),h Ej(x,y), βEj, and γEj are the j th mode electric and magnetic field distributions, propagation constant and power decaying factor due to absorption, respectively. Here, we assume that γj represents all absorption mechanisms in the MOF, including absorption due to the Beer-Lambert law [28

28. F. W. D. Rost, Fluorescence Microscopy (Cambridge University Press, Cambridge, UK, 1992).

].

For an arbitrary filled MOF both nE(x,y) and niE(x,y) (real and imaginary parts of refractive indices) are functions of transverse coordinates and hence the piece-wise integral in Eq. (2) can be integrated over the glass and hole (filled) regions. Eq. (1) indicates that although the absorption of the excitation mode occurs in the filled region, through Beer-Lambert law, the peak intensity also reduces, keeping the shape of the mode and the hole power fraction constant.

Upon absorbing the excitation photons, the fluorescent species in the holes behave as sources and emit fluorescent photons in all directions. Similar to the excitation field, the emission of this new fluorescent source can in general be written [27

27. A. W. Snyder and J. D. Love, Optical Waveguide Theory (Chapman and hall, 2–6 Boundary Row, London SE1 8HN, UK, 1995).

] as the sum of forward, backward, and radiation modes of the non-absorbing MOF with the consideration of power decay due to loss at the fluorescence frequency. Based on the formalisms developed in Ref. [27

27. A. W. Snyder and J. D. Love, Optical Waveguide Theory (Chapman and hall, 2–6 Boundary Row, London SE1 8HN, UK, 1995).

, 29

29. D. Marcuse, “Launching Light Into Fiber Cores from Sources Located in the Cladding,” J. Lightwave Technol. 6, 1273–1279 (1988). [CrossRef]

], we find the fluorescent power contribution to the jth forward mode of the MOF at the end of the filled region z=L, due to a small section Δz=z 2-z 1 [see Fig. 1(c)], and including its loss as:

dPFj(z)=πexp[γFj(Lz)]4ωFμ0nFHkFNFjHz1z2eFj2PD(r)dzdA.
(3)

Here, PD(r) is the radiation power density of any sources within the MOF, which for the case considered here is due to the fluorescent emission of the filling material. The density of fluorescent emission at point r depends on the absorption of excitation field from the beginning of the filled area up to the point r, see Fig. 1(a). Using equations (1) and (2), assuming that the fluorescent power density is proportional to the density of excitation power loss due to Beer-Lambert law in the filled region (proportionality constant ξ), and taking into account energy conservation, we have found PD(r) as:

PD(r)=12ξαBnEH(ε0μ0)12aEj2δEjHRe[(eEj×hEj*).ẑ]exp(γEjz),
(4)
δEjH=HeEj2dAH(eEj×hEj*).ẑdA.
(5)

Here, αB=ελC is the absorption coefficient due to Beer-Lambert law [28

28. F. W. D. Rost, Fluorescence Microscopy (Cambridge University Press, Cambridge, UK, 1992).

], where ε is the molar extinction coefficient of the filling material, C is the molar concentration, and superscript H refers to hole regions. Substituting Eq. (4) into Eq. (3), and taking the integral over z and the limit of z 1z 2, we find

dPFj(z)=πξαBnEH(ε0μ0)12aEj2δEjH8ωFμ0nFHkFNFjexp[γFj(Lz)]exp(γEjz)dz
×HeFj2Re[(eEj×hEj*).ẑ]dA.
(6)

Integrating the fluorescent contributions of the elements from z=0 to z=L, the fluorescence capture fraction (FCF) into the jth guided mode of the MOF can be expressed as

FCF=PFj(L)PEj(0)=ABjexp(γFjL)(γEjγFj){1exp[(γFjγEj)L]}
(7)
A=ξαBλ28π(nFH)2;Bj=nFHnEH(ε0μ0)δEjHHeFj2Re[(eEj×hEj*).ẑ]dA4NFjNEj.
(8)

In this equation A is a constant coefficient and PEj(0) is the input excitation field power at the beginning of the filled part of the fibre, whose length is shown by L [see Fig. 1(a)]. It should be noted that throughout the text we only consider FCF into the fundamental guided mode propagating in the forward direction. To find FCF into backward propagating modes, different loss calculations should be included in the above formalism which is beyond the scope of this paper. Also, in derivation of Eq. (6) and (7), it is assumed that the whole fibre length is completely filled. For fibres that are only partially filled, the mode mismatch between the filled and unfilled sections should be considered for both excitation and fluorescence frequencies, which is beyond the scope of this paper.

3. Modelling results and discussion

The model developed in Section 2 is general and can be applied to any filled MOF with arbitrary cross section structure. Here, we consider an MOF [shown in Fig. 1(b)], which consists of a core surrounded by three large, non-circular, air holes creating a somewhat triangular core supported by three struts. This type of fibre geometry has been studied [30

30. H. Ebendorff-Heidepriem, P. Petropoulos, S. Asimakis, V. Finazzi, R. C. Moore, K. Frampton, F. Koizumi, D. J. Richardson, and T. M. Monro, “Bismuth Glass Holey Fibers with High Nonlinearity,” Opt. Express 12, 5082–87 (2004). [CrossRef] [PubMed]

, 31

31. C. M. B. Cordeiro, M. A. R. Franco, C. J. S. Matos, F. Sircilli, V. A. Serrao, and C. H. B. Cruz, “Single-Design-Parameter Microstructured Optical Fiber for Chromatic Dispersion Tailoring and Evanescent Field Enhancement,” Opt. Lett. 32, 3324–26 (2007). [CrossRef] [PubMed]

] and is the simplest fibre geometry that can be fabricated giving rise to a well defined air-suspended core with large surrounding (fillable) air holes. To find the propagation constant and field distributions for the MOF, we solve the full vectorial form of Maxwell’s equations since, for the subwavelength scales considered here, a scalar approximation gives inaccurate results [32

32. A. Zheltikov, “Gaussian-Mode Analysis of Waveguide-Enhanced Kerr-Type Nonlinearity of Optical Fibers and Photonic Wires,” J. Opt. Soc. Am. B 22, 1100–1104 (2005). [CrossRef]

].

Fig. 1. Schematic of a filled MOF showing the parameters used in modelling (a) and the SEM image of the cross section of the MOF used for the modelling and experiment (b). Dashed circles in (b) show the idealized geometry used for modelling. The effective area of the fundamental mode for the geometry shown in (b) when the holes are filled with Rhodamine B in an isopropanol solution (c). The wavelength is 590 nm, refractive index of isopropanol is 1.3774 and different substrate glasses are marked.

Simulation results of FCF as a function of fibre length for constant core diameter and concentration, as shown in Fig. 2(a), indicate that there is an optimum fibre length Lopt=ln(γF/γE)/(γF-γE), which leads to maximal FCF for any fibre geometry [see Eq. (7)]. For L < Lopt increasing the fibre length increases the absorption in the filled region via the Beer-Lambert law, and thus increases FCF. Beyond this optimum length, fibre attenuation dominates and the fluorescent power decays as exp(-γFL). Unsurprisingly, as the results in Fig. 2(a) show, the use of lower index glasses results in a higher FCF since the relatively low core-cladding index contrast leads to a higher light-matter overlap within the holes [this is also evident in the behaviour of Aeff in Fig. 1(c)].

Numerical simulations of the FCF also identify a less obvious and particularly interesting regime [see Fig. 2(b)]. For small core diameters (d<0.8 µm), the FCF can be significantly enhanced by employing high index (soft) glasses. For example, the maximum FCF (FCF at fibre length Lopt) for bismuth-oxide fibres at d≈0.18 µm, is 2.2%, 10 times larger than the maximum FCF value for silica fibres (0.22%) at d≈0.52 µm. Also, at the core size of d≈0.2 µm the maximum FCF value for bismuth fibres is 2.1%, 88 times larger than that of silica fibres (0.024%). This is contradictory to the usual assumption that sensitivity is proportional to power fraction in the holes, since high index glasses result in lower power fraction in the holes compare to that of low index glasses at small core diameter. For example, at the core diameter of d≈0.2 µm hole power fraction at excitation frequency (defined as ηHE=nHE(ε 0/µ 0)1/2 (1/2NEj)∫H|e Ej|2 dA) for silica and bismuth fibres are 0.97 and 0.43 respectively.

Fig. 2. Numerical results of the fluorescence capture fraction (FCF) as a function of fibre length (a) and core diameter (b) for different substrate glasses. Other parameters are; core diameter 1.0 µm, in (a) and concentration 5×10-5 Mol in (a) and (b). Maximum FCF in (b) corresponds to optimum fibre length.

To understand this effect, we examine coefficient Bj in Eq. (8), which depends on the field distributions of the guided modes of the fibre and their overlap with the materials within the holes. We assume that the mode profiles of the excited and fluorescent fields are the same (i.e., NFj=NEj), which although not strictly true especially for filling materials such as quantum dots with large separation of absorbing and fluorescent wavelengths, can help provide physical insight. We rewrite coefficient Bj as Bj=NOIj/Aeff, where;

NOIj=nEHnFH(ε0μ0)12δEjHHej2Re[(ej×hj*).ẑ]dAARe[(ej×hj*).ẑ]2dA;Aeff=(ARe[(ej×hj*).ẑdA])2ARe[(ej×hj*).ẑ]2dA.

Here NOIj is a normalized field-matter overlap integral, which approaches 1 when the core diameter becomes very small and most of the light is located outside the core [see Fig. 3(a)]. Aeff, defined based on z component of the Poynting vector, is a generalised form of the usual definition of Aeff [33

33. P. Agrawal, Nonlinear Fiber Optics. Academic press, Burlington, (2007).

].

Inspecting Aeff [Fig. 1(c)] and NOI [Fig. 3(a)] at a core size of d=0.2 µm for both silica and bismuth, reveals that the field-matter overlap NOI for silica is 3.6 times larger than that of bismuth. However the effective area, Aeff, of the propagating mode for bismuth is 230 times smaller than that of silica for this core diameter, resulting in higher intensity values for bismuth and thus a larger FCF. Examining the intensity profiles of the fundamental mode for these silica and bismuth fibres [Fig. (4)], clearly shows that while the mode is well expanded into the hole region in the case of silica, it is well confined within the core for bismuth and forms a high intensity, thin layer at the core-hole interface within the filled region.

These localised high intensity regions are formed due to the discontinuity of the electric field at the interface of two dielectric media, as recently reported in slab waveguides [25

25. V. R. Almeida, Q. Xu, C. A. Barrios, and M. Lipson, “Guiding and Confining Light in Void Nanostructure,” Opt. Lett. 29, 1209–1211 (2004). [CrossRef] [PubMed]

] and MOFs [22

22. M. Nagel, A. Marchewka, and H. Kurz, “Low-Index Discontinuity Terahertz Waveguides,” Opt. Express 14, 9944 (2006). [CrossRef] [PubMed]

, 23

23. G. S. Wiederhecker, C. M. B. Cordeiro, F. Couny, F. Benabid, S. A. Maier, J. C. Knight, C. H. B. Cruz, and H. L. Fragnito, “Field Enhancement Within an Optical Fibre with a Subwavelength Air Core,” Nature Photonics 1, 115 (2007). [CrossRef]

]. The magnitude of the discontinuity is proportional to the ratio of the dielectric constants of the two media and hence soft glasses with higher refractive indices result in higher intensities at the glass-hole interface.

Fig. 3. Numerical results of Normalized Overlap Integral (NOI), defined in the text and calculated at the wavelength of 590 nm (a), and the fluorescent capture fraction (FCF) as a function concentration (b). In (b) dashed and solid lines correspond to core diameters 0.2 and 1.0 µm respectively, and the insets show the linear scale plot of the main graph over the same concentration range.

Fig. 4. Intensity distribution of the fundamental mode for Silica (a) and Bismuth (b). In both (a) and (b) core diameters are 0.2 µm and the wavelengths are 590 nm. The mode is more confined in (b) and a thin layer of high intensity region is formed at the glass-hole interface.

4. Experimental results

We have demonstrated experimentally in-fibre excitation and fluorescence recapturing within a filled, solid-core MOF. The holes of the MOF, shown in Fig. 1(b), were filled with Rhodamine B dissolved in isopropanol (n=1.3774) using capillary action. Using the experimental setup in Fig. 5(a), Fig. 5(b) shows the experimental measurements and theoretical prediction of the filling rate. We use the filling rate equation developed in Ref. [34

34. E. W. Washburn, “The Dynamics of Capillary Flow,” Physical Review 17, 273–283 (1921). [CrossRef]

] for a circular capillary tube, considering the following parameters for isopropanol, its interaction with glass, and the fibre geometry; density 785 kgm -3, surface tension 0.022 Nm -1, viscosity 2.27×10-3 Nsm -2, effective radius 6.11×10-6 m, contact angle 0°, coefficient of slip 0 m, and external pressure 0 Pa. To find the effective radius reff, we have assumed that the holes of the MOF in Fig. 1(b) are circular with the same area as that of the real fibre. This, strictly speaking, is inaccurate because capillary forces are mainly a surface effect, which depends on the radius of curvature of the different corners in the geometry, and we believe that this assumption is the main reason for the discrepancy between the theoretical and experimental results in Fig. 5(b). For these experimental measurements the position of the liquid in the holes was recorded by observing the fluorescent emission at the liquid interface in the backward direction of the laser beam in Fig. 5(a).

The setup sketched in Fig. 5(c) was used to excite the Rhodamine B molecules filled into the holes of the fibre and measure the captured fluorescence emission. The outer surface of the fibre was coated with an index matching liquid, DAG, to strip any fluorescent emission coupled to the cladding modes. This ensured that all the measured fluorescence had been captured by the relatively low-loss, core-guided modes of the fibre, as assumed by the theoretical model. The absorption and low concentration fluorescent peaks of Rhodamine B are at 540 nm [35

35. I. B. Berlman, Handbook of fluorescence spectra of aromatic molecules (Academic Press, New York, 1971).

] and 570 nm, respectively. The MOF used in the experiment has a core diameter of d=1.8 µm, core material of SF57 and its cross section is shown in Fig. 1(b). A CW laser at 532 nm was coupled into the MOF using an aspheric lens of f=2.75 mm and NA=0.65 and maximum coupling efficiency of around 19% was measured. The loss of the unfilled fibre at 532 nm is 5.5±0.5 dB/m, using the standard cutback method. At the output, we used a long pass filter to exclude the excitation frequency components. The fluorescence emission is then coupled into a single mode (SM) fibre, which was connected to an optical spectrum analyser for spectrum measurement.

The experimental results are presented in Fig. 5(d) clearly showing the expected fluorescence and also significant decay of the measured fluorescence over 960 seconds exposure to the excitation field. The decay in fluorescence was due to photobleaching, the photo-induced destruction of the fluorophore [28

28. F. W. D. Rost, Fluorescence Microscopy (Cambridge University Press, Cambridge, UK, 1992).

]. While partial recovery is possible, photobleaching has the potential to be problematic. For example, to measure FCF as a function of fibre length we fill a fibre and use a cut-back method to measure FCF at different lengths. However due to photobleaching effect and the time that takes to cleave, align, and couple the fluorescence beam into the OSA, it is very difficult to measure FCF as a function of length for Rhodamine B. A promising alternative is to replace organic dyes with quantum dots, which experience negligible photobleaching and have already found use in sensing such as for biological and medical applications [26

26. R. E. Bailey, A. M. Smith, and S. Nie, “Quantum Dots in Biology and Medicine,” Physica E 25, 1–12 (2004). [CrossRef]

, 36

36. E. Schartner, Y. Ruan, P. Hoffman, and T. M. Monro, “An Optical Fibre Protein Sensor,” in COIN-ACOFT 2007 Proceeding, pp. WeB1–3 (Australian Optical Society, 2007).

].

Fig. 5. Experimental setup for filling an MOF (a). The experimental and theoretical predications of filling time as a function of filled length (b). For the theoretical predictions it is assumed that the holes of the fibre are circles whose area are 1, 0.8, or 0.6 times of that of the real fibre in Fig. 1 (117, 94, and 70 µm 2 respectively). Experimental set up (c) and results (d) for capturing the fluorescent emission by the core of the MOF.

5. Discussion and conclusion

The fluorescence capture fraction is normalised to the input power in the fibre and hence, although the small core parameter regime degrades the coupling efficiency, higher incident power (below the damage threshold of the glass) can be used to attain certain power in the fibre. Additionally, by using advanced coupling techniques such as tapers or high numerical aperture buffer fibres [37

37. Y. Ruan, W. Li, R. Jarvis, N. Madsen, A. Rode, and B. Luther-Davies, “Fabrication and Characterization of Low Loss Rib Chalcogenide Waveguide Made by Dry Etching,” Opt. Express 12, 5140–5145(2004). [CrossRef] [PubMed]

], one should be able to minimise the coupling loss into small core fibres.

Our recent progress in fabricating soft glass MOFs with small cores, and the evidence that with careful fabrication processes fibre loss of order of <0.5 dB/m can be achieved [38

38. H. Ebendorff-Heidepriem, Y. Li, and T. M. Monro, “Reduced Loss in Extruded Microstructured Optical Fiber,” Electron. Lett. , 43, 1343–1345(2007). [CrossRef]

], provide an attractive new route towards the development of highly-sensitive fluorescence sensors.

Acknowledgements

We acknowledge the Defence Science and Technology Organization (DSTO), Australia, for supporting research in the Centre of Expertise in Photonics. We would also like to acknowledge the help and expertise of Dr Heike Ebendorff-Heidepriem with topics in glass chemistry and extrusion, Mr. John Debs with fibre filling experiments, and Mr. Roger Moore with fibre drawing.

References and links

1.

G. Stewart and B. Culshaw, “Optical Waveguide Modelling and Design for Evanescent Field Chemical Sensors,” Opt. Quantum Electron. 26, s249 (1994). [CrossRef]

2.

J. B. Jensen, P. E. Hoiby, G. Emiliyanov, O. Bang, L. H. Pedersen, and A. Bjarklev, “Selective Detection of Antibodies in Microstructured Polymer Optical Fibers,” Opt. Express 13, 5883–5889 (2005). [CrossRef] [PubMed]

3.

S. O. Konorov, A. M. Zheltikov, and M. Scalora, “Photonic-Crystal Fiber as a Multifunctional Optical Sensor and Sample Collector,” Opt. Express 13, 3454–3459 (2005). [CrossRef] [PubMed]

4.

L. Rindorf, P. E. Hoiby, J. B. Jensen, L. H. Pedersen, O. Bang, and O. Geschke, “Towards Biochips Using Microstructured Optical Fiber Sensors,” Anal. Bioanal. Chem. 385, 1370–1375 (2006). [CrossRef] [PubMed]

5.

C. M. B. Cordeiro, M. A. R. Franco, G. Chesini, E. C. S. Barretto, R. Lwin, C. H. B. Cruz, and M. C. J. Large, “Microstructured-Core Optical Fibre for Evanescent Sensing Applications,” Opt. Express 14, 13,056–13,066 (2006). [CrossRef]

6.

F. Warken, E. Vetsch, D. Meachede, M. Sokolowski, and A. Rauschenbeutel, “Ultra-Sensitive Surface Absorption Spectroscopy Using Sub-Wavelength Diameter Optical Fibers,” Opt. Express 15, 11,952–11,958 (2007). [CrossRef]

7.

S. Smolka, M. Barth, and O. Benson, “Highly Efficient Fluorescence Sensing with Hollow Core Photonic Crystal Fibers,” Opt. Express 15, 12,783 (2007). [CrossRef]

8.

W. Henry, “Evanescent Field Devices: A Comparison Between Tapered Optical Fibres and Polished or D-Fibres,” Opt. Quantum Electron. 26, s261–s272 (1994). [CrossRef]

9.

P. Lucas, M. R. Riley, C. Boussard-Pledel, and B. Bureau, “Advances in Chalcogenide Fiber Evanescent Wave Biochemical Sensing,” Anal. Biochem. 351, 1–10 (2006). [CrossRef]

10.

G. Stewart, W. Jin, and B. Culshaw, “Prospects for Fibre-Optic Evanescent-Field Gas Sensors Using Absorption in the Near-Infrared,” Sens. Actuators B 3839, 42–47 (1997). [CrossRef]

11.

J. Lou, L. Tong, and Z. Ye, “Modeling of Silica Nanowires for Optical Sensing,” Opt. Express 13, 2135–2140 (2005). [CrossRef] [PubMed]

12.

Y. Zhu, H. Du, and R. Bise, “Design of Solid-Core Microstructured Optical Fiber with Steering-Wheel Air Cladding for Optimal Evanescent-Field Sensing,” Opt. Express 14, 3541–3546 (2006). [CrossRef] [PubMed]

13.

J. B. Jensen, L. H. Pedersen, P. E. Hoiby, L. B. Nielsen, T. P. Hansen, J. R. Folkenberg, J. Riishede, D. Noordegraaf, K. Nielsen, A. Carlsen, and A. Bjarklev, “Photonic Crystal Fiber Based Evanescent-Wave Sensor for Detection of Biomolecules in Aqueous Solutions,” Opt. Lett. 29, 1974–1976 (2004). [CrossRef] [PubMed]

14.

Y. K. Lize, E. Magi, V. Taeed, J. Bolger, P. Steinvurzel, and B. Eggleton, “Microstructured Optical Fiber Photonic Wires with Subwavelength Core Diameter,” Opt. Express 12, 3209–3217 (2004). [CrossRef] [PubMed]

15.

K. J. Rowland, S. Afshar V, and T. M. Monro, “Nonlinearity Enhancement of Filled Microstructured Fibers Operating in Nanowire Regime,” in Proceedings of OFC 2006, p. OTuH3 (2006).

16.

L. Tong, J. Lou, and E. Mazur, “Single-Mode Guiding Properties of Subwavelength-Diameter Silica and Silicon Wire Waveguides,” Opt. Express 12, 1025–1035 (2004). [CrossRef] [PubMed]

17.

S. Smolka, M. Barth, and O. Benson, “Selectively Coated Photonic Crystal Fiber for Highly Sensitive Fluorescence Detection,” Appl. Phys. Lett. 90, 111,101 (2007). [CrossRef]

18.

Z. Liu and J. Pawliszyn, “Capillary Isoelectric Focusing of Proteins with Liquid Core Waveguide Laser-Induced Fluorescence Whole Column Imaging Detection,” Anal. Chem. 75, 4887–4894 (2003). [CrossRef] [PubMed]

19.

Y. Huang, Y. Xu, and A. Yariv, “Fabrication of Functional Microstructured Optical Fibers Through a Selective-Filling Technique,” Appl. Phys. Lett. 85, 5182 (2004). [CrossRef]

20.

T. Ritari, J. Tuominen, H. Ludvigsen, J. Petersen, T. Sorensen, T. Hansen, and H. Simonsen, “Gas Sensing Using Air-Guiding Photonic Bandgap Fibers,” Opt. Express 12, 4080 (2004). [CrossRef] [PubMed]

21.

H. P. Kao, N. Yang, and J. S. Schoeniger, “Enhancement of Evanescent Fluorescence from Fiber-Optic Sensors by Thin-Film Sol-Gel Coating,” J. Opt. Soc. Am. A 15, 21632,170 (1998).

22.

M. Nagel, A. Marchewka, and H. Kurz, “Low-Index Discontinuity Terahertz Waveguides,” Opt. Express 14, 9944 (2006). [CrossRef] [PubMed]

23.

G. S. Wiederhecker, C. M. B. Cordeiro, F. Couny, F. Benabid, S. A. Maier, J. C. Knight, C. H. B. Cruz, and H. L. Fragnito, “Field Enhancement Within an Optical Fibre with a Subwavelength Air Core,” Nature Photonics 1, 115 (2007). [CrossRef]

24.

N. Ganesh and B. T. Cunningham, “Photonic Crystal Enhanced Fluorescence,” in Technical Digest, p. CThz5 (Optical Society of America, 2007).

25.

V. R. Almeida, Q. Xu, C. A. Barrios, and M. Lipson, “Guiding and Confining Light in Void Nanostructure,” Opt. Lett. 29, 1209–1211 (2004). [CrossRef] [PubMed]

26.

R. E. Bailey, A. M. Smith, and S. Nie, “Quantum Dots in Biology and Medicine,” Physica E 25, 1–12 (2004). [CrossRef]

27.

A. W. Snyder and J. D. Love, Optical Waveguide Theory (Chapman and hall, 2–6 Boundary Row, London SE1 8HN, UK, 1995).

28.

F. W. D. Rost, Fluorescence Microscopy (Cambridge University Press, Cambridge, UK, 1992).

29.

D. Marcuse, “Launching Light Into Fiber Cores from Sources Located in the Cladding,” J. Lightwave Technol. 6, 1273–1279 (1988). [CrossRef]

30.

H. Ebendorff-Heidepriem, P. Petropoulos, S. Asimakis, V. Finazzi, R. C. Moore, K. Frampton, F. Koizumi, D. J. Richardson, and T. M. Monro, “Bismuth Glass Holey Fibers with High Nonlinearity,” Opt. Express 12, 5082–87 (2004). [CrossRef] [PubMed]

31.

C. M. B. Cordeiro, M. A. R. Franco, C. J. S. Matos, F. Sircilli, V. A. Serrao, and C. H. B. Cruz, “Single-Design-Parameter Microstructured Optical Fiber for Chromatic Dispersion Tailoring and Evanescent Field Enhancement,” Opt. Lett. 32, 3324–26 (2007). [CrossRef] [PubMed]

32.

A. Zheltikov, “Gaussian-Mode Analysis of Waveguide-Enhanced Kerr-Type Nonlinearity of Optical Fibers and Photonic Wires,” J. Opt. Soc. Am. B 22, 1100–1104 (2005). [CrossRef]

33.

P. Agrawal, Nonlinear Fiber Optics. Academic press, Burlington, (2007).

34.

E. W. Washburn, “The Dynamics of Capillary Flow,” Physical Review 17, 273–283 (1921). [CrossRef]

35.

I. B. Berlman, Handbook of fluorescence spectra of aromatic molecules (Academic Press, New York, 1971).

36.

E. Schartner, Y. Ruan, P. Hoffman, and T. M. Monro, “An Optical Fibre Protein Sensor,” in COIN-ACOFT 2007 Proceeding, pp. WeB1–3 (Australian Optical Society, 2007).

37.

Y. Ruan, W. Li, R. Jarvis, N. Madsen, A. Rode, and B. Luther-Davies, “Fabrication and Characterization of Low Loss Rib Chalcogenide Waveguide Made by Dry Etching,” Opt. Express 12, 5140–5145(2004). [CrossRef] [PubMed]

38.

H. Ebendorff-Heidepriem, Y. Li, and T. M. Monro, “Reduced Loss in Extruded Microstructured Optical Fiber,” Electron. Lett. , 43, 1343–1345(2007). [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

ToC Category:
Fiber Optics and Optical Communications

History
Original Manuscript: October 23, 2007
Revised Manuscript: December 12, 2007
Manuscript Accepted: December 12, 2007
Published: December 14, 2007

Citation
Shahraam Afshar V., Stephen C. Warren-Smith, and Tanya M. Monro, "Enhancement of fluorescence-based sensing using microstructured optical fibres," Opt. Express 15, 17891-17901 (2007)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-15-26-17891


Sort:  Author  |  Year  |  Journal  |  Reset  

References

  1. G. Stewart and B. Culshaw, "Optical Waveguide Modelling and Design for Evanescent Field Chemical Sensors," Opt. Quantum Electron. 26, s249 (1994). [CrossRef]
  2. J. B. Jensen, P. E. Hoiby, G. Emiliyanov, O. Bang, L. H. Pedersen, and A. Bjarklev, "Selective Detection of Antibodies in Microstructured Polymer Optical Fibers," Opt. Express 13, 5883-5889 (2005). [CrossRef] [PubMed]
  3. S. O. Konorov, A. M. Zheltikov, and M. Scalora, "Photonic-Crystal Fiber as a Multifunctional Optical Sensor and Sample Collector," Opt. Express 13, 3454-3459 (2005). [CrossRef] [PubMed]
  4. L. Rindorf, P. E. Hoiby, J. B. Jensen, L. H. Pedersen, O. Bang, and O. Geschke, "Towards Biochips Using Microstructured Optical Fiber Sensors," Anal. Bioanal. Chem. 385, 1370-1375 (2006). [CrossRef] [PubMed]
  5. C. M. B. Cordeiro, M. A. R. Franco, G. Chesini, E. C. S. Barretto, R. Lwin, C. H. B. Cruz, and M. C. J. Large, "Microstructured-Core Optical Fibre for Evanescent Sensing Applications," Opt. Express 14, 13,056-13,066 (2006). [CrossRef]
  6. F. Warken, E. Vetsch, D. Meachede, M. Sokolowski, and A. Rauschenbeutel, "Ultra-Sensitive Surface Absorption Spectroscopy Using Sub-Wavelength Diameter Optical Fibers," Opt. Express 15, 11,952-11,958 (2007). [CrossRef]
  7. S. Smolka, M. Barth, and O. Benson, "Highly Efficient Fluorescence Sensing with Hollow Core Photonic Crystal Fibers," Opt. Express 15, 12,783 (2007). [CrossRef]
  8. W. Henry, "Evanescent Field Devices: A Comparison Between Tapered Optical Fibres and Polished or D-Fibres," Opt. Quantum Electron. 26, s261-s272 (1994). [CrossRef]
  9. P. Lucas, M. R. Riley, C. Boussard-Pledel, and B. Bureau, "Advances in Chalcogenide Fiber Evanescent Wave Biochemical Sensing," Anal. Biochem. 351, 1-10 (2006). [CrossRef]
  10. Q1. G. Stewart, W. Jin, and B. Culshaw, "Prospects for Fibre-Optic Evanescent-Field Gas Sensors Using Absorption in the Near-Infrared," Sens. Actuators B 38-39, 42-47 (1997). [CrossRef]
  11. J. Lou, L. Tong, and Z. Ye, "Modeling of Silica Nanowires for Optical Sensing," Opt. Express 13, 2135-2140 (2005). [CrossRef] [PubMed]
  12. Y. Zhu, H. Du, and R. Bise, "Design of Solid-Core Microstructured Optical Fiber with Steering-Wheel Air Cladding for Optimal Evanescent-Field Sensing," Opt. Express 14, 3541-3546 (2006). [CrossRef] [PubMed]
  13. J. B. Jensen, L. H. Pedersen, P. E. Hoiby, L. B. Nielsen, T. P. Hansen, J. R. Folkenberg, J. Riishede, D. Noordegraaf, K. Nielsen, A. Carlsen, and A. Bjarklev, "Photonic Crystal Fiber Based Evanescent-Wave Sensor for Detection of Biomolecules in Aqueous Solutions," Opt. Lett. 29, 1974-1976 (2004). [CrossRef] [PubMed]
  14. Y. K. Lize, E. Magi, V. Taeed, J. Bolger, P. Steinvurzel, and B. Eggleton, "Microstructured Optical Fiber Photonic Wires with Subwavelength Core Diameter," Opt. Express 12, 3209-3217 (2004). [CrossRef] [PubMed]
  15. K. J. Rowland, S. Afshar V., and T. M. Monro, "Nonlinearity Enhancement of Filled Microstructured Fibers Operating in Nanowire Regime," in Proceedings of OFC 2006, p. OTuH3 (2006).
  16. L. Tong, J. Lou, and E. Mazur, "Single-Mode Guiding Properties of Subwavelength-Diameter Silica and Silicon Wire Waveguides," Opt. Express 12, 1025-1035 (2004). [CrossRef] [PubMed]
  17. S. Smolka, M. Barth, and O. Benson, "Selectively Coated Photonic Crystal Fiber for Highly Sensitive Fluorescence Detection," Appl. Phys. Lett. 90, 111,101 (2007). [CrossRef]
  18. Z. Liu and J. Pawliszyn, "Capillary Isoelectric Focusing of Proteins with Liquid Core Waveguide Laser-Induced Fluorescence Whole Column Imaging Detection," Anal. Chem. 75, 4887-4894 (2003). [CrossRef] [PubMed]
  19. Y. Huang, Y. Xu, and A. Yariv, "Fabrication of Functional Microstructured Optical Fibers Through a Selective- Filling Technique," Appl. Phys. Lett. 85, 5182 (2004). [CrossRef]
  20. T. Ritari, J. Tuominen, H. Ludvigsen, J. Petersen, T. Sorensen, T. Hansen, and H. Simonsen, "Gas Sensing Using Air-Guiding Photonic Bandgap Fibers," Opt. Express 12, 4080 (2004). [CrossRef] [PubMed]
  21. H. P. Kao, N. Yang, and J. S. Schoeniger, "Enhancement of Evanescent Fluorescence from Fiber-Optic Sensors by Thin-Film Sol-Gel Coating," J. Opt. Soc. Am. A 15, 21632,170 (1998).
  22. M. Nagel, A. Marchewka, and H. Kurz, "Low-Index Discontinuity Terahertz Waveguides," Opt. Express 14, 9944 (2006). [CrossRef] [PubMed]
  23. Q2. G. S. Wiederhecker, C. M. B. Cordeiro, F. Couny, F. Benabid, S. A. Maier, J. C. Knight, C. H. B. Cruz, and H. L. Fragnito, "Field Enhancement Within an Optical Fibre with a Subwavelength Air Core," Nature Photonics 1, 115 (2007). [CrossRef]
  24. N. Ganesh and B. T. Cunningham, "Photonic Crystal Enhanced Fluorescence," in Technical Digest, p. CThz5 (Optical Society of America, 2007).
  25. V. R. Almeida, Q. Xu, C. A. Barrios, and M. Lipson, "Guiding and Confining Light in Void Nanostructure," Opt. Lett. 29, 1209-1211 (2004). [CrossRef] [PubMed]
  26. R. E. Bailey, A. M. Smith, and S. Nie, "Quantum Dots in Biology and Medicine," Physica E 25, 1-12 (2004). [CrossRef]
  27. A. W. Snyder and J. D. Love, Optical Waveguide Theory (Chapman and hall, 2-6 Boundary Row, London SE1 8HN, UK, 1995).
  28. F. W. D. Rost, Fluorescence Microscopy (Cambridge University Press, Cambridge, UK, 1992).
  29. D. Marcuse, "Launching Light Into Fiber Cores from Sources Located in the Cladding," J. Lightwave Technol. 6, 1273-1279 (1988). [CrossRef]
  30. H. Ebendorff-Heidepriem, P. Petropoulos, S. Asimakis, V. Finazzi, R. C. Moore, K. Frampton, F. Koizumi, D. J. Richardson, and T. M. Monro, "Bismuth Glass Holey Fibers with High Nonlinearity," Opt. Express 12, 5082-87 (2004). [CrossRef] [PubMed]
  31. C. M. B. Cordeiro, M. A. R. Franco, C. J. S. Matos, F. Sircilli, V. A. Serrao, and C. H. B. Cruz, "Single-Design- Parameter Microstructured Optical Fiber for Chromatic Dispersion Tailoring and Evanescent Field Enhancement," Opt. Lett. 32, 3324-26 (2007). [CrossRef] [PubMed]
  32. A. Zheltikov, "Gaussian-Mode Analysis of Waveguide-Enhanced Kerr-Type Nonlinearity of Optical Fibers and Photonic Wires," J. Opt. Soc. Am. B 22, 1100-1104 (2005). [CrossRef]
  33. P. Agrawal, Nonlinear Fiber Optics. Academic press, Burlington, (2007).
  34. E. W. Washburn, "The Dynamics of Capillary Flow," Physical Review 17, 273-283 (1921). [CrossRef]
  35. I. B. Berlman, Handbook of fluorescence spectra of aromatic molecules (Academic Press, New York, 1971).
  36. E. Schartner, Y. Ruan, P. Hoffman, and T. M. Monro, "An Optical Fibre Protein Sensor," in COIN-ACOFT 2007 Proceeding, pp. WeB1-3 (Australian Optical Society, 2007).
  37. Y. Ruan, W. Li, R. Jarvis, N. Madsen, A. Rode, and B. Luther-Davies, " Fabrication and Characterization of Low Loss Rib Chalcogenide Waveguide Made by Dry Etching, " Opt. Express 12, 5140-5145(2004). [CrossRef] [PubMed]
  38. H. Ebendorff-Heidepriem, Y. Li, and T. M. Monro, "Reduced Loss in Extruded Microstructured Optical Fiber," Electron. Lett.,  43, 1343-1345(2007). [CrossRef]

Cited By

Alert me when this paper is cited

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.


« Previous Article  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited