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Optical Materials Express

Optical Materials Express

  • Editor: David J. Hagan
  • Vol. 2, Iss. 7 — Jul. 1, 2012
  • pp: 929–941
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Guiding and thermal properties of a hybrid polymer-infused photonic crystal fiber

Christos Markos, Kyriakos Vlachos, and George Kakarantzas  »View Author Affiliations


Optical Materials Express, Vol. 2, Issue 7, pp. 929-941 (2012)
http://dx.doi.org/10.1364/OME.2.000929


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Abstract

In this work, we investigate the guiding properties of a hybrid polymer (poly-dimethylsiloxane)/silica photonic crystal fiber (PCF). In particular, we demonstrate how the basic guiding properties of a conventional PCF are changed due to the infusion of poly-dimethylsiloxane (PDMS) in its air-holes. We show that PDMS infiltration allows tuning of single mode operation, confinement loss, effective modal area (EMA) and numerical aperture (NA) with wavelength and/or temperature. This is primarily due to the enhancement of evanescent field interaction, lending some important characteristics for designing tunable fiber devices. Numerical calculations were performed for different relative hole sizes, d/Λ (0.35-0.75), of PCF for a 500-1700nm wavelength and 0-100°C temperature range, whereas direct comparison with a conventional air-filled PCF is also shown.

© 2012 OSA

1. Introduction

Photonic crystal fiber (often referred as microstructured or 'holey' fiber) possesses many distinguished properties and characteristics compared to conventional single mode fiber [1

1. P. St. J. Russell, “Photonic crystal fibers,” Science 299(5605), 358–362 (2003). [CrossRef] [PubMed]

]. This unique kind of optical fibers constitute micrometer-scaled holes running along their entire length which usually are arranged in a hexagonal pattern [2

2. J. C. Knight, T. A. Birks, P. St. J. Russell, and D. M. Atkin, “All-silica single-mode optical fiber with photonic crystal cladding,” Opt. Lett. 21(19), 1547–1549 (1996). [CrossRef] [PubMed]

]. This feature enables the infiltration of advanced materials and liquids such as liquid crystals [3

3. T. T. Larsen, A. Bjarklev, D. S. Hermann, and J. Broeng, “Optical devices based on liquid crystal photonic bandgap fibers,” Opt. Express 11(20), 2589–2596 (2003). [CrossRef] [PubMed]

6

6. D. C. Zografopoulos, E. E. Kriezis, and T. D. Tsiboukis, “Tunable highly birefringent bandgap-guiding liquid-crystal microstructured fibers,” J. Lightwave Technol. 24(9), 3427–3432 (2006). [CrossRef]

], high index liquids [7

7. R. T. Bise, R. S. Windeler, K. S. Kranz, C. Kerbage, B. J. Eggleton, and D. J. Trevor, “Tunable photonic band gap fiber,” in Proc. Opt. Fiber Commun. Conf. (OFC), Anaheim, CA, 2002, pp. 466–468.

], biolayers [8

8. 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). [CrossRef] [PubMed]

,9

9. C. Markos, W. Yuan, K. Vlachos, G. E. Town, and O. Bang, “Label-free biosensing with high sensitivity in dual-core microstructured polymer optical fibers,” Opt. Express 19(8), 7790–7798 (2011). [CrossRef] [PubMed]

], ferrofluids [10

10. A. Candiani, M. Konstantaki, W. Margulis, and S. Pissadakis, “A spectrally tunable microstructured optical fiber Bragg grating utilizing an infiltrated ferrofluid,” Opt. Express 18(24), 24654–24660 (2010). [CrossRef] [PubMed]

], metals [11

11. M. Hautakorpi, M. Mattinen, and H. Ludvigsen, “Surface-plasmon-resonance sensor based on three-hole microstructured optical fiber,” Opt. Express 16(12), 8427–8432 (2008). [CrossRef] [PubMed]

13

13. H. W. Lee, M. A. Schmidt, H. K. Tyagi, L. P. Sempere, and P. St. J. Russell, “Polarization-dependent coupling to plasmon modes on submicron gold wire in photonic crystal fiber,” Appl. Phys. Lett. 93(11), 111102 (2008). [CrossRef]

] as well as polymers [14

14. P. S. Westbrook, B. J. Eggleton, R. S. Windeler, A. Hale, T. A. Strasser, and G. L. Burdge, “Cladding-mode resonances in hybrid polymer-silica microstructured optical fiber gratings,” IEEE Photon. Technol. Lett. 12(5), 495–497 (2000). [CrossRef]

,15

15. C. Markos, K. Vlachos, and G. Kakarantzas, “Bending loss and thermo-optic effect of a hybrid PDMS/silica photonic crystal fiber,” Opt. Express 18(23), 24344–24351 (2010). [CrossRef] [PubMed]

], into the air-holes of the PCF. Infusion of the above mentioned different materials lends the ability to modify the guiding properties and Behaviour of these fibers develops tunable devices [16

16. B. T. Kuhlmey, B. J. Eggleton, and D. K. C. Wu, “Fluid-filled solid-core photonic bandgap fibers,” J. Lightwave Technol. 27(11), 1617–1630 (2009). [CrossRef]

,17

17. C. Kerbage, P. Steinvurzel, P. Reyes, P. S. Westbrook, R. S. Windeler, A. Hale, and B. J. Eggleton, “Highly tunable birefringent microstructured optical fiber,” Opt. Lett. 27(10), 842–844 (2002). [CrossRef] [PubMed]

], filters [18

18. P. Steinvurzel, B. J. Eggleton, C. M. de Sterke, and M. J. Steel, “Continuously tunable bandpass filtering using high-index inclusion microstructured optical fiber,” Electron. Lett. 41(8), 463–464 (2005). [CrossRef]

], attenuators [19

19. C. Kerbage, A. Hale, A. Yablon, R. S. Windeler, and B. J. Eggleton, “Integrated all-fiber variable attenuator based on hybrid microstructure fiber,” Appl. Phys. Lett. 79(19), 3191–3193 (2001). [CrossRef]

], sensors [20

20. 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). [CrossRef] [PubMed]

22

22. W. Qian, C. L. Zhao, S. He, X. Dong, S. Zhang, Z. Zhang, S. Jin, J. Guo, and H. Wei, “High-sensitivity temperature sensor based on an alcohol-filled photonic crystal fiber loop mirror,” Opt. Lett. 36(9), 1548–1550 (2011). [CrossRef] [PubMed]

] etc.

During the last decade, polymers have also attracted a lot of scientific interest because they are flexible materials with good mechanical properties, relatively low cost, and often suitable for photonic applications [23

23. Y. Fainman, L. P. Lee, D. Psaltis, and C. Yang, Optofluidics: Fundamentals, Devices, and Applications (McGraw-Hill, 2010).

]. Limited research has been carried out so far though on the development of polymer infused PCF-based devices. Kerbage et al. reported a highly tunable birefringent microstructured optical fiber, where the variation of the refractive index of the infused polymer allows tuning of the guiding properties [17

17. C. Kerbage, P. Steinvurzel, P. Reyes, P. S. Westbrook, R. S. Windeler, A. Hale, and B. J. Eggleton, “Highly tunable birefringent microstructured optical fiber,” Opt. Lett. 27(10), 842–844 (2002). [CrossRef] [PubMed]

]. The proposed device required however post-processing (tapering) for increasing the interaction of the evanescent field with the infused polymer, which may result in high losses. In addition, polymers can exhibit shrinkage during polymerization and create stress and often cracks [16

16. B. T. Kuhlmey, B. J. Eggleton, and D. K. C. Wu, “Fluid-filled solid-core photonic bandgap fibers,” J. Lightwave Technol. 27(11), 1617–1630 (2009). [CrossRef]

]. Consequently, the choice of the active polymer has a crucial role in the development of tunable devices.

A widely known and used polymer in the field of micro/optofluidics is the poly-dimethylsiloxane (PDMS). It has been used as stamp resin in the procedure of soft lithography, making it one of the most common materials used for flow delivery in microfluidics chips [23

23. Y. Fainman, L. P. Lee, D. Psaltis, and C. Yang, Optofluidics: Fundamentals, Devices, and Applications (McGraw-Hill, 2010).

]. PDMS is a low cost material and it has very good optical and mechanical properties as well as low shrinkage and it can be fabricated very easily [23

23. Y. Fainman, L. P. Lee, D. Psaltis, and C. Yang, Optofluidics: Fundamentals, Devices, and Applications (McGraw-Hill, 2010).

]. Its refractive index is around 1.41 and it is highly transparent to a wide range of wavelengths [24

24. F. Schneider, J. Draheim, R. Kamberger, and U. Wallrabe, “Process and material properties of polydimethylsiloxane (PDMS) for Optical MEMS,” Sens. Actuators A Phys. 151(2), 95–99 (2009). [CrossRef]

]. The combination of the unique optical properties of PDMS with the mature technology of PCFs can constitute an efficient route to development of compact cost-effectiveness tunable devices and sensors [15

15. C. Markos, K. Vlachos, and G. Kakarantzas, “Bending loss and thermo-optic effect of a hybrid PDMS/silica photonic crystal fiber,” Opt. Express 18(23), 24344–24351 (2010). [CrossRef] [PubMed]

].

2. Fiber samples preparation and loss measurements

In this section, basic absorption and loss measurements are provided to demonstrate the ease of fiber development as well as determine its loss performance. The poly-dimethylsiloxane (PDMS) was from Dow Corning (Sylgard-184) and was prepared by mixing elastomer and curing agent at 10:1 ratio [24

24. F. Schneider, J. Draheim, R. Kamberger, and U. Wallrabe, “Process and material properties of polydimethylsiloxane (PDMS) for Optical MEMS,” Sens. Actuators A Phys. 151(2), 95–99 (2009). [CrossRef]

]. For determining the absorption coefficient of PDMS, we drop casted the polymer in a glass substrate and measured the material absorption using a spectrophotometer and a step profilometer to define the film thickness of the sample. Figure 1
Fig. 1 Absorption coefficient of Poly-dimethylsiloxane (PDMS) material (logarithmic scale).
displays the absorption coefficient from 500-to-2000 nm wavelength spanning. At short wavelengths, the polymer exhibits a relative low absorption with only a high peak at 1186 nm and a minimum at 1320 nm. At longer wavelengths absorption coefficient increases significantly, exhibiting a maximum at ~1750nm.

In our experiments, we employed four different commercially available PCFs named as LMA-13, 12-01, 10, 5, (see [25] for fiber specifications), with different d and Λ each (where d corresponds to the diameter of the cladding-hole and Λ is the pitch of the fiber). Table 1

Table 1. Structural Parameters of the Fibers

table-icon
View This Table
shows the structural parameters (i.e. d and Λ) of the fibers. The fibers were infiltrated with PDMS using a custom-built pressure cell. The infiltration length depends on the viscosity of the material (in this case 3900 centipoise), the cladding-holes diameter of the fiber, and the applied pressure [26

26. K. Nielsen, D. Noordegraaf, T. Sorensen, A. Bjarklev, and T. P. Hansen, “Selective filling of photonic crystal fibers,” J. Opt. A, Pure Appl. Opt. 7(8), L13–L20 (2005). [CrossRef]

]. For example in the case of an LMA-5 fiber, applying a constant pressure of ~15 bars for 1.5 hours was enough to fill a fiber length of ~2 cm. Different samples were prepared and cured at room temperature for 48 hours according to the specifications of detailed in [24

24. F. Schneider, J. Draheim, R. Kamberger, and U. Wallrabe, “Process and material properties of polydimethylsiloxane (PDMS) for Optical MEMS,” Sens. Actuators A Phys. 151(2), 95–99 (2009). [CrossRef]

]. Figure 2(a)
Fig. 2 (a) Optical microscope image of the PDMS-filled PCF (LMA-13). (b) SEM image of a conventional (empty) PCF fiber.
shows the optical microscope image of the LMA-13 filled with the polymer and Fig. 2(b) shows the scanning electron microscope (SEM) image of the same air-filled fiber.

The loss performance of the PDMS-filled PCFs were measured using cut-back method by launching white light from a broadband supercontinuum laser source (500-1700nm). Figure 3
Fig. 3 Experimental set-up.
displays the experimental set-up. The output beam was collected with a 20 × microscope objective and a multimode fiber, while the transmitted signal was monitored on an optical spectrum analyzer. Any undesired cladding light was blocked by inserting an iris diaphragm into the beam path, such that only light from the waveguide core was recorded.

The corresponding measured losses of the polymer filled LMA-13, 12-01, 10, and 5 from 500 to 1700 nm is shown in Fig. 4
Fig. 4 Loss measurements (dB/cm) of LMA-13, 12-01, 10, and 5 from 500 to 1700 nm.
. LMA-13, 12-01 and 10 have relatively large core compared to LMA-5 and therefore confinement loss is directly affecting the total loss of the fiber. Therefore, LMA-13 has higher loss than 12-01, and 10. However, it can be clearly seen that the highest values of loss obtained for the case of LMA-5 where the light-polymer interaction is the highest compared to all the other cases. The corresponding calculated fraction of power in the cladding is ~1.33% at 600 nm while for example in LMA 12-01 is ~0.09% at the same wavelength. Similarly, at longer wavelengths, i.e. 1400 nm, the fraction of power in LMA 5 is ~14% while in LMA 12-01 is ~1.9%. Due to the high absorption coefficient of PDMS at long wavelengths (higher than 1320 nm) as demonstrated in Fig. 1, combined with high confinement loss (fundamental mode starts to become a leaky mode), LMA-5 exhibits consequently very high losses at these wavelengths as shown in Fig. 4. It should be also mentioned that the loss measurement performed with great care in order to minimize errors such as in/out coupling instabilities, power fluctuation, cleaving quality, etc.

3. Numerical modeling

In our calculations we considered a standard index-guiding photonic crystal fiber with the air-holes arranged in a hexagonal array as shown in Fig. 5(a)
Fig. 5 (a) Hybrid polymer/silica simulated PCF. (b) Refractive index profile of the hybrid structure. Example of the calculated fundamental guiding mode profile of the PCF with d/Λ = 0.35 at 1550 nm (c) with air and (d) infused with PDMS polymer
. We investigated five different structures with d/Λ = 0.35,0.45,0.55,0.65,0.75. The diameter of the cladding holes remained constant to d = 3.5 μm for all cases, which in experimental terms are big enough for the infiltration of a high viscosity polymer over several centimeters [26

26. K. Nielsen, D. Noordegraaf, T. Sorensen, A. Bjarklev, and T. P. Hansen, “Selective filling of photonic crystal fibers,” J. Opt. A, Pure Appl. Opt. 7(8), L13–L20 (2005). [CrossRef]

]. The host material of the fiber was fused silica while the air-holes of the PCF were unselectively filled with PDMS. The refractive index profile of the hybrid structure is shown in Fig. 5(b).

The numerical method we employed to find out the guiding and thermal properties of the PDMS-filled PCFs is the Yee-mesh-based full-vector finite difference method [27

27. C. P. Yu and H. C. Chang, “Yee-mesh-based finite difference eigenmode solver with PML absorbing boundary conditions for optical waveguides and photonic crystal fibers,” Opt. Express 12(25), 6165–6177 (2004). [CrossRef] [PubMed]

] which is an efficient and accurate numerical mode solver for the analysis of optical waveguides and PCF structures [27

27. C. P. Yu and H. C. Chang, “Yee-mesh-based finite difference eigenmode solver with PML absorbing boundary conditions for optical waveguides and photonic crystal fibers,” Opt. Express 12(25), 6165–6177 (2004). [CrossRef] [PubMed]

,28

28. Z. Zhu and T. Brown, “Full-vectorial finite-difference analysis of microstructured optical fibers,” Opt. Express 10(17), 853–864 (2002). [PubMed]

]. In Figs. 5(c) and 5(d) we show the calculated effective indices of the fundamental guiding mode at 1550 nm wavelength of a conventional (unfilled) and PDMS filled PCF. In order to achieve accurate predictions in the numerical computation of the presented hybrid PDMS/Silica PCF cases, it is important to select the appropriate mesh spacing (grid size). With respect to the discretization scheme that was used in the calculation, reasonably accurate results can be obtained by keeping the mesh spacing at: λ/15 [27

27. C. P. Yu and H. C. Chang, “Yee-mesh-based finite difference eigenmode solver with PML absorbing boundary conditions for optical waveguides and photonic crystal fibers,” Opt. Express 12(25), 6165–6177 (2004). [CrossRef] [PubMed]

]. The boundary condition is another critical factor for simulation of mode properties. An absorbing perfectly matched layer (PML) boundary condition [29

29. J. P. Berenger, “A perfectly matched layer for the absorption of electromagnetic waves,” J. Comput. Phys. 114(2), 185–200 (1994). [CrossRef]

] was employed in our case for the truncation of computation domain without reflection. In all cases, we considered only the x-polarized mode since the difference between the two orthogonal polarizations was negligible.

Numerical results are divided into two sections. Section 3.1 considers the guiding properties of the hybrid PCF from 500 nm to 1700 nm wavelength. In our study, we have considered both the dispersion of fused silica and PDMS. The refractive index of silica was calculated using Palik's parameters [30

30. E. Palik, Handbook of Optical Constants of Solids I–III (Academic, 1998).

], while the real part of the refractive index of PDMS using its Sellmeier equation, where the coefficients were experimentally demonstrated in [24

24. F. Schneider, J. Draheim, R. Kamberger, and U. Wallrabe, “Process and material properties of polydimethylsiloxane (PDMS) for Optical MEMS,” Sens. Actuators A Phys. 151(2), 95–99 (2009). [CrossRef]

]. The imaginary part of the refractive index was extracted based on the absorption measurements of the material (see Section 2).

3.1 Guiding properties of the polymer-infused PCF

In this section, we analyze the guiding mechanism of the PDMS-filled PCF for a wavelength range of 500 nm up to 1700 nm, for different relative hole sizes, d/Λ, at room temperature. Depending on the structural dimensions of hole diameter d and pitch Λ, the fiber comprises both single- and multi-mode guidance. The V-parameter (normalized frequency) is an essential factor which determines the guiding properties of the fiber. The formulation of the V-parameter for a PCF is given by [31

31. M. Nielsen and N. Mortensen, “Photonic crystal fiber design based on the V-parameter,” Opt. Express 11(21), 2762–2768 (2003). [CrossRef] [PubMed]

]:
Vparameter=2πΛλnFM2(λ)nFSM2(λ)
(1)
Despite the fact, that this mathematical formula is similar to the expression for the standard optical fibers, the unique structure of PCF is taken into account. In Eq. (1), the term nFM2(λ)corresponds to the effective index of the fundamental guiding mode at a particular wavelength and respectively nFSM2(λ) corresponds to the effective index of the first cladding mode in the infinite cladding structure which is usually defined as the fundamental space filling mode. For the fully detailed analysis of this expression refer to [32

32. N. A. Mortensen, J. R. Folkenberg, M. D. Nielsen, and K. P. Hansen, “Modal cutoff and the V parameter in photonic crystal fibers,” Opt. Lett. 28(20), 1879–1881 (2003). [CrossRef] [PubMed]

].

Figure 6
Fig. 6 Numerical calculations of the V-parameter of the PDMS filled PCF for different relative hole sizes. The dashed lines correspond to the conventional unfilled PCF. The black dashed line indicates the single-mode operation threshold.
shows the calculated V-parameter of the hybrid polymer/silica PCF versus wavelength operating wavelength for different d/Λ. The dashed lines correspond to the conventional unfilled PCF of the corresponding same d/Λ, while the black dashed line indicates the higher-order mode cut-off and is associated with a value of VPCF = π, as demonstrated by Mortensen et al [32

32. N. A. Mortensen, J. R. Folkenberg, M. D. Nielsen, and K. P. Hansen, “Modal cutoff and the V parameter in photonic crystal fibers,” Opt. Lett. 28(20), 1879–1881 (2003). [CrossRef] [PubMed]

] and validated in [33

33. J. R. Folkenberg, N. A. Mortensen, K. P. Hansen, T. P. Hansen, H. R. Simonsen, and C. Jakobsen, “Experimental investigation of cutoff phenomena in nonlinear photonic crystal fibers,” Opt. Lett. 28(20), 1882–1884 (2003). [CrossRef] [PubMed]

]. From Fig. 6, it can be clearly seen that PDMS inclusion in PCF, converts a multimode fiber (see conventional air-filled PCF in Fig. 6) to endlessly single-mode according to the relative hole size d/Λ for specific wavelength ranges. This is an important feature for developing tunable fiber devices. For example, in the case of d/Λ = 0.55, the PDMS-filled PCF exhibits single mode operation above 800 nm wavelength, while the structures with d/Λ = 0.65 and 0.75 above 1100 nm and 1300 nm, respectively. The corresponding conventional unfilled PCF exhibits multimode operation across the whole wavelength span.

Finally, we have calculated how the evanescent field changes due to the infusion of PDMS. As expected, the infiltration of a polymer into the holes of a PCF substantially increases the light-matter interaction, thus enhancing the evanescent field. Figure 9
Fig. 9 Fraction of power in the PDMS-filled holes of the PCF versus wavelength for different relative hole sizes. Right inset represents a graphical representation of the evanescent field for the case of d/Λ = 0.75 at 1700 nm wavelength.
shows the calculated percentage of energy in the PDMS-filled holes for a particular fiber mode (fundamental guiding mode in our case). This is calculated by integrating the optical power inside the PCF holes and dividing it by the total power carried by that mode as expressed in [39

39. 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 fiber for evanescent sensing applications,” Opt. Express 14(26), 13056–13066 (2006). [CrossRef] [PubMed]

]:
fractionofpower=holesRe(ExHy*EyHx*)dxdyTotalRe(ExHy*EyHx*)dxdy×100
(4)
In Eq. (4), Ex, Ey and Hx, Hy are the respective transverse electric and magnetic fields of the fundamental guiding mode. As the d/Λ increases the interaction of the light with polymer becomes stronger and the fraction of power in the holes of the PCF can be as high as ~13% at 1700 nm. It should be noted that in case of the conventional unfilled PCFs, the fraction of power in the air-holes is negligible for all d/Λ structures.

3.2 Thermal properties of the polymer-infused PCF

In this section, we present the thermal properties of the hybrid PDMS infused PCF. All calculations were performed at 633 nm, where PDMS exhibits relative low absorption as well as at 1550nm, which is a widely used wavelength. PDMS exhibit a unique capability to operate over a wide range of wavelengths as compared with polymer or liquids, bearing a potential for developing thermally tune fiber devices (i.e. sensors). In our calculations, the thermo-optic coefficient of PDMS was set to dn/dT = −4.5x10−4/ °C [15

15. C. Markos, K. Vlachos, and G. Kakarantzas, “Bending loss and thermo-optic effect of a hybrid PDMS/silica photonic crystal fiber,” Opt. Express 18(23), 24344–24351 (2010). [CrossRef] [PubMed]

], while it was neglected for silica. This is because the thermo-optic coefficient as well as any thermal effect induced is insignificant for low temperatures as high as 100°C [40

40. H. R. Sørensen, J. Canning, J. Lægsgaard, and K. Hansen, “Control of the wavelength dependent thermo-optic coefficients in structured fibers,” Opt. Express 14(14), 6428–6433 (2006). [CrossRef] [PubMed]

]. To this end, based on the thermally induced change of the refractive index of PDMS, we calculated the corresponding effective indices of the fundamental guiding mode. Figures 10(a)
Fig. 10 Effective index difference variation, Δn of the polymer-filled PCF for different relative hole sizes versus temperature at (a) 633nm and (b) 1550 nm. Single-mode operation cut-off (V-parameter) for different temperatures at (c) 633 and (d) 1550nm wavelength.
and 10(b) show the effective index difference (Δn) defined as the difference of the effective indices between the initial (T0 = 0°C) and actual temperature (x-axis) at 633 and 1550 nm, respectively. From Fig. 10(a), it can be seen, that the change of the effective refractive index with temperature is limited due to the high confinement of the fundamental mode at 633nm. For d/Λ = 0.75, the difference in the effective indices reaches a maximum of ~2.4x10−4 at 100°C. For the same structure at l550nm, the change of the effective index can be as high as 30x10−4 (see Fig. 10(b)). This is due to the large overlap between the guiding mode and PDMS-filled cladding providing a significantly capability for designing thermally tuned devices at 1550nm. Figures 10(c) and 10(d) show the unique feature to tune the V-parameter by varying temperature. Figure 10(c) shows the change of the V-parameter at 633 nm, over which the effect is not very strong due to the high confinement of the mode at short wavelengths. In contrast, at 1550nm wavelength, the effect is much stronger as shown in Fig. 10(d).

Figure 11
Fig. 11 Confinement loss of the hybrid PDMS infused PCF for different relative hole sizes at 1550 nm.
displays the corresponding confinement loss variation only for 1550nm, since at 633 is insignificantly small. In general the increase of temperature induces an increase in the refractive index contrast between cladding and core also increases, allowing the fundamental guiding mode to be highly confined to the core of the fiber. From Fig. 11, it can be seen that for relative hole sizes greater than 0.55, the confinement loss is significantly reduced starting from 0.01 dB/m at 0°C to less than 1x10−8 at 70°C. In contrast for d/Λ = 0.45 και 0.35, confinement loss reduces more smoothly, starting from a high value of 10dB/m (see d/Λ = 0.35 curve) to only 1x10−4 at 100°C (see d/Λ = 0.45 curve).

Figures 12(c) and 12(d) display the corresponding NA variation with temperature. As previously mentioned, the change of NA with temperature is directly linked to EMA; therefore at short wavelengths (i.e. 633 nm) the variation of NA is small (see Fig. 12(c)), while at 1550nm NA notably increases with temperature. For example, for the case of d/Λ = 0.75, NA increases from 0.12 to 0.18 for a 100°C temperature increase. It should be noted here again that for a conventional unfilled PCF, temperature changes do not affect EMA and NA due to very low thermo-optic coefficient of silica. Tuning EMA and NA with temperature is an important feature especially as for example collecting light from non-linear fiber, alleviating the need for fiber post processing.

Finally, we have also calculated, the fraction of power (%) inside the PDMS-filled cladding for different relative hole sizes from 0°C to 100°C. At 633 nm, the high confinement of the mode allows limited interaction with the cladding and thus the fraction of power varies from around 0.1 to 1.25% as shown in Fig. 14(a)
Fig. 14 Fraction of power in the cladding of the hybrid polymer/silica PCF at (a) 633 nm and (B) 1550 nm from 0°C to 100°C.
. However, the same effect is much stronger at 1550 nm and from Fig. 14(b), it can be seen that the fraction of power in the PDMS infused holes spans from 2% to 16% at 0°C for the different relative holes sizes.

4. Conclusions

Acknowledgments

This work was supported by the Greek NSRF Program with Grant No. 09SYN-24-769 and European Defense Agency (EDA) with Grant No A-0931-RT. Authors would like to thank Dr. G. Mousdis for his support with the absorption measurements.

References and links

1.

P. St. J. Russell, “Photonic crystal fibers,” Science 299(5605), 358–362 (2003). [CrossRef] [PubMed]

2.

J. C. Knight, T. A. Birks, P. St. J. Russell, and D. M. Atkin, “All-silica single-mode optical fiber with photonic crystal cladding,” Opt. Lett. 21(19), 1547–1549 (1996). [CrossRef] [PubMed]

3.

T. T. Larsen, A. Bjarklev, D. S. Hermann, and J. Broeng, “Optical devices based on liquid crystal photonic bandgap fibers,” Opt. Express 11(20), 2589–2596 (2003). [CrossRef] [PubMed]

4.

T. T. Alkeskjold, J. Lægsgaard, A. Bjarklev, D. Hermann, A. Anawati, J. Broeng, J. Li, and S. T. Wu, “All-optical modulation in dye-doped nematic liquid crystal photonic bandgap fibers,” Opt. Express 12(24), 5857–5871 (2004). [CrossRef] [PubMed]

5.

W. Yuan, L. Wei, T. T. Alkeskjold, A. Bjarklev, and O. Bang, “Thermal tunability of photonic bandgaps in liquid crystal infiltrated microstructured polymer optical fibers,” Opt. Express 17(22), 19356–19364 (2009). [CrossRef] [PubMed]

6.

D. C. Zografopoulos, E. E. Kriezis, and T. D. Tsiboukis, “Tunable highly birefringent bandgap-guiding liquid-crystal microstructured fibers,” J. Lightwave Technol. 24(9), 3427–3432 (2006). [CrossRef]

7.

R. T. Bise, R. S. Windeler, K. S. Kranz, C. Kerbage, B. J. Eggleton, and D. J. Trevor, “Tunable photonic band gap fiber,” in Proc. Opt. Fiber Commun. Conf. (OFC), Anaheim, CA, 2002, pp. 466–468.

8.

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). [CrossRef] [PubMed]

9.

C. Markos, W. Yuan, K. Vlachos, G. E. Town, and O. Bang, “Label-free biosensing with high sensitivity in dual-core microstructured polymer optical fibers,” Opt. Express 19(8), 7790–7798 (2011). [CrossRef] [PubMed]

10.

A. Candiani, M. Konstantaki, W. Margulis, and S. Pissadakis, “A spectrally tunable microstructured optical fiber Bragg grating utilizing an infiltrated ferrofluid,” Opt. Express 18(24), 24654–24660 (2010). [CrossRef] [PubMed]

11.

M. Hautakorpi, M. Mattinen, and H. Ludvigsen, “Surface-plasmon-resonance sensor based on three-hole microstructured optical fiber,” Opt. Express 16(12), 8427–8432 (2008). [CrossRef] [PubMed]

12.

C. G. Poulton, M. A. Schmidt, G. J. Pearce, G. Kakarantzas, and P. St. J. Russell, “Numerical study of guided modes in arrays of metallic nanowires,” Opt. Lett. 32(12), 1647–1649 (2007). [CrossRef] [PubMed]

13.

H. W. Lee, M. A. Schmidt, H. K. Tyagi, L. P. Sempere, and P. St. J. Russell, “Polarization-dependent coupling to plasmon modes on submicron gold wire in photonic crystal fiber,” Appl. Phys. Lett. 93(11), 111102 (2008). [CrossRef]

14.

P. S. Westbrook, B. J. Eggleton, R. S. Windeler, A. Hale, T. A. Strasser, and G. L. Burdge, “Cladding-mode resonances in hybrid polymer-silica microstructured optical fiber gratings,” IEEE Photon. Technol. Lett. 12(5), 495–497 (2000). [CrossRef]

15.

C. Markos, K. Vlachos, and G. Kakarantzas, “Bending loss and thermo-optic effect of a hybrid PDMS/silica photonic crystal fiber,” Opt. Express 18(23), 24344–24351 (2010). [CrossRef] [PubMed]

16.

B. T. Kuhlmey, B. J. Eggleton, and D. K. C. Wu, “Fluid-filled solid-core photonic bandgap fibers,” J. Lightwave Technol. 27(11), 1617–1630 (2009). [CrossRef]

17.

C. Kerbage, P. Steinvurzel, P. Reyes, P. S. Westbrook, R. S. Windeler, A. Hale, and B. J. Eggleton, “Highly tunable birefringent microstructured optical fiber,” Opt. Lett. 27(10), 842–844 (2002). [CrossRef] [PubMed]

18.

P. Steinvurzel, B. J. Eggleton, C. M. de Sterke, and M. J. Steel, “Continuously tunable bandpass filtering using high-index inclusion microstructured optical fiber,” Electron. Lett. 41(8), 463–464 (2005). [CrossRef]

19.

C. Kerbage, A. Hale, A. Yablon, R. S. Windeler, and B. J. Eggleton, “Integrated all-fiber variable attenuator based on hybrid microstructure fiber,” Appl. Phys. Lett. 79(19), 3191–3193 (2001). [CrossRef]

20.

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). [CrossRef] [PubMed]

21.

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

22.

W. Qian, C. L. Zhao, S. He, X. Dong, S. Zhang, Z. Zhang, S. Jin, J. Guo, and H. Wei, “High-sensitivity temperature sensor based on an alcohol-filled photonic crystal fiber loop mirror,” Opt. Lett. 36(9), 1548–1550 (2011). [CrossRef] [PubMed]

23.

Y. Fainman, L. P. Lee, D. Psaltis, and C. Yang, Optofluidics: Fundamentals, Devices, and Applications (McGraw-Hill, 2010).

24.

F. Schneider, J. Draheim, R. Kamberger, and U. Wallrabe, “Process and material properties of polydimethylsiloxane (PDMS) for Optical MEMS,” Sens. Actuators A Phys. 151(2), 95–99 (2009). [CrossRef]

25.

http://www.nktphotonics.com/lmafibers-specifications

26.

K. Nielsen, D. Noordegraaf, T. Sorensen, A. Bjarklev, and T. P. Hansen, “Selective filling of photonic crystal fibers,” J. Opt. A, Pure Appl. Opt. 7(8), L13–L20 (2005). [CrossRef]

27.

C. P. Yu and H. C. Chang, “Yee-mesh-based finite difference eigenmode solver with PML absorbing boundary conditions for optical waveguides and photonic crystal fibers,” Opt. Express 12(25), 6165–6177 (2004). [CrossRef] [PubMed]

28.

Z. Zhu and T. Brown, “Full-vectorial finite-difference analysis of microstructured optical fibers,” Opt. Express 10(17), 853–864 (2002). [PubMed]

29.

J. P. Berenger, “A perfectly matched layer for the absorption of electromagnetic waves,” J. Comput. Phys. 114(2), 185–200 (1994). [CrossRef]

30.

E. Palik, Handbook of Optical Constants of Solids I–III (Academic, 1998).

31.

M. Nielsen and N. Mortensen, “Photonic crystal fiber design based on the V-parameter,” Opt. Express 11(21), 2762–2768 (2003). [CrossRef] [PubMed]

32.

N. A. Mortensen, J. R. Folkenberg, M. D. Nielsen, and K. P. Hansen, “Modal cutoff and the V parameter in photonic crystal fibers,” Opt. Lett. 28(20), 1879–1881 (2003). [CrossRef] [PubMed]

33.

J. R. Folkenberg, N. A. Mortensen, K. P. Hansen, T. P. Hansen, H. R. Simonsen, and C. Jakobsen, “Experimental investigation of cutoff phenomena in nonlinear photonic crystal fibers,” Opt. Lett. 28(20), 1882–1884 (2003). [CrossRef] [PubMed]

34.

T. P. White, R. C. McPhedran, C. M. de Sterke, L. C. Botten, and M. J. Steel, “Confinement losses in microstructured optical fibers,” Opt. Lett. 26(21), 1660–1662 (2001). [CrossRef] [PubMed]

35.

K. Petermann, “Fundamental mode micro bending loss in graded index and w fibers,” Opt. Quantum Electron. 9(2), 167–175 (1977). [CrossRef]

36.

D. Marcuse, “Loss analysis of single-mode fiber splices,” Bell Syst. Tech. J. 56, 703 (1977).

37.

N. A. Mortensen, J. R. Folken, P. M. W. Skovgaard, and J. Broeng, “Numerical aperture of single-mode photonic crystal fibers,” IEEE Photon. Technol. Lett. 14(8), 1094–1096 (2002). [CrossRef]

38.

N. A. Mortensen, “Effective area of photonic crystal fibers,” Opt. Express 10(7), 341–348 (2002). [PubMed]

39.

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 fiber for evanescent sensing applications,” Opt. Express 14(26), 13056–13066 (2006). [CrossRef] [PubMed]

40.

H. R. Sørensen, J. Canning, J. Lægsgaard, and K. Hansen, “Control of the wavelength dependent thermo-optic coefficients in structured fibers,” Opt. Express 14(14), 6428–6433 (2006). [CrossRef] [PubMed]

OCIS Codes
(060.2290) Fiber optics and optical communications : Fiber materials
(160.6840) Materials : Thermo-optical materials
(230.1150) Optical devices : All-optical devices
(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: February 8, 2012
Revised Manuscript: May 27, 2012
Manuscript Accepted: June 16, 2012
Published: June 19, 2012

Citation
Christos Markos, Kyriakos Vlachos, and George Kakarantzas, "Guiding and thermal properties of a hybrid polymer-infused photonic crystal fiber," Opt. Mater. Express 2, 929-941 (2012)
http://www.opticsinfobase.org/ome/abstract.cfm?URI=ome-2-7-929


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References

  1. P. St. J. Russell, “Photonic crystal fibers,” Science299(5605), 358–362 (2003). [CrossRef] [PubMed]
  2. J. C. Knight, T. A. Birks, P. St. J. Russell, and D. M. Atkin, “All-silica single-mode optical fiber with photonic crystal cladding,” Opt. Lett.21(19), 1547–1549 (1996). [CrossRef] [PubMed]
  3. T. T. Larsen, A. Bjarklev, D. S. Hermann, and J. Broeng, “Optical devices based on liquid crystal photonic bandgap fibers,” Opt. Express11(20), 2589–2596 (2003). [CrossRef] [PubMed]
  4. T. T. Alkeskjold, J. Lægsgaard, A. Bjarklev, D. Hermann, A. Anawati, J. Broeng, J. Li, and S. T. Wu, “All-optical modulation in dye-doped nematic liquid crystal photonic bandgap fibers,” Opt. Express12(24), 5857–5871 (2004). [CrossRef] [PubMed]
  5. W. Yuan, L. Wei, T. T. Alkeskjold, A. Bjarklev, and O. Bang, “Thermal tunability of photonic bandgaps in liquid crystal infiltrated microstructured polymer optical fibers,” Opt. Express17(22), 19356–19364 (2009). [CrossRef] [PubMed]
  6. D. C. Zografopoulos, E. E. Kriezis, and T. D. Tsiboukis, “Tunable highly birefringent bandgap-guiding liquid-crystal microstructured fibers,” J. Lightwave Technol.24(9), 3427–3432 (2006). [CrossRef]
  7. R. T. Bise, R. S. Windeler, K. S. Kranz, C. Kerbage, B. J. Eggleton, and D. J. Trevor, “Tunable photonic band gap fiber,” in Proc. Opt. Fiber Commun. Conf. (OFC), Anaheim, CA, 2002, pp. 466–468.
  8. 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. Express14(18), 8224–8231 (2006). [CrossRef] [PubMed]
  9. C. Markos, W. Yuan, K. Vlachos, G. E. Town, and O. Bang, “Label-free biosensing with high sensitivity in dual-core microstructured polymer optical fibers,” Opt. Express19(8), 7790–7798 (2011). [CrossRef] [PubMed]
  10. A. Candiani, M. Konstantaki, W. Margulis, and S. Pissadakis, “A spectrally tunable microstructured optical fiber Bragg grating utilizing an infiltrated ferrofluid,” Opt. Express18(24), 24654–24660 (2010). [CrossRef] [PubMed]
  11. M. Hautakorpi, M. Mattinen, and H. Ludvigsen, “Surface-plasmon-resonance sensor based on three-hole microstructured optical fiber,” Opt. Express16(12), 8427–8432 (2008). [CrossRef] [PubMed]
  12. C. G. Poulton, M. A. Schmidt, G. J. Pearce, G. Kakarantzas, and P. St. J. Russell, “Numerical study of guided modes in arrays of metallic nanowires,” Opt. Lett.32(12), 1647–1649 (2007). [CrossRef] [PubMed]
  13. H. W. Lee, M. A. Schmidt, H. K. Tyagi, L. P. Sempere, and P. St. J. Russell, “Polarization-dependent coupling to plasmon modes on submicron gold wire in photonic crystal fiber,” Appl. Phys. Lett.93(11), 111102 (2008). [CrossRef]
  14. P. S. Westbrook, B. J. Eggleton, R. S. Windeler, A. Hale, T. A. Strasser, and G. L. Burdge, “Cladding-mode resonances in hybrid polymer-silica microstructured optical fiber gratings,” IEEE Photon. Technol. Lett.12(5), 495–497 (2000). [CrossRef]
  15. C. Markos, K. Vlachos, and G. Kakarantzas, “Bending loss and thermo-optic effect of a hybrid PDMS/silica photonic crystal fiber,” Opt. Express18(23), 24344–24351 (2010). [CrossRef] [PubMed]
  16. B. T. Kuhlmey, B. J. Eggleton, and D. K. C. Wu, “Fluid-filled solid-core photonic bandgap fibers,” J. Lightwave Technol.27(11), 1617–1630 (2009). [CrossRef]
  17. C. Kerbage, P. Steinvurzel, P. Reyes, P. S. Westbrook, R. S. Windeler, A. Hale, and B. J. Eggleton, “Highly tunable birefringent microstructured optical fiber,” Opt. Lett.27(10), 842–844 (2002). [CrossRef] [PubMed]
  18. P. Steinvurzel, B. J. Eggleton, C. M. de Sterke, and M. J. Steel, “Continuously tunable bandpass filtering using high-index inclusion microstructured optical fiber,” Electron. Lett.41(8), 463–464 (2005). [CrossRef]
  19. C. Kerbage, A. Hale, A. Yablon, R. S. Windeler, and B. J. Eggleton, “Integrated all-fiber variable attenuator based on hybrid microstructure fiber,” Appl. Phys. Lett.79(19), 3191–3193 (2001). [CrossRef]
  20. A. Hassani and M. Skorobogatiy, “Design of the microstructured optical fiber-based surface plasmon resonance sensors with enhanced microfluidics,” Opt. Express14(24), 11616–11621 (2006). [CrossRef] [PubMed]
  21. D. K. C. Wu, B. T. Kuhlmey, and B. J. Eggleton, “Ultrasensitive photonic crystal fiber refractive index sensor,” Opt. Lett.34(3), 322–324 (2009). [CrossRef] [PubMed]
  22. W. Qian, C. L. Zhao, S. He, X. Dong, S. Zhang, Z. Zhang, S. Jin, J. Guo, and H. Wei, “High-sensitivity temperature sensor based on an alcohol-filled photonic crystal fiber loop mirror,” Opt. Lett.36(9), 1548–1550 (2011). [CrossRef] [PubMed]
  23. Y. Fainman, L. P. Lee, D. Psaltis, and C. Yang, Optofluidics: Fundamentals, Devices, and Applications (McGraw-Hill, 2010).
  24. F. Schneider, J. Draheim, R. Kamberger, and U. Wallrabe, “Process and material properties of polydimethylsiloxane (PDMS) for Optical MEMS,” Sens. Actuators A Phys.151(2), 95–99 (2009). [CrossRef]
  25. http://www.nktphotonics.com/lmafibers-specifications
  26. K. Nielsen, D. Noordegraaf, T. Sorensen, A. Bjarklev, and T. P. Hansen, “Selective filling of photonic crystal fibers,” J. Opt. A, Pure Appl. Opt.7(8), L13–L20 (2005). [CrossRef]
  27. C. P. Yu and H. C. Chang, “Yee-mesh-based finite difference eigenmode solver with PML absorbing boundary conditions for optical waveguides and photonic crystal fibers,” Opt. Express12(25), 6165–6177 (2004). [CrossRef] [PubMed]
  28. Z. Zhu and T. Brown, “Full-vectorial finite-difference analysis of microstructured optical fibers,” Opt. Express10(17), 853–864 (2002). [PubMed]
  29. J. P. Berenger, “A perfectly matched layer for the absorption of electromagnetic waves,” J. Comput. Phys.114(2), 185–200 (1994). [CrossRef]
  30. E. Palik, Handbook of Optical Constants of Solids I–III (Academic, 1998).
  31. M. Nielsen and N. Mortensen, “Photonic crystal fiber design based on the V-parameter,” Opt. Express11(21), 2762–2768 (2003). [CrossRef] [PubMed]
  32. N. A. Mortensen, J. R. Folkenberg, M. D. Nielsen, and K. P. Hansen, “Modal cutoff and the V parameter in photonic crystal fibers,” Opt. Lett.28(20), 1879–1881 (2003). [CrossRef] [PubMed]
  33. J. R. Folkenberg, N. A. Mortensen, K. P. Hansen, T. P. Hansen, H. R. Simonsen, and C. Jakobsen, “Experimental investigation of cutoff phenomena in nonlinear photonic crystal fibers,” Opt. Lett.28(20), 1882–1884 (2003). [CrossRef] [PubMed]
  34. T. P. White, R. C. McPhedran, C. M. de Sterke, L. C. Botten, and M. J. Steel, “Confinement losses in microstructured optical fibers,” Opt. Lett.26(21), 1660–1662 (2001). [CrossRef] [PubMed]
  35. K. Petermann, “Fundamental mode micro bending loss in graded index and w fibers,” Opt. Quantum Electron.9(2), 167–175 (1977). [CrossRef]
  36. D. Marcuse, “Loss analysis of single-mode fiber splices,” Bell Syst. Tech. J.56, 703 (1977).
  37. N. A. Mortensen, J. R. Folken, P. M. W. Skovgaard, and J. Broeng, “Numerical aperture of single-mode photonic crystal fibers,” IEEE Photon. Technol. Lett.14(8), 1094–1096 (2002). [CrossRef]
  38. N. A. Mortensen, “Effective area of photonic crystal fibers,” Opt. Express10(7), 341–348 (2002). [PubMed]
  39. 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 fiber for evanescent sensing applications,” Opt. Express14(26), 13056–13066 (2006). [CrossRef] [PubMed]
  40. H. R. Sørensen, J. Canning, J. Lægsgaard, and K. Hansen, “Control of the wavelength dependent thermo-optic coefficients in structured fibers,” Opt. Express14(14), 6428–6433 (2006). [CrossRef] [PubMed]

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