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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 16, Iss. 22 — Oct. 27, 2008
  • pp: 17227–17236
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Optical properties of photonic crystal fiber with integral micron-sized Ge wire

H. K. Tyagi, M. A. Schmidt, L. Prill Sempere, and P. St.J. Russell  »View Author Affiliations


Optics Express, Vol. 16, Issue 22, pp. 17227-17236 (2008)
http://dx.doi.org/10.1364/OE.16.017227


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Abstract

Using a selective hole closure technique, individual hollow channels in silica-air photonic crystal fibers are filled with pure Ge by pumping in molten material at high pressure. The smallest channels filled so far are 600 nm in diameter, which is 10× smaller than in previous work. Electrical conductivity and micro-Raman measurements indicate that the resulting cm-long wires have a high degree of crystallinity. Optical transmission spectra are measured in a sample with a single wire placed adjacent to the core of an endlessly single-mode photonic crystal fiber. This renders the fiber birefringent, as well as causing strongly polarization-dependent transmission losses, with extinction ratios as high as 30 dB in the visible. In the IR, anti-crossings between the glass-core mode and resonances on the high index Ge wire create a series of clear dips in the spectrum transmitted through the fiber. The measurements agree closely with the results of finite-element simulations in which the wavelength dependence of the dielectric constants is taken fully into account. A toy model based on a multilayer structure is used to help interpret the results. Finally, the temperature dependence of the anti-crossing wavelengths is measured, the preliminary results suggesting that the structure might form the basis of a compact optical thermometer. Since Ge provides electrical conductance together with low-loss guidance in the mid-IR, Ge-filled PCF seems likely to lead to new kinds of in-fiber detector and sensor, as well as having potential uses in ultra-low-threshold nonlinear optical devices.

© 2008 Optical Society of America

1. Introduction

The transverse microstructure of air-silica photonic crystal fibers (PCFs) provides great flexibility in terms of dispersion and mode profile, as well as offering opportunities for the fabrication of a wide range of different in-fiber devices. The structures discussed here are formed from a strand of pure silica glass with a regular arrangement of hollow channels extending along its entire length. The central air hole is omitted, creating a solid glass core or “lattice defect” for trapping light [1

1. P. St.J. Russell, “Photonic-crystal fibers,” IEEE J. Lightwave Technol. 24, 4729–4749 (2006), http://www.opticsinfobase.org/abstract.cfm?URI=JLT-24-12-4729. [CrossRef]

]. In the case of a hexagonal lattice of holes, such a core supports only the fundamental guided mode at all wavelengths provided the hole diameter to spacing ratio is less than ~0.4. The result is a fiber that is endlessly single-mode (ESM) and usable at all wavelengths where the glass is transparent [2

2. T. A. Birks, J. C. Knight, and P. St.J. Russell, “Endlessly single-mode photonic crystal fiber,” Opt. Lett. 22, 961–963 (1997), http://www.opticsinfobase.org/abstract.cfm?URI=ol-22-13-961. [CrossRef] [PubMed]

].

Over the past several years, methods for further enhancing the versatility of PCF have been proposed and explored. For example, fiber post-processing can be used to create longitudinal changes in core size and air filling fraction [3

3. S. G. Leon-Saval, T. A. Birks, W. J. Wadsworth, P. St.J. Russell, and M. W. Mason, “Supercontinuum generation in submicron fibre waveguides,” Opt. Express 12, 2864–2869 (2004), http://www.opticsinfobase.org/abstract.cfm?URI=oe-12-13-2864. [CrossRef] [PubMed]

, 4

4. G. Kakarantzas, T. A. Birks, and P. St.J. Russell, “Structural long-period gratings in photonic crystal fibers,” Opt. Lett. 27, 1013–1015 (2002), http://www.opticsinfobase.org/abstract.cfm?URI=ol-27-12-1013. [CrossRef]

], and the hollow channels filled with materials such as polymers [5

5. P. S. Westbrook, B. J. Eggleton, R. S. Windeler, A. Hale, T. A. Strasser, and G. L. Burdge, “Claddingmode resonances in hybrid polymer-silica microstructured optical fiber gratings,” IEEE Photon. Technol. Lett. 12, 495–497 (2000). doi: 10.1109/68.841264 [CrossRef]

], liquid crystals [6

6. T. R. Wolinski, S. Ertman, P. Lesiak, A. W. Domanski, A. Czapla, R. Dabrowski, E. Nowinowski-Kruszelnicki, and J. Wojcik, “Photonic liquid crystal fibers - a new challenge for fiber optics and liquid crystals photonics,” Opto-Electron. Rev. 14, 329–334 (2006). [CrossRef]

] or metals [7

7. X. Zhang, R. Wang, F. M. Cox, B. T. Kuhlmey, and M. C. J. Large, “Selective coating of holes in microstructured optical fiber and its application to in-fiber absorptive polarizers,” Opt. Express 15, 16270–16278 (2007), http://www.opticsinfobase.org/abstract.cfm?URI=oe-15-24-16270. [CrossRef] [PubMed]

, 8

8. J. Hou, D. Bird, A. George, S. Maier, B. T. Kuhlmey, and J. C. Knight, “Metallic mode confinement in microstructured fibres,” Opt. Express 16, 5983–5990 (2008), http://www.opticsinfobase.org/abstract.cfm?URI=oe-16-9-5983. [CrossRef] [PubMed]

]. High pressure chemical vapor deposition has been used to deposit Ge wires of diameter 5 µm in PCF [9

9. D. J. Won, M. O. Ramirez, H. Kang, V. Gopalan, N. F. Baril, J. Calkins, J. V. Badding, and P. J. A. Sazio, “All-optical modulation of laser light in amorphous silicon-filled microstructured optical fibers,” Appl. Phys. Lett. 91, 161112 (2007), http://link.aip.org/link/?APPLAB/91/161112/1. [CrossRef]

]. We recently reported that arrays of high quality metallic nanowires can be formed by pumping molten gold and silver into the hollow channels [10

10. M. A. Schmidt, L. N. P. Sempere, H. K. Tyagi, C. G. Poulton, and P. St.J. Russell, “Waveguiding and plasmon resonances in two-dimensional photonic lattices of gold and silver nanowires,” Phys. Rev. B 77, 033417 (2008), http://link.aps.org/abstract/PRB/v77/e033417. [CrossRef]

, 11

11. H. W. Lee, M. A. Schmidt, H. K. Tyagi, L. N. Prill Sempere, and P. St.J. Russell, “Polarization-dependent coupling to plasmon modes on submicron gold wire in photonic crystal fiber,” Appl. Phys. Lett. 93, 111102 (2008), http://link.aip.org/link/?APPLAB/93/111102/1.

]. Coupling into guided plasmon modes on these metallic nanowires was shown to occur at wavelengths where the modes of both glass core and nanowire are phase-matched. In this Letter we report on the material and optical properties of PCFs filled with germanium, a material that can provide electrical conductance together with low-loss guidance in the mid-IR, at the same time potentially allowing construction of different kinds of in-fiber detector and sensor. The fabrication procedure involved selective hole closure followed by pumping in molten Ge at high pressure [12

12. M. A. Schmidt, H. K. Tyagi, L. N. Prill Sempere, and P. St.J. Russell, “Polarization properties of PCF with Ge-nanowire,” in CLEO (Optical Society of America, San Jose, 2008), http://www.opticsinfobase.org/abstract.cfm?URI=CLEO-2008-CFO4.

]. As we shall show, the resulting wires are of high purity and excellent optical quality.

Fig. 1. (a) Scanning electron micrograph (SEM) of a PCF in which two channels 600 nm in diameter (at each end of the rectangular core) have been filled with Ge. (b) SEM of an ESM-PCF with a single Ge-wire adjacent to its glass core (hole spacing 2.90 µm, hole diameter 1.7 µm).

2. Sample preparation and material characterization

Before filling with Ge, the PCFs were thermally processed so as to close all holes except selected ones on the fiber end-face. The procedure involved a combination of hole-blockage (using polymeric glue) and in-hole pressure at the softening temperature of the glass. Pure Ge was then pumped into the remaining open holes at a pressure of ~60 bar and a temperature of ~1000°C. To avoid oxidation of Ge at these temperatures, the pressure cell was continuously flushed with argon. Filled lengths of a few cm were routinely achieved. Fig. 1 shows scanning electron micrographs (SEMs) of the cross-sectional microstructure of two such filled PCFs, one with a pair of wires 600 nm in diameter, and the other with a single wire of diameter 1.7 µm, adjacent to the core.

2.1 Conductivity

To check the quality of the wires, the electrical conductivity was measured by placing the end-faces of a 2.2 cm long sample of the two-wire PCF into liquid Ga and measuring its resistance with a Hewlett-Packard 4339A meter. These measurements yielded a resistivity of 49 Ω.cm, compared to 47 Ω.cm for pure undoped crystalline Ge [13

13. E. M. Conwell, “Properties of silicon and germanium,” PROC. of the I.R.E. 40, 1327–1337 (1952). [CrossRef]

]. The slightly lower conductivity we attribute to polycrystallinity, which causes trapping of charge carriers in surface states at grain boundaries, forming energy barriers against subsequent carrier motion [14

14. J. Y. W. Seto, “The electrical properties of polycrystalline silicon films,” J. Appl. Phys. 46, 5247–5254 (1975), http://link.aip.org/link/?JAPIAU/46/5247/1. [CrossRef]

].

2.2 Raman spectrum

Next, a micro-Raman spectrometer (Jobin Yvon LabRAM HR 800) was used to probe a Ge wire (diameter 1.9 µm) at a sequence of different positions along the fiber. Light from a HeNe laser (wavelength 632.8 nm) was focused through the cladding with a 100× objective and the back-scattered light was coupled into the spectrometer. A representative spectrum is depicted in Fig. 2. At all measured positions, the spectra showed a highly symmetric peak at around 298 cm-1, which corresponds to the transverse optical (TO) Raman-active mode of the Ge crystal. The position of the peak is shifted to lower frequency by ~2 cm-1 compared to bulk single-crystal Ge, which has a Raman shift of 300 cm-1 [15

15. C. E. Finlayson, A. Amezcua-Correa, P. J. A. Sazio, N. F. Baril, and J. V. Badding, “Electrical and Raman characterization of silicon and germanium-filled microstructured optical fibers,” Appl. Phys. Lett. 90, 132110 (2007), http://link.aip.org/link/?APPLAB/90/132110/1. [CrossRef]

, 16

16. J. H. Parker, D. W. Feldman, and M. Ashkin, “Raman scattering by silicon and germanium,” Phys. Rev. 155, 712–714 (1967), http://link.aps.org/abstract/PR/v155/p712. [CrossRef]

]. Since the TO peak in amorphous Ge is located at a yet lower frequency (~270 cm-1), and displays a characteristic shoulder on its low-frequency side [17

17. J. S. Lannin, N. Maley, and S. T. Kshirsagar, “Raman scattering and short range order in amorphous germanium,” Solid State Commun. 53, 939–942 (1985). doi: 10.1016/0038-1098(85)90464-8 [CrossRef]

, 18

18. N. Maley and J. S. Lannin, “Raman coupling-parameter variation in amorphous germanium,” Phys. Rev. B 35, 2456–2459 (1987), http://link.aps.org/abstract/PRB/v35/p2456. [CrossRef]

], it seems likely that the Ge in our samples has a high degree of crystallinity. In addition, the measured TO-peak has a width (~3.6 cm-1) only slightly wider than that of single crystal Ge (2.4 cm-1), and much narrower than for amorphous Ge (>50 cm-1) [16

16. J. H. Parker, D. W. Feldman, and M. Ashkin, “Raman scattering by silicon and germanium,” Phys. Rev. 155, 712–714 (1967), http://link.aps.org/abstract/PR/v155/p712. [CrossRef]

], which further supports this conclusion.

Fig. 2. Micro-Raman spectrum taken through the side of a capillary containing a Ge wire of diameter 1.9 µm.

3. Optical set-up

The set-up used to measure the transmission spectrum of light guided in the glass core of Ge-filled PCF is shown in Fig. 3. Since the transmission losses were extremely high when all holes were filled, only a single hole adjacent to the glass-core was filled with Ge. This was sufficient to produce strong spectral and polarization-dependent changes in the transmitted signal. Fig. 1(b) shows an SEM of the sample used in the experiments. Optical measurements were performed after cleaving away the thermally-processed section close to the end-face of the fiber, resulting in a few cm of PCF filled with a single Ge wire.

Light from a PCF-based supercontinuum source (400-1600 nm) was launched into the unfilled end of the Ge-PCF using an achromatic 40× microscope objective. Since the unfilled section of ESM-PCF supports only one guided core-mode at all wavelengths, the launching conditions into the Ge-filled section are well-defined and reproducible, although there is the possibility that higher order modes might be excited by imperfections at the filled/unfilled transition. At the output end of the Ge-PCF, light was collected using a second achromatic objective and passed through a broad-band polarizer to allow selection of specific output polarization states. We define x-polarization as the state when light is polarized along the axis joining the center of the PCF with the center of the wire (Fig. 1(b)). Light of a desired polarization can be selected by rotating the output polarizer. Finally, the output was coupled into an optical spectrum analyzer. Polarization-dependent measurements of the transmission were performed by rotating the output polarizer to different angles and recording the respective spectrum. Each individual spectrum was normalized to that of an unfilled ESM-PCF measured at the same angle.

Fig. 3. Schematic diagram of optical measurement setup (L: Nd-YAG microchip laser; SCF: 20 cm long endlessly-single mode fiber for supercontinuum generation; MO: 40× microscope objective; MO1: 20× microscope objective; PL: broad-band polarizer; M: mirrors; OSA: optical spectrum analyzer; MS: microscope slide with index-matching oil to strip off cladding modes).

4. Results

The experimental results were compared to numerical solutions obtained using a commercially available finite-element solver (JCMWave). The simulations were for an ideal structure with identical equally-spaced circular holes. Data for the complex-valued dielectric constant of Ge was taken from the literature [19

19. H. R. Philipp and E. A. Taft, “Optical constants of germanium in the region 1 to 10 eV,” Phys. Rev. 113, 1002–1005 (1959), http://link.aps.org/abstract/PR/v113/p1002. [CrossRef]

] and the Sellmeier expansion was used for the refractive index of silica [20

20. G. P. Agrawal, Nonlinear Fiber Optics (Academic Press, San Diego, 2007).

]. The finite-element simulations produce a large number of modes, only one of which has a field distribution in the glass-core that corresponds to a fundamental mode. This mode was selected and used in the comparisons with experiment.

4.1 Transmission in the range 500 to 1050 nm

In Fig. 5, Tx/Ty (expressed in dB) is plotted as a function of wavelength for a sample length of 1.7 mm. The transmission at fixed wavelength (950 nm) is plotted as a function of analyzer angle in the inset of Fig. 5. It drops rapidly to a minimum at as the pure x-polarized state is approached.

Fig. 4. Experimental (a) and modeled (b) transmission spectra for x- and y-polarization (Tx and Ty) in a PCF with a single Ge wire (diameter 1.7 µm; length 0.8 mm) positioned adjacent to the glass core. The inset in (a) is a CCD image of the transmitted mode pattern for y-polarization. In the simulations, the fundamental mode of the glass core was selected from the numerical solutions. A calculated example of this mode at wavelength 550 nm is depicted in the inset of (b), showing the axial component of the Poynting vector (y-polarization).

The transmission ratio also increases at longer wavelengths, reaching a maximum of 28 dB at around 850 nm. This high value can be explained by the fact that the power absorbed at the surface of a conductor is proportional to the tangential magnetic field inside the conductor (H parallel to surface) [21

21. J. D. Jackson, Classical Electrodynamics (John Wiley & Sons, New York, 1998).

]. For x-polarization, the tangential magnetic field in the wire is much stronger than in the orthogonal case. Since Ge has finite conductivity at optical frequencies, higher losses are expected for x-polarized light. Apart from some weak features, the transmission in this wavelength range is quite flat without any pronounced dips, suggesting that the structure could be used as an in-fiber polarizer.

4.2 Transmission in the range 1050 to 1500 nm

Measured and simulated loss spectra for x- and y- polarization in the wavelength range 1050 to 1500 nm are shown in Fig. 6, normalized to those of an unfilled fiber. The spectra display multiple pronounced peaks, caused by coupling of the glass-core mode to successive resonances on the Ge wire. These peaks occur at wavelengths where the dispersion curves for the wire-resonances and PCF core-mode anti-cross, causing light to couple strongly to the Ge wire and enhancing the loss. The modes guided in the glass-core have effective phase indices that lie below that of silica and above that of the fundamental space-filling mode (FSM) in the PCF cladding, which means that the anti-crossings occur at Mie resonances on the wire. By comparing the axial Poynting vector distributions inside the wire at each anti-crossing wavelength (calculated using the finite-element code) with those at resonances in an isolated Ge-wire embedded in silica, the resonance order could be identified. Three such examples are shown in Fig. 7. At longer wavelengths, when coupling to the Mie resonances is stronger, the mode patterns differ more noticeably, although it is still possible to identify the mode order accurately.

Fig. 5. Ratio (in dB) between minimum (x-pol.) and maximum (y-pol.) transmission as a function of wavelength. The inset depicts the transmission versus analyzer angle at a fixed wavelength (λ 0=950 nm). Sample length 1.7 mm.

The experimental positions of the transmission dips agree with finite-element simulations to within 1%, despite the idealized structure used in the simulations and uncertainties in the value of the Ge dielectric function in the IR (especially Im(εGe)). The dips for orthogonal polarizations are not always located at the same position, indicating that the mode coupling is somewhat polarization-dependent. This is especially clear for the loss peaks marked TM05 and TE05 in Fig. 6; for x-polarization, this peak appears at around 1206 nm whereas for y-polarization it is at 1182 nm.

Fig. 6. Loss of a PCF with a single Ge wire (length 0.8 mm) adjacent to the core. The red curves are simulations (fundamental glass-core mode) and the black are experiments. The labels on the loss peaks refer to the resonances on the Ge wire that phase-match to the glass-core mode. (a) x-polarization. (b) y-polarization. The three encircled points correspond to the modes whose Poynting vector distributions are shown in Fig. 7.

It is noticeable that for y-polarization the loss peak near 1450 nm is not clearly resolved in the experiments (Fig. 6(b)). As discussed earlier, we believe this is because light guided in higher-order glass-core modes contributes significantly to the overall measured transmission at longer wavelengths, masking the loss peak for the fundamental mode. The calculated TE04 and TM04 modes show a spectral splitting that is weakly present only in the experimental x-polarized spectrum.

Fig. 7. Axial Poynting vector distributions in vicinity of Ge-wire (a-c) in PCF, calculated using finite-element modelling and (d-f) for Ge wire embedded in silica, calculated by directly solving Maxwell’s equations for Mie resonances on the wire. The wire radius in both cases is R=0.85 µm. The calculations refer to the three points marked by small blue circles in Fig. 6: (a) and (d) are at wavelength 1110 nm for y-polarization, resonance order EH16; (b) and (e) are at wavelength 1201 nm for x-polarization, resonance order TM05; (c) and (f) are at wavelength 1397 nm for x-polarization, resonance order HE24. In (d-f), the fields outside the wire (since the resonance is unbound, these grow in amplitude) have been removed from the plot so as to highlight the internal field patterns.

5. Discussion and toy model

Fig. 8. (a) Loss in dB/mm of the fundamental TE and TM guided modes in a silica layer 4 µm thick, placed adjacent to a Ge layer 1 µm thick, sandwiched between transparent cladding regions of index 1.35. The full dispersion of Ge and silica is included. The main features are qualitatively very similar to those seen for Ge-filled PCF: loss peaks at wavelengths beyond 900 nm, much higher loss for the TM mode, and a gradual reduction in average loss at shorter wavelengths. (b) Modulus squared of the electric field for the four modes marked A, B, C and D in (a). The presence of a resonance in the Ge layer causes the loss to peak strongly (B and D). In between resonances, the loss falls below its average value. At wavelengths below 900 nm, the loss in the Ge is so high that resonances cannot form, resulting in an absence of strong loss peaks.

6. Temperature dependence of loss peaks

Next, finite-element calculations, including the temperature dependence of the dielectric functions for both Ge and silica, were used to evaluate the slope dλ/dT for the resonances. The simulations yielded slopes of 0.36 nm/K, 0.30 nm/K and 0.37 nm/K for the TE05, EH15 and EH24 modes respectively, and show that the shift is almost entirely due to the temperature dependence of Ge (i.e., the contribution from silica is negligible). That these values are higher than the experimental ones (see the plot in Fig. 9), we attribute to temperature-dependent changes in stress in the composite Ge:silica structure. This is quite likely to be the case, since Ge expands when it solidifies from the liquid state [23

23. G. K. Teal and J. B. Little, “Growth of Ge single crystals,” Phys. Rev. 78, 647 (1950).

].

Although a thorough assessment of Ge-filled PCF as a fiber-based thermometer belongs in a separate paper, it is perhaps worthwhile to compare its measured sensitivity with that obtained in other fiber-based devices. Bragg grating sensors provide ~0.01 nm/K [24

24. J. Jung, H. Nam, B. H. Lee, J. O. Byun, and N. S Kim, “Fiber Bragg grating temperature sensor with controllable sensitivity,” Appl. Opt. 38, 2752–2754 (1999), http://www.opticsinfobase.org/abstract.cfm?URI=ao-38-13-2752. [CrossRef]

], and long-period gratings are somewhat more sensitive, yielding ~0.1 nm/K [25

25. V. Bhatia and A. M. Vengsarkar, “Optical fiber long-period grating sensors,” Opt. Lett. 21, 692–694 (1996), http://www.opticsinfobase.org/abstract.cfm?URI=ol-21-9-692. [CrossRef] [PubMed]

, 26

26. G. Rego, O. Okhotnikov, E. Dianov, and V. Sulimov, “High-temperature stability of long-period fiber gratings produced using an electric arc,” J. Lightwave Technol. 19, 1574–1579 (2001), http://www.opticsinfobase.org/abstract.cfm?URI=JLT-19-10-1574. [CrossRef]

]. The use of hybrid structures can enhance the sensitivity considerably in each case, up to 19 nm/K (over a <2 K range) in the case of long-period gratings in standard fiber [27

27. S. W. James and R. P. Tatam, “Optical fibre long-period grating sensors: characteristics and applications,” Meas. Sci. Technol. 14, R49–R61 (2003). doi: 10.1088/0957-0233/14/5/201 [CrossRef]

] and ~10 nm/K in hollow-core PCF filled with fluids or liquid crystals [28

28. D. Noordegraaf, L. Scolari, J. Lægsgaard, L. Rindorf, and T. T. Alkeskjold, “Electrically and mechanically induced long period gratings in liquid crystal photonic bandgap fibers,” Opt. Express 15, 7901–7912 (2007), http://www.opticsinfobase.org/abstract.cfm?URI=oe-15-13-7901. [CrossRef] [PubMed]

, 29

29. P. Steinvurzel, E. D. Moore, E. C. Mägi, and B. J. Eggleton, “Tuning properties of long period gratings in photonic bandgap fibers,” Opt. Lett. 31, 2103–2105 (2006), http://www.opticsinfobase.org/abstract.cfm?URI=ol-31-14-2103. [CrossRef] [PubMed]

], although the temperature range over which such hybrid devices operate is often quite restricted. Device length is also an important consideration, and here the 0.8 mm long Ge-silica device leads the field. For comparable sensitivities, it is between 10 and 100 times shorter than the Bragg grating and long-period grating devices reported in the literature, which are typically between 1 and 10 cm long.

Fig. 9. Measured relative spectral shift of the position of three of the resonance peaks in Fig. 6(b), plotted versus temperature, for y-polarization. The slopes of the fitted linear curves are shown in units of nm/K.

7. Conclusions

Ge wires of high material and optical quality can be produced by pumping molten Ge into the hollow channels of silica-air PCF. In ESM-PCF, the presence of a single Ge wire placed adjacent to the core renders the waveguide birefringent, causing strongly polarization-dependent transmission losses (~30 dB at 850 nm). In the IR (900 to 1500 nm), anti-crossings between the glass-core mode and Mie resonances on the Ge wire are seen at a series of different wavelengths, resulting in clear dips in the signal transmitted through the fiber. In the range 500 to 900 nm the high absorption in Ge prevents the formation of resonances. In both cases, the transmission loss is much higher for electric field polarized along the x-axis (joining the glass core and the Ge wire), and the device operates as an effective broad-band polarizer for wavelengths <900 nm. The loss peaks in the IR move to longer wavelength at a rate of ~0.2 nm/K, suggesting that the structure could form the basis for a new kind of in-fiber thermometer. Numerical simulations based on finite-element modeling show excellent agreement with the experimental results in all cases.

Acknowledgment

The authors are grateful to Dr.-Ing. Gerhard Frank (Institute of Microcharacterisation and Central Facility for High-Resolution Electron Microscopy at the University of Erlangen-Nuremberg) for measuring the micro-Raman spectra.

References and links

1.

P. St.J. Russell, “Photonic-crystal fibers,” IEEE J. Lightwave Technol. 24, 4729–4749 (2006), http://www.opticsinfobase.org/abstract.cfm?URI=JLT-24-12-4729. [CrossRef]

2.

T. A. Birks, J. C. Knight, and P. St.J. Russell, “Endlessly single-mode photonic crystal fiber,” Opt. Lett. 22, 961–963 (1997), http://www.opticsinfobase.org/abstract.cfm?URI=ol-22-13-961. [CrossRef] [PubMed]

3.

S. G. Leon-Saval, T. A. Birks, W. J. Wadsworth, P. St.J. Russell, and M. W. Mason, “Supercontinuum generation in submicron fibre waveguides,” Opt. Express 12, 2864–2869 (2004), http://www.opticsinfobase.org/abstract.cfm?URI=oe-12-13-2864. [CrossRef] [PubMed]

4.

G. Kakarantzas, T. A. Birks, and P. St.J. Russell, “Structural long-period gratings in photonic crystal fibers,” Opt. Lett. 27, 1013–1015 (2002), http://www.opticsinfobase.org/abstract.cfm?URI=ol-27-12-1013. [CrossRef]

5.

P. S. Westbrook, B. J. Eggleton, R. S. Windeler, A. Hale, T. A. Strasser, and G. L. Burdge, “Claddingmode resonances in hybrid polymer-silica microstructured optical fiber gratings,” IEEE Photon. Technol. Lett. 12, 495–497 (2000). doi: 10.1109/68.841264 [CrossRef]

6.

T. R. Wolinski, S. Ertman, P. Lesiak, A. W. Domanski, A. Czapla, R. Dabrowski, E. Nowinowski-Kruszelnicki, and J. Wojcik, “Photonic liquid crystal fibers - a new challenge for fiber optics and liquid crystals photonics,” Opto-Electron. Rev. 14, 329–334 (2006). [CrossRef]

7.

X. Zhang, R. Wang, F. M. Cox, B. T. Kuhlmey, and M. C. J. Large, “Selective coating of holes in microstructured optical fiber and its application to in-fiber absorptive polarizers,” Opt. Express 15, 16270–16278 (2007), http://www.opticsinfobase.org/abstract.cfm?URI=oe-15-24-16270. [CrossRef] [PubMed]

8.

J. Hou, D. Bird, A. George, S. Maier, B. T. Kuhlmey, and J. C. Knight, “Metallic mode confinement in microstructured fibres,” Opt. Express 16, 5983–5990 (2008), http://www.opticsinfobase.org/abstract.cfm?URI=oe-16-9-5983. [CrossRef] [PubMed]

9.

D. J. Won, M. O. Ramirez, H. Kang, V. Gopalan, N. F. Baril, J. Calkins, J. V. Badding, and P. J. A. Sazio, “All-optical modulation of laser light in amorphous silicon-filled microstructured optical fibers,” Appl. Phys. Lett. 91, 161112 (2007), http://link.aip.org/link/?APPLAB/91/161112/1. [CrossRef]

10.

M. A. Schmidt, L. N. P. Sempere, H. K. Tyagi, C. G. Poulton, and P. St.J. Russell, “Waveguiding and plasmon resonances in two-dimensional photonic lattices of gold and silver nanowires,” Phys. Rev. B 77, 033417 (2008), http://link.aps.org/abstract/PRB/v77/e033417. [CrossRef]

11.

H. W. Lee, M. A. Schmidt, H. K. Tyagi, L. N. Prill Sempere, and P. St.J. Russell, “Polarization-dependent coupling to plasmon modes on submicron gold wire in photonic crystal fiber,” Appl. Phys. Lett. 93, 111102 (2008), http://link.aip.org/link/?APPLAB/93/111102/1.

12.

M. A. Schmidt, H. K. Tyagi, L. N. Prill Sempere, and P. St.J. Russell, “Polarization properties of PCF with Ge-nanowire,” in CLEO (Optical Society of America, San Jose, 2008), http://www.opticsinfobase.org/abstract.cfm?URI=CLEO-2008-CFO4.

13.

E. M. Conwell, “Properties of silicon and germanium,” PROC. of the I.R.E. 40, 1327–1337 (1952). [CrossRef]

14.

J. Y. W. Seto, “The electrical properties of polycrystalline silicon films,” J. Appl. Phys. 46, 5247–5254 (1975), http://link.aip.org/link/?JAPIAU/46/5247/1. [CrossRef]

15.

C. E. Finlayson, A. Amezcua-Correa, P. J. A. Sazio, N. F. Baril, and J. V. Badding, “Electrical and Raman characterization of silicon and germanium-filled microstructured optical fibers,” Appl. Phys. Lett. 90, 132110 (2007), http://link.aip.org/link/?APPLAB/90/132110/1. [CrossRef]

16.

J. H. Parker, D. W. Feldman, and M. Ashkin, “Raman scattering by silicon and germanium,” Phys. Rev. 155, 712–714 (1967), http://link.aps.org/abstract/PR/v155/p712. [CrossRef]

17.

J. S. Lannin, N. Maley, and S. T. Kshirsagar, “Raman scattering and short range order in amorphous germanium,” Solid State Commun. 53, 939–942 (1985). doi: 10.1016/0038-1098(85)90464-8 [CrossRef]

18.

N. Maley and J. S. Lannin, “Raman coupling-parameter variation in amorphous germanium,” Phys. Rev. B 35, 2456–2459 (1987), http://link.aps.org/abstract/PRB/v35/p2456. [CrossRef]

19.

H. R. Philipp and E. A. Taft, “Optical constants of germanium in the region 1 to 10 eV,” Phys. Rev. 113, 1002–1005 (1959), http://link.aps.org/abstract/PR/v113/p1002. [CrossRef]

20.

G. P. Agrawal, Nonlinear Fiber Optics (Academic Press, San Diego, 2007).

21.

J. D. Jackson, Classical Electrodynamics (John Wiley & Sons, New York, 1998).

22.

L. Vina, S. Logothetidis, and M. Cardona, “Temperature dependence of the dielectric function of germanium,” Phys. Rev. B 30, 1979–1991 (1984), http://link.aps.org/abstract/PRB/v30/p1979. [CrossRef]

23.

G. K. Teal and J. B. Little, “Growth of Ge single crystals,” Phys. Rev. 78, 647 (1950).

24.

J. Jung, H. Nam, B. H. Lee, J. O. Byun, and N. S Kim, “Fiber Bragg grating temperature sensor with controllable sensitivity,” Appl. Opt. 38, 2752–2754 (1999), http://www.opticsinfobase.org/abstract.cfm?URI=ao-38-13-2752. [CrossRef]

25.

V. Bhatia and A. M. Vengsarkar, “Optical fiber long-period grating sensors,” Opt. Lett. 21, 692–694 (1996), http://www.opticsinfobase.org/abstract.cfm?URI=ol-21-9-692. [CrossRef] [PubMed]

26.

G. Rego, O. Okhotnikov, E. Dianov, and V. Sulimov, “High-temperature stability of long-period fiber gratings produced using an electric arc,” J. Lightwave Technol. 19, 1574–1579 (2001), http://www.opticsinfobase.org/abstract.cfm?URI=JLT-19-10-1574. [CrossRef]

27.

S. W. James and R. P. Tatam, “Optical fibre long-period grating sensors: characteristics and applications,” Meas. Sci. Technol. 14, R49–R61 (2003). doi: 10.1088/0957-0233/14/5/201 [CrossRef]

28.

D. Noordegraaf, L. Scolari, J. Lægsgaard, L. Rindorf, and T. T. Alkeskjold, “Electrically and mechanically induced long period gratings in liquid crystal photonic bandgap fibers,” Opt. Express 15, 7901–7912 (2007), http://www.opticsinfobase.org/abstract.cfm?URI=oe-15-13-7901. [CrossRef] [PubMed]

29.

P. Steinvurzel, E. D. Moore, E. C. Mägi, and B. J. Eggleton, “Tuning properties of long period gratings in photonic bandgap fibers,” Opt. Lett. 31, 2103–2105 (2006), http://www.opticsinfobase.org/abstract.cfm?URI=ol-31-14-2103. [CrossRef] [PubMed]

OCIS Codes
(230.0230) Optical devices : Optical devices
(160.4236) Materials : Nanomaterials
(060.5295) Fiber optics and optical communications : Photonic crystal fibers
(250.5403) Optoelectronics : Plasmonics

ToC Category:
Photonic Crystal Fibers

History
Original Manuscript: June 19, 2008
Revised Manuscript: August 25, 2008
Manuscript Accepted: October 10, 2008
Published: October 13, 2008

Citation
H. K. Tyagi, M. A. Schmidt, L. Prill Sempere, and P. S. Russell, "Optical properties of photonic crystal fiber with integral micron-sized Ge wire," Opt. Express 16, 17227-17236 (2008)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-16-22-17227


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References

  1. P. St.J. Russell, "Photonic-crystal fibers," IEEE J. Lightwave Technol. 24, 4729-4749 (2006), http://www.opticsinfobase.org/abstract.cfm?URI=JLT-24-12-4729. [CrossRef]
  2. T. A. Birks, J. C. Knight, and P. St.J. Russell, "Endlessly single-mode photonic crystal fiber," Opt. Lett. 22, 961-963 (1997), http://www.opticsinfobase.org/abstract.cfm?URI=ol-22-13-961. [CrossRef] [PubMed]
  3. S. G. Leon-Saval, T. A. Birks, W. J. Wadsworth, P. St.J. Russell, and M. W. Mason, "Supercontinuum generation in submicron fibre waveguides," Opt. Express 12, 2864-2869 (2004), http://www.opticsinfobase.org/abstract.cfm?URI=oe-12-13-2864. [CrossRef] [PubMed]
  4. G. Kakarantzas, T. A. Birks, and P. St.J. Russell, "Structural long-period gratings in photonic crystal fibers," Opt. Lett. 27, 1013-1015 (2002), http://www.opticsinfobase.org/abstract.cfm?URI=ol-27-12-1013. [CrossRef]
  5. 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, 495-497 (2000). doi: 10.1109/68.841264 [CrossRef]
  6. T. R. Wolinski, S. Ertman, P. Lesiak, A. W. Domanski, A. Czapla, R. Dabrowski, E. Nowinowski-Kruszelnicki, and J. Wojcik, "Photonic liquid crystal fibers - a new challenge for fiber optics and liquid crystals photonics," Opto-Electron. Rev. 14, 329-334 (2006). [CrossRef]
  7. X. Zhang, R. Wang, F. M. Cox, B. T. Kuhlmey, and M. C. J. Large, "Selective coating of holes in microstructured optical fiber and its application to in-fiber absorptive polarizers," Opt. Express 15, 16270-16278 (2007), http://www.opticsinfobase.org/abstract.cfm?URI=oe-15-24-16270. [CrossRef] [PubMed]
  8. J. Hou, D. Bird, A. George, S. Maier, B. T. Kuhlmey, and J. C. Knight, "Metallic mode confinement in microstructured fibres," Opt. Express 16, 5983-5990 (2008), http://www.opticsinfobase.org/abstract.cfm?URI=oe-16-9-5983. [CrossRef] [PubMed]
  9. D. J. Won, M. O. Ramirez, H. Kang, V. Gopalan, N. F. Baril, J. Calkins, J. V. Badding, and P. J. A. Sazio, "All-optical modulation of laser light in amorphous silicon-filled microstructured optical fibers," Appl. Phys. Lett. 91, 161112 (2007), http://link.aip.org/link/?APPLAB/91/161112/1. [CrossRef]
  10. M. A. Schmidt, L. N. P. Sempere, H. K. Tyagi, C. G. Poulton, and P. St.J. Russell, "Waveguiding and plasmon resonances in two-dimensional photonic lattices of gold and silver nanowires," Phys. Rev. B 77, 033417 (2008), http://link.aps.org/abstract/PRB/v77/e033417. [CrossRef]
  11. H. W. Lee, M. A. Schmidt, H. K. Tyagi, L. N. Prill Sempere, and P. St.J. Russell, "Polarization-dependent coupling to plasmon modes on submicron gold wire in photonic crystal fiber," Appl. Phys. Lett. 93, 111102 (2008), http://link.aip.org/link/?APPLAB/93/111102/1.
  12. M. A. Schmidt, H. K. Tyagi, L. N. Prill Sempere, and P. St.J. Russell, "Polarization properties of PCF with Ge-nanowire," in CLEO (Optical Society of America, San Jose, 2008), http://www.opticsinfobase.org/abstract.cfm?URI=CLEO-2008-CFO4.
  13. E. M. Conwell, "Properties of silicon and germanium," PROC. of the I.R.E. 40, 1327-1337 (1952). [CrossRef]
  14. J. Y. W. Seto, "The electrical properties of polycrystalline silicon films," J. Appl. Phys. 46, 5247-5254 (1975), http://link.aip.org/link/?JAPIAU/46/5247/1. [CrossRef]
  15. C. E. Finlayson, A. Amezcua-Correa, P. J. A. Sazio, N. F. Baril, and J. V. Badding, "Electrical and Raman characterization of silicon and germanium-filled microstructured optical fibers," Appl. Phys. Lett. 90, 132110 (2007), http://link.aip.org/link/?APPLAB/90/132110/1. [CrossRef]
  16. J. H. ParkerJr., D. W. Feldman, and M. Ashkin, "Raman scattering by silicon and germanium," Phys. Rev. 155, 712-714 (1967), http://link.aps.org/abstract/PR/v155/p712. [CrossRef]
  17. J. S. Lannin, N. Maley, and S. T. Kshirsagar, "Raman scattering and short range order in amorphous germanium," Solid State Commun. 53, 939-942 (1985). doi: 10.1016/0038-1098(85)90464-8 [CrossRef]
  18. N. Maley and J. S. Lannin, "Raman coupling-parameter variation in amorphous germanium," Phys. Rev. B 35, 2456-2459 (1987), http://link.aps.org/abstract/PRB/v35/p2456. [CrossRef]
  19. H. R. Philipp and E. A. Taft, "Optical constants of germanium in the region 1 to 10 eV," Phys. Rev. 113, 1002-1005 (1959), http://link.aps.org/abstract/PR/v113/p1002. [CrossRef]
  20. G. P. Agrawal, Nonlinear Fiber Optics (Academic Press, San Diego, 2007).
  21. J. D. Jackson, Classical Electrodynamics (John Wiley & Sons, New York, 1998).
  22. L. Vina, S. Logothetidis, and M. Cardona, "Temperature dependence of the dielectric function of germanium," Phys. Rev. B 30, 1979-1991 (1984), http://link.aps.org/abstract/PRB/v30/p1979. [CrossRef]
  23. G. K. Teal and J. B. Little, "Growth of Ge single crystals," Phys. Rev. 78, 647 (1950).
  24. J. Jung, H. Nam, B. H. Lee, J. O. Byun, and N. S Kim, "Fiber Bragg grating temperature sensor with controllable sensitivity," Appl. Opt. 38, 2752-2754 (1999), http://www.opticsinfobase.org/abstract.cfm?URI=ao-38-13-2752. [CrossRef]
  25. V. Bhatia and A. M. Vengsarkar, "Optical fiber long-period grating sensors," Opt. Lett. 21, 692-694 (1996), http://www.opticsinfobase.org/abstract.cfm?URI=ol-21-9-692. [CrossRef] [PubMed]
  26. G. Rego, O. Okhotnikov, E. Dianov, and V. Sulimov, "High-temperature stability of long-period fiber gratings produced using an electric arc," J. Lightwave Technol. 19, 1574-1579 (2001), http://www.opticsinfobase.org/abstract.cfm?URI=JLT-19-10-1574. [CrossRef]
  27. S. W. James and R. P. Tatam, "Optical fibre long-period grating sensors: characteristics and applications," Meas. Sci. Technol. 14, R49-R61 (2003). doi: 10.1088/0957-0233/14/5/201 [CrossRef]
  28. D. Noordegraaf, L. Scolari, J. Lægsgaard, L. Rindorf, and T. T. Alkeskjold, "Electrically and mechanically induced long period gratings in liquid crystal photonic bandgap fibers," Opt. Express 15, 7901-7912 (2007), http://www.opticsinfobase.org/abstract.cfm?URI=oe-15-13-7901. [CrossRef] [PubMed]
  29. P. Steinvurzel, E. D. Moore, E. C. Mägi, and B. J. Eggleton, "Tuning properties of long period gratings in photonic bandgap fibers," Opt. Lett. 31, 2103-2105 (2006), http://www.opticsinfobase.org/abstract.cfm?URI=ol-31-14-2103. [CrossRef] [PubMed]

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