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Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 22, Iss. 15 — Jul. 28, 2014
  • pp: 17890–17896
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Multifunctional optical nanofiber polarization devices with 3D geometry

Jin-hui Chen, Ye Chen, Wei Luo, Jun-long Kou, Fei Xu, and Yan-qing Lu  »View Author Affiliations


Optics Express, Vol. 22, Issue 15, pp. 17890-17896 (2014)
http://dx.doi.org/10.1364/OE.22.017890


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Abstract

Here a reliable fabrication process enabling the integration of multiple functions in a single rod with one optical nano/microfiber (ONM) was proposed, which represents a further step in the “lab-on-a-rod” technology roadmap. With a unique 3D geometry, the all-fiber in-line devices based on lab-on-a-rod techniques have more freedom and potential for compactness and functionality than conventional fiber devices. With the hybrid polymer–metal–dielectric nanostructure, the coupling between the plasmonic and waveguide modes leads to hybridization of the fundamental mode and polarization-dependent loss. By functionalizing the rod surface with a nanoscale silver film and tuning the coil geometry, a broadband polarizer and single-polarization resonator, respectively, were demonstrated. The polarizer has an extinction ratio of more than 20 dB over a spectral range of 450 nm. The resonator has a Q factor of more than 78,000 with excellent suppression of polarization noise. This type of miniature single-polarization resonator is impossible to realize by conventional fabrication processes and has wide applications in fiber communication, lasing, and especially sensing.

© 2014 Optical Society of America

1. Introduction

Maintaining and manipulating the polarization state of light are of great importance in fiber systems including communication, sensor, and laser systems. Compared with bulk polarization-controlling devices, fiber-based polarization-controlling components (PCCs) have many advantages: easier alignment, smaller insertion loss, and compatibility with fiber systems. Numerous different types of fiber PCCs have been proposed and developed over the past decades. For example, the most important PCC, the in-line fiber polarizer, can be fabricated from specialized W-profile fibers [1

1. J. Simpson, R. Stolen, F. Sears, W. Pleibel, J. MacChesney, and R. Howard, “A single-polarization fiber,” J. Lightwave Technol. 1(2), 370–374 (1983). [CrossRef]

] and hole-assisted fibers [2

2. D. A. Nolan, G. E. Berkey, M. J. Li, X. Chen, W. A. Wood, and L. A. Zenteno, “Single-polarization fiber with a high extinction ratio,” Opt. Lett. 29(16), 1855–1857 (2004). [CrossRef] [PubMed]

], or by coating a side-polished single-mode fiber (SMF) with a metallic thin film [3

3. R. B. Dyott, J. Bello, and V. A. Handerek, “Indium-coated D-shaped-fiber polarizer,” Opt. Lett. 12(4), 287–289 (1987). [CrossRef] [PubMed]

5

5. S. M. Tseng, S. P. Ma, K. F. Chen, and K. Y. Hsu, “Method for preparing fiber-optic polarizer,” US Patent 5,781,675 (1998).

], birefringent polymers [6

6. R. B. Dyott, R. Ulrich, and J. D. Meyer, “Optical fiber polarizer,” US Patent 4,589,728, (1986).

], or graphene [7

7. Q. Bao, H. Zhang, B. Wang, Z. Ni, C. H. Y. X. Lim, Y. Wang, D. Y. Tang, and K. P. Loh, “Broadband graphene polarizer,” Nat. Photon. 5(7), 411–415 (2011). [CrossRef]

]. These fabrication methods are either complicated or costly. Most of the fibers are too thick (diameter > 100 µm) to be bent into a small coil and have to be carefully kept as straight as possible to prevent additional birefringence. In real applications, different single-function PCCs have to be spliced or connected and carefully assembled as well as aligned to achieve optical performance. The system will inflate quickly and is sensitive to external perturbations such as changes in position and temperature, and bending or twisting of the fiber pigtails. Moreover, it is also very difficult to combine multiple functions in one component such as a miniature single-polarization resonator, which is important for rotation and current sensing.

2. Schematic of a polarization-related ONM Lab-on-a-rod device

Figure 1
Fig. 1 Schematic of ONM lab-on-a-rod device. The rod surface is functionalized using nanostructure. The pitches between adjacent turns can be tuned for coupling or decoupling. Multifunction integration can be realized by modifying the rod surface and turn pitches. In our experiment, the PMMA (red) rod is coated with Teflon (white) and silver (yellow) films.
illustrates the 3D structure of an ONM lab-on-a-rod device. A circular ONM is wrapped on a rod that is modified using different surface structures or materials. The rod serves only as a supporting element and can be made of any material as long as the surface is sufficiently smooth. We generally use a polymethyl methacrylate (PMMA) or silica rod. Multifunction integration can be realized by specializing the coil geometry and rod surface pattern. Here we functionalize a PMMA rod by coating it with a low-index polymer, Teflon (Teflon® AF 601S1-100-6, a production of DuPont) and a metal, silver. Teflon is first coated on the rod’s surface to smooth it and avoid loss from the surface roughness and high refractive index of the PMMA rod. The nanoscale silver film serves as a polarization-dependent absorber. The pitches between adjacent turns can be tuned for different functions. When two coils are decoupled and far from each other, no energy is exchanged between the light propagating in the coils. A broadband in-line polarizer can be realized because of the difference in propagation loss for the transverse electric (TE) and transverse magnetic (TM) modes. In contrast, when two coils are sufficiently close, a strong coupling effect leads to light traveling from one to the other, and a single-polarization ONM resonator can be formed. Here we investigate both of these two extreme cases.

3. Functionalizing of rod surface and realization of polarization functions

In our experiment, the PMMA rod (2 mm in diameter) is dipped coated with Teflon tens of micrometers in thickness. Then a thin silver film with a thickness of approximately 100 nm is deposited on the rod by physical vapor deposition. The thickness of silver film is controlled by the deposition rate and time. We use a flame-brushing technique to draw an ONM from a conventional SMF. The radius of the average ONM is around 1~2 µm. Then the ONM is wrapped (two turns) around the silver-coated rod with the aid of a microscope and a rotational stage. The pitches between adjacent turns can be controlled for coupling or decoupling.

Without loss of generality, we select numerical results at a wavelength of 1400 nm to compare with the experimental results. From Fig. 3(b), the calculated extinction ratio is 1.72 dB/mm (@1400 nm), so the total extinction ratio amounts to 21.5 dB (LONM = 12.5 mm), which shows good agreement with the experimental result (23 dB). Moreover, the extinction ratio will be increased much further as the number of turns of the ONM coil increases, and the insertion loss of the device will be inevitably increased. To some degrees, increasing the diameter of the rod is equivalent to increasing the number of ONM coils. However, if the diameter of the rod is too small and reach the critical bending radius of ONM, the bending loss of will be greatly multiplied, and a rod with smaller radius of curvature will also increase the difficulties of depositing uniform silver film.

When the adjacent coils of the ONM are sufficiently close, it forms a single-polarization single-mode resonator [13

13. R. Ismaeel, T. Lee, M. Ding, M. Belal, and G. Brambilla, “Optical microfiber passive components,” Laser Photon. Rev. 7(3), 350–384 (2013). [CrossRef]

, 14

14. X. Guo, Y. Li, X. Jiang, and L. Tong, “Demonstration of critical coupling in microfiber loops wrapped around a copper rod,” Appl. Phys. Lett. 91, 073512 (2007).

]. We carefully wrap two turns of an ONM around the silver-coated rod with the help of microscope to make sure that the coils of the ONM are close to each other for coupling, as illustrated in Fig. 5(d)
Fig. 5 Single-polarization single-mode resonator. (a) Transmission spectrum of a coil resonator as recorded from an optical spectrum analyzer. (b) Transmission spectrum around 1550 nm. Inset: The difference between TE mode and TM modes. (c) The output spectrum of TE mode and TE + TM mode, which is obtained from (b). (d) Optical image of sample, the scale bar is 20µm. The two turns of the MF were almost touching each other and formed a resonator.
. In Fig. 5(a), we showed the transmission spectra of the coil resonator for two orthogonal modes (TE and TM) as recorded from an optical spectrum analyzer. It is natural that the spectra of the two modes are separated because they suffer different propagation losses. From Fig. 5(b), we can find that around 1550 nm, the FSR is 0.24 nm, which agrees well with our theoretical calculation, and its full width at half-maximum is <0.02 nm, which is limited by the OSA resolution. Thus, the Q factor and finesse of our device are greater than 78,000 and 12, respectively. The inset of Fig. 5(b) shows the extinction ratio difference between TE and TM modes, the average value is about 10 dB. To illustrate the excellence of suppression of polarization noise of the device, we compared the output power of TE mode and TE + TM mode, as shown in Fig. 5(c). It is clearly demonstrated that the output TM mode power has little influence on TE mode even the input power for TE and TM modes are the same.

4. Conclusion

Acknowledgments

This work is supported by National 973 program under contract No. 2012CB921803 and 2011CBA00205, National Science Fund for Excellent Young Scientists Fund (61322503) and National Science Fund for Distinguished Young Scholars (61225026).The authors also acknowledge the support from PAPD and the Fundamental Research Funds for the Central Universities, and the help on FEM simulation by Prof. Xiaoshun Jiang and Xuejing Zhang.

References and links

1.

J. Simpson, R. Stolen, F. Sears, W. Pleibel, J. MacChesney, and R. Howard, “A single-polarization fiber,” J. Lightwave Technol. 1(2), 370–374 (1983). [CrossRef]

2.

D. A. Nolan, G. E. Berkey, M. J. Li, X. Chen, W. A. Wood, and L. A. Zenteno, “Single-polarization fiber with a high extinction ratio,” Opt. Lett. 29(16), 1855–1857 (2004). [CrossRef] [PubMed]

3.

R. B. Dyott, J. Bello, and V. A. Handerek, “Indium-coated D-shaped-fiber polarizer,” Opt. Lett. 12(4), 287–289 (1987). [CrossRef] [PubMed]

4.

K. Thyagarajan, S. Diggavi, A. K. Ghatak, W. Johnstone, G. Stewart, and B. Culshaw, “Thin-metal-clad waveguide polarizers: analysis and comparison with experiment,” Opt. Lett. 15(18), 1041–1043 (1990). [CrossRef] [PubMed]

5.

S. M. Tseng, S. P. Ma, K. F. Chen, and K. Y. Hsu, “Method for preparing fiber-optic polarizer,” US Patent 5,781,675 (1998).

6.

R. B. Dyott, R. Ulrich, and J. D. Meyer, “Optical fiber polarizer,” US Patent 4,589,728, (1986).

7.

Q. Bao, H. Zhang, B. Wang, Z. Ni, C. H. Y. X. Lim, Y. Wang, D. Y. Tang, and K. P. Loh, “Broadband graphene polarizer,” Nat. Photon. 5(7), 411–415 (2011). [CrossRef]

8.

Y. Chen, F. Xu, and Y. Q. Lu, “Teflon-coated microfiber resonator with weak temperature dependence,” Opt. Express 19(23), 22923–22928 (2011). [CrossRef] [PubMed]

9.

J. L. Kou, Y. Chen, F. Xu, and Y. Q. Lu, “Miniaturized broadband highly birefringent device with stereo rod-microfiber-air structure,” Opt. Express 20(27), 28431–28436 (2012). [CrossRef] [PubMed]

10.

M. Consales, A. Ricciardi, A. Crescitelli, E. Esposito, A. Cutolo, and A. Cusano, “Lab-on-fiber technology: toward multifunctional optical nanoprobes,” ACS Nano 6(4), 3163–3170 (2012). [CrossRef] [PubMed]

11.

P. B. Johnson and R.-W. Christy, “Optical constants of the noble metals,” Phys. Rev. B 6(12), 4370–4379 (1972). [CrossRef]

12.

R. F. Oulton, V. J. Sorger, D. Genov, D. Pile, and X. Zhang, “A hybrid plasmonic waveguide for subwavelength confinement and long-range propagation,” Nat. Photon. 2(8), 496–500 (2008). [CrossRef]

13.

R. Ismaeel, T. Lee, M. Ding, M. Belal, and G. Brambilla, “Optical microfiber passive components,” Laser Photon. Rev. 7(3), 350–384 (2013). [CrossRef]

14.

X. Guo, Y. Li, X. Jiang, and L. Tong, “Demonstration of critical coupling in microfiber loops wrapped around a copper rod,” Appl. Phys. Lett. 91, 073512 (2007).

15.

F. Bonaccorso, Z. Sun, T. Hasan, and A. Ferrari, “Graphene photonics and optoelectronics,” Nat. Photonics 4(9), 611–622 (2010). [CrossRef]

OCIS Codes
(060.2310) Fiber optics and optical communications : Fiber optics
(060.2340) Fiber optics and optical communications : Fiber optics components
(130.5440) Integrated optics : Polarization-selective devices

ToC Category:
Fiber Optics

History
Original Manuscript: May 26, 2014
Revised Manuscript: July 9, 2014
Manuscript Accepted: July 10, 2014
Published: July 16, 2014

Citation
Jin-hui Chen, Ye Chen, Wei Luo, Jun-long Kou, Fei Xu, and Yan-qing Lu, "Multifunctional optical nanofiber polarization devices with 3D geometry," Opt. Express 22, 17890-17896 (2014)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-22-15-17890


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References

  1. J. Simpson, R. Stolen, F. Sears, W. Pleibel, J. MacChesney, and R. Howard, “A single-polarization fiber,” J. Lightwave Technol.1(2), 370–374 (1983). [CrossRef]
  2. D. A. Nolan, G. E. Berkey, M. J. Li, X. Chen, W. A. Wood, and L. A. Zenteno, “Single-polarization fiber with a high extinction ratio,” Opt. Lett.29(16), 1855–1857 (2004). [CrossRef] [PubMed]
  3. R. B. Dyott, J. Bello, and V. A. Handerek, “Indium-coated D-shaped-fiber polarizer,” Opt. Lett.12(4), 287–289 (1987). [CrossRef] [PubMed]
  4. K. Thyagarajan, S. Diggavi, A. K. Ghatak, W. Johnstone, G. Stewart, and B. Culshaw, “Thin-metal-clad waveguide polarizers: analysis and comparison with experiment,” Opt. Lett.15(18), 1041–1043 (1990). [CrossRef] [PubMed]
  5. S. M. Tseng, S. P. Ma, K. F. Chen, and K. Y. Hsu, “Method for preparing fiber-optic polarizer,” US Patent 5,781,675 (1998).
  6. R. B. Dyott, R. Ulrich, and J. D. Meyer, “Optical fiber polarizer,” US Patent 4,589,728, (1986).
  7. Q. Bao, H. Zhang, B. Wang, Z. Ni, C. H. Y. X. Lim, Y. Wang, D. Y. Tang, and K. P. Loh, “Broadband graphene polarizer,” Nat. Photon.5(7), 411–415 (2011). [CrossRef]
  8. Y. Chen, F. Xu, and Y. Q. Lu, “Teflon-coated microfiber resonator with weak temperature dependence,” Opt. Express19(23), 22923–22928 (2011). [CrossRef] [PubMed]
  9. J. L. Kou, Y. Chen, F. Xu, and Y. Q. Lu, “Miniaturized broadband highly birefringent device with stereo rod-microfiber-air structure,” Opt. Express20(27), 28431–28436 (2012). [CrossRef] [PubMed]
  10. M. Consales, A. Ricciardi, A. Crescitelli, E. Esposito, A. Cutolo, and A. Cusano, “Lab-on-fiber technology: toward multifunctional optical nanoprobes,” ACS Nano6(4), 3163–3170 (2012). [CrossRef] [PubMed]
  11. P. B. Johnson and R.-W. Christy, “Optical constants of the noble metals,” Phys. Rev. B6(12), 4370–4379 (1972). [CrossRef]
  12. R. F. Oulton, V. J. Sorger, D. Genov, D. Pile, and X. Zhang, “A hybrid plasmonic waveguide for subwavelength confinement and long-range propagation,” Nat. Photon.2(8), 496–500 (2008). [CrossRef]
  13. R. Ismaeel, T. Lee, M. Ding, M. Belal, and G. Brambilla, “Optical microfiber passive components,” Laser Photon. Rev.7(3), 350–384 (2013). [CrossRef]
  14. X. Guo, Y. Li, X. Jiang, and L. Tong, “Demonstration of critical coupling in microfiber loops wrapped around a copper rod,” Appl. Phys. Lett.91, 073512 (2007).
  15. F. Bonaccorso, Z. Sun, T. Hasan, and A. Ferrari, “Graphene photonics and optoelectronics,” Nat. Photonics4(9), 611–622 (2010). [CrossRef]

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