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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 19, Iss. 26 — Dec. 12, 2011
  • pp: B848–B861
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Polymer microstructured optical fibers for terahertz wave guiding

Bora Ung, Anna Mazhorova, Alexandre Dupuis, Mathieu Rozé, and Maksim Skorobogatiy  »View Author Affiliations


Optics Express, Vol. 19, Issue 26, pp. B848-B861 (2011)
http://dx.doi.org/10.1364/OE.19.00B848


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Abstract

We outline the most recent technological advancements in the design, fabrication and characterization of polymer microstructured optical fibers (MOFs) for applications in the terahertz waveband. Focusing on specific experimental demonstrations, we show that polymer optical fibers provide a very flexible route towards THz wave guiding. Crucial incentives include the large variety of the low-cost and relatively low absorption loss polymers, the facile fiber preform fabrication by molding, drilling, stacking and extrusion, and finally, the simple fabrication through fiber drawing at low forming temperatures.

© 2011 OSA

1. Introduction

2. Main challenges of the plastic-based THz fiber optics

2.1 Losses

Currently, the main obstacle in the design of THz dielectric waveguides resides in the large material losses that significantly limit the waveguide transmission efficiency. Plastic materials possess some of the lowest losses in the THz; however as shown in Fig. 1(b)
Fig. 1 (a) Refractive index and (b) bulk absorption coefficient in (cm−1) of common polymers used in the fabrication of THz waveguides. Legend: low-density polyethylene (LDPE), cyclic olefin copolymer (TOPAS®), high-density polyethylene (HDPE), Poly-tetrafluoroethylene (PTFE), polycarbonate (PC), polymethyl-methacrylate (PMMA), polyimide (Kapton®), polystyrene (PS), Polypropylene (PP). Data taken from Refs [810].
, polymers still exhibit significant losses (~cm-1) in the terahertz frequency range [8

8. Y.-S. Jin, G.-J. Kim, and S.-Y. Jeon, “Terahertz dielectric properties of polymers,” J. Korean Phys. Soc. 49, 513–517 (2006).

10

10. P. D. Cunningham, N. N. Valdes, F. A. Vallejo, L. M. Hayden, B. Polishak, X.-H. Zhou, J. Luo, A. K. Jen, J. C. Williams, and R. J. Twieg, “Broadband terahertz characterization of the refractive index and absorption of some important polymeric and organic electro-optic materials,” J. Appl. Phys. 109(4), 043505 (2011). [CrossRef]

].

fα=αmodeαmat=Re(nmat)mat|E|2dA2totalSzdA
(1)

Solid core subwavelength fibers

One of the simplest plastic fibers that provide for a high fraction of power in the low-loss regions is the subwavelength core fiber introduced by Chen et al. [12

12. L.-J. Chen, H.-W. Chen, T.-F. Kao, J.-Y. Lu, and C.-K. Sun, “Low-loss subwavelength plastic fiber for terahertz waveguiding,” Opt. Lett. 31(3), 308–310 (2006). [CrossRef] [PubMed]

] and effectively used in signal delivery and imaging applications [13

13. J.-Y. Lu, C.-C. Kuo, C.-M. Chiu, H.-W. Chen, Y.-J. Hwang, C.-L. Pan, and C.-K. Sun, “THz interferometric imaging using subwavelength plastic fiber based THz endoscopes,” Opt. Express 16(4), 2494–2501 (2008). [CrossRef] [PubMed]

,14

14. C.-M. Chiu, H.-W. Chen, Y.-R. Huang, Y.-J. Hwang, W.-J. Lee, H.-Y. Huang, and C.-K. Sun, “All-terahertz fiber-scanning near-field microscopy,” Opt. Lett. 34(7), 1084–1086 (2009). [CrossRef] [PubMed]

]. The fiber is a simple plastic wire having circular cross-section of subwavelength diameter. This step-index fiber allows single-mode HE11 operation via total internal reflection guiding mechanism. Due to the subwavelength diameter of the solid core, the fundamental guided mode has a strong presence in the low-loss air cladding [see Fig. 2(c)
Fig. 2 (a) Schematic of the cross-section of a porous fiber with N = 3 layers of holes. (b) Fundamental mode profile at 1 THz in a subwavelength porous core PE fiber (dfiber = 120 µm, dhole = 9 µm), and (c) in a subwavelength solid core PE fiber (dfiber = 120 µm).
].

Porous core subwavelength fibers

Cutback measurements of the propagation losses [Fig. 3(c)
Fig. 3 Transmission and cutback loss measurements of porous and non-porous subwavelength PE fibers of (a)-(b)-(c) small diameter fibers (d ~450 μm), and (d)-(e)-(f) larger diameter fiber (d ~700 μm). Adapted from [19]
and Fig. 3(f)] demonstrate that propagation losses as low as 0.01-0.02 cm−1 can be consistently achieved with porous and solid core fibers, even when bulk material loss is as large as 0.2 cm−1. Although not explicitly shown in Fig. 3, one indeed typically observes that the minimal transmission loss of a porous fiber is smaller than that of a solid core fiber of a comparable diameter.

Additionally, it was demonstrated that porous fibers allows to both broaden and shift the transmission window towards higher THz frequencies compared to non-porous fibers of equal diameter [19

19. A. Dupuis, A. Mazhorova, F. Désévédavy, M. Rozé, and M. Skorobogatiy, “Spectral characterization of porous dielectric subwavelength THz fibers fabricated using a microstructured molding technique,” Opt. Express 18(13), 13813–13828 (2010). [CrossRef] [PubMed]

], as revealed in the transmission spectra presented in Fig. 3(b) and Fig. 3(e).

Fabrication of the porous core subwavelength fibers

Similarly to standard solid core subwavelength fibers, porous polymer fibers are produced by drawing a plastic cylindrical preform − pierced by several holes − into a fiber. The main challenge in the fabrication of porous fibers then resides in preventing the holes from collapsing or getting partially obstructed during fiber drawing. We here present two different approaches for fabricating porous fibers that were successfully demonstrated: the sacrificial polymer technique, and the microstructured molding technique, as schematically presented in Fig. 4(a)
Fig. 4 (a) Schematics of the fabrication procedures of porous subwavelength fibers via (a) the sacrificial polymer technique, and (b) the microstructured molding technique. Adapted from [19].
and Fig. 4(b) respectively.

In the sacrificial polymer technique [Fig. 4(a)], rods of the sacrificial polymer (in this case PMMA plastic) are first stacked in a triangular lattice inside a polymer tube (here PTFE plastic) while ensuring the rods do not touch each other [18

18. A. Dupuis, J.-F. Allard, D. Morris, K. Stoeffler, C. Dubois, and M. Skorobogatiy, “Fabrication and THz loss measurements of porous subwavelength fibers using a directional coupler method,” Opt. Express 17(10), 8012–8028 (2009). [CrossRef] [PubMed]

,19

19. A. Dupuis, A. Mazhorova, F. Désévédavy, M. Rozé, and M. Skorobogatiy, “Spectral characterization of porous dielectric subwavelength THz fibers fabricated using a microstructured molding technique,” Opt. Express 18(13), 13813–13828 (2010). [CrossRef] [PubMed]

]. All the remaining interstices in the tube preform are filled with granules of the fiber core polymer (in this example low-density PE). The ensuing all-polymer preform is then drawn at a temperature of 210°C. Finally, the drawn fiber is placed into a solvent bath so as to dissolve all the PMMA from the fiber and reveal the holes. Drawing of porous fibers is greatly simplified with the sacrificial polymer technique since the resultant perform is fully solid such that hole collapse is prevented. However, a post-processing step is required to remove the sacrificial polymer, which has currently limited the length of porous fibers that could readily be fabricated to several meters.

Porous fibers can also be fabricated using the microstructured molding technique [Fig. 4(b)] where the fiber preform is cast in a microstructured mold [19

19. A. Dupuis, A. Mazhorova, F. Désévédavy, M. Rozé, and M. Skorobogatiy, “Spectral characterization of porous dielectric subwavelength THz fibers fabricated using a microstructured molding technique,” Opt. Express 18(13), 13813–13828 (2010). [CrossRef] [PubMed]

]. The resulting preform features air holes which have to be pressurized during drawing to prevent hole collapse. A schematic of the fabrications steps is shown in [Fig. 4(b)]. First, a microstructured mold featuring suitably aligned capillaries (or rods) made from silica glass is fabricated, and PE granules are added to fill the entire preform. The tubular preform is then heated in a furnace so as to melt all the PE, and left to cool down. The bulk glass structure is removed from the preform by hand, with any glass residues dissolved in hydrofluoric acid. The preform is subsequently drawn under pressure. The pressure must be controlled to prevent holes from collapsing, or to further inflate the holes. This enables fabrication of fibers with porosities higher than the initial porosity of a preform. We note in passing that complex preforms for polymer MOFs have also been demonstrated using the extrusion method [21

21. H. Ebendorff-Heidepriem and T. M. Monro, “Extrusion of complex preforms for microstructured optical fibers,” Opt. Express 15(23), 15086–15092 (2007). [CrossRef] [PubMed]

].

2.2 Dispersion

Another key obstacle which pertains to the transmission of broadband THz pulses is presented by the need of low waveguide dispersion. Many of the currently used THz sources emit broadband picosecond pulses. Therefore the efficient waveguide delivery of such pulses requires low transmission losses in the whole spectral window covered by the pulse, as well as low group velocity dispersion to prevent degradation of the pulse shape. In principle, for linear systems, dispersion compensation can be used to counteract the effects of waveguide dispersion and to reconstruct the original pulse shape; however this approach has not yet been explored in the THz frequency range.

Typical dispersion values for the fundamental mode of a solid core subwavelength fiber are presented in Fig. 5(a)
Fig. 5 (a) Dispersion parameter of non-porous (a) and porous (b) PE fibers based on finite-element simulations. Porosity is defined as the ratio of the net surface of all the air holes to the total area of the fiber cross-section. Adapted from [19].
for various values of the fiber core diameter. As seen from this figure, the calculated GVD for the fundamental mode of a solid core subwavelength PE fiber can be quite high, reaching ~40 ps/THz/cm between 0.1 and 0.5 THz.

Within their low-loss transmission windows, the chromatic dispersion of the fundamental or dominant waveguide mode in hollow-core fibers is generally negligible, with reported values below 0.01 ps/THz/cm [9

9. A. Dupuis, K. Stoeffler, B. Ung, C. Dubois, and M. Skorobogatiy, “Transmission measurements of hollow-core THz Bragg Fibers,” J. Opt. Soc. Am. B 28(4), 896–907 (2011). [CrossRef]

,23

23. O. Mitrofanov and J. A. Harrington, “Dielectric-lined cylindrical metallic THz waveguides: mode structure and dispersion,” Opt. Express 18(3), 1898–1903 (2010). [CrossRef] [PubMed]

]. The low-dispersion stems from the fact that the HE11 and TE01 modes − the main modes of interest in hollow-core fibers with a diameter much larger than the wavelength of light − have most of their guided power within the low-loss and dispersion-less air core, and outside the dielectric cladding, thus resulting in the low-loss and low-dispersion waveguiding.

2.3 Packaging of subwavelength fibers

While a highly delocalized field is favorable for lowering absorption losses in the material; on the other hand it is a major inconvenience when handling the fiber during normal operation because of the strong perturbation induced to the mode through direct manipulation of the fiber or via holders (such as strings and other apparatus) used for maintaining the fiber into position. Hence the issue of core encapsulation is crucial for subwavelength dielectric fibers.

There are two principal incentives for encapsulating the solid/porous core of a fiber within an outer polymer tube as shown in Fig. 6
Fig. 6 Refractive index maps of (a) the suspended solid core fiber (OD = 5.1 mm; dcore = 150 µm), and (b) the suspended porous core fiber (OD = 3 mm; dcore = 900 µm), retrieved from the microscope images (Insets) of the fiber cross-sections.
. First, the solid tubular cladding confers greater mechanical stability and shielding for the subwavelength-sized core, thus allowing smaller bending radii and protection against the accumulation of dust and other surface contaminants. Second, the outer tube cladding prevents the highly delocalized core-guided mode from interacting with the surrounding environment, thus eliminating cross-talk noise with adjacent waveguides, and perturbation-induced losses incurred by direct manipulation of the fibers or due to fiber holders. Moreover, core encapsulation opens the way for the simple and economical purging of the low volume tube cladding with dry air so as to eliminate losses due to water vapor typically present in the ambient environment.

Figure 6 presents two types of suspended core fibers that were both fabricated using low-density polyethylene (PE) and demonstrated propagation losses as low as 0.02 cm−1 [24

24. M. Rozé, B. Ung, A. Mazhorova, M. Walther, and M. Skorobogatiy, “Suspended core subwavelength fibers: towards practical designs for low-loss terahertz guidance,” Opt. Express 19(10), 9127–9138 (2011). [CrossRef] [PubMed]

]. A combination of drilling and stacking techniques were used to fabricate a solid suspended core fiber [Fig. 6(a)] featuring a 150 µm core suspended in the middle of a 5.1 mm outer diameter (OD) fiber; along with a suspended porous core fiber [Fig. 6(c)] having a 900 µm diameter core with ~10% porosity inside a 3 mm OD fiber.

Images of the output Ex-polarized near-field profiles from both fibers were obtained using a terahertz near-field imaging system that utilizes a scanning photoconductive antenna as a near-field probe. More details on the utilized near-field microscopy setup will be given in Section 4 (“Experimental characterization of THz waveguides”).

3. Hollow-core fibers

Another practical approach to low-loss guiding is presented by guiding THz radiation in the hollow-core fibers. A classical result for guiding in straight capillaries predicts propagation losses scaling as λ2/a3 with the bore radius a. Therefore in principle, propagation losses can be set arbitrarily low simply by enlarging the bore diameter. However, the downside of increasing the bore diameter is in the increased bending losses and the highly multimode guidance resulting in a low spatial quality of the guided beams.

3.1 Anti-resonant reflecting optical fibers

The first type of hollow-core fiber consists of a thin tube that guides using anti-resonant reflections from its walls to confine the light in the hollow core. Such fibers are typically referred as ARROW waveguide for “anti-resonant reflecting optical waveguide” [25

25. C.-H. Lai, B. You, J.-Y. Lu, T.-A. Liu, J.-L. Peng, C.-K. Sun, and H.-C. Chang, “Modal characteristics of antiresonant reflecting pipe waveguides for terahertz waveguiding,” Opt. Express 18(1), 309–322 (2010). [CrossRef] [PubMed]

]. Making use of a simple Fabry-Pérot resonator model, one can predict the periodic spacing between two adjacent resonant frequencies in the fiber transmission spectrum [25

25. C.-H. Lai, B. You, J.-Y. Lu, T.-A. Liu, J.-L. Peng, C.-K. Sun, and H.-C. Chang, “Modal characteristics of antiresonant reflecting pipe waveguides for terahertz waveguiding,” Opt. Express 18(1), 309–322 (2010). [CrossRef] [PubMed]

]:
Δf=c2tnclad2ncore2,
(3)
where ncore and nclad respectively designate the refractive indices of the gaseous core (usually air) and that of the polymer tube cladding, while c is the light velocity in vacuum, and t stands for the wall thickness of the tube cladding. From Eq. (3) we note that the periodic spacing between two resonant frequencies is inversely proportional to the wall thickness. Hence, in an ARROW fiber, in order to obtain the widest spectral separation between two resonant frequencies (and consequently the widest transmission windows) it is necessary to have the thinnest possible wall, often below sub-millimeter dimensions.

ARROW guidance is demonstrated in Fig. 8
Fig. 8 Images of cross-sections of (a) 1.6 mm thick PE tube and (c) 0.30 mm thin PTFE tube. Transmission intensity through the (b) thick-walled and (d) thin-walled ARROW fibers. Reproduced from [31] with permission.
where the transmission spectra of two polymer tubes, one 1.6 mm-thick polyethylene (PE) tube and a 0.30 mm-thick Teflon (PTFE) tube, are compared. We note that the refractive index values of bulk PE and PTFE remain relatively constant, at 1.534 and 1.560 respectively, inside the investigated range of frequencies. The output spectrum of the thick-wall tube [Fig. 8(b)] exhibits many narrowly spaced transmission windows of roughly 0.08 THz bandwidth; while that of the thinner tube [Fig. 8(d)] has wider transmission windows of nearly 0.52 THz.

3.2 Bragg fibers

The main drawbacks of thin-walled tubes are that they are challenging to fabricate, highly fragile and very sensitive to external perturbations while handling them. An alternative and more robust solution to light confinement in the hollow core, namely Bragg fibers, exploits resonant reflections from a periodic multilayer reflector surrounding the hollow core region. The periodic reflectors in Bragg fibers are composed of two alternating dielectrics featuring a high-refractive-index contrast [example in Fig. 9(a)
Fig. 9 (a) Schematic of hollow Bragg fiber with N = 5 bilayers of high-index and low-index layers. (b) Fabricated Bragg fiber with high-index TiO2 doped layers and low-index PE layers. (c) Fabricated Bragg fiber with high-index PE layers separated by PMMA particles from the low-index air layers. (d) Fundamental HE11 mode profile at 1 THz inside the TiO2-doped Bragg fiber of Fig. (b) with dcore = 6.63 mm, dH = 135 µm and dL = 100 µm.
] in order to maximize fiber transmission bandwidth [26

26. S. Johnson, M. Ibanescu, M. Skorobogatiy, O. Weisberg, T. Engeness, M. Soljacic, S. Jacobs, J. Joannopoulos, and Y. Fink, “Low-loss asymptotically single-mode propagation in large-core OmniGuide fibers,” Opt. Express 9(13), 748–779 (2001). [CrossRef] [PubMed]

]. The potential of all-polymer Bragg fibers for the transmission of terahertz light was first identified [27

27. M. Skorobogatiy and A. Dupuis, “Ferroelectric all-polymer hollow Bragg fibers for terahertz guidance,” Appl. Phys. Lett. 90(11), 113514 (2007). [CrossRef]

] and later achieved in [9

9. A. Dupuis, K. Stoeffler, B. Ung, C. Dubois, and M. Skorobogatiy, “Transmission measurements of hollow-core THz Bragg Fibers,” J. Opt. Soc. Am. B 28(4), 896–907 (2011). [CrossRef]

]. The transmission characteristics of Bragg fibers are mainly determined by the first few layers in the reflector adjacent to the hollow core. Bragg fibers can therefore have a thick cladding that confers greater mechanical stability and lower sensitivity to the environment compared to the thin-walled ARROW fibers.

Two types of the high-refractive-index-contrast polymer Bragg fibers for terahertz wave guiding have been recently fabricated and characterized [9

9. A. Dupuis, K. Stoeffler, B. Ung, C. Dubois, and M. Skorobogatiy, “Transmission measurements of hollow-core THz Bragg Fibers,” J. Opt. Soc. Am. B 28(4), 896–907 (2011). [CrossRef]

,28

28. B. Ung, A. Dupuis, K. Stoeffler, C. Dubois, and M. Skorobogatiy, “High-refractive-index composite materials for terahertz waveguides: trade-off between index contrast and absorption loss,” J. Opt. Soc. Am. B 28(4), 917–921 (2011). [CrossRef]

]. In Figs. 9(b)-(c) we show the fiber cross-sections and in Fig. 9(d) the theoretical energy flux distribution of the fundamental HE11 mode propagating in such fibers. The first type of Bragg fiber [Fig. 9(b)] comprises a reflector made of the low refractive index (nL=1.567) pure PE layers and high refractive index (nH=2.985) 80 wt.% TiO2-doped PE layers. The second type of fabricated Bragg fiber [Fig. 9(c)] is made of air-polymer bilayers. In the last case, fine PMMA powder particles are used as spacers in order to maintain a certain air gap between each PE layers.

To fabricate the air-polymer Bragg fiber, a PMMA powder with an average particle size of 150 μm was randomly laid out on top of two touching 127 μm thick PTFE films. The films were subsequently rolled around a mandrel to form the Bragg fiber. The resulting air-polymer Bragg fiber had an inner diameter (ID) of 6.73 mm and a reflector composed of five bilayers consisting of 254 μm PTFE and 150 μm thick air layers. To fabricate the titania-doped PE Bragg fiber, a mixture of 80 wt.% TiO2 powder and PE was prepared using a twin-screw extruder. The extrudate was cut into pellets and subsequently extruded into film. An all-solid bilayer was formed by pressing doped and undoped films together with a hot press, yielding high-index doped PE layers and low-index undoped PE layers of 135 μm and 100 μm thickness respectively. The bilayer was then rolled into a Bragg fiber (ID = 6.63 mm).

4. Experimental characterization of THz waveguides

4.1 Fast reconfigurable THz-TDS setup for fiber transmission measurement

Contrary to standard Terahertz Time-Domain Spectroscopy (THz-TDS) setups that are tuned for pointwise measurements of samples in the focal-point-to-focal-point configuration (using off-axis parabolic mirrors), elongated waveguides require a different setup in order to accommodate waveguides of widely different lengths. To this end, we here describe a reconfigurable setup featuring an adaptable path length capable of accommodating waveguides of different lengths [19

19. A. Dupuis, A. Mazhorova, F. Désévédavy, M. Rozé, and M. Skorobogatiy, “Spectral characterization of porous dielectric subwavelength THz fibers fabricated using a microstructured molding technique,” Opt. Express 18(13), 13813–13828 (2010). [CrossRef] [PubMed]

].

4.2 THz near-field imaging for fiber mode profiling

Fig. 11 Schematic of the THz near-field microscopy setup for fiber mode profiling. Adapted from [35].

This powerful characterization technique provides subwavelength spatial resolution (~λ/20) images with time-frames of sub-picosecond temporal precision. After Fourier transform of the time-domain data, frequency-dependent, two-dimensional near-field maps (x-y distribution) of the transverse |Ex|-field were captured by raster scanning of the fiber cross-section with the probe detector yielding a 60×60 pixels resolution in a 6 mm2 area that covered the whole output facet of the fibers. By rotating the polarization-sensitive detector by 90 allows further mapping of |Ey|-field component. This technique thus enables the separate in-plane vector field reconstruction of the waveguide mode profiles.

5. Conclusion

We have presented a review of the recent advances of the past 5 years in the theory and the experimental fabrication and characterization of polymer microstructured optical fibers for the terahertz range. Strong emphasis has recently been put towards reducing the propagation losses stemming from the large intrinsic losses of most materials in the terahertz range. We presented several innovative designs − of both solid core fibers and hollow-core fibers − that attempt to mitigate these losses by maximizing the fraction of guided power outside of the solid material, and within low-loss air. The same strategy works for reducing the detrimental effects of waveguide dispersion on THz pulse propagation, as demonstrated using porous fibers. We note that the choice of type of fiber, solid (or porous) core fiber versus hollow-core fiber, depends essentially on the intended user application. For example, if the priority is beam quality, as in fiber-scanning near-field imaging, then a subwavelength (solid / porous) core fiber is the most suitable solution because of the single-moded and Gaussian-like mode profile. However, for efficient THz signal delivery one might prefer hollow-core fibers that theoretically provide lower losses and lower dispersion capabilities, as well as the possibility to engineer relatively wide bandgaps at higher frequencies.

Moreover, two relatively recent and complementary techniques for the optical characterization of THz waveguides were presented. A fast reconfigurable THz-TDS setup capable of accommodating straight waveguides of up to 50 cm in length, and measuring their THz transmission, was first described. The use of THz near-field imaging for assessing the output mode profile of polymer fibers was also discussed.

The recent results show that polymer-based waveguide technology is well suited to tackle the challenges of THz wave guiding. Towards that end, polymer materials possess several key incentives: they constitute relatively low-loss THz materials, offer a wide variety of chemical formulations with different thermo-mechanical properties, are cost-effective and easy to process, and thus amenable to an industrial-scale deployment of plastic-based THz waveguides and devices.

Acknowlegment

We acknowledge the contribution of Dr. Markus Walther (Freiburg University) for producing the near-field data used in Figure 7.

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A. Dupuis, J.-F. Allard, D. Morris, K. Stoeffler, C. Dubois, and M. Skorobogatiy, “Fabrication and THz loss measurements of porous subwavelength fibers using a directional coupler method,” Opt. Express 17(10), 8012–8028 (2009). [CrossRef] [PubMed]

19.

A. Dupuis, A. Mazhorova, F. Désévédavy, M. Rozé, and M. Skorobogatiy, “Spectral characterization of porous dielectric subwavelength THz fibers fabricated using a microstructured molding technique,” Opt. Express 18(13), 13813–13828 (2010). [CrossRef] [PubMed]

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H. Ebendorff-Heidepriem and T. M. Monro, “Extrusion of complex preforms for microstructured optical fibers,” Opt. Express 15(23), 15086–15092 (2007). [CrossRef] [PubMed]

22.

K. Nielsen, H. K. Rasmussen, A. J. L. Adam, P. C. M. Planken, O. Bang, and P. U. Jepsen, “Bendable, low-loss Topas fibers for the terahertz frequency range,” Opt. Express 17(10), 8592–8601 (2009). [CrossRef] [PubMed]

23.

O. Mitrofanov and J. A. Harrington, “Dielectric-lined cylindrical metallic THz waveguides: mode structure and dispersion,” Opt. Express 18(3), 1898–1903 (2010). [CrossRef] [PubMed]

24.

M. Rozé, B. Ung, A. Mazhorova, M. Walther, and M. Skorobogatiy, “Suspended core subwavelength fibers: towards practical designs for low-loss terahertz guidance,” Opt. Express 19(10), 9127–9138 (2011). [CrossRef] [PubMed]

25.

C.-H. Lai, B. You, J.-Y. Lu, T.-A. Liu, J.-L. Peng, C.-K. Sun, and H.-C. Chang, “Modal characteristics of antiresonant reflecting pipe waveguides for terahertz waveguiding,” Opt. Express 18(1), 309–322 (2010). [CrossRef] [PubMed]

26.

S. Johnson, M. Ibanescu, M. Skorobogatiy, O. Weisberg, T. Engeness, M. Soljacic, S. Jacobs, J. Joannopoulos, and Y. Fink, “Low-loss asymptotically single-mode propagation in large-core OmniGuide fibers,” Opt. Express 9(13), 748–779 (2001). [CrossRef] [PubMed]

27.

M. Skorobogatiy and A. Dupuis, “Ferroelectric all-polymer hollow Bragg fibers for terahertz guidance,” Appl. Phys. Lett. 90(11), 113514 (2007). [CrossRef]

28.

B. Ung, A. Dupuis, K. Stoeffler, C. Dubois, and M. Skorobogatiy, “High-refractive-index composite materials for terahertz waveguides: trade-off between index contrast and absorption loss,” J. Opt. Soc. Am. B 28(4), 917–921 (2011). [CrossRef]

29.

K. Nielsen, H. K. Rasmussen, P. U. Jepsen, and O. Bang, “Porous-core honeycomb bandgap THz fiber,” Opt. Lett. 36(5), 666–668 (2011). [CrossRef] [PubMed]

30.

S. Atakaramians, S. V. Afshar, M. Nagel, H. K. Rasmussen, O. Bang, T. M. Monro, and D. Abbott, “Direct probing of evanescent fields for characterization of porous terahertz fibers,” Appl. Phys. Lett. 98, 121104 (2011).

31.

A. Dupuis, Dielectric THz waveguides (PhD thesis, Ecole Polytechnique de Montréal, 2010).

32.

O. Mitrofanov, T. Tan, P. R. Mark, B. Bowden, and J. A. Harrington, “Waveguide mode imaging and dispersion analysis with terahertz near-field microscopy,” Appl. Phys. Lett. 94(17), 171104 (2009). [CrossRef]

33.

J. R. Knab, A. J. L. Adam, R. Chakkittakandy, and P. C. M. Planken, “Terahertz near-field microspectroscopy,” Appl. Phys. Lett. 97(3), 031115 (2010). [CrossRef]

34.

A. Bitzer, A. Ortner, and M. Walther, “Terahertz near-field microscopy with subwavelength spatial resolution based on photoconductive antennas,” Appl. Opt. 49(19), E1–E6 (2010). [CrossRef] [PubMed]

35.

M. Walther and A. Bitzer, “Electromagnetic Wave Propagation Close to Microstructures Studied by Time and Phase-Resolved THz Near-Field Imaging,” J. Infrared Millim. Terahz. Waves 32(8-9), 1020–1030 (2011). [CrossRef]

OCIS Codes
(060.2280) Fiber optics and optical communications : Fiber design and fabrication
(160.5470) Materials : Polymers
(060.4005) Fiber optics and optical communications : Microstructured fibers
(300.6495) Spectroscopy : Spectroscopy, teraherz
(110.6795) Imaging systems : Terahertz imaging

ToC Category:
Fibers, Fiber Devices, and Amplifiers

History
Original Manuscript: September 30, 2011
Revised Manuscript: November 18, 2011
Manuscript Accepted: November 22, 2011
Published: December 7, 2011

Virtual Issues
(2011) Advances in Optics and Photonics
European Conference on Optical Communication 2011 (2011) Optics Express

Citation
Bora Ung, Anna Mazhorova, Alexandre Dupuis, Mathieu Rozé, and Maksim Skorobogatiy, "Polymer microstructured optical fibers for terahertz wave guiding," Opt. Express 19, B848-B861 (2011)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-26-B848


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References

  1. G. Imeshev, M. E. Fermann, K. L. Vodopyanov, M. M. Fejer, X. Yu, J. S. Harris, D. Bliss, and C. Lynch, “High-power source of THz radiation based on orientation-patterned GaAs pumped by a fiber laser,” Opt. Express 14(10), 4439–4444 (2006). [CrossRef] [PubMed]
  2. M. Tang, H. Minamide, Y. Wang, T. Notake, S. Ohno, and H. Ito, “Dual-wavelength single-crystal double-pass KTP optical parametric oscillator and its application in terahertz wave generation,” Opt. Lett. 35(10), 1698–1700 (2010). [CrossRef] [PubMed]
  3. Y. Cai, I. Brener, J. Lopata, J. Wynn, L. Pfeiffer, J. B. Stark, Q. Wu, X. C. Zhang, and J. F. Federici, “Coherent terahertz radiation detection: Direct comparison between free-space electro-optic sampling and antenna detection,” Appl. Phys. Lett. 73(4), 444–446 (1998). [CrossRef]
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  7. G. J. Wilmink, B. L. Ibey, T. Tongue, B. Schulkin, N. Laman, X. G. Peralta, C. C. Roth, C. Z. Cerna, B. D. Rivest, J. E. Grundt, and W. P. Roach, “Development of a compact terahertz time-domain spectrometer for the measurement of the optical properties of biological tissues,” J. Biomed. Opt. 16(4), 047006 (2011). [CrossRef] [PubMed]
  8. Y.-S. Jin, G.-J. Kim, and S.-Y. Jeon, “Terahertz dielectric properties of polymers,” J. Korean Phys. Soc. 49, 513–517 (2006).
  9. A. Dupuis, K. Stoeffler, B. Ung, C. Dubois, and M. Skorobogatiy, “Transmission measurements of hollow-core THz Bragg Fibers,” J. Opt. Soc. Am. B 28(4), 896–907 (2011). [CrossRef]
  10. P. D. Cunningham, N. N. Valdes, F. A. Vallejo, L. M. Hayden, B. Polishak, X.-H. Zhou, J. Luo, A. K. Jen, J. C. Williams, and R. J. Twieg, “Broadband terahertz characterization of the refractive index and absorption of some important polymeric and organic electro-optic materials,” J. Appl. Phys. 109(4), 043505 (2011). [CrossRef]
  11. M. Skorobogatiy and J. Yang, Fundamentals of Photonic Crystal Guiding (Cambridge University Press, 2009).
  12. L.-J. Chen, H.-W. Chen, T.-F. Kao, J.-Y. Lu, and C.-K. Sun, “Low-loss subwavelength plastic fiber for terahertz waveguiding,” Opt. Lett. 31(3), 308–310 (2006). [CrossRef] [PubMed]
  13. J.-Y. Lu, C.-C. Kuo, C.-M. Chiu, H.-W. Chen, Y.-J. Hwang, C.-L. Pan, and C.-K. Sun, “THz interferometric imaging using subwavelength plastic fiber based THz endoscopes,” Opt. Express 16(4), 2494–2501 (2008). [CrossRef] [PubMed]
  14. C.-M. Chiu, H.-W. Chen, Y.-R. Huang, Y.-J. Hwang, W.-J. Lee, H.-Y. Huang, and C.-K. Sun, “All-terahertz fiber-scanning near-field microscopy,” Opt. Lett. 34(7), 1084–1086 (2009). [CrossRef] [PubMed]
  15. M. Nagel, A. Marchewka, and H. Kurz, “Low-index discontinuity terahertz waveguides,” Opt. Express 14(21), 9944–9954 (2006). [CrossRef] [PubMed]
  16. A. Hassani, A. Dupuis, and M. Skorobogatiy, “Low loss porous terahertz fibers containing multiple subwavelength holes,” Appl. Phys. Lett. 92(7), 071101 (2008). [CrossRef]
  17. A. Hassani, A. Dupuis, and M. Skorobogatiy, “Porous polymer fibers for low-loss Terahertz guiding,” Opt. Express 16(9), 6340–6351 (2008). [CrossRef] [PubMed]
  18. A. Dupuis, J.-F. Allard, D. Morris, K. Stoeffler, C. Dubois, and M. Skorobogatiy, “Fabrication and THz loss measurements of porous subwavelength fibers using a directional coupler method,” Opt. Express 17(10), 8012–8028 (2009). [CrossRef] [PubMed]
  19. A. Dupuis, A. Mazhorova, F. Désévédavy, M. Rozé, and M. Skorobogatiy, “Spectral characterization of porous dielectric subwavelength THz fibers fabricated using a microstructured molding technique,” Opt. Express 18(13), 13813–13828 (2010). [CrossRef] [PubMed]
  20. S. Atakaramians, S. Afshar V, H. Ebendorff-Heidepriem, M. Nagel, B. M. Fischer, D. Abbott, and T. M. Monro, “THz porous fibers: design, fabrication and experimental characterization,” Opt. Express 17(16), 14053–15062 (2009). [CrossRef] [PubMed]
  21. H. Ebendorff-Heidepriem and T. M. Monro, “Extrusion of complex preforms for microstructured optical fibers,” Opt. Express 15(23), 15086–15092 (2007). [CrossRef] [PubMed]
  22. K. Nielsen, H. K. Rasmussen, A. J. L. Adam, P. C. M. Planken, O. Bang, and P. U. Jepsen, “Bendable, low-loss Topas fibers for the terahertz frequency range,” Opt. Express 17(10), 8592–8601 (2009). [CrossRef] [PubMed]
  23. O. Mitrofanov and J. A. Harrington, “Dielectric-lined cylindrical metallic THz waveguides: mode structure and dispersion,” Opt. Express 18(3), 1898–1903 (2010). [CrossRef] [PubMed]
  24. M. Rozé, B. Ung, A. Mazhorova, M. Walther, and M. Skorobogatiy, “Suspended core subwavelength fibers: towards practical designs for low-loss terahertz guidance,” Opt. Express 19(10), 9127–9138 (2011). [CrossRef] [PubMed]
  25. C.-H. Lai, B. You, J.-Y. Lu, T.-A. Liu, J.-L. Peng, C.-K. Sun, and H.-C. Chang, “Modal characteristics of antiresonant reflecting pipe waveguides for terahertz waveguiding,” Opt. Express 18(1), 309–322 (2010). [CrossRef] [PubMed]
  26. S. Johnson, M. Ibanescu, M. Skorobogatiy, O. Weisberg, T. Engeness, M. Soljacic, S. Jacobs, J. Joannopoulos, and Y. Fink, “Low-loss asymptotically single-mode propagation in large-core OmniGuide fibers,” Opt. Express 9(13), 748–779 (2001). [CrossRef] [PubMed]
  27. M. Skorobogatiy and A. Dupuis, “Ferroelectric all-polymer hollow Bragg fibers for terahertz guidance,” Appl. Phys. Lett. 90(11), 113514 (2007). [CrossRef]
  28. B. Ung, A. Dupuis, K. Stoeffler, C. Dubois, and M. Skorobogatiy, “High-refractive-index composite materials for terahertz waveguides: trade-off between index contrast and absorption loss,” J. Opt. Soc. Am. B 28(4), 917–921 (2011). [CrossRef]
  29. K. Nielsen, H. K. Rasmussen, P. U. Jepsen, and O. Bang, “Porous-core honeycomb bandgap THz fiber,” Opt. Lett. 36(5), 666–668 (2011). [CrossRef] [PubMed]
  30. S. Atakaramians, S. V. Afshar, M. Nagel, H. K. Rasmussen, O. Bang, T. M. Monro, and D. Abbott, “Direct probing of evanescent fields for characterization of porous terahertz fibers,” Appl. Phys. Lett. 98, 121104 (2011).
  31. A. Dupuis, Dielectric THz waveguides (PhD thesis, Ecole Polytechnique de Montréal, 2010).
  32. O. Mitrofanov, T. Tan, P. R. Mark, B. Bowden, and J. A. Harrington, “Waveguide mode imaging and dispersion analysis with terahertz near-field microscopy,” Appl. Phys. Lett. 94(17), 171104 (2009). [CrossRef]
  33. J. R. Knab, A. J. L. Adam, R. Chakkittakandy, and P. C. M. Planken, “Terahertz near-field microspectroscopy,” Appl. Phys. Lett. 97(3), 031115 (2010). [CrossRef]
  34. A. Bitzer, A. Ortner, and M. Walther, “Terahertz near-field microscopy with subwavelength spatial resolution based on photoconductive antennas,” Appl. Opt. 49(19), E1–E6 (2010). [CrossRef] [PubMed]
  35. M. Walther and A. Bitzer, “Electromagnetic Wave Propagation Close to Microstructures Studied by Time and Phase-Resolved THz Near-Field Imaging,” J. Infrared Millim. Terahz. Waves 32(8-9), 1020–1030 (2011). [CrossRef]

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