Investigation on spectral loss characteristics of subwavelength terahertz fibers

Chen, Hung Wen; Li, Yu Tai; Pan, Ci‐Ling; Kuo, Jeng Liang; Lu, Ja Yu; Chen, Li Jin; Sun, Chi‐Kuang

doi:10.1364/ol.32.001017

Cited by 43 publications

(13 citation statements)

References 7 publications

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“…For the arbitrary wavelength λ and refractive index n of the microfiber, the smallest possible radius of the waveguiding microfiber is found as From Figure 4, the threshold corresponds to a change in the microfiber radius of only several nanometers, which indicates a significant variation of the transmission spectrum with nanoscale change of the microfiber radius. These predictions have found excellent experimental confirmation both for the silica microfibers considered in the next subsection and for THz fibers [29].…”

Section: How Thin Can a Microfiber Be And Still Guide Light?supporting

confidence: 52%

Nanophotonics of optical fibers

Sumetsky¹

2013

Nanophotonics

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This review is concerned with nanoscale effects in highly transparent dielectric photonic structures fabricated from optical fibers. In contrast to those in plasmonics, these structures do not contain metal particles, wires, or films with nanoscale dimensions. Nevertheless, a nanoscale perturbation of the fiber radius can significantly alter their performance. This paper consists of three parts. The first part considers propagation of light in thin optical fibers (microfibers) having the radius of the order of 100 nanometers to 1 micron. The fundamental mode propagating along a microfiber has an evanescent field which may be strongly expanded into the external area. Then, the cross-sectional dimensions of the mode and transmission losses are very sensitive to small variations of the microfiber radius. Under certain conditions, a change of just a few nanometers in the microfiber radius can significantly affect its transmission characteristics and, in particular, lead to the transition from the waveguiding to non-waveguiding regime. The second part of the review considers slow propagation of whispering gallery modes in fibers having the radius of the order of 10-100 microns. The propagation of these modes along the fiber axis is so slow that they can be governed by extremely small nanoscale changes of the optical fiber radius. This phenomenon is exploited in SNAP (surface nanoscale axial photonics), a new platform for fabrication of miniature super-low-loss photonic integrated circuits with unprecedented sub-angstrom precision. The SNAP theory and applications are overviewed. The third part of this review describes methods of characterization of the radius variation of microfibers and regular optical fibers with sub-nanometer precision.

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Section: How Thin Can a Microfiber Be And Still Guide Light?supporting

confidence: 52%

Nanophotonics of optical fibers

Sumetsky¹

2013

Nanophotonics

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“…Several methods towards this have been proposed. One strategy first demonstrated by Chen et al is to use a subwavelength core surrounded by an air cladding [7,8]. In order to further reduce the loss, a porous structure of sub-wavelength holes can be introduced into the already sub-wavelength solid core of the fiber [10][11][12][13][14][28][29][30], as first predicted numerically by Hassani et al [10,28] and then demonstrated by Dupuis et al [29] and later Atakaramians et al [13].…”

Section: Introductionmentioning

confidence: 99%

Fabrication and characterization of porous-core honeycomb bandgap THz fibers

Bao

Nielsen²,

Rasmussen³

et al. 2012

Opt. Express

138

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We present a numerical and experimental investigation of a lowloss porous-core honeycomb fiber for terahertz wave guiding. The introduction of a porous core with hole size of the same dimension as the holes in the surrounding honeycomb cladding results in a fiber that can be drawn with much higher precision and reproducibility than a corresponding air-core fiber. The high-precision hole structure provides very clear bandgap guidance and the location of the two measured bandgaps agree well with simulations based on finite-element modeling. Fiber loss measurements reveal the frequency-dependent coupling loss and propagation loss, and we find that the fiber propagation loss is much lower than the bulk material loss within the first band gap between 0.75 and 1.05 THz.

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“…Although theory predicts lower losses for the porous fibers, we are unable to distinguish between the already very small losses of the porous and non-porous fibers within the error of our experimental setup. As we demonstrate in the following section the transmission peak (bell-shaped transmission curve) results from the balance between absorption loss (at high frequencies), scattering loss (at low frequencies), 9 and frequency dependent coupling loss.…”

Section: Transmission and Loss Measurementsmentioning

confidence: 73%

“…Experimentally measured transmission spectra through subwavelength fibers all feature bell-like profiles with frequencies of the transmission maxima defined by the competition between several loss mechanisms such as coupling, material absorption, and scattering on fiber imperfections 9,12 . Particularly, at higher frequencies, both the absorption loss and coupling loss increase substantially leading to a decrease in the fiber transmission (see Figures 3(c,g), and Figures 4 (b,c), for example).…”

Section: Theoretical Modelingmentioning

confidence: 99%

“…6 Recent efforts on metallic wires have demonstrated the use of a dual-wire suspended in air waveguide, 8 which supports a more easily excitable TEM mode at the expense of a more complicated waveguide geometry that requires maintaining a constant sub-millimeter distance between the two wires. On the other hand, dielectric subwavelength wires 3,[9][10][11] feature low-loss single-mode regime with a linearly-polarized HE 11 fundamental mode which is very easy to excite with a gaussian-like beam of a THz source. Main disadvantage of the dielectric wires is a relatively high dispersion, and a limited operational bandwidth due to onset of large absorption losses at higher frequencies.…”

Section: Introductionmentioning

confidence: 99%

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Spectral characterization of porous dielectric subwavelength THz ﬁbers fabricated using a microstructured molding technique

et al. 2010

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We report two novel fabrication techniques, as well as THz spectral transmission and propagation loss measurements of subwavelength plastic wires with highly porous (up to 86%) and non-porous transverse geometries. The two fabrication techniques we describe are based on the microstructured molding approach. In one technique the mold is made completely from silica by stacking and fusing silica capillaries to the bottom of a silica ampoule. The melted material is then poured into the silica mold to cast the microstructured preform. Another approach uses a microstructured mold made of a sacrificial plastic which is co-drawn with a cast preform. Material from the sacrificial mold is then dissolved after fi ber drawing. We also describe a novel THz-TDS setup with an easily adjustable optical path length, designed to perform cutback measurements using THz fibers of up to 50 cm in length. We fi nd that while both porous and non-porous subwavelength fibers of the same outside diameter have low propagation losses (alpha

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Investigation on spectral loss characteristics of subwavelength terahertz fibers

Cited by 43 publications

References 7 publications

Nanophotonics of optical fibers

Nanophotonics of optical fibers

Fabrication and characterization of porous-core honeycomb bandgap THz fibers

Spectral characterization of porous dielectric subwavelength THz ﬁbers fabricated using a microstructured molding technique

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