Spectral characterization of helicoidal long-period fiber gratings in photonic crystal fibers

Shin, Woojin; Lee, Yeung Lak; Yu, Bong-Ahn; Noh, Young Chul; Oh, Kyunghwan

doi:10.1016/j.optcom.2009.05.063

Cited by 36 publications

(15 citation statements)

References 17 publications

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“…In addition, in the high-transmission windows between the dips, twisted PCF exhibits optical activity via a non resonant geometrical effect that can only be understood if both spin and orbital angular momentum are considered [22,23]. It has previously been reported that twisted PCF can be used as a torsion sensor [16]. In this Letter, we show that the torsion and tension-induced shifts of resonant wavelength in a twisted PCF scale linearly with the applied twist rate and axial strain.…”

mentioning

confidence: 71%

“…Such fibers offer an alternative means of manipulating the loss and polarization state of guided light [1][2][3][4][5][6], and have found applications in current sensing [7][8][9] and suppression of higher-order modes in fiber lasers [10][11][12]. Some of these ideas have also been applied to photonic crystal fibers (PCFs) [13][14][15][16][17][18]. Because they offer properties that are unattainable in conventional optical fibers, PCFs are having an increasing impact in many fields of optics as well as in other scientific disciplines such as chemistry and biology [19,20].…”

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confidence: 99%

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Measuring mechanical strain and twist using helical photonic crystal fiber

et al. 2013

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Solid-core photonic crystal fiber (PCF) with a permanent helical twist exhibits dips in its transmission spectrum at certain wavelengths. These are associated with the formation of orbital angular momentum states in the cladding. Here we investigate the tuning of these states with mechanical torque and axial tension. The dip wavelengths are found to scale linearly with both axial strain and mechanical twist rate. Analysis shows that the tension-induced shift in resonance wavelength is determined both by the photoelastic effect and by the change in twist rate, while the torsion-induced wavelength shift depends only on the change in twist rate. Twisted PCF can act as an effective optically monitored torque-tension transducer, twist sensor, or strain gauge.

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confidence: 71%

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confidence: 99%

Measuring mechanical strain and twist using helical photonic crystal fiber

et al. 2013

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“…An unusual feature of helically twisted PCF with a single central glass core is a series of dips in its transmission spectrum, first observed experimentally [23]. These turn out to be caused by anti-crossings between the core mode and leaky cladding modes carrying OAM, each dip corresponding to a different OAM order [24].…”

Section: Topological Effectsmentioning

confidence: 99%

Helically twisted photonic crystal fibres

Russell¹,

Beravat²,

Wong³

2017

Phil. Trans. R. Soc. A.

117

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Recent theoretical and experimental work on helically twisted photonic crystal fibres (PCFs) is reviewed. Helical Bloch theory is introduced, including a new formalism based on the tight-binding approximation. It is used to explore and explain a variety of unusual effects that appear in a range of different twisted PCFs, including fibres with a single core and fibres with N cores arranged in a ring around the fibre axis. We discuss a new kind of birefringence that causes the propagation constants of left- and right-spinning optical vortices to be non-degenerate for the same order of orbital angular momentum (OAM). Topological effects, arising from the twisted periodic ‘space’, cause light to spiral around the fibre axis, with fascinating consequences, including the appearance of dips in the transmission spectrum and low loss guidance in coreless PCF. Discussing twisted fibres with a single off-axis core, we report that optical activity in a PCF is opposite in sign to that seen in a step-index fibre. Fabrication techniques are briefly described and emerging applications reviewed. The analytical results of helical Bloch theory are verified by an extensive series of ‘numerical experiments’ based on finite-element solutions of Maxwell's equations in a helicoidal frame.This article is part of the themed issue ‘Optical orbital angular momentum’.

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“…21 The LPGs are fundamentally different from the well-known fiber Bragg gratings (FBGs) in that an FBG has an index perturbation period of half the irradiation wavelength (thus also termed short period grating) and that it couples light from the forward-propagating core mode to a backward-propagating core mode. 22 LPGs both in conventional fibers and in IG-PCFs are increasingly being developed for use as telecommunication components 23,24 as well as for physical and chemical sensors. [25][26][27] In general, the evanescent wave sensing can only be used for detection of species with low refractive index as a possible approach in conventional optical fiber, in which evanescent field is very weak.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation of cladding mode overlap of evanescent waves with air channels in index-guiding photonic crystal fiber long-period gratings

Zheng¹,

Zhu²,

Krishnaswamy³

2010

Health Monitoring of Structural and Biological Systems 2010

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The array of axially aligned air channels and the robust waveguide characteristics of index-guiding photonic crystal fibers (IG-PCFs) integrated with long-period gratings (LPGs) make them a powerful platform for chemical sensing and detection. Compared to their conventional all-solid fiber counterpart, the IG-PCFs are a particularly attractive sensing device as they are both a waveguide and a vapor/aqueous transmission cell, permitting light intensity-analyte interaction over long path length without the removal of fiber cladding. While the fundamental core-mode in the IG-PCF has been utilized for evanescent field based sensing, there exist two inherent limitations: (1) only short distance extended by evanescent waves from the guiding core to the surrounding PCF cladding air channels to restrict the probing of an analyte only in the inner most ring of the air channels in cladding, and (2) less than 1% power of the core-mode overlap with the surrounding air channels leading to weak light intensity-analyte interactions due to the localization of the coremode in the fiber core area. Should a cladding-mode with maximum overlap in air channels be excited by an LPG, it would fundamentally increase the evanescent field sensitivity. In this work, we present the simulation for the mode properties of selected IG-PCF for optimization of mode field distribution and light power overlap with air channels in fiber cladding. The numerical calculation reveals that if the optimized cladding-mode is selectively coupled, the evanescent wave overlap (at wavelength of 1550 nm) with cladding air channels of the round and hexagonal structures can be increased from 0.11% and 0.13% up to 4.01% and 6.54%, respectively.

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Spectral characterization of helicoidal long-period fiber gratings in photonic crystal fibers

Cited by 36 publications

References 17 publications

Measuring mechanical strain and twist using helical photonic crystal fiber

Measuring mechanical strain and twist using helical photonic crystal fiber

Helically twisted photonic crystal fibres

Numerical investigation of cladding mode overlap of evanescent waves with air channels in index-guiding photonic crystal fiber long-period gratings

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