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Spectral Characteristics of Square-Wave-Modulated Type II Long-Period Fiber Gratings Inscribed by a Femtosecond Laser. SENSORS 2021; 21:s21093278. [PMID: 34068560 PMCID: PMC8126127 DOI: 10.3390/s21093278] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Revised: 04/30/2021] [Accepted: 05/07/2021] [Indexed: 11/17/2022]
Abstract
We study here the spectral characteristics of square-wave-modulated type II long-period fiber gratings (LPFGs) inscribed by a femtosecond laser. Both theoretical and experimental results indicate that higher-order harmonics refractive index (RI) modulation commonly exists together with the fundamental harmonic RI modulation in such LPFGs, and the duty cycle of a square wave has a great influence on the number and amplitudes of higher-order harmonics. A linear increase in the duty cycle in a series of square wave pulses will induce another LPFG with a minor difference in periods, which is useful for expanding the bandwidth of LPFGs. We also propose a method to reduce insertion loss by fabricating type II LPFGs without higher-order harmonic resonances. This work intensifies our comprehension of type II fiber gratings with which novel optical fiber sensors can be fabricated.
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2
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Li W, Meng F, Chen Y, Li YF, Huang X. Topology Optimization of Photonic and Phononic Crystals and Metamaterials: A Review. ADVANCED THEORY AND SIMULATIONS 2019. [DOI: 10.1002/adts.201900017] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Weibai Li
- Faculty of Science, Engineering and Technology Swinburne University of Technology Hawthorn VIC 3122 Australia
| | - Fei Meng
- Faculty of Science, Engineering and Technology Swinburne University of Technology Hawthorn VIC 3122 Australia
| | - Yafeng Chen
- Faculty of Science, Engineering and Technology Swinburne University of Technology Hawthorn VIC 3122 Australia
| | - Yang fan Li
- Faculty of Science, Engineering and Technology Swinburne University of Technology Hawthorn VIC 3122 Australia
| | - Xiaodong Huang
- Faculty of Science, Engineering and Technology Swinburne University of Technology Hawthorn VIC 3122 Australia
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3
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Zhang W, Yao J. A fully reconfigurable waveguide Bragg grating for programmable photonic signal processing. Nat Commun 2018; 9:1396. [PMID: 29643383 PMCID: PMC5895633 DOI: 10.1038/s41467-018-03738-3] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 03/07/2018] [Indexed: 11/09/2022] Open
Abstract
Since the discovery of the Bragg's law in 1913, Bragg gratings have become important optical devices and have been extensively used in various systems. In particular, the successful inscription of a Bragg grating in a fiber core has significantly boosted its engineering applications. However, a conventional grating device is usually designed for a particular use, which limits general-purpose applications since its index modulation profile is fixed after fabrication. In this article, we propose to implement a fully reconfigurable grating, which is fast and electrically reconfigurable by field programming. The concept is verified by fabricating an integrated grating on a silicon-on-insulator platform, which is employed as a programmable signal processor to perform multiple signal processing functions including temporal differentiation, microwave time delay, and frequency identification. The availability of ultrafast and reconfigurable gratings opens new avenues for programmable optical signal processing at the speed of light.
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Affiliation(s)
- Weifeng Zhang
- Microwave Photonic Research Laboratory, School of Electrical Engineering and Computer Science, University of Ottawa, 25 Templeton Street, Ottawa, ON, K1N 6N5, Canada
| | - Jianping Yao
- Microwave Photonic Research Laboratory, School of Electrical Engineering and Computer Science, University of Ottawa, 25 Templeton Street, Ottawa, ON, K1N 6N5, Canada.
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4
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Yan Z, Sun B, Li X, Luo J, Shum PP, Yu X, Zhang Y, Wang QJ. Widely tunable Tm-doped mode-locked all-fiber laser. Sci Rep 2016; 6:27245. [PMID: 27263655 PMCID: PMC4893705 DOI: 10.1038/srep27245] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Accepted: 04/27/2016] [Indexed: 11/25/2022] Open
Abstract
We demonstrated a widely tunable Tm-doped mode-locked all-fiber laser, with the widest tunable range of 136 nm, from 1842 to 1978 nm. Nonlinear polarization evolution (NPE) technique is employed to enable mode-locking and the wavelength-tunable operation. The widely tunable range attributes to the NPE-induced transmission modulation and bidirectional pumping mechanism. Such kind of tunable mode-locked laser can find various applications in optical communications, spectroscopy, time-resolved measurement, and among others.
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Affiliation(s)
- Zhiyu Yan
- Center for Optoelectronics and Biophotonics, School of Electrical and Electronic Engineering & The Photonics Institute, Nanyang Technological University, 50 Nanyang Ave, 639798, Singapore
- Precision Measurements Group, Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, 638075, Singapore
| | - Biao Sun
- Precision Measurements Group, Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, 638075, Singapore
| | - Xiaohui Li
- Center for Optoelectronics and Biophotonics, School of Electrical and Electronic Engineering & The Photonics Institute, Nanyang Technological University, 50 Nanyang Ave, 639798, Singapore
- School of Physics and Information Technology, Shaanxi Normal University, Xi’an 710062, P.R. China
| | - Jiaqi Luo
- Center for Optoelectronics and Biophotonics, School of Electrical and Electronic Engineering & The Photonics Institute, Nanyang Technological University, 50 Nanyang Ave, 639798, Singapore
- Precision Measurements Group, Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, 638075, Singapore
| | - Perry Ping Shum
- Center for Optoelectronics and Biophotonics, School of Electrical and Electronic Engineering & The Photonics Institute, Nanyang Technological University, 50 Nanyang Ave, 639798, Singapore
| | - Xia Yu
- Precision Measurements Group, Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, 638075, Singapore
| | - Ying Zhang
- Precision Measurements Group, Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, 638075, Singapore
| | - Qi Jie Wang
- Center for Optoelectronics and Biophotonics, School of Electrical and Electronic Engineering & The Photonics Institute, Nanyang Technological University, 50 Nanyang Ave, 639798, Singapore
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5
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Yao BC, Wu Y, Zhang AQ, Wang F, Rao YJ, Gong Y, Zhang WL, Wang ZG, Chiang KS, Sumetsky M. Graphene Bragg gratings on microfiber. OPTICS EXPRESS 2014; 22:23829-23835. [PMID: 25321961 DOI: 10.1364/oe.22.023829] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Graphene Bragg gratings (GBGs) on microfiber are proposed and investigated in this paper. Numerical analysis and simulated results show that the mode distribution, transmission loss, and central wavelength of the GBG are controllable by changing the diameter of the microfiber or the refractive index of graphene. Such type of GBGs with tunability may find important applications in optical fiber communication and sensing as all-fiber in-line devices.
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Zhong X, Wang Y, Qu J, Liao C, Liu S, Tang J, Wang Q, Zhao J, Yang K, Li Z. High-sensitivity strain sensor based on inflated long period fiber grating. OPTICS LETTERS 2014; 39:5463-5466. [PMID: 26466298 DOI: 10.1364/ol.39.005463] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We demonstrated a high-sensitivity strain sensor based on an inflated long period fiber grating (I-LPFG). The I-LPFG was inscribed, for the first time to the best of our knowledge, by use of the pressure-assisted CO(2) laser beam scanning technique to inflate periodically air holes of a photonic crystal fiber. Such periodic inflations enhanced the sensitivity of the LPFG-based strain sensor to -5.62 pm/με. After high temperature annealing, the I-LPFG achieved a good repeatability and stability of temperature response with a sensitivity of 11.92 pm/°C.
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7
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Statkiewicz-Barabach G, Olszewski J, Mergo P, Urbanczyk W. Higher-order rocking filters induced mechanically in fibers with different birefringence dispersion. APPLIED OPTICS 2014; 53:1258-1267. [PMID: 24663352 DOI: 10.1364/ao.53.001258] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Accepted: 01/14/2014] [Indexed: 06/03/2023]
Abstract
We studied the transmission characteristics of higher-order rocking filters induced mechanically in birefringent microstructured fibers and standard elliptical core fibers with varying spectral dependence of phase modal birefringence. We demonstrated the effect of birefringence dispersion on polarization mode coupling induced by a point-like force. We also investigated the spectral dependence of the resonance depth and force-induced resonance wavelength shift in mechanical rocking filters. The observed phenomena were explained by a numerical model linking the spectral dependence of the polarization mode coupling coefficient with the dispersion of intrinsic fiber birefringence and applied force.
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9
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Tian F, Kanka J, Zou B, Chiang KS, Du H. Long-period gratings inscribed in photonic crystal fiber by symmetric CO2 laser irradiation. OPTICS EXPRESS 2013; 21:13208-13218. [PMID: 23736575 DOI: 10.1364/oe.21.013208] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Long-period gratings (LPGs) inscribed in endlessly single mode (ESM) photonic crystal fibers (PCFs) with symmetric and asymmetric CO2 laser irradiation are investigated both numerically and experimentally. Parallel results from conventional single mode fibers (SMFs) are presented for comparison. Theoretical predictions, transmission measurements, and near-field imaging indicate that, regardless of the fiber type, symmetric index perturbation induced by laser irradiation with the aid of a 120° gold-coated reflecting mirror results in LP(0n) symmetric mode coupling, while asymmetric irradiation without using the mirror leads to LP(1n) asymmetric mode coupling. Our results show that, because of the azimuthally anisotropic hexagonal cladding structure, symmetric irradiation yields far more reproducible LPGs in PCFs than asymmetric irradiation. On the other hand, the irradiation symmetry has little effect on the reproducibility of LPGs inscribed in SMFs due to the isotropy of its all-solid cladding structure.
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Affiliation(s)
- Fei Tian
- Department of Chemical Engineering and Materials Science, Stevens Institute of Technology, Hoboken, New Jersey 07030, USA.
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10
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Prudenzano F, Mescia L, Palmisano T, Surico M, De Sario M, Righini GC. Optimization of pump absorption in MOF lasers via multi-long-period gratings: design strategies. APPLIED OPTICS 2012; 51:1420-1430. [PMID: 22441490 DOI: 10.1364/ao.51.001420] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2011] [Accepted: 01/13/2012] [Indexed: 05/31/2023]
Abstract
Different strategies for designing optical couplers, optimized to enhance the pump absorption in the rare-earth-doped core of microstructured fiber lasers, are illustrated. Three kinds/configurations of optical couplers have been designed and compared as examples of the different design strategies which can be followed. Their effectiveness to enhance the performance of an ytterbium-doped, double cladding, microstructured optical fiber laser has been accurately simulated. They consist of a suitable cascade of multiple long-period gratings (MLPGs) inscribed in the fiber core region. The characteristics of the MLPG couplers have been simulated via a homemade computer code based on both rate equations and an extended coupled mode theory. The proposed MLPG couplers seem particularly useful in the case of low rare-earth concentration but, even for a middle-high ytterbium concentration, as N(Yb)=5×10(25) ions/m(3), the slope efficiency S can be increased up to 20%, depending on the fiber length.
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Affiliation(s)
- Francesco Prudenzano
- Dipartimento di Elettrotecnica ed Elettronica Politecnico di Bari Via E. Orabona 4-70125 Bari, Italy.
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11
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Liou JH, Chang TH, Lin T, Yu CP. Reversible photo-induced long-period fiber gratings in photonic liquid crystal fibers. OPTICS EXPRESS 2011; 19:6756-6761. [PMID: 21451702 DOI: 10.1364/oe.19.006756] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
A novel light-controllable long-period fiber grating (LPFG) is demonstrated by making use of a PCF infiltrated with a photoresponsive liquid crystal (LC) mixture consisting of nematic LC molecules and light-sensitive 4-methoxyazobenzene (4MAB). With the aid of the photo-induced isomerization of 4MAB, the refractive index of the LC mixture can be modulated and the periodic index perturbation along the fiber can be achieved by exposing the PCF to a blue laser through a mask. The resonance wavelength and dip depth of the LPFG can be controlled by using different blue-laser irradiation time, numbers of period, and 4MAB concentrations. In addition, the photo-induced LPFG is erasable under green-laser illumination.
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Affiliation(s)
- Jia-hong Liou
- Department of Photonics, Institute of Electro-optical Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan
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12
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Do Lim S, Park HC, Hwang IK, Lee SB, Kim BY. Experimental excitation and characterization of cladding modes in photonic crystal fiber. OPTICS EXPRESS 2010; 18:1833-1840. [PMID: 20174011 DOI: 10.1364/oe.18.001833] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We extend the previous theoretical study on the effect of outer silica cladding to the analysis on real field profiles in a practical PCF. Clear field profiles for the first higher-order cladding modes are presented and discussed. The observed mode fields are reproduced by numerical calculations, and it turns out that they correspond to LP(16) mode groups. Optical properties of the observed modes such as lobe direction and polarization are also investigated. The results of this study will be useful in the design of the PCF-based optical devices utilizing cladding mode coupling.
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Affiliation(s)
- Sun Do Lim
- Department of Physics, Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, South Korea.
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13
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Kim SD, Kim GH, Hwang KJ, Lim SD, Lee KI, Kim SH, Lee SB. Investigation of an Arc-induced Long Period Fiber Grating Inscribed in a Photonic Crystal Fiber with Two Large Air Holes. ACTA ACUST UNITED AC 2009. [DOI: 10.3807/josk.2009.13.4.428] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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14
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Wei L, Weirich J, Alkeskjold TT, Bjarklev A. On-chip tunable long-period grating devices based on liquid crystal photonic bandgap fibers. OPTICS LETTERS 2009; 34:3818-3820. [PMID: 20016624 DOI: 10.1364/ol.34.003818] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We design and fabricate an on-chip tunable long-period grating device by integrating a liquid crystal photonic bandgap fiber on silicon structures. The transmission axis of the device can be electrically rotated in steps of 45 degrees as well as switched on and off with the response time in the millisecond range. The strength of the loss peak is controlled electrically, and the spectral position of the loss peak is thermally tunable. This compact design results in a stable grating and permits this device to be more easily applied in practical systems.
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Affiliation(s)
- Lei Wei
- DTU Fotonik, Department of Photonics Engineering, Technical University of Denmark, DK-2800 Lyngby, Denmark.
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15
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Zhu T, Shi CH, Rao YJ, Shi LL, Chiang KS. All-fiber bandwidth-tunable band-rejection filter based on a composite grating induced by CO2 laser pulses. OPTICS EXPRESS 2009; 17:16750-16755. [PMID: 19770891 DOI: 10.1364/oe.17.016750] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We propose an all-fiber band-rejection filter with a tunable bandwidth, which is realized by putting a normal long-period fiber grating in series with a rotary long-period fiber grating written in a twisted single-mode fiber by CO(2) laser pulses. Bandwidth tuning is achieved by applying torsion to the composite grating. Our experimental filter shows a bandwidth tuning of approximately 16.3 nm at a rejection level of approximately 15 dB and a polarization-dependent loss lower than approximately 0.9 dB.
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Affiliation(s)
- T Zhu
- Key Lab of Optoelectronic Technology and Systems (Education Ministry of China), Chongqing University, Chongqing, 400044, China.
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16
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Lee HW, Chiang KS. CO2 laser writing of long-period fiber grating in photonic crystal fiber under tension. OPTICS EXPRESS 2009; 17:4533-4539. [PMID: 19293882 DOI: 10.1364/oe.17.004533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We demonstrate that the efficiency of CO(2) laser writing of long-period fiber gratings in a solid-core photonic crystal fiber (PCF) can be enhanced greatly by applying tension to the fiber during the writing process through the mechanism of frozen-in viscoelasticity. Using this mechanism, we are able to write strong gratings in PCFs with a dosage of CO(2) laser radiation low enough not to cause any significant fiber structure deformation.
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Affiliation(s)
- H W Lee
- Department of Electronic Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China
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17
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Mayteevarunyoo T, Malomed BA. Gap solitons in grating superstructures. OPTICS EXPRESS 2008; 16:7767-7777. [PMID: 18545487 DOI: 10.1364/oe.16.007767] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We report results of the investigation of gap solitons (GSs) in the generic model of a periodically modulated Bragg grating (BG), which includes periodic modulation of the BG chirp or local refractive index, and periodic variation of the local reflectivity. We demonstrate that, while the previously studied reflectivity modulation strongly destabilizes all solitons, the periodic chirp modulation, which is a novel feature, stabilizes a new family of double-peak fundamental BGs in the side bandgap at negative frequencies (gap No. -1), and keeps solitons stable in the central bandgap (No. 0). The two soliton families demonstrate bistability, coexisting at equal values of energy. In addition, stable 4-peak bound states are formed by pairs of fundamental GSs in bandgap -1. Self-trapping and mobility of the solitons are studied too.
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Affiliation(s)
- Thawatchai Mayteevarunyoo
- Department of Telecommunication Engineering, Mahanakorn University of Technology, Bangkok 10530, Thailand.
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18
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Jang HS, Park KN, Lee KS. Characterization of tunable photonic crystal fiber directional couplers. APPLIED OPTICS 2007; 46:3688-93. [PMID: 17538662 DOI: 10.1364/ao.46.003688] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
We present a tunable photonic crystal fiber (PCF) directional coupler fabricated by a side-polishing method. The PCF directional coupler was modeled as a typical single-mode fiber-based directional coupler and analyzed using the improved effective-index method (IEIM). The characteristics of the PCF directional coupler such as the coupling coefficient and the coupling ratio were measured and found to be in good agreement with those predicted by the theoretical model. The PCF directional coupler exhibited an insertion loss of approximately 2 dB for a 3 dB coupler and was able to tune the coupling ratio between 0% and 100% by tilting the angle of the top side-polished quartz block against the fixed-bottom quartz block.
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Affiliation(s)
- Hyun Soo Jang
- School of Information and Communications Engineering, Sungkyunkwan University, Suwon, South Korea
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19
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He Z, Zhu Y, Du H. Effect of macro-bending on resonant wavelength and intensity of long-period gratings in photonic crystal fiber. OPTICS EXPRESS 2007; 15:1804-1810. [PMID: 19532418 DOI: 10.1364/oe.15.001804] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We report the spectral characteristics of CO(2)-laser inscribed long-period gratings (LPGs) in endlessly single mode photonic crystal fiber (PCF) subject to macro-bending. The coupling modes as a result of bending were studied by examining the shifts of resonant wavelengths, the splits of attenuation bands, and the variation in coupling strength of the transmission spectra. A bending coefficient of ~ 27.9 nm.m was determined in the PCF at 180 degrees rotational orientation relative to the point of laser inscription in the curvature range from 2.6 m(-1) to 3.5 m(-1). Compared with conventional fiber LPGs fabricated using the same method, the PCF-based LPGs possess higher sensitivity both to bending and orientation, making them promising for sensor applications.
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20
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Ceballos-Herrera DE, Torres-Gómez I, Martínez-Ríos A, Anzueto-Sánchez G, Alvarez-Chávez JA, Selvas-Aguilar R, Sánchez-Mondragón JJ. Ultra-widely tunable long-period holey-fiber grating by the use of mechanical pressure. APPLIED OPTICS 2007; 46:307-11. [PMID: 17228374 DOI: 10.1364/ao.46.000307] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
We report an ultra-widely tunable long-period holey-fiber grating, which combines the wide-range single-mode behavior and transverse strain sensitivity of the holey fibers with the advantages of mechanically induced long-period fiber gratings. We obtain a versatile widely tunable long-period holey-fiber grating with attractive transmission spectral characteristics for optical communications, fiber-based amplifiers, and lasers. The mechanically induced long-period holey-fiber grating shows a continuous tuning range over 500 nm, more than 12 dB depth notches with less than 0.75 dB out-of-band losses, and bandwidth control from 10 to 40 nm.
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21
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Brambilla G, Fotiadi AA, Slattery SA, Nikogosyan DN. Two-photon photochemical long-period grating fabrication in pure-fused-silica photonic crystal fiber. OPTICS LETTERS 2006; 31:2675-7. [PMID: 16936854 DOI: 10.1364/ol.31.002675] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
We report what is to our knowledge the first photochemical fabrication of a long-period grating in a pure-fused-silica photonic crystal fiber. The inscription technique is based on a two-photon absorption mechanism and does not require a specially designed photonic crystal fiber with a photosensitive Ge-doped core. The characteristic fluence value for the inscription is an order of magnitude less than that for a standard telecom fiber irradiated under similar conditions with the same grating parameters.
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22
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Kim J, Paek UC, Lee BH, Hu J, Marks B, Menyuk CR. Impact of interstitial air holes on a wide-bandwidth rejection filter made from a photonic crystal fiber. OPTICS LETTERS 2006; 31:1196-8. [PMID: 16642057 DOI: 10.1364/ol.31.001196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
We have investigated the spectral properties of a band rejection filter made with a long-period fiber grating written in photonic crystal fiber that has interstitial air holes. Experiments showed that only one mode was coupled strongly to the fundamental core mode over a 600 nm spectral range. The central wavelength of the filter could be tuned over that range without being appreciably affected by any other mode. By using the multipole method, we found that the interstitial air holes of the photonic crystal fiber played a critical role in limiting the number of modes that could strongly interact with the fundamental mode and in obtaining well-separated resonance peaks. Excellent agreement between theory and experiment was obtained.
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Affiliation(s)
- Jinchae Kim
- Department of Information and Communications, Gwangju Institute of Science and Technology, Gwangju, Korea
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23
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Park KN, Lee KS. Improved effective-index method for analysis of photonic crystal fibers. OPTICS LETTERS 2005; 30:958-60. [PMID: 15906969 DOI: 10.1364/ol.30.000958] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
We propose, for the first time to our knowledge, an improved effective-index method (IEIM) that has the advantage of high speed and much better accuracy than the conventional effective-index method. The modal properties computed with the IEIM, such as effective index and dispersion, are closely matched to those of the multipole method as well as to experimental values.
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Affiliation(s)
- Kwang N Park
- School of Information and Communications Engineering, Sungkyunkwan University, Suwon 440-746, South Korea
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24
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Efimenko K, Rackaitis M, Manias E, Vaziri A, Mahadevan L, Genzer J. Nested self-similar wrinkling patterns in skins. NATURE MATERIALS 2005; 4:293-7. [PMID: 15750598 DOI: 10.1038/nmat1342] [Citation(s) in RCA: 360] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2004] [Accepted: 01/27/2005] [Indexed: 05/23/2023]
Abstract
Stiff thin films on soft substrates are both ancient and commonplace in nature; for instance, animal skin comprises a stiff epidermis attached to a soft dermis. Although more recent and rare, artificial skins are increasingly used in a broad range of applications, including flexible electronics, tunable diffraction gratings, force spectroscopy in cells, modern metrology methods, and other devices. Here we show that model elastomeric artificial skins wrinkle in a hierarchical pattern consisting of self-similar buckles extending over five orders of magnitude in length scale, ranging from a few nanometres to a few millimetres. We provide a mechanism for the formation of this hierarchical wrinkling pattern, and quantify our experimental findings with both computations and a simple scaling theory. This allows us to harness the substrates for applications. In particular, we show how to use the multigeneration-wrinkled substrate for separating particles based on their size, while simultaneously forming linear chains of monodisperse particles.
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Affiliation(s)
- Kirill Efimenko
- Department of Chemical Engineering, North Carolina State University, Raleigh, North Carolina 27695-7905, USA
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25
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Zhu Y, Shum P, Bay HW, Yan M, Yu X, Hu J, Hao J, Lu C. Strain-insensitive and high-temperature long-period gratings inscribed in photonic crystal fiber. OPTICS LETTERS 2005; 30:367-369. [PMID: 15762430 DOI: 10.1364/ol.30.000367] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We fabricate and demonstrate strain-insensitive and high-temperature long-period gratings in endlessly single-mode photonic crystal fiber by use of focused pulses of a CO2 laser and a periodic stress relaxation technique without geometrical deformation and elongation of the fiber. The thermal dependence of mode coupling at 1299.59 nm is 10.9 pm/degrees C from 24 to 992 degrees C, whereas the coefficient of strain sensitivity is -0.192 pm/muepsilon up to the maximum strain of 2.74%epsilon. It is found for what is believed to be the first time that, in contrast with the traditional fiber case, the coupling resonance shifts toward shorter wavelengths under applied strain, indicating that the refractive index of the core is decreased as a result of the rebuilding of tension attributed to the stress-elastic effect, and the cladding modes is highly dispersive because of airholes arranged in the fiber cladding.
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Affiliation(s)
- Yinian Zhu
- Network Technology Research Center, Nanyang Technological University, 50 Nanyang Drive, Research TechnoPlaza, Singapore 637553.
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Zhu Y, Shum P, Bay HW, Chen X, Tan CH, Lu C. Wide-passband, temperature-insensitive, and compact pi-phase-shifted long-period gratings in endlessly single-mode photonic crystal fiber. OPTICS LETTERS 2004; 29:2608-2610. [PMID: 15552660 DOI: 10.1364/ol.29.002608] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We demonstrate what is believed to be the first fabrication of a wide-passband, temperature-insensitive, and compact spectral filter based on a pi-phase-shifted long-period grating in an endless single-mode photonic crystal fiber. By introducing a pi-phase shift in the middle of a 12-period long-period grating, two symmetrical rejection bands at wavelengths of 1252.65 and 1418.7 nm are obtained with isolation higher than 18 dB and a passband bandwidth of 84.15 nm. The pi-phase-shifted long-period gratings are inscribed by the relaxation of mechanical stress with the focused pulses of a CO2 laser and a point-by-point technique without geometric deformation. The length of the spectral filter is approximately 6.6 mm with a sensitivity of 8 pm/ degrees C at a medium temperature range of 23-190 degrees C.
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Affiliation(s)
- Yinian Zhu
- Network Technology Research Center, Nanyang Technological University, 50 Nanyang Drive, Research TechnoPlaza, Singapore 637553.
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