Depolarization of light in microstructured fibers filled with liquid crystals

In the paper we analyze microstructured optical fibers filled with typical nematic liquid crystals, i.e., 5CB and 6CHBT under influence of external electric field or temperature. We use the modified Mueller matrix method with an additional depolarization matrix to calculate degree of polarization changes of the light propagating in the liquid-crystal infiltrated microstructured optical fibers. Preliminary experimental results of light depolarization measurements during propagation in these microstructured fibers are also presented.     

Hollow-core microstructured polymer optical fiber

We have fabricated microstructured polymer optical fibers that guide light in a hollow core using the photonic bandgap mechanism. The hollow core allows the use of polymer fibers to be extended to wavelength ranges where material absorption typically prohibits their use, with attenuation lower than the material loss observed in the infrared. The fabrication method is similar to other microstructured polymer optical fibers, which has favorable implications for the feasibility of manufacturing such bandgap fibers.     

Investigation of modal properties of microstructured optical fibers with large depressed-index cores

We present what is, to the best of our knowledge, the first systematic study on how negative core-cladding index difference influences microstructured optical fiber's modal behavior. Single-mode lasing has been realized for short-length cladding-pumped phosphate glass microstructured fibers with large depressed-index Er(3+)-Yb(3+)-codoped cores.     

基于高非线性微结构光纤的全光再生研究

提出了利用高非线性微结构光纤自相位调制效应进行全光再生的研究方案。分析了一组微结构光纤的色散和非线性特性。结果显示光纤的非线性系数与光纤结构有密切关系。通过减小有效模面积,可以提高光纤的非线性系数。采用一种高空气填充比的高非线性微结构光纤作为非线性介质,进行了基于自相位调制效应的全光再生研究。结果表明,由于微结构光纤的高非线性,采用较短的光纤长度就可以实现较好的再生效果。同时,输入微结构光纤的峰值功率、滤波器的参量选择对光再生的效果有重要的影响,它们必需满足一定要求,才能实现光再生。此外,对再生器的传输特性进行了研究。通过调整输入峰值功率和滤波器的参量,可以对不同宽度的光脉冲信号进行全光再生。     

Antiresonant guiding microstructured optical fibers for sensing applications

A novel refractometric sensor utilizing unique spectral properties of antiresonant-guiding microstructured optical fibers is proposed. The sensor operation is based on the wavelength shift of the transmission spectrum in response to the refractive index change of a sample loaded in the air-holes of the microstructured optical fiber. Refractive index changes on the order of 0.1% can be detected using less than a nanoliter of a sample.     

Method of integral equations in the theory of microstructured optical fibers

A method for designing microstructured optical fibers that is based on exact integral equations for the transverse components of the magnetic field of the mode is proposed. A solution to the vector waveguide problem for fibers with a finite number of circular capillaries in the round cavity of the cladding can be refined successively. Quartz fibers with hexagonal capillary rings are also studied.     

Stress-induced birefringence in microstructured optical fibers

We present a numerical study of stress-induced birefringence in microstructured optical fibers (MOFs), using a finite-element method. MOFs under lateral forces and twists are considered separately. Compared with that in standard single-mode optical fibers, stress-induced linear birefringence in MOFs under a lateral force is reduced with increasing air-hole size, whereas twist-induced circular birefringence in MOFs is enhanced when the air-hole size is small.     

Single-mode microstructured optical fiber for the middle infrared

Microstructured crystalline optical fiber from silver halides is described. Both experimental and theoretical evidences are presented to establish that the fiber is effectively single mode at wavelength 10.6 micro m with numerical aperture NA=0.16 and optical losses of approximately 2 dB/m. Crystalline microstructured optical fibers offer key advantages over step-index optical fibers from silver halide crystals. The wide transmission range of wavelengths 2-20 micro m provides great potential for applications in spectroscopy and for the development of a range of new crystalline-based nonlinear optical fibers.     

椭圆空气孔微结构光纤限制损耗的分析

以完美匹配层为边界条件,用复有限元法分析了椭圆空气孔三角形微结构光纤中基模的限制损耗.数值结果表明: 当孔间距,空气填充率和空气孔环数增大时,基模的限制损耗减小.从计算结果还可以得出:限制损耗与基模的偏振有关,随着孔间距,空气填充率和孔的椭圆率的增大,y偏振模与x偏振模的限制损耗比也增大.最后,提出了两种可实现光单偏振,单模传输的高非线性微结构光纤. 关键词： 微结构光纤 限制损耗 复有限元法 完美匹配层     

A Bragg-like chirped clad all-solid microstructured optical fiber with ultra-wide bandwidth for short pulse delivery and pulse reshaping

Chirped cladding is proposed as a novel tailoring tool to simultaneously attain wider transmission window and reduced temporal dispersion in an all-solid Bragg-like microstructured optical fiber as compared to its perfectly periodic cladding counterpart. This design route for photonic bandgap microstructured fibers could be exploited as an additional degree of freedom for bandgap engineering. A suitably chirped clad fiber could be gainfully exploited to deliver femto-second pulse with ultra wide bandwidth. Further, generation of self-similar parabolic profile pulse is demonstrated by simulating propagation of an input Gaussian pulse through a 2 m long sample of such a linearly tapered Bragg like fiber.     

Symmetry and degeneracy in microstructured optical fibers

The symmetry of an optical waveguide determines its modal degeneracies. A fiber with rotational symmetry of order higher than 2 has modes that either are nondegenerate and support the complete fiber symmetry or are twofold degenerate pairs of lower symmetry. The latter case applies to the fundamental modes of perfect microstructured optical fibers, guaranteeing that such fibers are not birefringent. We explore two numerical methods and demonstrate their agreement with these symmetry constraints.     

Fabrication and study of microstructured optical fibers with elliptical holes

We report the fabrication of what are believed to be the first microstructured optical fibers with uniformly oriented elliptical holes. A high degree of hole ellipticity is achieved with a simple technique that relies on hole deformation during fiber draw. Both form and stress-optic birefringence are characterized over a broad wavelength range. These measurements are in excellent agreement with numerical modeling and demonstrate a birefringence as high as 1.0 x 10(-4) at a wavelength of 850 nm.     

Optimum intermediate fibers for reducing interconnection loss: exact solution

We derive an exact analytical solution for a transmission line of N single-mode intermediate optical fibers that minimize the interconnection loss between any two dissimilar fiber modes that are well described by that paraxial scalar wave equation. Our solution shows that N optimum intermediate fibers reduce the original interconnection loss by a factor of least 1/(N+1) and that the total interconnection loss is only a function of N and the original direct interconnection loss. Our solution is not restricted to axisymmetric fibers or mode fields and therefore could be useful for reducing the interconnection loss between microstructured optical fibers, between certain slab waveguides, or between fibers and optical sources or detectors.     

四方阵列聚苯乙烯/聚甲基丙烯酸甲酯微结构光纤的制造与光学特性

用聚苯乙烯光纤填充625孔聚甲基丙烯酸甲酯微结构光纤预制棒中的空气孔制备了新型微结构光纤预制棒.拉伸后得到了四方阵列聚苯乙烯/聚甲基丙烯酸甲酯微结构聚合物光纤.该光纤的纵方向可以作为传递图像介质,而纵截面上折射率的周期性结构可以作为透射光栅使用,该光栅产生的moiré条纹可以用于测量小角度移动.     

Twisted clad microstructured optical fibers: revisited

The paper discusses confinements corresponding to low-order sustained hybrid modes in twisted clad microstructured optical fiber with twists in the form of conducting sheath helix structure introduced at the core–clad interface and inclined at certain angles. Dispersion relations for such fiber structures are deduced under strict electromagnetic boundary conditions. Varying the angle of pitch (of the introduced conducting sheath helix), investigations in respect of the dependence of power confinements due to the existing low-order hybrid modes have been carried out. The obtained results indicate the usefulness of such microstructured fibers for attenuation or amplification of power in the guide.     

Simulation of femtosecond pulse propagation in sub-micron diameter tapered fibers

Ultrashort pulse propagation and supercontinuum generation in tapered and microstructured optical fibers is usually simulated using the corrected nonlinear Schrödinger equation. One of the underlying approximations is the use of a wavelength-independent effective area or, equivalently, of a constant nonlinear coefficient . In very thin waveguide structures with strong light confinement, including silica wires and sub-micron tapered fibers and some microstructured fibers, the validity of such an approximation comes into question. In this paper we present an improved model in which all modal properties are fully taken into account as functions of the wavelength. We use comparative numerical simulation to identify certain regimes in which an improved model is needed for quantitatively correct results. PACS 02.70.Hm; 02.60.Cb; 42.65.Wi; 42.65.Re; 42.81.Pp     

Sol-gel matrix modified microstructured optical fibre towards a fluoride sensitive optical probe

In this article, we report an optical fluoride probe based on microstructured polymer optical fibers (MPOFs) which is modified with morin-Al complex doped silica gel film. This probe is fabricated by sol-gel fluxion coating process. Sol solution doped with morin-Al is directly inhaled into array holes of MPOF and then forms morin-Al-gel matrix film in them. The sensing probe shows different fluorescence intensity to different fluoride ion concentrations in the aqueous solution. The range of response is 5-50 mmol/L, under the condition of pH 4.6.     

A colloidal crystal microstructure fiber: fabrication and characterization

A method of fabricating colloidal crystal microstructured fiber is presented. The proposed structure relies on partial etching of the cladding layer of a single-mode fiber and growth of colloidal photonic crystals inside eroded area. The photonic crystal cylindrical annulus embedded in fiber is characterized by optical and scanning electron microscopy. The optical characterization was analyzed by optical transmission spectroscopy. The measurement results show a about 1550-nm band gap. The results also reveal the possibility of cladding cylindrical fibers with three-dimensional photonic crystals.     

倏逝波型光纤气体传感器研究进展

介绍了倏逝波的概念和反映倏逝波光纤气体传感特性的穿透深度参数Z_m。讨论了D形、锥形、纤芯裸露形、纤芯失配型和微结构光纤等不同倏逝波型气体传感的原理和特点,评述了其最新研究进展,对比分析了各传感器的优缺点。对倏逝波型光纤气体传感器的发展趋势进行了展望。     

Supercontinuum and gas cell in a single microstructured fiber

We exploit both the high nonlinearity and the holey structure of microstructured fibers to combine a broad-band light source and a gas cell in a single microstructured fiber. A broadband supercontinuum is formed by launching nanosecond pulses from a compact, Q-switched Nd:YAG laser into a microstructured fiber filled with acetylene. This continuum is self-referenced to the acetylene lines in the 1500 nm region. The performance of different index-guiding narrow-core microstructured fibers as nonlinear and host media is evaluated. The concept offers many possibilities and can be applied to various gases absorbing at different wavelengths.