一种近红外波段的高双折射高非线性光子晶体光纤

提出了一种具有中心缺陷孔的新型非对称椭圆光子晶体光纤,采用全矢量有限元法研究了其双折射、色散和非线性等特性。通过改变第一层椭圆孔的角度,加强了结构的双折射性能,同时还能改善结构的色散表现。分析计算结果得出,设计合适的结构参数可在波长1.55μm处获得3.05×10~(-2)的高双折射,同时在X和Y偏振方向获得较高非线性系数。此外,在保持高双折射的同时,此PCF也可获得1 000~1 550 nm近550 nm的负色散平坦区。该新型近红外波段的高双折射高非线性负平坦色散的光子晶体光纤在偏振控制、非线性光学及光纤通信等领域具有广泛的应用前景。     

An analysis of high birefringence fibers

A fiber is birefringent if it has a non-circular core and/or cladding, or is subjected to anisotropic stress. As a result of anisotropic stress, the fibers become biaxial. In this work, a theoretical study on the fields and dispersion of polarization modes in biaxial fibers is presented. The analysis is based on a perturbation method. In particular, the inclusion or exclusion of a term is determined by the differential equations, the boundary conditions and the symmetry of the problem, and does not rely on the prior knowledge of the fields in the fibers. The dependence of the fiber birefringence on the index difference and index anisotropy are determined. With the fields known, the excitation of high birefringent fibers can be analyzed. Methods for studying these excitation problems are indicated and some of the results are presented.     

光子带隙型光子晶体光纤

光子晶体光纤（PCF）有着许多奇异的特点和广泛的应用前景。目前,光子晶体光纤的技术发展很快,其潜在应用不断被发掘出来。文章简要分析了光子带隙（PBG）型PCF的导光机制,介绍了它的典型结构、制作工艺和PBG的形成机理。探讨了其在光通信中的应用。     

高双折射光纤中矢量调制不稳定性

利用光脉冲在光纤中传播时所遵守的相干非线性薛定谔耦合方程,研究了偏振方向沿两个双折射轴的分量强度相等时,在反常色散区和正常色散区所产生的调制不稳定性.结果表明在反常色散区和正常色散区,对应不同的功率区域输入脉冲有不同的增益谱,并且当双折射性质变化时导致增益谱表现出明显的不同.     

Photonic bandgap surfaces with interdigitated corrugations

For a given operational frequency, the unit cell surface area of a metallo-dielectric photonic bandgap structure (MBPG) is reduced by increasing the capacitance between adjacent unit cell elements. An MPBG structure possessing interdigitated corrugations is proposed in order to achieve this increase. The structure is incorporated, as the ground plane, in a microstrip transmission line and it is experimentally characterised over the 50 MHz-4 GHz frequency band.     

Photonic bandgap dielectric waveguide filter

The application of photonic bandgap (PBG) structures as the sidewall of the printed circuit board (PCB) dielectric waveguide filter is investigated. The effect of different PBG parameters on the Q-value of PBG dielectric waveguide resonator is evaluated. A PBG dielectric waveguide three-pole Chebyshev bandpass filter is realized. The measured performance matched well with the calculated results. The newly proposed I/O coupling structure makes the filter much easier for mass production     

High birefringence photonic bandgap fiber with elliptical air holes

In this paper, we proposed a high birefringence photonic bandgap fiber (PBGF) with elliptical air holes in cladding and circular air hole in core. The forbidden gaps of the honeycomb structure are calculated when the circular air holes are deformed to the elliptical shape. And the birefringence of the PBGFs is investigated by using a full-vector finite element method (FEM) and the numerical results are presented.     

高双折射全内反射光子晶体光纤的特性研究

文章应用全矢量有效折射率方法(FVEIM)对芯区具有两个椭圆小空气孔的全内反射光子晶体光纤(TIR-PCF)进行了研究.结果表明,光子晶体光纤(PCF)的芯区折射率与包层区等效折射率的差随波长的增大而增大;固定包层空气孔的相对孔径,PCF基模的两个正交偏振态简并被打破,呈现出模式高双折射;随着芯区小空气孔椭圆率变大,模式双折射增大,PCF的总色散曲线变平坦.     

Photonic bandgap fibre oscillators and amplifiers

In the search for ever higher output power or energy from fibre oscillators or amplifiers a nowadays mature technology relies on enlarging the fibre mode area. Broadening of the core diameter, all other things being equal, inevitably yields a multimode fibre, thereby dramatically limiting the device usefulness. Various strategies have been deployed to design and manufacture single transverse mode fibre oscillators and amplifiers, among which making use of the so-called photonic bandgap effect to restrict the modal population seems promising. Helped by efficient and reliable numerical tools the design of large mode area singlemode photonic bandgap fibres is presented. Two fibres with 20-μm and 40-μm core diameter, both of them heavily doped with Yb³⁺ ions, have been fabricated by the widespread modified chemical vapour deposition process and are shown to behave properly when used as the core element of either continuous wave oscillators or femtosecond amplifiers. Good output beam quality (M² parameter spanning from 1.12 to 1.5 for the set of fibres studied) and high slope efficiency of 80% in cw oscillation regime are demonstrated. Furthermore the 40-μm core diameter fibre is shown to be resilient to tight bending down to 7.5-cm radius. The stack-and-draw process makes it easy to tailor the outer cladding so that a large numerical aperture can be reached. Subsequently, from this air-clad fibre, 500 fs 47 W pulses at 35 MHz are obtained from a two-stage chirped pulse amplification system.     

分层手征介质的光子带隙特性

导出了分层手征介质中的斜入射电磁波的传输矩阵,由传输矩阵可以计算分层手征介质的反射和透射系数,研究了由手征介质构成的一维周期结构的光子带隙特性及其与入射角的变化关系,讨论了光子带隙与手征导纳之间的关系.研究表明,手征导纳可以控制光子带隙的特性,在适当的参数条件下,可以获得非常理想的多通道滤波特性.     

高双折射光子晶体保偏光纤研究进展

光子晶体光纤的问世,使得光子晶体保偏光纤(Polarization maintained photonic crystal fibers,PM-PCF)的研究一直是光通信领域的研究热点.在综述国内外大量文献的基础上,对高双折射光子晶体保偏光纤的传输机理和保偏原理进行分析,评述了高双折射光子晶体保偏光纤的各种设计方案,并进一步对光子晶体保偏光纤的研究现状、应用和发展前景进行了展望.     

Photonic bandgap formation and tunability in certainself-organizing systems

We describe the microfabrication and band structure of large scale three-dimensional (3D) photonic bandgap (PBG) materials based on self-organizing templates. The simplest of these templates is an fcc lattice of close-packed, weakly sintered spheres. Other templates include hcp and hexagonal AB₂ self-organizing photonic crystals. These photonic crystals may be converted into PEG materials by partially infiltrating the template with high refractive index semiconductors such as Si, Ge, or GaP and subsequently removing the template. The resulting “inverse opal” structure exhibits both a photonic pseudogap and a complete (3D) PBG in the near visible spectrum, spanning up to 15% of the gap center frequency. The local density of states (LDOS) for photons exhibits considerable variation from point to point in coordinate space and reveals large spectral gaps even in the absence of a PEG in the total density of states. These gaps in the LDOS may lead to novel effects in quantum and nonlinear optics when active atoms or molecules are placed within the PBG material. These effects include anomalous, low threshold nonlinear response, collective atomic switching, and low-threshold all-optical transistor action. When an optically birefringent nematic liquid crystal is infiltrated into the void regions of the “inverse” opal PBG material, the resulting composite material exhibits a completely tunable PBG. In particular, the 3D PBG can be completely opened or closed by applying an electric field which rotates the axis of the nematic molecules relative to the inverse opal backbone     

Explicit birefringence analysis for anisotropic fibers

A hyper-perturbation approach is used to find the Taylor expansion formulas for the dispersion curves of arbitrarily indexed optical fibers. These formulas are then used to give analytically the birefringence characteristics of optical fibers with biaxially anisotropic core and cladding. The dependence of the fiber birefringence on the index difference, index anisotropy, and the normalized frequency is explicitly determined. Simple, accurate analytic formulas have been presented for anisotropic fibers with step- and parabolic-index profiles. Numerical results are in good agreement with the literature results     

Confinement losses in air-guiding photonic bandgap fibers

The wavelength dependence and the structural dependence of confinement losses in air-guiding photonic bandgap fibers (PBGFs) are, for the first time, investigated by using a full-vector finite element method. It is confirmed from computed results that one of the main causes of transmission losses in air-guiding PBGFs is the confinement loss and that, even if using large air holes of diameter to pitch ratio of 0.9, at least twenty rings of air hole arrays are required in the cladding region to reduce the confinement loss to a level of 0.01 dB/km.     

光子带隙光纤准直器回波损耗研究

研究了一种光子带隙光纤准直器。为了降低回波对光源的干扰,通常光纤准直器的回波损耗不应低于60 dB。由于带隙光纤端面没有反射,因此满足这一条件的带隙光纤准直器GRIN透镜入射面的倾斜角与普通光纤准直器不同。从高斯光束通过光学系统的一般模型出发,利用矩阵光学和高斯光束耦合理论,推导了光线传输矩阵。结合实际应用中光纤及GRIN透镜的参数,仿真分析了尾纤与GRIN透镜之间的间距及GRIN透镜的参数对准直器回波损耗的影响。结果表明,镀有增透膜时,当光子带隙光纤准直器的GRIN透镜入射面倾角等于3时,回波损耗大于60 dB。研究结果对进行光子带隙光纤准直器的设计具有指导意义。     

Research on highly nonlinear photonic bandgap fibers

Since thefirst photonic crystal fiber (PCF) wasfabri-cated by Knight J C and his colleagues[1]at 1996 ,thistype of fibers ,consisting of a central defect region sur-rounded by multiple air holes running alongits length,has been the subject of much interes…     

Stress-induced birefringence of side-tunnel type polarization-maintaining fibers

Stress-induced birefringence of side-tunnel type polarization-maintaining optical fibers is presented. After checking the accuracy of finite-element calculations, the thermal stress analyses of various side-tunnel fibers are performed and the relation between the fiber parameters and the stress-induced birefringence is systematically investigated compared with the geometrical birefringence. As a result, it is found that for some cross-sectional shape, the stress-induced birefringence is more dominant than the geometrical one even in the side-tunnel fibers. We also investigate in detail the axial refractive-index and the axial stress of the fiber and compare them with those of ordinary step-index circular fibers.     

带有无序填充气线石英介质的光子晶体光纤

简述了无序光子局域化和光子晶体带隙的关系，介绍了国外多孔光子晶体光纤的研究现状；提出了研制带有无序填充气线石英介质的光子晶体光纤的设想，以及这种新型光纤的优势和它的潜在应用。     

一种带热滞回保护的高精度高电源抑制比带隙基准源

To meet the accuracy requirement for the bandgap voltage reference by the increasing data conversion precision of integrated circuits, a high-order curvature-compensated bandgap voltage reference is presented employing the characteristic of bipolar transistor current gain exponentially changing with temperature variations. In addition, an over-temperature protection circuit with a thermal hysteresis function to prevent thermal oscillation is proposed. Based on the CSMC 0.5 μ m 20 V BCD process, the designed circuit is implemented; the active die area is 0.17 × 0.20 mm². Simulation and testing results show that the temperature coefficient is 13.7 ppm/K with temperature ranging from –40 to 150 ℃, the power supply rejection ratio is –98.2 dB, the line regulation is 0.3 mV/V, and the power consumption is only 0.38 mW. The proposed bandgap voltage reference has good characteristics such as small area, low power consumption, good temperature stability, high power supply rejection ratio, as well as low line regulation. This circuit can effectively prevent thermal oscillation and is suitable for on-chip voltage reference in high precision analog, digital and mixed systems.     

一种高电源抑制比带隙基准源的设计

带隙基准源是LDO中的重要模块,其性能的好坏直接影响到LDO整个系统的性能,为此本文针对以上问题进行相关研究,设计一种具有较高的PSRR和较低的稳定输出电压的带隙基准电压源。文中结合工程实际的要求设计了一款具有高的电源抑制比（PSRR）、低的输出基准电压的带隙基准电压源。本设计采用SMIC公司的0.18μm工艺进行仿真,Hspice的仿真结果表明该基准源在电源抑制比（PSRR）、温度特性等方面有良好的性能。