Design of diamond-shape photonic crystal fiber polarization filter based on surface plasma resonance effect

A novel plasmonic polarization filter based on the diamond-shape photonic crystal fiber(PCF) is proposed. The resonant coupling characteristics of the PCF polarization filter are investigated by the full-vector finite-element method. By optimizing the geometric parameters of the PCF, when the fiber length is 5 mm, the polarization filter has a bandwidth of 990 nm and an extinction ratio(ER) of lower than -20 dB. Moreover, a single wavelength polarization filter can also be achieved, along with an ER of -279.78 dB at wavelength 1.55 μm. It is believed that the proposed PCF polarization filter will be very useful in laser and optical communication systems.     

Polarisation-sensitive four-wave mixing and soliton self-frequency shift effect in the highly birefringent photonic crystal fibre

By adjusting the polarisation state of the pump at 805 nm parallel to slow (x) and fast (y) axes of the highly birefringent photonic crystal fibre with zero dispersion wavelengths 790 nm and 750 nm,this paper demonstrates the efficient polarisation-sensitive four wave mixing involved in pump,anti-Stokes and Stokes signals and soliton selffrequency shift effects induced by the phase-matching between red-shifted solitons and blue-shifted dispersive waves.If the reduction of coupling efficiency to the circular pump laser mode or other circular fibres due to asymmetry of the core is neglected,more than 98% of the total input power is kept in a single linear polarisation.Controlled dispersion characteristic of the doublet of fundamental guided-modes results in achieving light field strongly confined in principal axes of photonic crystal fibre,and enhancing the corresponding nonlinear-optical process through the remarkable nonlinear birefringence.     

传输可见光的空芯光子带隙光纤的研究

利用全矢量平面波展开法(FVPWM)对采用改进的两次堆积法制备的空芯光子带隙光纤进行了数值模拟.在特定传播常数β下，光纤在500—1000 nm的波段内出现多条宽窄不同的有效光子带隙.依据有效折射率的不同，部分带隙中的空气-导模将以不同的形式存在.经过实验测试，发现测得的带隙位置相对于模拟结果向短波段发生了较明显的移动，主要原因被认为是光纤结构的纵向不均匀性和包层节点处间隙孔的存在. 关键词： 空芯光子带隙光纤 全矢量平面波展开法 有效光子带隙 空气-导模     

Design on a highly birefringent and nonlinear photonic crystal fiber in the C waveband

In this paper, a novel photonic crystal fiber （PCF） with high birefringence and nonlinearity is designed. The charac- teristics of birefringence, dispersion and nonlinearity are studied by using the full-vector finite element method （FVFEM）. The numerical results show that the phase birefringence and nonlinear coefficient of PCF can be up to 4.51× 10-3 and 32.8972 w-l.km-1 at 1.55 μm, respectively. The proposed PCF could be found to have important applications in the polarization-dependent nonlinear optics such as the pulse compress and reshaping in the C waveband.     

Highly sensitive digital optical sensor with large measurement range based on the dual-microring resonator with waveguide-coupled feedback

We propose a novel high-performance digital optical sensor based on the Mach-Zehnder interferential effect and the dual-microring resonators with the waveguide-coupled feedback. The simulation results show that the sensitivity of the sensor can be orders of magnitude higher than that of aconventional sensor, and high quality factor is not critical in it. Moreover, by optimizing the length of the feedback waveguide to be equal to the perimeter of the ring, the measurement range of the proposed sensor is twice as much as that of the conventional sensor in the weak coupling case.     

Investigation on Guided-Mode Characteristics of Hollow-Core Photonic Crystal Fibre at Near-Infrared Wavelengths

Guided-mode characteristics of hollow-core photonic crystal fibre （HC-PCF） are experimentally and theoretically investigated. The transmission spectrum in the range from 755 to 845nm is observed and the loss is measured to be 0.12dB/m at 800nm by cut-back method. Based on the full-vector beam propagation method and the full-vector plane-wave method, the characteristics of mode field over propagation distance 1 m are simulated, and the results show that the propagation efficiency can be above 80%. Compared with the fundamental guided mode well confined in air core within shorter propagation distance, the second-order guided mode leaks into the cladding region and gradually attenuates due to larger refractive index difference. The primary loss factors in HC-PCF and the corresponding solutions are elementarily discussed.     

Six-bit all-optical quantization using photonic crystal fiber with soliton self-frequency shift and pre-chirp spectral compression techniques

In this paper,we propose an optical quantization scheme for all-optical analog-to-digital conversion that facilitates photonics integration.A segment of 10-m photonic crystal fiber with a high nonlinear coefficient of 62.8 W 1/km is utilized to realize large scale soliton self-frequency shift relevant to the power of the sampled optical signal.Furthermore,a 100-m dispersion-increasing fiber is used as the spectral compression module for further resolution enhancement.Simulation results show that 317-nm maximum wavelength shift is realized with 1550-nm initial wavelength and 6-bit quantization resolution is obtained with a subsequent spectral compression process.     

Highly efficient Cherenkov radiation generation in the irregular point of hollow-core photonic crystal fiber

Highly efficient Cherenkov radiation(CR) is generated by the soliton self-frequency shift(SSFS) in the irregular point of a hollow-core photonic crystal fiber(HC-PCF) in our laboratory.The impacts of pump power and wavelength on the CR are investigated,and the corresponding nonlinear processes are discussed.When the average power of the 120 fs pump pulse increases from 500 mW to 700 mW,the Raman soliton shifts from 2210 nm to 2360 nm,the output power of the CR increases by 2.3 times,the maximum output power ratio of the CR at 539 nm to that of the residual pump is calculated to be 24.32:1,the width of the output optical spectrum at the visible wavelength broadens from 35 nm to 62 nm,and the conversion efficiency η of the CR in the experiment can be above 32%.     

微结构光纤近红外色散波产生的研究

采用有限元法对实验室自制的非线性微结构光纤进行理论分析, 表明该光纤具有良好的非线性和色散波产生的相位匹配特性. 为实现微结构光纤非线性的全光纤化, 本实验采用中心波长为1032 nm的光纤飞秒激光器作为抽运源, 获得了753–789 nm 的近红外色散波. 实验中发现色散波中心波长和带宽随着抽运功率的改变会产生明显变化, 并且在不同光纤长度时, 色散波的频移量不同, 脉冲展宽及频谱也会有明显的变化. 实验结果与理论分析一致. 这些结果对实现微结构光纤非线性的全光纤化具有良好的借鉴作用, 为生物医疗应用特别是非线性光学显微成像术的近红外光源研究打下基础.     

一种新型的多包层光子晶体光纤的分析方法

传统有效折射率方法只能模拟具有相同空气孔大小的单包层光子晶体光纤.针对这一问题，提出了一种改进的有效折射率法，能够计算具有不同孔径的多包层光子晶体光纤的传输特性.并用此方法对三包层光子晶体光纤的基模有效折射率和色散等特性进行了数值模拟，结果与多极法模拟出的结果符合得很好.这种改进的有效折射率法拓展了传统有效折射率法的适用范围，对快速准确地分析和设计具有不同传输特性的多包层光子晶体光纤提供了理论依据. 关键词： 光子晶体光纤 多包层 有效折射率方法 色散