非对称光纤反射镜的可调谐光纤激光器

提出一种非对称窄带光纤环形反射镜结构的可调谐掺铒光纤激光器。980nm泵浦光对掺铒有源光纤进行抽运,高双折射光纤、偏振控制器（PC）和光纤耦合器构成窄带光纤反射镜,窄带光纤反射镜和普通光纤反射镜组成激光谐振腔,利用窄带光纤反射镜工作带宽纳米量级的特性得到单纵模激光。调整偏振控制器改变反射镜对不同波长的反射率,实现可变波长的激光输出。实验表明,该激光器的工作带宽为8nm,120mW泵浦光条件下最大输出功率为4mW,3dB带宽（脉冲的半高宽度）小于0．2nm,边模抑制比为20dB以上,在1527nm～1535nm的波长范围内观察到稳定激光输出。     

Liquid-level sensor with a high-birefringence-fiber loop mirror

A novel liquid-level sensor with a high-birefringence-fiber loop mirror (HBFLM) based on a uniform-strength cantilever beam (UCB) is proposed and demonstrated. Part of the high-birefringence fiber is pasted onto the central surface of the UCB. A hollow suspending pole is utilized to apply force at the end of the beam. The applied force varies with the change of the liquid level, leading to a change of transmission intensity. Thus the variation of liquid level can be determined via the laser wavelength within the quasi-linear transmission range of the HBFLM filter. Its sensitivity, resolution, and linear measurement range reach 0.047/cm, 10 mm, and 140 mm, respectively. The advantages of the sensor include simple structure, high sensitivity, low cost, and good repeatability, etc. The sensing signal can be directly detected by a photodetector and does not require complicated demodulation devices.     

Resonant frequencies of Fabry-Perot interferometers with ultrathin mirror spacings

Fabry-Perot interferometers (FPIs) with multilayer dielectric mirrors and mirror spacings as low as 0.7% of the operating wavelength are studied. It is shown how these low-order FPIs are affected by the phase dispersion characteristics of multilayer dielectric mirrors. Because experimental results in the optical regime are extremely difficult to obtain, radio frequency experiments are performed with coaxial cable FPI structures. Experimental results show excellent agreement with theory. These phase effects in FPIs with ultrathin mirror spacings are of great interest in the design of tunable microcavities with possible applications in optical communications.     

Theory and design of a simple tunable Sagnac loop filter for multiwavelength fiber lasers

We present a novel design for a Sagnac loop filter (SLF) whose periodic output spectrum can be fully controlled by cascading a small-birefringence loop (SBL) with a high-birefringence loop (HBL). We develop a detailed theoretical analysis, using the Jones vector method, to calculate the transfer function of the tunable SLF. It has been quantitatively shown that both the transmission coefficient and the phase of the SLF can be controlled by adjusting the orientation angle of the birefringent axes of the SBL in the plane of polarization. The theory has been confirmed by experimental results where a stress-induced SBL was mechanically rotated to tune both the wavelength and the power of a periodic output spectrum. Such a tunable SLF is used in the design of a multiwavelength erbium-doped fiber laser in the C band.     

A novel temperature sensor and variable optical attenuator based on a high-birefringence fiber loop mirror

A novel variable optical attenuator based on a high-birefringence fiber loop mirror is described. The fiber loop mirror is placed in a controlled-temperature chamber. As the temperature is increased, the transmission spectrum exhibits a shift, while virtually not changing its shape. The degree of attenuation at a wavelength of 1558 nm exceeds 30 dB, while the introduced losses are about 2.5 dB. The temperature-induced shift of the spectrum is strictly linear. The response of the temperature sensor based on this effect is linear with a correlation coefficient of 0.9997. The obtained experimental data are interpreted based on the results of numerical modeling.     

聚合物光纤及其应用

本文综述国内外聚合物光纤的最新进展 ,介绍降低聚合物光纤损耗的氘化和氟化的方法 ,提出宽带的梯度折射率聚合物光纤 .分析聚合物的光学特性 ,报道功能聚合物光纤、聚合物光纤的无源和有源器件的研究 .     

High-repetition-rate, narrow-band dye lasers with water as a solvent for dyes

The performance of a copper vapor laser-pumped narrow-band dye laser in oscillator-amplifier configuration with water-based binary mixture solvents is described. Although oscillator efficiency in water-surfactant (sodium lauryl sulfate) solvent was comparable with that that employed pure ethanolic solvent, amplifier efficiency was found to be lower. Experiments that were carried out with vertically polarized pump beams and either horizontally or vertically polarized signal beams show that, in case of both the pump and signal having orthogonal polarization (horizontal) and same polarization (vertical), the extraction efficiency for both ethanolic and water-micelle media increased substantially from 15.7% to 18.5% and from 10% to 12.5%, respectively. However, the relative difference remained nearly the same, indicating that a slower orientational diffusion of excited dye molecules in a micellar medium is not responsible for a decrease in amplifier efficiency. Amplifier efficiency comparable with that containing ethanolic dye solutions could be obtained with a binary solvent that comprises a mixture of water and about 30% n-propanol. The performances of two efficient dyes, Rhodamine-6G and Kiton Red S, using water-based solvents were studied.     

Auto-oscillations in neodymium fiber lasers with micro-optomechanical structures

Auto-oscillations in neodymium-doped fiber lasers with intracavity micro-optomechanical elements have been studied. Experimental results can be explained in the framework of ideas on the internal resonance in a laser system.     

External cavity lasers using stripe mirrors with different mirror width

We present the study of an external cavity laser using a stripe mirror and a grating for the optical feedback. As the most important parameter in this system, the width of the stripe mirror has been systematically studied, which strongly affects the device performances. Furthermore, the size of the focused laser spots and the distance between the spots of adjacent modes have been obtained. The measured results agree with the theoretical calculation very well. These parameters are very important for the design and construction of this kind of external cavity lasers.     

Rapid prototyping with high power fiber lasers

Laser rapid prototyping technologies comprise a set of technologies used in a wide range of materials to produce prototypes or small batches of complex shaped components. This paper presents a research work on rapid prototyping technology with laser additive manufacture of wire based alloy Ti-6Al-4V with an 8 kW fiber laser for the production of components with cylindrical geometry. For this, an engineering system was developed, a demonstration part produced and the deposition process was characterized. Two processing parameters were investigated: and these were the relative position between the wire feeding system and the substrate and the laser beam to wire width ratio. The former affects the molten metal transfer mode and the pressure exerted by the wire tip on the molten pool, while the laser beam to wire width ratio affects the process efficiency, since this is a compromise of process stability and process speed. Both parameters control surface finishing and the smoothness of the part. The melting efficiency of the process is low when compared to alternative processes involving powder pre deposition, but the density of the part is improved with homogeneous structural characteristics.     

Q-switched fiber lasers with carbon nanotubes hosted in ceramics

Q-switched fiber ring lasers operated by single-walled carbon nanotubes (SWNTs) hosted in SiO(2) matrix are demonstrated by highlighting their stable operation and dramatically improved thermal damage threshold. Employing aerosol deposition process, SWNTs are incorporated into the ceramic host at room-temperature without solubility limitation. After experiencing the intracavity optical power higher than 15.3 dBm, the hosted SWNTs survive to provide Q-switching operation. The continuous repetition rate tuning is achieved in the range of 11.1-32.2 kHz with the pulse-duration of 7.1-15.8 μs at 1558.5 nm.     

苎麻纤维复合材料及其应用

综述了国内外苎麻纤维复合材料的研究现状,主要包括影响苎麻纤维复合材料力学性能的因素,并介绍了复合材料界面和改善界面的方法,以及苎麻复合材料的应用.     

Development of recycled PET fiber and its application as concrete-reinforcing fiber

We describe a method that can be used to produce concrete-reinforcing PET fiber from used PET bottles. Using this method, the concrete and PET fibers are easily mixed at a fiber contents as high as 3%. The primary characteristic of the PET fiber is that it is easy to handle. The issue of concern in the development of PET fiber is its alkali resistance; however, we encountered no problems when using the fiber in normal concrete. The wetting tension of PET was found to be lower than that of PVA but higher than that of PP. No toxic gas was generated during a combustion test of the PET fiber. We describe two example applications: a gateway support at Hishikari Mine, Japan, and the pavement of bush roads.     

Birefringence measurement in double-clad fiber lasers with large cross section

We report on birefringence measurements in double-clad fibers with large cross section, doped with neodymium and ytterbium. The experimental results for rectangular double-clad fibers are compared with those for single-clad circular neodymium-doped fibers, taking into account existing models of stress- and geometry-induced birefringence. We demonstrated that the ellipticity of an outer silica cladding has no effect on birefringence in large-area double-clad fibers. The stress-induced birefringence is shown to depend on the ratio between the diameter of an internal silica support and the linear dimensions of the rectangular outer cladding. The stress-distribution pattern is derived to prove the experimental results.     

Recirculation fiber loop interferometer with a Faraday reflector

A new optical scheme of the recirculation fiber loop interferometer with a Faraday reflector and a broadband radiation source is suggested. It is experimentally established that this scheme provides for a more than tenfold decrease in the instrument zero response caused by a spurious polarization modulation in the phase modulator. Factors leading to additional shifts in the instrument zero response are revealed.     

单皮层中空纤维超滤膜及其应用

简要介绍了单皮层中空纤维超滤膜制备的思路、原理和工艺方法，并对其在各个领域中的应用进行了讨论．     

Polarization properties of fiber lasers with twist-induced circular birefringence

We have experimentally observed and theoretically analyzed the polarization properties of fiber lasers with twist-induced birefringence. Twisting a fiber induces the circular birefringence of a fiber laser cavity, and this birefringence reduces the effects of intrinsic linear birefringence on the polarization properties of fiber lasers. The frequencies of their polarization eigenmodes coincide with each other gradually as the twist rate increases, and the directions of polarization eigenmodes deviate from the birefringence axis at a much larger twist rate than the magnitude of intrinsic linear birefringence. We describe the successful experimental results for Nd and Er fiber lasers.     

Characterization of fiber distributed-feedback lasers with an index-perturbation method

We demonstrate the characterization of fiber distributed-feedback lasers by scanning a heat-induced index perturbation along the cavity and by measuring the induced laser frequency shift. The measured shift is shown to be a good indicator for the intensity distribution in the cavity, and the experimental results reveal that the sensitivity of fiber distributed-feedback laser sensors with frequency readout is highly localized near the grating phase-shift position. Use of the characterization data to determine the grating coupling parameter kappa, the polarization dependence of kappa, and birefringence nonuniformities as well as for identification of the order of longitudinal mode operation are discussed and demonstrated experimentally. Asymmetrically phase-shifted lasers with highly directional output are also investigated.     

150 W high-average-power, single-frequency nanosecond fiber laser in strictly all-fiber format

We demonstrate an all-fiber, single-frequency nanosecond laser with both high peak power and average power based on a master oscillator power amplifier (MOPA) configuration. The MOPA produced a single-frequency pulsed laser with pulse duration of ～8 ns. The average and peak power were as much as 139.3 W and 1.07 kW, respectively, when the repetition rate was 10 MHz, and 153.1 and 668 W, respectively, when the repetition rate was 20 MHz. Higher output power can be obtained by increasing pump power of the main amplifier.