Influences of cavity dispersion distribution on the output pulse properties of an all-normal-dispersion fiber laser

In this paper, the influences of the dispersion distribution in the cavity on the output pulse properties of the all-normaldispersion（ANDi） fiber laser are investigated. Our simulations show that, as the relative length of the dispersion fiber increases, the temporal width and the spectral bandwidth of the output pulse for an ANDi fiber laser with fixed total cavity dispersion or fiber length are decreased, while the pulse energy is enhanced and the compressed pulse width is increased.These simulation predictions have been proved by our experimental results. The reason may be that the nonlinear phase shift accumulated in the nonlinear fiber is more than that in the dispersion fiber if they have the same length.

Mid-IR dual-wavelength difference frequency generation in uniform grating PPLN using index dispersion control

A novel widely tunable dual-wavelength mid-IR difference frequency generation （DFG） scheme with uniform grating periodically poled lithium niobate （PPLN） is presented in this paper. By using the temperature-dependent dispersion property of PPLN, the quasi-phase matching （QPM） peak for the pump may evolve into two separate ones and the wavelength spacing between them increases with the decrease of the crystal temperature. Such two pump QPM peaks may allow simultaneous dual-wavelength mid-IR laser radiations while properly setting the two fundamental pump wavelengths. With this scheme, mid-IR dual-wavelength laser radiations at around 3.228 and 3.548, 3.114 and 3.661, and 3.019 and 3.76 μm, are experimentally achieved for the crystal temperatures of 90, 65, and 30 ℃, respectively, based on the fiber laser fundamental lights.

带掺铒光纤放大器（EDFA）的干涉型光纤陀螺仪（IFOG）结构及特点

陀螺仪，它们敏感绝对角速率的变化，分为干涉型光纤陀螺仪（IFOG），环型激光陀螺仪（RLG）和微机电系统（MEMS）陀螺仪，与加速度计一起，是导航系统的关键元件。由于在性能和成本方面都绝对优于其它类型的陀螺仪．因而光纤陀螺已经广泛地应用于测量．尤其是国防／航空工业。本文介绍了由土耳其国家计量学院光学实验室制造的IFOG样机的光学元件，电子元件的设计细节，作为绝对角速率敏感器，它的敏感机理是Sagnac相位变化原理。该IFOG样机，采用了开环结构，分别使用单模通信光纤和1549．0nmDFB激光器泵浦的DEFA作为敏感线圈和宽带光源。应用相位跟踪电位路提取载有Sagnac相移的电压数据。相位跟踪电路包括一个有源RC带通滤波器，可调增益放大器，及作为锁定装置的AD630平衡调制器芯片。该IFOG样机可以获得8（°／h）峰-峰噪声，1．57（°。／h）零偏稳定性，而且，推导出标度因数为13．83（°／h）／mv，其重复性为0．73％。

Surface defects incorporated diamond machining of silicon

This paper reports the performance enhancement benefits in diamond turning of the silicon wafer by incorporation of the surface defect machining(SDM)method.The hybrid micromachining methods usually require additional hardware to leverage the added advantage of hybrid technologies such as laser heating,cryogenic cooling,electric pulse or ultrasonic elliptical vibration.The SDM method tested in this paper does not require any such additional baggage and is easy to implement in a sequential micro-machining mode.This paper made use of Raman spectroscopy data,average surface roughness data and imaging data of the cutting chips of silicon for drawing a comparison between conventional single-point diamond turning(SPDT)and SDM while incorporating surface defects in the(i)circumferential and(ii)radial directions.Complementary 3D finite element analysis(FEA)was performed to analyse the cutting forces and the evolution of residual stress on the machined wafer.It was found that the surface defects generated in the circumferential direction with an interspacing of 1 mm revealed the lowest average surface roughness(Ra)of 3.2 nm as opposed to 8 nm Ra obtained through conventional SPDT using the same cutting parameters.The observation of the Raman spectroscopy performed on the cutting chips showed remnants of phase transformation during the micromachining process in all cases.FEA was used to extract quantifiable information about the residual stress as well as the sub-surface integrity and it was discovered that the grooves made in the circumferential direction gave the best machining performance.The information being reported here is expected to provide an avalanche of opportunities in the SPDT area for low-cost machining solution for a range of other nominal hard,brittle materials such as SiC,ZnSe and GaAs as well as hard steels.

Dark soliton interaction in optical time division multiplexed system with randomly varying birefringence and random dispersion map

Correlated perturbations caused by both randomly varying birefringence and random dispersion map are considered in optical time division multiplexed dispersion-managed dark soliton system, and their effects on soliton interaction are investigated numerically. These perturbations enhance soliton interaction, and their effects relate to the strength of perturbation, separation, and pulse width. The correlation plays an important role ar d reinforces these effects. Moreover, there is a stochastic limit between two perturbations in the system, where the effect is the largest and the corresponding interaction distance is the shortest.

Optical focal plane based on MEMS light lead-in for geometric camera calibration

The focal plane of a collimator used for the geometric calibration of an optical camera is a key element in the calibration process.The traditional focal plane of the collimator has only a single aperture light lead-in,resulting in a relatively unreliable calibration accuracy.Here we demonstrate a multi-aperture micro-electro-mechanical system(MEMS)light lead-in device that is located at the optical focal plane of the collimator used to calibrate the geometric distortion in cameras.Without additional volume or power consumption,the random errors of this calibration system are decreased by the multi-image matrix.With this new construction and a method for implementing the system,the reliability of high-accuracy calibration of optical cameras is guaranteed.

Highly Birefringent Photonic Crystal Fibers B Using Asymmetric Core Design

We demonstrate a highly birefringent photonic crystal fiber by utilizing the asymmetric core design. Based on spectral measurements of the polarization mode interfering, we estimate that the fiber has a beat length of about 0.33 mm at 1545 nm.

Effects of Gamma Irradiation for Sterilization on Aqueous Dispersions of Length Sorted Carbon Nanotubes

当前作为为 nanotherapeutics 和另外的医药应用的交货容器对碳 nanotubes 的潜在的使用有大兴趣。然而，没有数据在 nanotube 分散的性质上的消毒方法的效果上是可得到的，很医药的应用程序将在被处理的形式。这里，我们在水的分散在分散和单个墙的碳 nanotubes 的光性质上从 60Co 来源显示出 gamma 照耀的效果。不同精制长度的人口的样品在 ampoules 被封上并且暴露了到约 28 kGy 的剂量，对足够的水平保证分散的绝育。与稳固阶段的 nanotube 样品的文学结果相对照，分散和 nanotube 样品的光性质上的 gamma 照耀的效果被发现最小。把结果基于这些， gamma 照耀显得足够地非破坏性为 nanotube 分散的消毒工业上有用。

Efficient multi-bands image compression method for remote cameras

In this Letter, we propose an efficient compression algorithm for multi-spectral images having a few bands. First,we propose a low-complexity removing spectral redundancy approach to improve compression performance.Then, a bit plane encoding approach is applied to each band to complete the compression. Finally, the experiments are performed on multi-spectral images. The experiment results show that the proposed compression algorithm has good compressive property. Compared with traditional approaches, the proposed method can decrease the average peak signal noise ratio by 0.36 d B at 0.5 bpp. The processing speed reaches23.81 MPixels/s at the working frequency of 88 MHz, which is higher than the traditional methods. The proposed method satisfies the project application.