Effects of Ce^(3+) doping on the structure and magnetic properties of Mn-Zn ferrite fibers

Ce3+-doped Mn-Zn ferrite fibers were successfully prepared by the organic gel-thermal decomposition method from metal salts and citric acid. The composition,structure,and magnetic properties of these ferrite fibers were characterized by X-ray diffraction (XRD),scanning electron microscopy (SEM),and vibrating sample magnetometer (VSM). The results show that Mn0.2Zn0.8Fe2-xCexO4 (x = 0-0.04) fibers are featured with an average grain size of 11.6-12.7 nm,with diameters ranging between 1.0 to 3.5 μm and a high aspect ratio (length/diameter). The Ce3+ ion doping has not resulted in crystal structural changes of the Mn-Zn ferrite phase and all the as-prepared ferrite fibers have a simple spinel phase structure,although this influences the morphologies of Mn0.2Zn0.8Fe2-xCexO4 ferrite fibers possibly owing to the lattice dis-tortion and internal-stress. Both the lattice constant and grain size increase slightly with the increase of the Ce3+ ion doping content. The soft magnetic properties of Mn-Zn ferrite fibers can be improved by a small amount of Ce3+ ion doping with an increase of the saturated magnetization and a decrease of the coercivity.

3.6 W compact all-fiber Pr3+-doped green laser at 521 nm

Green semiconductor lasers are still undeveloped,so high-power green lasers have heavily relied on nonlinear frequency conversion of near-infrared lasers,precluding compact and low-cost green laser systems.Here,we report the first Watt-level all-fiber CW Pr3t-doped laser operating directly in the green spectral region,addressing the aforementioned difficulties.The compact all-fiber laser consists of a double-clad Pr3t-doped fluoride fiber,two homemade fiber dichroic mirrors at visible wavelengths,and a 443-nm fiber-pigtailed pump source.Benefitting from>10 MW∕cm2 high damage intensity of our designed fiber dielectric mirror,the green laser can stably deliver 3.62-W of continuous-wave power at∼521 nm with a slope efficiency of 20.9%.To the best of our knowledge,this is the largest output power directly from green fiber lasers,which is one order higher than previously reported.Moreover,these green all-fiber laser designs are optimized by using experiments and numerical simulations.Numerical results are in excellent agreement with our experimental results and show that the optimal gain fiber length,output mirror reflectivity,and doping level should be considered to obtain higher power and efficiency.This work may pave a path toward compact high-power green all-fiber lasers for applications in biomedicine,laser display,underwater detection,and spectroscopy.

Raman scattering enhancement characteristic of NbCl_5-and Nb_20_5-doped silica fibers

Two kinds of Nb-doped silica fibers, an NbCl5-doped fiber and an Nb205-doped fiber, are fabricated and char- acterized in this Letter. First, the refractive index profiles of both fibers are obtained, and then their Raman spectra are measured with 785 nm exciting light. The Nb-doped fibers＇ Raman spectra are compared with a conventional GeO2-doped single-mode silica fiber that is prepared with the same method and under the same conditions. As a result, the Raman gain coefficients of the Nb-doped silica fiber core are obtained. The exper- imental results show that Nb2O5 doping can enhance the Raman scattering intensity of the optical fibers.

Multiphoton process and optical amplification in Er^(3+)-Yb^(3+)-doped fiber pumped by Ti:Al_2O_3 tunable laser at 980-nm band

The .Er3+-Yb3+-doped fiber has a broadened absorption spectrum, which means the pumping sources can work efficiently from 810 to 1100nm. Among them 980nm is the maximum.absorption （10 dB/km） wavelength. By energy transferring and multiphoton process, the visible and ultraviolet radiation occurs when the Er3+-Yb3+-doped fiber is pumped by the laser at 980-nm band. Further researches on the mechanism of the fluorescence of Er3+-Yb3+-doped silica fiber pumped by Ti: A12O3 tunable laser at 980-nm band are helpful

一种新型的高功率双波长自相似抛物线脉冲激光器（英文）

基于正色散单模光纤、掺Yb^(3+)增益光纤和多模光纤光栅,提出了一种可调高功率双波长自相似抛物线脉冲激光器。采用非线性薛定谔方程描述双波长自相似抛物线脉冲的传输和演化过程,并利用分步傅里叶方法进行数值模拟。输入脉冲在正色散单模光纤与掺镱增益光纤中产生自相似抛物线脉冲,多模光纤布拉格光栅对激光器进行双波长选择,通过调节偏振控制器实现双波长稳定运行。数值模拟分析结果表明该激光器的运行是可行且有效的。

Generation of 100 nJ pulse,1 W average power at 2μm from an intermode beating mode-locked all-fiber laser

We report on the investigation of intermode beating mode-locked(IBML)pulse generation in a simple all-fiber Tm^3+-doped double clad fiber laser(TDFL).This IBML TDFL is implemented by matching longitudinal-mode frequency between 793 nm laser and TDFL without extra mode locker.The central wavelength of 1983 nm,the fundamental pulse frequency of 9.6 MHz and the signal-to-noise ratio(SNR)of>50 dB are achieved in this IBML TDFL.With laser cavity optimization,the IBML TDFL can finally generate an average output power of 1.03 W with corresponding pulse energy of 107 nJ.These results can provide an easily accessible way to develop compact large-energy,highpower TDFLs.

掺Yb^(3+)光纤中光暗化的研究概述

光暗化现象大大限制了掺Yb3+光纤的激光输出功率。掺Yb3+光纤激光输出功率的提高需要对光暗化现象采取有效的抑制措施。为此,从掺Yb3+光纤中光暗化现象中色心产生的原因、主要影响因素和抑制措施三方面概述近年来国内外研究学者对掺Yb3+光纤光暗化现象的研究,为今后掺Yb3+光纤光暗化的研究提供指引。