三能级光纤激光器速率方程组的阈值解析解

 在考虑了泵浦损耗及激光损耗的情况下，解析求解了阈值泵浦下的三能级光纤激光器速率方程组，获得了泵浦功率阈值的显函数解析表达式，泵浦功率沿光纤变化的隐函数表达式，以及用功率变化表示的各个能级的粒子数密度随位置变化的显函数表达式。并利用这些表达式对光纤激光器的阈值特性进行了研究，研究表明：泵浦功率阈值随泵浦损耗系数增大而增大；激光上能级粒子数密度随归一化位置呈下降趋势，而下能级粒子数密度的变化与此相反；泵浦功率阈值越大(光纤长度越长),净增益系数随归一位置下降就越快。所获得的结果适用于单包层和双包层光纤激光器。     

掺镱全光纤激光器研究

依据速率方程和边界条件,对高功率多点抽运全光纤激光器进行了研究.通过自制的级联侧面泵浦耦合器搭建全光纤激光器,级联耦合器的单点泵浦效率为96%,泵浦传输损耗为10%,信号光损耗分别是0.18dB和0.87dB;线性谐振腔结构中:前向抽运的光-光转换效率为69%,低于后向抽运中70%的光-光转换效率,与理论分析一致;双向泵浦方式中,在单臂输入975nm泵浦功率为110 W的条件下,激光功率输出为311 W,中心波长为1 080nm,光谱宽度为1.6nm,光-光转换效率为70%,光束质量约为1.3.激光器性能稳定,若增加单臂泵浦功率或级联泵浦耦合器个数,可获得更高功率的激光输出.     

多泵浦光纤喇曼放大器的模拟分析

通过使用综合理论模型对不同配置条件下的多泵浦分布式光纤喇曼放大器的增益谱进行了数值模拟研究,该理论模型包含了瑞利散射、放大自发辐射和不同交互效应,包括泵浦与泵浦、泵浦与信号和信号与信号之间的交互与能量转移.模拟研究了泵浦源功率、泵浦源波长间隔及光纤损耗对喇曼增益谱的影响,结果表明设计多泵浦光纤喇曼放大器需要对泵浦源功率、泵浦源波长间隔光纤损耗谱进行综合考虑,需对泵浦源功率、泵浦源波长间隔进行合理配置.在本文的泵浦源波长设定条件下,考虑实际光纤的损耗谱特性,为了获得大的增益带宽和小的增益不平坦度,短波长泵浦源和最长波长的泵浦源需要更高的泵浦功率,中间波长泵浦源的功率应较低.     

太阳光泵浦激光器侧面泵浦效率的提高

太阳光泵浦激光器直接利用太阳光作为泵浦源,实现了太阳光能量到激光能量的直接转化。设计了分腔水冷型金属锥形泵浦腔,以直径8mm,长115mm的Nd:YAG晶体棒作为激光工作物质,用有效面积1.03m2菲涅尔透镜会聚太阳光,实验获得了23.7 W的稳定激光输出,斜效率为7.87%。通过对比实验,改进后的分腔水冷型太阳光泵浦激光器较原有锥形腔激光器有55.92%的激光输出功率提升。分别从侧面泵浦光在冷却水中的吸收损耗以及其耦合效率等方面对新型腔体结构进行了分析,证实了分腔水冷型腔体结构对侧面泵浦效率的提高,并提出了陶瓷漫反射材质的分腔水冷型激光腔的设计。     

被动锁模光纤激光器中泵浦滞后现象的研究

研究了基于非线性偏振旋转技术的被动锁模光纤激光器中的泵浦滞后现象.用非线性传输模型对泵浦功率滞后的机理进行了分析,发现此激光器中的泵浦滞后现象起因于光纤双折射与偏振选择共同作用引起的激光腔内非线性损耗特性.对泵浦滞后现象进行数值模拟和实验验证,结果与非线性传输模型分析的结论一致,并进一步证实了泵浦滞后现象不仅在连续光锁模产生孤子时存在,在锁模态下孤子的产生和泯灭过程中仍然存在.此外,随着激光腔内孤子数目的增多泵浦滞后现象愈加明显.     

双端泵浦保偏光纤激光器

 以两台808 nm半导体激光器LD1和LD2为泵浦源,对光纤激光器双端泵浦进行了研究,获得了6.5 W的激光输出。实验分别测出了LD1和LD2半导体激光器单端泵浦和双端泵浦时的输出功率,对双端泵浦输出功率与单端泵浦功率之和进行了比较,利用双端泵浦提高了泵浦效率和输出激光功率。同时测量了输出激光的偏振度,通过计算得到双端泵浦输出激光的偏振度为0.5。     

被动锁模光纤激光器中泵浦滞后现象的研究

研究了基于非线性偏振旋转技术的被动锁模光纤激光器中的泵浦滞后现象.用非线性传输模型对泵浦功率滞后的机理进行了分析,发现此激光器中的泵浦滞后现象起因于光纤双折射与偏振选择共同作用引起的激光腔内非线性损耗特性.对泵浦滞后现象进行数值模拟和实验验证,结果与非线性传输模型分析的结论一致,并进一步证实了泵浦滞后现象不仅在连续光锁模产生孤子时存在,在锁模态下孤子的产生和泯灭过程中仍然存在.此外,随着激光腔内孤子数目的增多泵浦滞后现象愈加明显.     

热键合技术的Cr4+:YAG被动调Q激光器理论和实验研究

 采用数值求解被动调Q速率方程，并讨论了基于热键合技术被动调Q激光器的优化方法。通过数值仿真讨论分析了谐振腔的损耗、饱和吸收体的初始透过率、输出镜的反射率和泵浦功率等参数对激光输出的影响。结果表明：输出镜存在最佳透过率，使得输出功率最高和脉冲能量最大；减小饱和吸收体的初始透过率能有效提高脉冲能量，并压缩脉宽，但是会增加阈值泵浦功率；泵浦功率与脉冲重复率和输出功率近似成线性增加，增大泵浦功率可以压缩脉宽。并通过实验验证了理论分析的正确性。     

2μm泵浦中红外硫化玻璃光纤拉曼激光器的理论分析与优化

根据2μm掺铥光纤激光泵浦中红外硫化玻璃光纤拉曼激光器的模型,采用非线性耦合方程组对激光器的性能进行了研究与分析。同时,对激光器各参数包括光纤长度、输出耦合器反射率、光纤散射损耗对激光器性能的影响进行了分析并给出了优化结果。数值仿真结果表明,在一定条件下,2μm泵浦硫化玻璃光纤产生拉曼激光的斜率效率可以超过85%。另外,光纤长度和输出耦合器反射率不仅对输出激光功率的影响很大,而且是相互影响的,必须同时进行优化。结果也表明,输出激光的功率随光纤散射损耗增加急剧线性下降。以上的结果可以用于硫化玻璃光纤级联拉曼激光器的实验指导和优化设计。     

基于双频泵浦正常色散富硅氮化硅微环谐振腔的光频率梳设计

提出一种利用锁相双频激光作为泵浦源输入正常色散富硅氮化硅微环谐振腔产生光频率梳的方案。对富硅氮化硅微环谐振腔进行色散调控,实现1550 nm波段平坦正常色散优化设计。利用LLE (Lugiato Lefever equation)方程进行光频率梳产生仿真,分析改变泵浦失谐时光频率梳产生的时域和频域演化过程。同时,探究各项参数对光频率梳产生的影响,包括泵浦功率、双频激光功率占比、微腔波导损耗、微腔色散、双频激光频率间隔。仿真实现的光频率梳带宽可覆盖1520 nm到1580 nm。     

Development of a new soft ferrite core for power applications

Manganese-substituted nickel–zinc ferrites have been investigated as power core materials for applications in switched-mode-power supplies. High frequency operation of these power supplies requires high performance cores with low power losses. The main contributors to the power loss are eddy current loss, hysteresis loss and residual loss. The ferrites have been synthesized by the citrate precursor technique and their electromagnetic properties such as resistivity, permeability, saturation magnetization and Curie temperature studied. A power loss of 500 mW/cc could be obtained at a frequency of 500 kHz, flux density of 50 mT and temperature 100 °C.     

Study of eddy current power loss in an RCS vacuum chamber

In a Rapid Cycling Synchrotron (RCS), power loss due to an eddy current on the metal vacuum chamber would cause heating of the vacuum chamber. It is important to study the effect for estimating eddy current induced power loss and temperature growth. Analytical formulas for eddy current power loss for various types of vacuum chambers are derived for dipole and quadrupole repectively. By using the prototype of dipole of CSNS/RCS, an experiment was done to test the analytical formula. The derived formulas were applied to calculating the eddy current power loss on some special structures of an RCS vacuum chamber.     

侧边抛磨光纤中传输光功率变化的实验研究

针对轮式光纤侧边抛磨法制备的侧边抛磨光纤,研究了在侧边抛磨区覆盖不同折射率的材料时,侧边抛磨光纤传输光功率随覆盖材料折射率变化的特性.研究表明,侧边抛磨光纤中传输光功率会随抛磨区覆盖材料折射率的变化而改变.当覆盖材料的折射率小于1.437 8时,光功率损耗近似为零；而当覆盖材料的折射率逐渐增大接近1.452 1时,光功率损耗迅速增大至最大值.当覆盖材料的折射率由1.453 2逐渐增大时,光功率损耗由最大值逐渐减小,最终维持在某个确定的值.侧边抛磨光纤并不是抛磨深度越深,损耗就越大.侧边抛磨光纤中传输的光功率存在波长相关损耗(WDL）.实验结果与理论结论符合较好.     

表面离子阱的衬底效应模型研究及新型离子阱设计

通过分析表面离子阱衬底的功率损失和电势损失对离子阱阱深和离子加热速率的影响,提出考虑衬底效应的阱深和离子加热速率的解析分析模型.研究发现,硅基衬底的电势损失对表面离子阱阱深的降幅达17.19%,功率损失对离子加热速率的加速达13.37%.为了降低衬底效应的不利影响,设计了衬底真空隔离结构的表面离子阱,在离子阱射频电极和直流电极间的衬底表面刻蚀出多条隔离槽,从而减小衬底的等效电导和等效电容,达到降低衬底功率和电势损失的目的.模拟结果显示,相比于一般结构,真空隔离结构的硅基表面离子阱能够使阱深加深20.22%,使衬底功率损失降低54.55%.     

Power loss to generating ion current in radio-frequency ion thrusters and technological sources of ions

The balance of power in a radio-frequency ion source is constructed by calculating the inevitable power loss at surfaces bordering the inductive discharge plasma and power loss to the generation and preliminary acceleration of working-gas ions. The relationship between the specific radio-frequency power consumption per ion-current unit emerging from the source and electron temperature and geometric parameters of the gas discharge chamber is determined.     

准各向同性高温超导股线交流损耗的实验研究

高温超导体的交流损耗直接影响超导电力装置的运行成本和稳定性,是判断超导电力设备设计是否合理的重要特性之一.在阐述准各向同性高温超导股线结构特点的基础上,首先对准各向同性高温超导股线的交流损耗和磁滞损耗进行仿真研究,利用有限元软件Comsol Multiphysics分析了交流背景磁场下的损耗,然后在对光纤布拉格光栅(optical fiber Bragg grating,简称FBG)波长与损耗关系标定的基础上,使用光纤布拉格光栅测量交流背景磁场下的交流损耗.理论计算与实验结果相吻合,表明在工频和液氮温度下股线的交流损耗以磁滞损耗为主.     

Output power analyses for the thermodynamic cycles of thermal power plants

Thermal power plant is one of the important thermodynamic devices, which is very common in all kinds of power generation systems. In this paper, we use a new concept, entransy loss, as well as exergy destruction, to analyze the single reheating Rankine cycle unit and the single stage steam extraction regenerative Rankine cycle unit in power plants. This is the first time that the concept of entransy loss is applied to the analysis of the power plant Rankine cycles with reheating and steam extraction regeneration. In order to obtain the maximum output power, the operating conditions under variant vapor mass flow rates are optimized numerically, as well as the combustion temperatures and the off-design flow rates of the flue gas. The relationship between the output power and the exergy destruction rate and that between the output power and the entransy loss rate are discussed. It is found that both the minimum exergy destruction rate and the maximum entransy loss rate lead to the maximum output power when the combustion temperature and heat capacity flow rate of the flue gas are prescribed. Unlike the minimum exergy destruction rate, the maximum entransy loss rate is related to the maximum output power when the highest temperature and heat capacity flow rate of the flue gas are not prescribed.     

特种非对称低损耗1×5光分路器

设计和优化了一种新型低损耗、低偏振的基于二氧化硅的特种非对称1×5光分路器.在设计Y分支结构时,输入端采用缓变展宽波导结构和直波导过渡波导相结合的结构,此结构可以使输入光场缓慢展宽,进行分束前的准备,大大减小分支结构的辐射损耗和模式转换损耗.非对称1×5光分路器第一个端口输出功率占50%,第二至五端口输出功率占50%.利用三维光束传播法模拟和优化了特种非对称1×5光分路器,模拟结果表明,该结构具有均匀性好、器件尺寸小、低损耗和低偏振等优点,1×5光分路器在1 250~1 650 nm波长范围内,第一个输出端口附加损耗小于0.07 dB,均匀性小于0.023 dB,偏振相关损耗小于0.009 dB,第二到五端口附加损耗小于0.45 dB,均匀性小于0.41 dB,偏振相关损耗小于0.06 dB.     

A MICROSTRIP PROBE COAXIAL WAVEGUIDE POWER DIVIDER/COMBINER

A novel power divider/combiner using microstrip probes array in the oversized coaxial waveguide is proposed in this paper. The simple electromagnetic modeling of this power dividing/combining structure has been developed. Analysis based on equivalent circuits gives the design formula for perfect power dividing/combining. A four-way waveguide power divider has been designed and fabricated. The measured results agree well with the simulated results. The measured 15-dB return loss bandwidth of this waveguide power divider is demonstrated to be 28.6% and its 0.5-dB insertion loss bandwidth 41.3%.     

Spectral power handling capability caused by stimulated Raman scattering effect in silica optical fibers

Spectral characteristics of the stimulated Raman scattering (SRS) in silica fibers was studied for the purpose of obtaining higher power transmission capability in single-mode silica optical fibers. When the input power exceeds a critical input power, which depends on the wavelength, nonlinear transmission loss caused by SRS gives rise to excess loss and signal waveform distortion. The SRS effect is reduced under the condition of sufficiently large spectral loss at the first Stokes wavelength.