基于模式耦合的低弯曲损耗大模场带隙光纤研究

提出一种大模场带隙光纤,由排布在正方结构网 格中的高折射率介质柱形成导光机制。采用有 限元法分析了直光纤与弯曲光纤下的模式损耗与模场面积等特性。研究结果表明:这种光纤 具有较宽的带 隙,可同时支持基模和高阶模的传输,两种模式的泄漏损耗均低于1×10－3 dB/m。当光纤弯曲时,其包层会 产生具有强泄露损耗的包层模,并在一定的弯曲半径下与纤芯的高阶模发生强耦合。当弯曲 半径在15～20cm 之间时,基模弯曲损耗小于0.01dB/m,而高阶模损耗大于1dB/m, 因而光纤可以经弯曲实现大模场单模传 输。在1064nm波长处,其直光纤的基模模场面 积为1319.62μm², 而在弯曲状态下的模场仍可达到975.00μm²以上,因而可实现大 模场的低弯曲损耗传输。     

A fiber Bragg grating current sensor with temperature compensation

A novel fiber Bragg grating （FBG） current sensor with temperature compensation has been proposed. The fiber Bragg grating is glued on the surface of an isosceles triangle cantilever beam, which has a step thickness along the beam axis. Due to the electromagnetic force created by a solenoid and a permanent magnet mounted on the top of the beam, a step strain is applied on the fiber Bragg grating. The change of the electric current in the solenoid makes the spectrum of the fiber Bragg grating split. By monitoring the shift difference of the two split center wavelengths, which is related to the electric current in the solenoid, a current sensor with temperature compensation is obtained. The test range of 0-400 mA is achieved. The experimental results also show that the relationship between the shift difference of the two split center wavelengths of the FBG and the electric current has a linearity of 0.9937, and the sensitivity is about 2.64 nm/A; the test results are independent of the temoerature, so the cross sensitive problem is solved.     

高能应变率下钛合金靶材层裂模拟研究

针对激光诱导冲击波的力学效应,建立了TC4钛合金靶材在单脉冲纳秒激光和单脉冲飞秒激光加载下的有限元仿真模型,分别分析了纳飞秒激光加载下的TC4钛合金靶材层裂与靶材厚度的关系。仿真结果表明高能激光加载下拉应力以及材料表面发生的形变都与靶材的厚度有关,因此层裂程度与靶材厚度相关,表现为TC4钛合金靶材厚度越大越难以发生层裂。对于纳秒激光,峰值压强为6.945 GPa的条件下,靶材厚度在0.3 mm和0.8 mm时,靶材发生层裂;当厚度为1 mm时,材料发生形变。对于飞秒激光,峰值压强为41.33 GPa的条件下,靶材厚度在0.01 mm时靶材破损;靶材厚度为0.05 mm时发生形变。     

用于远距离高温目标辐射探测的光谱系统设计

针对远距离高温目标多光谱辐射测温的需求,设计了一款多通道光谱探测系统。系统前端采用同轴两反卡塞格林式结构收集目标光谱辐射,后端包括用于目标定位的长波红外成像瞄准系统和分别工作在380～1050 nm、980～2550 nm双波段光谱系统。光谱系统采用Czerny-Turner结构,在380～1050 nm波段分辨率优于5 nm, 980～2550 nm波段分辨率优于15 nm,光谱通道数量大于220个。400 m目标外场实验和700～2300℃高温黑体温度实验表明,多通道光谱探测系统能够进行远距离目标的瞄准和光谱探测。本文设计的多通道光谱探测系统有望用于地面、航空及航天等远距离的温度探测。     

激光扫描弧形柱面聚焦系统的研究

为了解决在柱面等曲面上激光打孔的问题和提高打孔成型效果,提出了一种扫描弧形柱面聚焦方案,系统将CO2激光器发射的脉冲激光调制后,入射到柱面聚焦镜压缩为线性光斑,之后经由旋转反射棱镜实现激光扫描,线性扫描光斑在经过弧形柱面聚焦镜后在曲面上聚焦为圆形光斑,实现了对光束的整形和曲面打孔。结果表明实现了在曲面上0.15mm大小的光斑,满足了包括烟支在内的工业生产需求,与传统的平面聚焦打孔方式相比本方案有更大的应用空间。