色散会聚透镜系统中的微米焦开关

Micron focal switch in dispersion focused lens system

为了研究宽带TEM_(22)模厄米-高斯光束通过受光阑限制色散会聚透镜系统的微米焦开关现象,采用数值计算方法对TEM_(22)模厄米-高斯光束的光强分布进行了分析,取得了传输轴上光强分布的数据。结果表明,带宽变化引起轴上TEM_(22)模厄米-高斯光束两个光强极大的相对大小改变,结果导致光强主极大位置跃变;当相对带宽γ=0.231且菲涅耳数F_(w)=100时,光强主极大位置跃变距离为2.5μm,出现微米焦开关现象;带宽和菲涅耳数是影响光束微米焦开关的重要因素;菲涅耳数较大时,较窄的带宽就可以诱导微米焦开关,反之则需要较宽的带宽。此研究结果有助于光通信技术中微纳光学器件的设计和制作。

In order to know micron focal switch of polychromatic TEM_(22)mode Hermite-Gaussian(HG)beams passing through an apertured dispersion lens system,numerical calculation examples were used to study the beam’s intensity distributions.The data of the axial intensity distributions were achieved.It is found that variation of the bandwidth results in change of two maximal intensities of TEM_(22)mode(HG)beams and thus position of the principle maximal intensity shifts rapidly.When relative bandwidthγis 0.231 and Fresnel number F_(w)is 100,the position varies 2.5μm and the phenomenon of micron focal switch presents.The bandwidth and Fresnel number are important factors that induce the micron focal switch.A narrow bandwidth is enough to induce the focal switch of TEM_(22)mode(HG)beams in the system with large Fresnel number whereas a broad bandwidth is required in the system with small Fresnel number.Results in this paper help the design and manufacture of micro and nano optical devices in optical communication technique.