扫描近场光学显微镜光纤锥中导波反射特性

Reflection Properties of Guided Wave in Fiber Taper Used for Scanning Near Field Optical Microscopy

利用局部模耦合模型理论上分析了扫描近场光学显微镜光纤锥的光场性质，给出光纤锥中存在的正、反向传播的基模场微分方程，以及基模反向耦合系数的数值计算结果，其最高反射系数达１％左右。这种反射光可起着光纤锥激光器谐振腔输出端镜的作用。另外，抛物型光纤锥探针的反向耦合系数比截锥型的低。并给出光纤锥中光波逆向反射的实验结果。

The local mode coupled model is used to analyze theoretically the light field property of fiber taper in scanning near field optical microscopy. Differential equations of the forward and backward fundamental mode fields in fiber taper are given. The backward coupling coefficient of fundamental mode is obtained numerically, and it can reach about 1% at most. The reflection makes the fiber taper act as an output mirror of tapered fiber laser resonator. It is also shown that the parabolic taper has a lower reflected coupling coefficient than the truncated taper. the experimental results of the reflection wave from fiber probe are given.