消逝场耦合圆柱形微腔中回音壁模式结构的实验研究

Whispering-gallery modes based on evanescent field in cylindrical micro-cavity

采用石英圆柱形微腔与锥形光纤通过消逝场耦合的方式,在实验上观察到了不同半径的柱形微腔中清晰的回音壁模式,耦合效率接近10%.利用柱形微腔回音壁模式位置和间隔的解析近似公式,对实验所得的透射光谱做了模式的精确标定,共振波长的实验值和标定值间的误差小于0.05 nm.引入回音壁模式的"模场半径"概念,由"模场半径"计算出的模式间隔和实验测量值之间符合很好.利用透射光谱中的共振波长和理论标定波长间的差值,得到了实验光谱范围内(1295—1320 nm)石英光纤的色散曲线,折射率精度达10-5.

We present the observation of whispering-gallery modes （WGMs） in cylindrical micro-cavity coupled to a fiber taper based on evanescent field with a coupling efficiency of about 10%. All the WGMs spectra of cylindrical micro-cavities with four different diameters are precisely indexed by an explicit asymptotic formula with the positions and separation as parameters. By introducing the parameter ＂mode field radius＂ of WGMs, the mode separations calculated by mode field radius agree well with the experimental results. And by determining the difference between experimental resonant wavelengths and the theoretically assigned ones, the dispersive curve of quartz fiber is corrected over the spectrum range of 1295-1320 nm and the precision of refractive index determination is as high as 10^-5 .