波导耦合回音壁模式光学微球腔结构耦合特性分析

提出了一种耦合微球和波导系统的有效方法,并在数值和实验上进行了论证.为了研究微球腔和波导系统的耦合特性,首先通过耦合模理论研究了这个系统的2D模型.通过有限时域差分法设计了一个数值仿真系统.在快速傅里叶变换(FFT)处理样本数据后,得到了波长范围从600 nm到1 000 nm的相对强度谱曲线和传输谱曲线.在实验中,采用熔融单模光纤顶端的方法制得了石英材料微球腔.采用热拉技术制得了锥形光纤,用来作为激发微球腔中回音壁模式的波导.测试了这个微球腔-锥形光纤耦合系统,通过优化微球腔与锥形光纤的相对位置得到其品质因数高达2.3×106,耦合效率高达92.5%.这些耦合特性可以很好地用理论结果解释.这些特性表明了其在实际微腔传感和微型激光器中极具潜力.

Analysis for coupling characteristics of optical microsphere cavity in waveguide coupled whispering gallery mode

An efficient method for a coupled microsphere and waveguide system is proposed and demonstrated numerically and experimentally. In order to study the coupling characteristics of the microsphere-waveguide system, a two-dimensional ( 2D) model is exploited by the coupled theory firstly. A numerical simulation system is designed with the finite difference time domain ( FDTD) method. The relative intensity spectra and transmission spectra in the wavelength range from 600 nm to 1000 nm are acquired by processing the sample data after fast fourier transformation ( FFT) . In the experiment, the quartz-microsphere is fabricated by melting the tip of a single-mode optical fiber. The tapered fiber, fabricated by using the heat-and-pull technique, is chosen as a waveguide to excite whispering gallery modes ( WGMs) of the microsphere. The microsphere-taper coupling system is tested and the results indicate that a very high quality ( Q) factor up to 2. 3 × 106 and a high coupling efficiency up to 92. 5% can be achieved by optimizing the microsphere position and orientation relative to the tapered fiber. These coupling characteristics can be well explained with the theoretical results. Such properties show its great potential in practical microcavity sensing and micro-lasers.