An integrated in-fiber coupler for excitation of whispering-gallery modes (WGMs) of a microsphere resonator is proposed. The device is fabricated by embedding a microsphere into an optical fiber inner air-cavity through an open micro-channel to excite various WGMs via evanescent field coupling. The asymmetric Fano resonance line shape and the symmetrical Lorentzian line shape with a slope of −13.88 dB/nm and a quality (Q)-factor of $1.81\times 10^{3}$ are observed in the transmission spectrum of the device. Such an in-fiber WGM resonator coupling structure has the features of compactness, low-cost, robust and alignment-free.

中文翻译：

---

用于微球谐振器中回音壁模式激发的光纤内耦合器。

提出了一种用于激发微球谐振器回音壁模式 (WGM) 的集成光纤耦合器。该装置是通过将微球通过开放微通道嵌入光纤内部气腔中来制造的，以通过渐逝场耦合激发各种 WGM。非对称 Fano 共振线形状和对称洛伦兹线形状，斜率为 -13.88 dB/nm，质量 (Q) 因子为 $1.81\乘以 10^{3}$ 在器件的透射光谱中观察到。这种光纤内WGM谐振器耦合结构具有紧凑、低成本、坚固和免对准的特点。