The microring resonator based on lithium niobate on insulator (LNOI) is a promising platform for broadband nonlinearity process because of its strong second-order nonlinear coefficients, the capability of dispersion engineering, etc. It is important to control the energy transmitted into the resonator at different wavelengths, as this becomes difficult for two bands across an octave. In this Letter, we study the effect of different pulley bus-resonator configurations on phase mismatching and mode field overlap. We achieve the control of energy transmission coefficients at different wavebands simultaneously and provide a general design methodology for coupled structures for broadband applications. This paper can contribute to quantum and classical optical broadband applications based on LNOI microring resonators.

The temporal coupled-mode theory (TCMT) has made significant progress in recent years, and is widely applied in explaining a variety of optical phenomena. In this paper, the optical characteristics of the metasurface composed of nano-bars and nano-rings are simulated. The simulation results are well explained by TCMT under the coupled basis vector. However, when the structural asymmetry is large, the fitting of results shows that the total radiation loss is not conservative, in contradiction to the requirement of traditional TCMT. We solved this inconsistency by introducing the propagation phase into the near-field coupling term of TCMT. The studies show that, unlike the local mode near the exceptional point which corresponds to the radiation loss of the bright mode, the global mode near the diabolic point is closely related to the propagation phase. Furthermore, the structure near the diabolic point shows characteristic cross-coupling with the change of period. This study proposes a new theoretical framework for comprehending the interaction of light and matter and offers some guiding implications for the application of TCMT to a variety of related domains.

A 2-mm-long silicon-on-insulator grating emitter with a narrow angular full width at half-maximum (FWHM) and a high sideband suppression ratio (SSR) is proposed and designed. It consists of a Si3N4/Si grating with an approximate Gaussian emission profile along the grating length, which aims to reduce the sidelobe intensity of the scanning light in the far-field, thereby improving the resolution of the longitudinal steering resolution of the light detection and ranging (lidar). Numerical analysis shows that the angular FWHM of the emitted beam could be as low as 0.026° for a grating length of 2.247 mm and the input TE-like waveguide mode at 1550 nm, and the SSR could be more than 32.622 dB. Moreover, this Si3N4/Si grating exhibits a favorable fabrication error tolerance when considering the width and length variation of the Si3N4 overlayer in practice. Our design offers a promising platform for realizing integrated optical phased arrays for the long-distance solid-state lidar.

设计了一种基于双芯光纤耦合效应和游标效应的高灵敏度温度传感器，传感器是由2个相差一定长度的双芯光子晶体光纤和单模光纤级联构成。双芯光子晶体光纤通过级联实现游标效应，同时对纤芯中间的气孔填充乙醇实现温度传感。仿真结果表明，该温度传感器在35 ℃～45 ℃范围内的平均温度灵敏度可达−20.37 nm/℃。与单纯依靠双芯光子晶体光纤能量耦合效应的传感器相比，该传感器的温度检测灵敏度提高了10倍。

考虑实际光纤铺设过程存在的弯曲和扭转等扰动影响，对耦合模理论和耦合功率理论分别进行优化，得到多芯光纤串扰估计的一般模型。在不同光纤距离和弯曲半径情况下对串扰进行了仿真。结果表明，优化的耦合模理论模型的串扰呈震荡上升趋势，在相位匹配点附近，串扰累积增加，在非相位匹配点附近，串扰几乎不变，因此可以更好地反应光纤物理结构的波动情况。优化的耦合功率理论模型的串扰是线性的平均串扰，但是计算速度快。可以针对不同的实际情况选取适合的理论模型来估算串扰。