Zhou Guangzhu, Qu Shi-Wei, Wu Jieyun, Yang Shiwen
Opt Express. 2021 Aug 2;29(16):25399-25411. doi: 10.1364/OE.434538.
Coupling light from in-plane guided light into free space or optical fibers is crucial for many photonic integrated circuits and vice versa. However, traditional grating couplers or waveguide grating antennas suffer from low upward coupling efficiency due to the light radiating in both upward and downward directions simultaneously. In this paper, a compact aperture-coupling nanoslot antenna array is proposed for high-efficiency unidirectional radiation, where a two-dimensional high-contrast grating (HCG) is employed as a mirror to reflect the undesired downward radiation. Upon the HCG separated by a low-index spacing layer, a thin silver layer is deposited. Finally, a series of H-shaped slots are patterned on the silver thin film to arrange the aperture fields and radiate the in-plane guided light into free space. The proposed nanoslot antenna array features a front-to-back ratio (F/B) over 10 dB within the wavelength range of 1500 ∼ 1600 nm. At the same time, a high radiation efficiency of over 75% and a maximum radiation efficiency of 87.6% are achieved within the 100 nm bandwidth. The high-efficiency unidirectional antenna array is promising for the integrated photonic applications including wireless optical communications, light detection and ranging, and fiber input/output couplers.
将平面内的导波光耦合到自由空间或光纤中对于许多光子集成电路至关重要，反之亦然。然而，传统的光栅耦合器或波导光栅天线由于光同时向上和向下辐射，导致向上耦合效率较低。本文提出了一种紧凑的孔径耦合纳米槽天线阵列，用于高效单向辐射，其中采用二维高对比度光栅（HCG）作为反射镜，以反射不需要的向下辐射。在由低折射率间隔层隔开的HCG上，沉积一层薄银层。最后，在银薄膜上图案化一系列H形槽，以排列孔径场并将平面内的导波光辐射到自由空间中。所提出的纳米槽天线阵列在1500～1600nm波长范围内的前后比（F/B）超过10dB。同时，在100nm带宽内实现了超过75%的高辐射效率和87.6%的最大辐射效率。这种高效单向天线阵列在包括无线光通信、光探测与测距以及光纤输入/输出耦合器在内的集成光子应用中具有广阔前景。
