Cala' Lesina Antonio, Goodwill Dominic, Bernier Eric, Ramunno Lora, Berini Pierre
Opt Express. 2020 Oct 12;28(21):31637-31657. doi: 10.1364/OE.402894.
Optical phased arrays are of strong interest for beam steering in telecom and LIDAR applications. A phased array ideally requires that the field produced by each element in the array (a pixel) is fully controllable in phase and amplitude (ideally constant). This is needed to realize a phase gradient along a direction in the array, and thus beam steering in that direction. In practice, grating lobes appear if the pixel size is not sub-wavelength, which is an issue for many optical technologies. Furthermore, the phase performance of an optical pixel may not span the required 2π phase range or may not produce a constant amplitude over its phase range. These limitations result in imperfections in the phase gradient, which in turn introduce undesirable secondary lobes. We discuss the effects of non-ideal pixels on beam formation, in a general and technology-agnostic manner. By examining the strength of secondary lobes with respect to the main lobe, we quantify beam steering quality and make recommendations on the pixel performance required for beam steering within prescribed specifications. By applying appropriate compensation strategies, we show that it is possible to realize high-quality beam steering even when the pixel performance is non-ideal, with intensity of the secondary lobes two orders of magnitude smaller than the main lobe.
光学相控阵在电信和激光雷达应用中的波束控制方面具有极大的吸引力。理想情况下，相控阵要求阵列中的每个元件（一个像素）产生的场在相位和幅度上完全可控（理想情况下是恒定的）。这是实现沿阵列中一个方向的相位梯度从而在该方向上进行波束控制所必需的。实际上，如果像素尺寸不是亚波长的，就会出现栅瓣，这对许多光学技术来说都是一个问题。此外，光学像素的相位性能可能无法覆盖所需的2π相位范围，或者在其相位范围内可能无法产生恒定的幅度。这些限制导致相位梯度存在缺陷，进而引入不希望出现的旁瓣。我们以一种通用且与技术无关的方式讨论非理想像素对波束形成的影响。通过检查旁瓣相对于主瓣的强度，我们量化波束控制质量，并就规定规格内波束控制所需的像素性能提出建议。通过应用适当的补偿策略，我们表明即使像素性能不理想，也有可能实现高质量的波束控制，此时旁瓣强度比主瓣小两个数量级。
