A 4 × 4 reconfigurable Mach–Zehnder interferometer (MZI)-based linear optical processor is investigated through its theoretical analyses and characterized experimentally. The linear transformation matrix of the structure is theoretically determined using its building block, which is a 2 × 2 reconfigurable MZI. To program the device, the linear transformation matrix of a given application is decomposed into that of the constituent MZIs of the structure. Thus, the required phase shifts for implementing the transformation matrix of the application by means of the optical processor are determined theoretically. Due to random phase offsets in the MZIs resulting from fabrication process variations, they are initially configured through an experimental protocol. The presented calibration scheme allows to straightforwardly characterize the MZIs to mitigate the possible input phase errors and determine the bar and cross states of each MZI for tuning it at the required sate before programming the device. After the configuration process, the device can be programmed to construct the linear transformation matrix of the application. In this regard, using the required bias voltages, the phase shifts obtained from the decomposition process are applied to the phase shifters of the MZIs in the device.

中文翻译：

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基于 4×4 可重构 MZI 的线性光处理器的理论和实验分析

通过理论分析和实验表征，研究了基于 4 × 4 可重构马赫-曾德干涉仪 (MZI) 的线性光学处理器。该结构的线性变换矩阵在理论上是使用其构建块确定的，它是一个 2 × 2 可重构 MZI。为了对器件进行编程，将给定应用的线性变换矩阵分解为结构的组成 MZI 的线性变换矩阵。因此，通过光学处理器实现应用的变换矩阵所需的相移在理论上被确定。由于制造工艺变化导致 MZI 中的随机相位偏移，它们最初是通过实验协议配置的。所提出的校准方案允许直接表征 MZI，以减轻可能的输入相位误差，并确定每个 MZI 的条形和交叉状态，以便在对器件进行编程之前将其调整到所需的状态。在配置过程之后，可以对设备进行编程以构建应用程序的线性变换矩阵。在这方面，使用所需的偏置电压，将从分解过程中获得的相移应用于器件中 MZI 的移相器。