Silicon photonic integrated circuit for high-resolution multimode fiber imaging system

Abstract

We propose and demonstrate a silicon photonic integrated circuit (PIC) for exciting different spatial modes launched into a multimode-fiber (MMF) speckle imaging system. The PIC consists of a 45-channel optical phased array and an array of nanoantennas to bridge the PIC and MMF. The nanoantenna array can excite a wide range of spatial modes in the MMF with a mode-group dependent loss of less than 3 dB. A high spatial resolution, which approaches the theoretical limit determined by the number of modes in the MMF, is realized by using the proposed PIC. An equivalent resolution of 1.75 µm is experimentally attained across a field of view of 105 µm. Two different algorithms for image reconstruction are compared. The algorithm based on truncated singular value decomposition is computationally efficient and suitable for real-time image reconstruction, whereas the algorithm based on total-variation regularization produces higher imaging quality. The number of resolvable points is derived to be ∼3000, which is more than the square of the number of phase shifters. These results represent the highest spatial resolution yet demonstrated in a PIC-based MMF imaging system.