Special Solid State & Optics Seminar Series
Dr .Wade Hsu, University of Southern California, Viterbi School of Engineering
Tuesday, March 28th at 1:00 PM
Multi-channel optics: from deep-tissue imaging to fast solvers
Light scattering couples the many degrees of freedom in the electromagnetic fields. In this talk, I will present recent work on two complementary aspects: 1) how we overcome light scattering to image deeper inside biological tissue, and 2) how we develop fast solvers to compute the multi-channel response of complex optical systems. A common thread is the “scattering matrix” of the system, which relates the incident wavefront to the outgoing wavefront. We present “scattering matrix tomography” (SMT), which uses the measured scattering matrix to perform digital spatiotemporal gating and wavefront optimization, enabling high-resolution 3D tomography deep inside opaque media [1]. With SMT, we experimentally achieve one-micron isotropic resolution at one millimeter beneath mouse brain tissue, with a depth-over-resolution ratio exceeding 900. In the second part of the talk, I will describe a full-wave simulation method we call “augmented partial factorization” (APF) [2]. By augmenting the Maxwell operator with the input and output profiles, APF computes the scattering matrix without solving for internal field profiles and without looping over the inputs, achieving 3 to 7 orders of magnitude speed-up compared to existing frequency-domain solvers. We have made this code open source [3]. We use APF to demonstrate two-photon coherent backscattering from disorder [4], open channel for 3D vectorial waves, and the inverse design of nonlocal metasurfaces [5].
[1] Y. Zhang et al. [2] H.-C. Lin, Z. Wang, and C. W. Hsu, Nature Computational Science 2, 815–822 (2022) [3] https://github.com/complexphoton/MESTI.m [4] M. Safadi, O. Lib, H.-C. Lin, C. W. Hsu, A. Goetschy, and Y. Bromberg. Nature Physics (2023). [5] S. Li, H.-C. Lin, and C. W. Hsu.