Title: Physically Interpreting Negative and Imaginary Time Delays of Light in Scattering Systems
Abstract: The time a wave spends in a scattering system before exiting is called time delay, which becomes complex in subunitary scattering systems [1]. The real part of this quantity has been examined thoroughly, but little has been done in exploring the physical meaning behind the imaginary part. In 2016, authors in ref. [2]Theoretically demonstrated a connection between complex time delay and the propagation properties of a Gaussian pulse. Specifically, they found that the real part of complex time delay corresponds to a shift in transmission time of the pulse, and the imaginary part to be a shift in the center frequency of the pulse. We were able to experimentally test these predictions using a two port microwave ring graph setup and found excellent agreement between the predictions made by the authors in [2] and our experimental results.
For this talk I plan to first give some brief background on scattering systems and time delay. I then will be giving a brief overview of the past work on negative real time delay and how it is physically interpreted. Next I'll discuss imaginary time delay and the predictions made by Asano, et al. [2]. I will then present the experiment we designed to test these predictions, our results, and how we interpret them.
[1] Lei Chen, Steven M. Anlage, and Yan V. Fyodorov,“Generalization of Wigner Time Delay to Sub-Unitary Scattering Systems,” Phys. Rev. E 103, L050203 (2021).
[2] M. Asano, K. Y.Bliokh, Y. P. Bliokh, A. G. Kofman, R. Ikuta, T. Yamamoto, Y. S. Kivshar, L.Yang, N. Imoto, S. K. Ozdemir, and F. Nori, Anomalous time delays and quantum weak measurements in optical micro-resonators, Nat. Comm. 7, 13488 (2016).