Friday, Jan 27, 1:00 pm (PST) in-person in Henley 1010
Optical frequency combs (OFCs) – whose spectra consist of a large number of equidistant modes – stand as the cornerstone of modern optics with applications ranging from fundamental science to sensing and spectroscopy. In this pursuit, semiconductor lasers have recently gained vast attention as an electrically-driven platform for self-starting OFCs, without the need for any additional components that are necessary for standard mode-locked lasers. Here, we explain the multitude of mechanisms that arise from fast gain dynamics of these lasers leading to rich nonlinear behavior.
We first concentrate on the free-running combs in Fabry-Perot resonators, which are characterized by a linear frequency chirp and a continuous-wave intensity. We reveal the conditions for the formation of these frequency-modulated (FM) combs along with the optimization techniques that increase their spectral bandwidth [1,2]. Alternatively, ring resonators support unidirectional fields, where the multimode regime occurs only in the presence of the parametric gain, allowing the sidebands to overcome the lasing threshold . We show that sensitive interplay between the dispersion and resonant Kerr nonlinearity  leads to the emission of OFCs and the formation of localized patterns in the laser output – ultimately enabling soliton generation.
 N. Opačak, et al., Phys. Rev. Lett. 123, 243902 (2019).
 M. Beiser, et al., Opt. Lett. 46, 3416 (2021).
 M. Piccardo, et al., Nature 582, 360 (2020).
 N. Opačak, et al., Phys. Rev. Lett. 127, 093902 (2021).
Nikola Opačak obtained his PhD at the Technical University of Vienna in 2022, in the group of Prof. Benedikt Schwarz. His work focuses on semiconductor lasers, nonlinear dynamics, optical frequency combs, and band structure and carrier transport modeling. Nikola is currently a PostDoc at the Technical University of Vienna at the Institute of Solid State Electronics, and a research associate in the Capasso Group at Harvard University.
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