CrSBr—A New Platform for Nonlinear Opto-Magnonics

The nonlinear dynamics of collective excitations offer both intriguing fundamental phenomena and significant practical applications. Demonstration of the frequency mixing processes seen in nonlinear optics in other quasiparticles holds considerable potential for practical applications in phononics and magnonics, emerging fields that leverage collective excitations for novel material control and coherent information transfer. In this talk, I will demonstrate the optical generation and detection of abundant magnonic frequency mixing processes in the antiferromagnetic semiconductor CrSBr by employing above-gap pump pulses to launch coherent magnons and optically measuring them via strong magnon-exciton coupling. The data shows a series of magnon sidebands arising from high-harmonic generation and, when breaking the system symmetry, the mixing of discrete magnon modes to produce sum and difference frequency generation (SFG & DFG). Further, we demonstrate control over the DFG in CrSBr by rotating an external magnetic field to tune its frequency over a broad range. This tuning allows us to push the DFG mode into resonance with one of the fundamental magnon modes, where we can controllably induce parametric amplification. Finally, I will show how we can generate broad magnonic frequency combs, opening a pathway to GHz magnonic metrology and spectroscopy. These findings herald the opening of a new domain in nonlinear opto-magnonic coupling, offering innovative functionalities for hybrid quantum magnonics.