Modeling and enhancing of the micro-focused Brillouin light scattering
Dr. Ondrej Wojewoda, Central European Institute of Technology, Brno, Czech Republic

Date, Time
20.03, 15:00 - 16:00

Location
Link to MS Teams

The field of magnonics has emerged as a promising area of research, focusing on collective magnetic excitations known as spin waves and their associated quasiparticles, magnons [1]. One of the most versatile tools used to investigate magnons is micro-focused Brillouin light scattering (µ-BLS). However, despite its extensive use, there has been no theoretical approach to model its signal. We use a semi-analytical approach to optics and the microscopic theory of inelastic scattering to model the induced polarization currents. Using Green’s function formalism, the light emitted by these polarization currents can be propagated to the detector and the resulting µ-BLS signal can be modeled [1].

This theoretical approach allowed us to thoroughly understand all the processes involved in µ-BLS signal formation. Based on this understanding, we employed dielectric nanoresonators  to enhance the detection limit to wavelength shorter than 30 nm (larger than 200 rad/µm), which is more than one order of magnitude improvement over standard µ-BLS on the bare film (400 nm, <16 rad/µm)[3,4,5]. The dielectric structures can also be utilized to introduce full wavevector resolution (angle and magnitude). This opens new, previously impossible experiments, such as the measurement of incoherent nanoscale spin currents or the measurement of the dispersion relation in the unprecedented wavevector range.

Figure 1. Modeling and enhancement of the μ-BLS signal. (a), Schematics of the μ-BLS setup. (b), Schematics of the modeling of the μ-BLS signal using semi-analytical approach and the microscopic theory of inelastic scattering. (c), Periodic nanoscale dielectric resonators for enhancement of the detectable spin-wave wavevectors. (d), Overview of the spin-wave dispersion relation and available methods for its measurement over the whole Brillouin zone.