No abstract

Brillouin light scattering ͑BLS͒ has been used to observe and confirm the existence of nonlinear three magnon splitting and confluence processes for propagating spin waves in the magnetostatic backward volume wave configuration. Wave vector and frequency selective BLS techniques were also used to provide a quantitative map of the wave vector make-up for the parametrically excited half-frequency dipole-exchange spin wave ͑DESW͒ split magnons and the confluence magnons that result from the recombination of these DESW modes. The experimental wave vector maps for the product splitting and confluence magnons matched nicely with those expected from spin-wave theory. The data were obtained with ͑1͒ a strip line excitation/detection transducer structure, ͑2͒ forward-scattering BLS optics, ͑3͒ a fixed magnetic field of 352 Oe applied along the propagation direction, ͑4͒ pumping frequencies from 2.5 down to 2.1 GHz, ͑5͒ and cw input powers from 200 W to 6 mW. The wave vector selective measurements utilized variable diameter circular diaphragms, rotatable slit apertures, and circular light blocks to access spin waves with wave numbers from about 100 to 3.6ϫ 10 4 rad/ cm and the full 360°range of propagation angles.

A hexagonal ferrite-based millimeter wave notch filter was demonstrated. The filter consists of an M-type BaFe12O19 (BaM) slab sitting on top of a stripline. The band-stop filtering response originates from the ferromagnetic resonance absorption in the BaM slab. The BaM slab has an in-plane uniaxial anisotropy field of 17 kOe. This anisotropy field facilitates the operation of the filter beyond 50 GHz without a need of high external fields. The operating frequency increases linearly with the external field, while the bandwidth versus field profile shows a U-shaped response. The physical mechanisms for these responses were discussed.

We investigate the chiro-optical properties of the electromagnetic near-field associated with the excitation of collective optical resonances (surface lattice resonances) in achiral plasmonic lattices. These arrays are specially designed to support dispersive resonances with nontrivial, multipolar near-field distributions in the surroundings of the nanostructure, which gives rise to an enhanced chiro-optical response. The presence of these multipolar resonances in lattices without explicitly broken mirror symmetry is experimentally confirmed by far-field extinction measurements, while the angular, spectral, and spatial dependence of the associated chiral near-field are numerically simulated. In contrast with typical pseudochiral systems, the extended chiro-optical near-field response appears even at normal incidence. We believe that surface lattice resonances in achiral plasmonic lattices can be potentially utilized as a substrate for enhanced background-free enantioselectivity and tunable chiral molecule recognition over large areas.