Cross-coupling between magnetism and electricity in a solid can be hosted by multiferroics with both magnetic and ferroelectric orders. In multiferroics, the collective spin excitations active for both electric and magnetic fields, termed electromagnons, play a crucial role in the elementary process of magnetoelectric (ME) coupling. Here we report the colossal dynamical (optical) ME effect, or more specifically the magnetochiral (MCh) effect, in the electromagnon resonance for the screw spin helimagnet CuFe 1 À x Ga x O 2 (x ¼ 0.035). The MCh effect shows up as the nonreciprocal directional dichroism; the extinction coefficient is different for counter-propagating lights, as large as by 400%. The MCh effect derived from the screw spin order is proved by control of the magnetic helicity of helimagnetism and its magnetization. The results point to the general presence of the MCh effect in helimagnets, paving a way to the ME control of electromagnetic wave in the giga-to tera-hertz region.

We have studied magnetic excitations in a field-induced noncollinear commensurate ferrimagnetic phase of Ba 2 Mg 2 Fe 12 O 22 by means of polarized inelastic neutron scattering (PINS) and terahertz (THz) time-domain optical spectroscopy under magnetic field. A previous THz spectroscopy study reported that the field-induced phase exhibits electric-dipole-active excitations with energies of around 5 meV [Kida et al., Phys. Rev. B 83, 064422 (2011)]. In the present PINS measurements, we observed inelastic scattering signals around 5 meV at the zone center in the spin-flip channel.This directly shows that the electric-dipole-active excitations are indeed of magnetic origin, that is, electromagnons. In addition, the present THz spectroscopy confirms that the excitations have oscillating electric polarization parallel to the c axis. In terms of the spin-current model (KatsuraNagaosa-Balatsky model), the noncollinear magnetic order in the field-induced phase can induce static electric polarization perpendicular to the c axis, but not dynamic electric polarization along the c axis. We suggest that the electromagnon excitations can be explained by applying the magnetostriction model to the out-of-phase oscillations of the magnetic moments, which is deduced from the present experimental results.

Nikon has been developing the Digital Scanner (DS), an optical maskless exposure tool with a DUV light source and a micromirror-type spatial light modulator (SLM). Rasterized digital data, essentially huge bitmap files, are used to drive the SLM. The DS enables new applications such as large area printing and chip customization because its digital pattern data are easily modified. Flexible and fast data preparation software was developed for the new applications. As a standard operation of DS data preparation software, a CAD file (GDS or OASIS) is converted into bitmap files. In addition, bitmap file generation by a scripting language is available without a CAD file. This is useful when the CAD file includes a lot of polygons in which each polygon is similar but not identical, resulting in a huge file. As an example of application, a metasurface consists of sub-wavelength periodic patterns with various shapes, which are arranged to achieve the desired optical effect. The shape of each pattern at a grid point can be determined by a computer program, i.e., a pattern generator script. On the other hand, data preparation time can be shortened for periodic pattern which is often seen in semiconductor circuits. We report those data preparation methods for the DS, which have been used for our recent exposure experiments.

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