Enhancement of a Diffracted Beam in a Domain–Wall–Motion-Type Light Modulator Array

We fabricated a domain–wall–motion-type light modulator array to measure the diffraction characteristics of a magneto-optical-type spatial light modulator (MO-SLM) driven by current-induced domain wall motion. The array imitated the structure of an SLM and displayed a predetermined 2-D magnetic grating by applying an external magnetic field. The pitch of the modulator was designed to be
$1\,\,\mu \text{m}\,\,\times 2\,\,\mu \text{m}$
. We investigated the relationship between the intensity of the diffracted beam and the figure of merit (FOM), which is the product of the reflectance and the square of the complex Kerr angle. We varied the multiple-reflection conditions by changing the incident beam angle and the cap layer thickness to compare the behavior of the diffracted beam and the FOM. The diffracted beam’s intensity was enhanced by adjusting the FOM. Furthermore, the diffracted beam exhibited polarization dependence even though the FOM was independent of the polarization direction. The diffracted beam’s intensity was enhanced by the incident beam polarized in the longitudinal direction of the modulator. This work demonstrates that not only FOM maximization but also polarization direction optimization is important for the enhancement of diffracted beams in narrow-pixel-pitch MO-SLMs with non-square pixel shapes.