A Magneto-Optical Spatial Light Modulator Driven by Spin Transfer Switching for 3D Holography Applications

We have successfully fabricated a basic magneto -optical spatial light modulator (MO-SLM) device driven by spin-transfer-switching (STS), which we call Spin-SLM technology. The SLM device is comprised of a one dimensional ten-pixel light modulation array (1 $\times$ 10 pixels) with a fine pitch of 1 $\mu{\hbox{m}}$ . The light modulation pixels were composed of Gd-Fe based giant magneto resistance (GMR) devices, with a free layer of Gd-Fe, an Ag spacer and a Co-Fe/Tb-Fe-Co pinned layer. The GMR devices were sandwiched by a Cu bottom and Indium zinc oxide top electrodes in order to inject current perpendicular to the film plane for switching. Incident light penetrating the transparent top electrode can be modulated due to its magneto-optic Kerr effect with the Gd-Fe free layer. The fabricated device cell size is ${\hbox{220}}\times {\hbox{300}}\ {\hbox{nm}}^{2}$ . We confirmed successful switching of the individual free layers, which was controlled by STS. We have also fabricated magnetic hologram patterns with the same magnetic materials used in the light modulation layer of the Spin-SLM device in order to determine its feasibility in display applications. The pixel pitch of the pattern was one micron and a reconstructed image by laser light was successfully observed with a wide viewing zone angle as 38 deg, which is nearly the same value expected from calculations. Although these patterns do not have an electrode to switch the magnetization direction, we confirmed the potential of Spin-SLM technology as a display device for 3D holography applications.