Magneto-optical microimaging for hydrogen reaction on Fabry–Pérot cavity elements

Magneto-optical (MO) microimaging of hydrogen reactions on Fabry–Pérot cavity elements in a polar Kerr configuration was investigated. The MO cavity elements comprised surface half-mirror/MO interference layer/total-reflection mirror multilayers and hydrogen was detected via hydrogen reactions on the PdAu surface half-mirror. Kerr hysteresis measurements indicated MO polarity reversal via hydrogen absorption into the PdAu layer, which was theoretically attributed to MO resonance shifts. Additionally, distinct changes occurred in the MO microimages upon hydrogen exposure, which depended on the initial MO state and PdAu surface layer thickness. In the polar Kerr images, the regions of magnetization reversal appeared as dark lines under resonance conditions because the MO effect did not occur in these regions where the magnetization was optically zero. Furthermore, the hydrogen reaction reversed the magnetic domain contrast. This imaging technique possesses various chemical and biological applications if the surface half-mirror comprises suitable materials.