Mid-infrared optical valve based on <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>VO</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>

We demonstrate an efficient optical binary-switch effect in nanoslit arrays achieved via the temperature-induced phase transition of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:msub><a:mi>VO</a:mi><a:mn>2</a:mn></a:msub></a:math>. Experimental measurements reveal a polarization-dependent 60% reduction in reflectivity during the insulator-to-metal transition. Tuning a single parameter of the slit enables control over the “optical-valve” effect. Full numerical simulations support these findings, predicting a reflectivity reduction up to 90%. The nearly one-to-null transition in reflectivity mimics the operation of a digital switch, with the high-reflectivity and the low-reflectivity states providing a binary response much like digital electronics.