This paper investigates the utilization of optical control in diverse planar devices, focusing on the Metal-Insulator-Semiconductor (MIS) microstrip transmission line on a semiconductor substrate as a specific example. Optical illumination induces intriguing e®ects in this structure, wherein the metal layer can serve as a transparent conductive oxide when illuminated. The MIS interconnect, crucial in modern high-speed Very Large-Scale Integration (VLSI) circuits, has undergone extensive scrutiny regarding Electromagnetic (EM) wave behavior using various analytical approaches. Controlling wave propagation and manipulating MIS-type planar transmission lines enable the design of delay lines, phase shifters, filters, etc. Energy dissipation in MIS-layer-type transmission lines is also explored due to its significant impact on interconnect design. This paper employs theoretical and experimental models to analyze MIS line characteristics and performance. Optical control presents opportunities to enhance planar device functionality and e±ciency, particularly in MIS microstrip transmission lines, driving advancements in high-speed VLSI circuits and fostering innovative applications across industries.