Abstract: The present invention improves multi-chip module (MCM) testability by using a new technique to detect on-substrate electric field strength. The invention employs a non-invasive, laser-based instrument to probe the MCM structures fabricated with poled polyimide interlayer dielectrics and thin film metallizations on silicon carriers. Circuit element characteristics of MCMs are probed with laser to detect electric field strength. The electrical, mechanical and optical properties of the electro-optical dielectric layers are determined to investigate the effect of the poling and processing operations on the efficacy of the polyimide as both a dielectric layer and an electro-optic material suitable for laser probing.