Abstract Electro-optic probing is a proven technique for testing high-speed microwave circuits on substrates such as Gallium Arsenide (GaAs) and Indium Phosphide (InP) by making point-to-point electric field measurements directly in the substrate. The researchers have extended this technique to probe circuit structures on polyimide substrates that would be used for high-density packaging such as Multichip Modules (MCMs). Test results demonstrate the potential to probe circuit structures that are buried in the central layers of an MCM part
