Terahertz (THz) waves occupy a segment of the electromagnetic spectrum between the infrared and microwave bands. As such, they can be used for imaging and sensing in ways that are not possible with conventional technologies such as X-ray and microwave. Because THz radiation transmits through almost anything that is not metal or liquid, the waves can see through most materials that might be used to conceal explosives or other materials, such as packaging, corrugated cardboard, clothing, shoes, backpacks, and book bags. They are also safer than X-rays and microwaves for human tissue. This invention is directed to a method of improving the spatial resolution of a pump-probe terahertz imaging system for producing an image of an object. The technology provides a chopped optical gating beam focused on a semiconductive layer that is either part of the object or a discrete layer placed over the object. The method detects the measurable modulation of the transmitted Thz beam and compares and processes the alternating modulated THz beam resulting when the gating pulse beam is on and off.