Time as a contrast mechanism in near-field imaging

Any modulation of a detected signal can be used as a contrast mechanism in imaging applications. Insofar as the time dependence of optical properties of imaged structures can be used to elucidate material properties, such time dependences can provide a modulation which can then be used as a contrast mechanism in imaging. We introduce a system in which time can be used as a contrast mechanism in imaging. We introduce a system in which time can be used as a contrast mechanism to study material nanostructures. Single-crystal silicon wafers are imaged in the infrared using a HeNe laser while the wafer is simultaneously pulsed with visible radiation. By studying the time dependence of the infrared transmittance, defect distribution on the nanometer scale can be imaged, and sample nanostructure can be studied.