TIME AS A CONTRAST MECHANISM IN NEAR-FIELD IMAGING

Any modulation of a detected signal can be used as a contrast mechanis m in imaging applications. Insofar as the time dependence of optical p roperties of imaged structures can be used to elucidate material prope rties, such time dependences can provide a modulation which can then b e used as a contrast mechanism in imaging. We introduce a system in wh ich 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 ma terial 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 infrare d transmittance, defect distribution on the nanometer scale can be ima ged, and sample nanostructure can be studied.