Abstract

Using high intensity femtosecond laser pulses (>40 MW peak power), we have successfully performed second harmonic imaging through strongly scattering material. An object is illuminated by femtosecond pulses, and the back-scattered and reflected light from a different part of the object is gated by a femtosecond reference pulse through the second harmonic crystal. Three-dimensional images with high depth resolution are obtained by this range gating method. Very low reflecting surfaces, such as soft contact lenses merged in water solutions (normal surface intensity reflectivity is less than 1%), are also being detected by this imaging method. Different imaging objects have been tested. Results show a good signal to noise ratio by using a type II phase matching crystal. This new imaging method can be applied to medical diagnostics, such as imaging an object through human tissue or the low reflectivity fine structure of an eye. It is also an extension of conventional microwave image radar to the optical range with a much higher resolution.

© 1992 Optical Society of America