IR microscopy with a transient photo-induced near-field probe (tipless near-field microscopy)

Photo-induced reflectivity generated by picosecond pulses of light incident on the surface of semiconductors has been used to create transient mirrors with dimensions determined by the spot size of the visible light. These mirrors were used as near-field probes for scattering of the infrared (IR) laser beam. It has been verified that the IR light reflected from this transient mirror has a spatial resolution determined by the spot size of the visible light. This methodology enables IR microscopy of thin samples with the resolution of a visible microscope. Advantages of this approach are: (i) no need for near-field distance control, (ii) possibility of fast sample scanning, (iii) no attenuation of the IR beam in a tapered fiber probe, and (iv) the sample to be imaged can be covered by or encased in a transparent liquid or solid. Preliminary results, prospects and limitations are discussed. (C) 1998 Elsevier Science B.V.