Experimental demonstration for scanning near-field optical microscopy using a metal micro-slit probe at millimeter wavelengths

Scanning near-field optical microscopy using a slit-type probe is discussed. The slit-type probe has a width of much less than a wavelength, lambda, and a length on the order of lambda, and thus has high transmission efficiency. Two dimensional near-field images of objects have been constructed using an image reconstruction algorithm based on computerized tomographic imaging. Experiments performed at 60 GHz (lambda= 5 mm) show that this type of near-field microscopy can achieve a spatial resolution of better than lambda/45 for two dimensional imaging. A method for fabricating a submicron width slit probe at the end of an optical fiber is presented for extending this microscopy to optical waves. (C) 1997 American Institute of Physics. [S0003-6951(97)02250-X].