Millimeter-wave active and passive microscopies

Millimeter-wave scanning near-field microscopies operating in the active and passive modes are investigated to enhance the sensitivity attainable in these microscopic imaging techniques. For active microscopy, a knife blade with a tip radius of 6 μm and a width of 8 mm was used as a near-field probe. Experiments performed at 60 GHz show that this can enhance the signal intensity by ∼20 dB compared with an equivalent metal tip probe. For passive microscopy, a tapered slit-type probe featuring no cutoff was used as a scanning probe. Experiments performed at 50 GHz at various sample temperatures show that our passive microscope system can successfully image thermal radiation, even in the low temperature range where passive imaging systems in the infrared region are ineffective.