Microscope sees buried objects through superlens

Scanning near-field optical microscopy (SNOM) can visualize minuscule surface features, such as those on semiconductor chips, that are blurs at best in ordinary optical microscopes. Now, toolmakers at the Max Planck Institute for Biochemistry, in Martinsried, Germany, and at the University of Texas, Austin, have combined a so-called superlens with SNOM's tip to create an instrument they say "allows for subwavelength-scale resolved imaging of buried objects" (Science 2006, 313, 1595). With illumination from an infrared laser set at a wavelength of about 11 µm, the probe scans above a submicrometer-thick silicon carbide superlens placed over a gold layer riddled with a test pattern of different-sized holes. Electromagnetic field signals from the gold layer are focused upward by the superlens and picked up by the rastering probe. The researchers showed they can generate clear images of 1,200- and 860-nm holes and vague outlines of 540-nm holes (shown), which are one-twentieth as large as the illuminating IR wavelength. With other superlens-wavelength combos, the technique should enable "high-resolution optical imaging of various man-made or biological nanostructures," the researchers say.