Super Lensing in the Mid-Infrared

Physicists at the University of Texas at Austin have made a "super lens," a plane-shaped lens that can image a point source of light down to a focal spot only one-eighth of a wavelength wide. This is the first time such super lensing has been accomplished in a functional device in the mid-infrared range of the electromagnetic spectrum.

Historically, lensing required a lens-shaped (that is, lozenge-shaped) optical medium for bringing the diverging rays coming from a point source into focus on the far side of the lens. But in recent years, researchers have found that in "negative permittivity" materials, in which a material's response to an applied electric field is opposite that of most normal materials, light rays can be refracted in such a way as to focus planar waves into nearly a point -- albeit over a very truncated region, usually only a tenth or so of the wavelength of the light.

Such near-field optics are not suitable for such applications as reading glasses or telescopes, but have become an important technique for certain kinds of nanoscale imaging of large biological molecules than can be damaged by UV light. The micron-sized Texas lens, reported at the Frontiers in Optics meeting of the Optical Society of America, consists of a silicon carbide membrane between layers of silicon oxide. It focuses 11-micron-wavelength light, but the researchers hope to push on into the near-infrared range soon. Furthermore, the lensing effect seems to be highly sensitive to the imaging wavelength and to the lens thickness.

Gennady Shvets (gena@physics.utexas.edu) says that additional possible applications of the lens include direct laser nanolithography and making tiny antennas for mid-IR-wavelength free-space telecommunications.

The Frontiers in Optics meeting
Paper fMG2 at meeting
The Shvets Research Group