First perovskite-based superlens for the infrared
March 30, 2011
IR free-electron laser light source and perovskite superlens consisting of bismuth ferrite (BiFeO3) and strontium titanate (SrTiO3) layers. Imaged objects are strontium ruthenate patterns (orange) on a SrTiO3 substrate. The near-field probe is shown in blue and the evanescent waves in red (credit: Kehr, et al)
Researchers with Berkeley Lab have fabricated superlenses from materials that are simpler and easier to fabricate than metamaterials.
The superlenses are ideal for capturing light in the mid-infrared range (for infrared spectroscopy and thermal sensors, for example), says Ramamoorthy Ramesh, a materials scientist with Berkeley Lab’s Materials Sciences Division and colleague S.C. Kehr at the University of Saint Andrews in the UK.
The perovskites used to make the superlens, bismuth ferrite and strontium titanate, feature a low rate of photon absorption and can be grown as epitaxial multilayers with a highly crystalline quality that reduces interface roughness so there are few photons lost to scattering.
Atomic-force microscopy image showing strontium ruthenate rectangles that were imaged with perovskite-based superlens (credit: Kehr, et. al)
This combination of low absorption and scattering losses significantly improves the imaging resolution of the superlens.
The combination of near-field infrared microscopy and tunable free-electron laser provides the first detailed study of the spatial and spectral near-field responses of the superlens, using a near-field scattering probe (a metal-coated atomic-force microscope tip with a typical radius of 50 nanometers).
Ref.: S.C. Kehr, et al., Near-field examination of perovskite-based superlenses and superlens-enhanced probe-object coupling, Nature Communications, March 22, 2011.