Lecture by A/Prof. Yoshiaki Nishijima: “Focusing Mid-Infrared Thermal Emission with Radiative MIM Metalenses”

A scientist from Japan, Associate Professor Yoshiaki Nishijima of Yokohama National University, will visit FTMC and deliver a lecture.

Date: 20 October, 15:00

Venue: FTMC Hall A101 (Saulėtekio Ave. 3, Vilnius)

Abstract:

“Thermal radiation from metal-insulator-metal (MIM) metasurfaces is a promising route to compact, efficient light sources in the mid-infrared (mid-IR). Their emission, however, is broadly divergent, spreading over an angle of roughly 120°. Many mid-IR applications would therefore benefit from controlling the thermal emission directly at the source, without external optical components.

We introduce the concept of a radiative metalens: an MIM metasurface designed to focus its own thermal radiation. The design is based on the phase profiles of the Fresnel lens and the Fresnel zone plate. A Fresnel lens divides a spherical lens into concentric zones with a sawtooth cross-section, reducing its thickness while still acting as a refractive element.

Reducing this profile to binary, two-level concentric zones turns it into a Fresnel zone plate, which is a diffractive optical element. Using finite-difference time-domain (FDTD) simulations, we designed a radiative metasurface that encodes this phase pattern to focus its emission. We then fabricated a 5-mm-diameter radiative metalens by electron-beam lithography. Its focusing performance was validated experimentally by directly mapping the spatial distribution of the emitted thermal radiation,” says Dr Nishijima.

Bio:

Yoshiaki Nishijima received his PhD from Hokkaido University in 2009. After two years of postdoctoral research, he joined Yokohama National University in 2011, where he is now an Associate Professor in the Faculty of Engineering. His research spans plasmonics and nanophotonics, with a focus on new optical materials for chemical sensing by surface-enhanced Raman scattering and infrared absorption (SERS/SEIRA) and for photo-thermal and photo-electric energy conversion.

His group works extensively on mid-infrared metal–insulator–metal (MIM) metasurfaces and has recently demonstrated focused thermal radiation from such metasurfaces. He maintains long-standing international collaborations, including with researchers from Lithuania.

Source: FTMC