The new method integrates quantum dots with metasurfaces for enhanced luminescence

A study published in Nano Letters demonstrates the use of quantum dots to create metasurfaces, enabling two objects to exist in the same space.

Pohang University of Science and Technology (POSTECH) researchers used Nanoimprint Lithography (NIL) to fabricate metasurfaces embedded with quantum dots, increasing their luminescence efficiency. The team included Professor Junsuk Rho from the Department of Mechanical Engineering, Department of Chemical Engineering and Department of Electrical Engineering, Ph.D. candidates Minsu Jeong, Byoungsu Ko and Jaekyung Kim from the Department of Mechanical Engineering and Chunghwan Jung, Ph.D. candidate, from the Department of Chemical Engineering.

NIL, a process for creating optical metasurfaces, uses patterned stamps to quickly transfer complex patterns at the nanometer (nm) scale. This method offers cost advantages over electron beam lithography and other processes. It has the advantage of enabling the creation of metasurfaces using materials not available in conventional processes.

Metasurfaces have recently been the focus of extensive research on their ability to control the polarization and direction of light emission from quantum dots.

Quantum dots, which are nanoscale semiconductor particles, are highly efficient light emitters capable of emitting light at precise wavelengths. This makes them widely used in applications such as QLEDs and quantum computing. However, conventional processes cannot place quantum dots inside metasurfaces.

As a result, research has often involved fabricating metasurfaces and quantum dots separately and then combining them, which imposes limitations on controlling the luminescence of quantum dots.

In this study, the researchers integrated quantum dots with titanium dioxide (TiO₂), a material used in the NIL process, to create a metasurface. Unlike conventional methods, which involve separately fabricating the metasurface and quantum dots before combining them, this approach embeds the quantum dots directly into the metasurface during its creation.

The resulting metasurface increases the proportion of photons emitted by the quantum dots associated with the resonance mode of the metasurface. This advance allows more effective control over the specific direction of light emitted by quantum dots compared to previous methods.

Experiments showed that the more photons emitted by the quantum dots that were coupled to the resonant modes of the metasurface, the higher the luminescence efficiency. The team’s metasurface achieved up to 25 times greater luminescence efficiency compared to a simple layer of quantum dots.

Professor Rho, who led the research, said: “Using luminescence-controlled metasurfaces will enable sharper, brighter displays and more accurate and sensitive biosensing. Further research will allow us to control luminescence in a way more effective, leading to advances in areas such as optical nano-sensors, optoelectronic devices and quantum dot displays.”