Control of LED Emission with Functional Dielectric Metasurfaces

Commercial viability of technologies in optoelectronics and photonics, among others, depend critically on the availability of both (a) an efficient and low-cost light source with a small footprint of less than 1µm2, and (b) an efficient method to manipulate light in complex ways, such as programmable beam steering.  Light emitting diodes (LEDs) is an efficient, inexpensive and compact light source, with LEDs' low energy consumption and long lifetime unmatched by other light sources. However, existing methods for complex manipulation of light, such as metasurfaces, work well only for spatially coherent light sources such as lasers, and lose their functionalities completely when used with LEDs. 

This work proposed that LED light could be efficiently manipulated using a composite structure comprising a metasurface and a resonant cavity, and that efficient manipulation was possible for different types of light manipulation, as well as their combinations. Two different types of LED light manipulation – a simple beam deflection, and a complex manipulation to generate a vortex beam – were experimentally demonstrated using a silicon metasurface and a hybrid gold-Bragg cavity.

The applications of this proposed concept are myriad, as the concept works for all types of light sources, and is capable of complex manipulation functions as well as any desired combination of manipulation functions. In particular, this proposed concept allows all existing metasurfaces designed for coherent light sources (e.g. lasers) to be used for other light sources with the addition of a suitable resonant cavity.  Integrating metasurfaces and cavities with LEDs also retains the small footprint advantage associated with LEDs.  To the best of our knowledge, this is the first proposal of a concept capable of on-demand manipulation of light from any light source.

This research is funded by the five-year Pharos Programme on Dielectric Nanoantennas that aims to integrate dielectric metasurfaces consisting of sub-diffractive arrays of dielectric nanoantennas on top of or inside state-of-the-art LED devices. Such novel devices will provide compact and low-power consumption high-speed optoelectronics for various applications including solid-state lighting, displays, and communications. In particular, high-speed LED devices may become cheaper competitors of vertical cavity surface emitting lasers (VCSELs) for telecommunications.  

The article titled "Control of LED Emission with Functional Dielectric Metasurfaces" was published in Laser & Photonics Reviews (impact factor of 9.056) by researchers from IHPC, IMRE and NTU.  The IHPC researchers involved in this work are Dr Liu Zhengtong, Dr Yuriy Akimov, Dr Bai Ping, and Dr Jason Png.