Control of LED Emission with Functional Dielectric Metasurfaces

Abstract

The improvement of light-emitting diodes (LEDs) is one of the major goals of optoelectronics and photonics research. While emission rate enhancement is certainly one of the targets, in this regard, for LED integration to complex photonic devices, one would require to have, additionally, precise control of the wavefront of the emitted light. Metasurfaces are spatial arrangements of engineered scatters that may enable this light manipulation capability with unprecedented resolution. Most of these devices, however, are only able to function properly under irradiation of light with a large spatial coherence, typically normally incident lasers. LEDs, on the other hand, have angularly broad, Lambertian-like emission patterns characterized by a low spatial coherence, which makes the integration of metasurface devices on LED architectures extremely challenging. A novel concept for metasurface integration on LED is proposed, using a cavity to increase the LED spatial coherence through an angular collimation. Due to the resonant character of the cavity, extending the spatial coherence of the emitted light does not come at the price of any reduction in the total emitted power. The experimental demonstration of the proposed concept is implemented on a GaP LED architecture including a hybrid metallic-Bragg cavity. By integrating a silicon metasurface on top we demonstrate two different functionalities of these compact devices: directional LED emission at a desired angle and LED emission of a vortex beam with an orbital angular momentum. The presented concept is general, being applicable to other incoherent light sources and enabling metasurfaces designed for plane waves to work with incoherent light emitters.

Enhanced Directional Light Extraction from Patterned Rare‐Earth Phosphor Films

“…Specifically, different photonic structures have been proposed to improve the directional and spectral control over the phosphor luminescence. [7,[12][13][14][15][16][17][18] Some of the preferred approaches consist in covering the phosphor layer with a 2D array of dielectric scatterers, which enhance the coupling of emitted light to freespace, mostly applied to enhance the external efficiency in both organic [2,3] and inorganic [19][20][21] LEDs. From a technical perspective, the combination of such photonic architectures with phosphor-based devices is far from compatible with most traditional lithographies.…”

Geometrically Tunable Beamed Light Emission from a Quantum‐Dot Ensemble Near a Gradient Metasurface

“…The underlying operating principle involves the preferential excitation of guided waves (SPPs) via near‐field interactions, and their selective scattering into predetermined directions by a periodic NP array designed to suppress all radiative diffraction orders except for one. In passing, we note that a related approach, where the guided waves are provided by a vertical resonant cavity, has been reported recently 40. In the present work, highly directional radiation patterns are measured from colloidal QDs deposited on different GMSs, featuring pronounced emission beams with narrow divergence angles along geometrically tunable directions.…”

Spectral imaging and spectral LIDAR systems: moving toward compact nanophotonics-based sensing

“…Such phase discontinuity can be engineered to achieve the designed reflection angle of the optical beam. The integration of metasurface devices with active layers enables the active tuning and control of optics [92][93][94][95][96]. Furthermore, the metasurface can also be engineered to achieve desired dispersion [97].…”