Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106, United States.
Published: November 2023
AI Article Synopsis
Article Abstract
Phased-array metasurfaces enable the imprinting of complex beam structures onto coherent incident light. Recent demonstrations of phased-array metasurfaces highlight possibilities for achieving similar control in light-emitting diodes (LEDs). However, phased-array metasurface LEDs have not yet been demonstrated owing to the complexities of integrating device stacks and electrodes within nanopatterned metasurfaces. Here, we demonstrate metasurface LEDs that emit directional or focused light. We first design nanoribbon elements that achieve the requisite phase control within typical LED device constraints. Subsequently, we demonstrate unidirectional emission that can be engineered at will via phased-array concepts. This control is further exhibited in metasurface LEDs that directly emit focused beams. Finally, we show that these metasurface LEDs exhibit external quantum efficiencies (EQEs) superior to those of unpatterned LEDs. These results demonstrate metasurface designs that are compatible with high-EQE metal-free LED devices and portend opportunities for new classes of metasurface LEDs that directly produce complex beam structures.
Department of Physics of Information in Matter and Center for Nanophotonics, NWO-I Institute AMOLF, Science Park 104, NL 1098XG Amsterdam, The Netherlands.
Phosphor-converted micro-light emitting diodes (micro-LEDs) are a crucial technology for display applications but face significant challenges in light extraction because of the high refractive index of the blue pump die chip. In this study, we design and experimentally demonstrate a nanophotonic approach that overcomes this issue, achieving up to a 3-fold increase in light extraction efficiency. Our approach involves engineering the local density of optical states (LDOS) to generate quasi-guided modes within the phosphor layer by strategically inserting a thin low-index spacer in combination with a metasurface for mode extraction.
Near-eye displays are widely recognized as a groundbreaking technological advancement with the potential to significantly impact daily life. Within the realm of near-eye displays, micro-LEDs have emerged as a highly promising technology owing to their exceptional optical performance, compact form factor, and low power consumption. However, a notable challenge in integrating micro-LEDs into near-eye displays is the efficient light collimation across a wide spectrum range.
We present a simulation capability for micro-scale light-emitting diodes (µLEDs) that achieves comparable accuracy to CPU-based finite-difference time-domain simulation but is more than 10 times faster. Our approach is based on the Fourier modal method (FMM)-which, as we demonstrate, is well suited to modeling thousands of incoherent sources-with extensions that allow rapid convergence for µLED structures that are challenging to model with standard approaches. The speed of our method makes the inverse design of µLEDs tractable, which we demonstrate by designing a metasurface-enhanced µLED that doubles the light extraction efficiency of an unoptimized device.
Phased-array metasurfaces enable the imprinting of complex beam structures onto coherent incident light. Recent demonstrations of phased-array metasurfaces highlight possibilities for achieving similar control in light-emitting diodes (LEDs). However, phased-array metasurface LEDs have not yet been demonstrated owing to the complexities of integrating device stacks and electrodes within nanopatterned metasurfaces.
LEDs show Lambertian emission, necessitating secondary optics for tailored output based on application needs.
This research introduces plasmonic metasurfaces with aluminum nanodisks to improve the direction and efficiency of light emission from InGaN quantum wells in LEDs.
Integrating these metasurfaces can increase light intensity by up to 5 times and offers a more efficient way to control emission without additional optics or complex post-processing.
