Metasurface-Based\nPhosphor-Converted Micro-LED Architecture\nfor DisplaysCreating Guided Modes for Enhanced Directionality

Phosphor-converted micro-light emitting diodes (micro-LEDs)\nare\na crucial technology for display applications but face significant\nchallenges in light extraction because of the high refractive index\nof the blue pump die chip. In this study, we design and experimentally\ndemonstrate a nanophotonic approach that overcomes this issue, achieving\nup to a 3-fold increase in light extraction efficiency. Our approach\ninvolves engineering the local density of optical states (LDOS) to\ngenerate quasi-guided modes within the phosphor layer by strategically\ninserting a thin low-index spacer in combination with a metasurface\nfor mode extraction. We demonstrate the trade-offs between blue light\npumping, LDOS enhancement at the converted emission wavelength, and\nradiation pattern control using a stratified system solver for dipole\nemission. Experimentally, the integration of plasmonic antennas and\na silica spacer resulted in a 3-fold overall brightness enhancement,\nwith nearly a 4-fold increase in forward emission. This nanophotonic\nmetasurface waveguide design is a critical advancement for producing\nbright, directional micro-LEDs, particularly in augmented/virtual\nreality (AR/VR) devices and smartwatch displays, without the need\nfor bulky secondary optics or reflectors.