Metasurface-Based Phosphor-Converted Micro-LED Architecture for Displays─Creating Guided Modes for Enhanced...

Area of Science:

• Optoelectronics
• Nanophotonics
• Materials Science

Background:

• Phosphor-converted micro-light emitting diodes (micro-LEDs) are vital for displays but suffer from low light extraction efficiency due to the high refractive index of blue pump die chips.
• Efficient light extraction is a key challenge for realizing high-performance micro-LED displays.

Purpose of the Study:

• To design and demonstrate a nanophotonic approach to significantly enhance light extraction efficiency in micro-LEDs.
• To overcome the limitations imposed by the high refractive index of the blue pump die chip.

Main Methods:

• Engineered the local density of optical states (LDOS) within the phosphor layer by inserting a thin low-index spacer.
• Utilized a metasurface for efficient mode extraction.
• Employed a stratified system solver to analyze blue light pumping, LDOS enhancement, and radiation pattern control.
• Integrated plasmonic antennas and a silica spacer in experimental validation.

Main Results:

• Achieved up to a 3-fold increase in light extraction efficiency.
• Demonstrated a 3-fold overall brightness enhancement and a nearly 4-fold increase in forward emission.
• Successfully generated quasi-guided modes within the phosphor layer.

Conclusions:

• The developed nanophotonic metasurface waveguide design significantly improves micro-LED performance.
• This advancement is critical for bright, directional micro-LEDs in applications like AR/VR and smartwatches.
• The approach eliminates the need for bulky secondary optics or reflectors.