Phase disorder engineering in aperiodic distributed Bragg reflectors for sidelobe suppression

Area of Science:

• Optoelectronics
• Materials Science
• Photonics

Background:

• Vertically stacked RGB micro-LEDs require specialized distributed Bragg reflectors (DBRs) for efficient color channel separation.
• Traditional periodic quarter-wave DBRs suffer from spectral sidelobes, causing parasitic reflection and reduced light extraction efficiency.

Purpose of the Study:

• To investigate the use of aperiodic DBRs (aDBRs) to suppress spectral sidelobes in micro-LEDs.
• To improve light extraction efficiency and reduce optical crosstalk in vertically stacked RGB micro-LEDs.

Main Methods:

• Designed and optimized aperiodic DBRs with 30 independently varied layer thicknesses using stochastic optimization (proximal policy optimization).
• Analyzed the optical performance using kinematic phasor walk and exact admittance-locus analysis.
• Evaluated fabrication robustness using Monte Carlo simulations.

Main Results:

• Aperiodic DBRs effectively suppressed parasitic reflectance, reducing red-band reflectance by 8.3x and green-band reflectance by 18.5x.
• Achieved a 27.6% relative gain in red-channel extraction efficiency.
• Demonstrated high fabrication robustness with >95% yield for a 2 nm standard deviation in layer thickness.

Conclusions:

• Aperiodic DBRs offer a superior solution for color channel separation in micro-LEDs compared to traditional periodic DBRs.
• Controlled phase diversity in aDBRs enables effective sidelobe suppression without compromising high reflectance.
• The proposed aDBR design is robust and offers significant improvements in micro-LED performance.