Self-assembly of Janus microring from phase-segregated colloidal quantum dots for dual-wavelength laser

Integration of miniaturized micro-lasers with multi-wavelength emissions underpins advanced photonic circuits for massive data communications. Compared with discrete multiple micro-lasers, monolithic integration of gain materials with different band gaps into a single microcavity facilitates multi-wavelength outputs within a small footprint. Yet undesired energy transfer between gain materials destabilizes the multi-wavelength lasing output. Herein, we regulate the phase segregation of differently sized colloidal quantum dots (CQDs) to fabricate Janus microrings, achieving dual-wavelength lasing from a single microstructure. Exploiting capillary bridges with directional fluid flows, we achieve spontaneous size segregation of binary CQDs into distinct regions, reducing FRET efficiency from 32% to 5% and preserving stable dual-wavelength lasing with low thresholds (<13 μJ cm⁻²). Based on the Janus microring arrays, we encode lasing signals into a 29 × 29 optical quick-response (QR) code with 841 quaternary bits. Moreover, one-step self-assembly yields 772 pixels per inch (PPI) full-color laser arrays over a 2-inch area, demonstrating potential for high-resolution displays.