Shape-engineered multi-wavelength lasing in GaN-based microcavity arrays with lateral nanoporous DBRs.

Compact multi-wavelength laser sources are essential for high-capacity optical communication, optical computing, and multi-channel sensing in integrated photonic circuits. Here, we demonstrate a low-threshold GaN-based multi-wavelength microcavity laser array by engineering cavity shapes with lateral nanoporous distributed Bragg reflectors (DBRs). Circular, hexagonal, and square microcavities exhibit distinct lasing wavelengths of 459, 444, and 428 nm, covering a spectral span of 31 nm, with corresponding lasing threshold average power densities of 0.43, 0.99, and 3.75 W/cm2, respectively. The wavelength variation originates from the shape-dependent cavity loss and gain spectrum evolution under different excitation conditions. Numerical simulations further reveal the influence of cavity shape on optical confinement and mode properties. Our findings establish a straightforward and effective strategy for realizing multi-wavelength GaN-based microcavity laser arrays without complex epitaxial regrowth, paving the way toward chip-scale visible photonic systems.