Spatially Dispersive Lasing for Spectrally Encoded Imaging

Bound states in the continuum (BICs) enable low‐threshold on‐chip lasing, but current implementations are restricted to emission at discrete wavelengths or in discrete directions, limiting their use in scenarios that require broadband spectra or continuous angular dispersion. Here, we exploit the topological characteristics of BICs in a hexagonal photonic lattice to engineer a split‐BIC cavity, in which a higher‐order at‐Γ BIC is deliberately split into two off‐Γ fundamental BICs. This design supports a continuous band of high‑ Q resonances over an extended region of k ‐space, yielding an ultra‐compact laser source that intrinsically combines broadband emission with monotonic wavelength–angle mapping. We experimentally realize this concept by fabricating the split‐BIC microcavity in a TiO 2 photonic crystal and integrating it with organic dye molecules as the gain medium. Harnessing this built‐in spectral–angular correlation, we demonstrate spectrally encoded imaging, wherein one spatial dimension of an object is directly mapped onto the optical wavelength axis. Our work establishes a pathway toward fully integrated, diffractive‐optics‐free laser systems for miniaturized spectroscopic and imaging applications.