Recent Developments in Deep‐Ultraviolet Flat Optics

Deep‐ultraviolet flat optics (DUVFO) is rapidly emerging as a foundational platform for next‐generation photonic technologies. Operating in the 200–300‐nm regime, DUVFO unlocks capabilities inaccessible to conventional refractive optics, enabling compact beam shaping, high‐NA (HNA) focusing, and efficient nonlinear interactions within ultrathin form factors. This review provides a comprehensive overview of the materials, device concepts, and system‐level innovations driving the shift from bulky, absorption‐limited DUV optics toward scalable, chip‐compatible flat‐optical architectures. We highlight the critical role of wide‐bandgap semiconductors and low‐loss metal oxides in overcoming intrinsic transparency and stability challenges; examine the evolution of linear and nonlinear DUV devices, from HNA metalenses and integrated spectroscopic modules to frequency conversion metasurfaces and chip‐scale light sources; and discuss their emerging impact in lithography, bioimaging, metrology, and nanofabrication. Finally, we outline the key bottlenecks in dispersion engineering, optical characterization, and wafer‐scale manufacturing, emphasizing the interdisciplinary advances required to transition DUVFO from laboratory demonstrations to manufacturable, high‐performance photonic platforms.