Wavelength‐Agnostic 3D‐Nanoprinted Coupler

A photonic coupler is presented that exhibits effectively wavelength‐agnostic performance for ultra‐broadband optical interfacing. By incorporating a dual‐ellipsoidal geometry, the design facilitates quasi‐free‐space optical propagation. A hybrid modeling workflow is further proposed to employ a matrix optics–based approach as an efficient pre‐design tool, capturing critical geometry‐to‐mode mapping characteristics, significantly narrowing the parameter space required for subsequent full‐vectorial finite‐difference time‐domain (FDTD) simulations. The design achieves a 1 dB bandwidth exceeding 800 nm coupling from fibre to chip, with an insertion loss as low as 1.3 dB—to the best of the knowledge, a record for any reported photonic couplers. The additive manufacturing approach via 3D nano‐printing enables flexible geometry customization and sub‐micron integrated alignment features, facilitating seamless integration with photonic chips and optical fibers. Experimental validation demonstrates excellent stability and thermal robustness across diverse operational conditions, highlighting the design's suitability for integration into wide range of broadband photonic systems.