Photopolymer Packaging and Interconnects for Integrated Photonics: Alignment, Coupling Loss, Stress and Reliability

Three-dimensional photopolymer structures can bridge the geometric mismatch between optical fibres and photonic chips, connect dissimilar photonic dies and place freeform couplers directly at an interface. The principal engineering advantage is not merely printable geometry but the possibility of writing an optical interconnect after the positions of the assembled components are known. This changes the alignment problem from precision placement alone to a combined metrology, writing and optical-overlap problem. Published photonic-wire-bonding work has demonstrated broadband chip-to-chip polymer interconnects, and later multi-chip assemblies have reported sub-decibel average insertion loss across large sets of bonds. Recent 3D-nanoprinted interposers further integrate optical and mechanical alignment functions. These demonstrations also expose the qualification variables: modal overlap, waveguide propagation loss, interface reflections, surface roughness, cure shrinkage, thermal-expansion mismatch, cladding state and long-term positional drift. This review develops a qualification framework that separates initial coupling efficiency from package reliability and requires optical performance to be re-measured after environmental and mechanical stress. ER-427.