Ultra-Low-Loss Vertical Emitters

Photonics plays a crucial role in naval applications, where compact, high-performance photonic integrated circuits (PICs) are essential for microwave photonics, signal generation and sensing and secure communications. Different PIC platforms (Si, SiN, Thin-film Lithium Niobate (TFLN), InP, SiC) have different benefits. Achieving ultra-low-loss optical coupling between multiple PICs, particularly in vertically stacked configurations, which are critical for building optical systems that leverage multiple photonic integration platforms, has remained elusive. Current coupling techniques suffer from alignment sensitivity, high insertion loss (IL) and process variability, leading to increased signal degradation due to high optical losses between interconnected PICs. Narrow optical bandwidth and limited power and temperature handling are also detrimental to navy requirements. To address these challenges, we propose highly-efficient PIC-to-PIC vertical coupling enabled through two similar yet complementary approaches: microlensed Facet-attached Vertical Emitters (FaVE) fabricated through two-photon polymerization (2PP) and Turning  Micromirrors reflectors utilizing Grayscale Lithography (GL). The Phase I effort will evaluate both approaches through optical simulations and optimization, prototype fabrication, and experimental characterization to identify the most promising path forward for achieving 0.1dB vertical chip emitters with high misalignment tolerance, solder-reflow compatibility, and broadband operation, suitable for Navy systems.