Integrated, Heat Resistant, Glass Waveguides with 0.01 \text{dB}/\text{cm}$ Bend Loss for $50-\mu \mathrm{m}$ Pitch Conversion in High-Density Optical Interconnects

We demonstrate record low bend loss $(0.01 ~\text{dB} / \text{cm}$, $\mathrm{R}>6 ~\text{mm}, \lambda=1310 ~\text{nm}$) ion-exchanged glass waveguides for high-density fiber-to-chip pitch conversion (from $250 \mu ~\mathrm{m}$ to $50 \mu ~\mathrm{m}$) in optimized glass with ultra-low ion diffusivity ($\sim 5 \mathrm{E}-22 ~\mathrm{m}^{2} / \mathrm{s}$) resulting in an estimated heat-resistant lifetime of $>5$ years at 110° C for high-performance co-packaged optics (CPO) applications, having $<0.3 ~\text{dB}$ fiber coupling loss per facet, and 0.04 dB/cm propagation loss.