Fiber-to-Chip Packaging With Robust Fiber Fusion Splicing for Low-Temperature Applications

Photonic Integrated Circuits (PICs) have emerged as a promising technology to support applications including datacom, AI, RF signal processing, and quantum computing and sensing. A critical aspect of PIC-based systems is the ability to transmit optical signals between chips, which requires a low-loss, robust interface between the PIC-chip and optical fiber. Here we present a thorough examination of a fiber fusion attachment process to create such an interface. The process used a CO2 laser to heat and fuse the fiber to a silicon nitride chip and achieved a measured coupling loss of ~2.45 dB/facet for 1550 nm light, which represents a reduction in loss of 0.5dB/facet from prior to the fusion splice being formed. A force sensor was integrated into the fusion splicing process to allow for quantitative analysis of splicing conditions. Additionally, the robustness of the fusion splicing process was demonstrated by repeated temperature cycling of a spliced chip between 193 K and 293 K led to an increase in loss of only 0.3 dB after five cycles.