Photonic integrated circuits (PICs) are similar to computer chips but operate with light instead of electricity. They are a next-generation technology with potential impacts in high-bandwidth communications, deployable sensors, and computing interconnects. Quality assurance and process control of PICs require light outcoupling of individual device components for in-line testing. Currently, these tests require large patterned areas on chips, which increases circuit size and manufacturing complexity. Light probes are a solution to this problem, where a specialized sub-micron-diameter fiber optic is placed in proximity to a light circuit device to perform tests. These probes are reusable and can be repositioned to test multiple devices for rapid sequential testing. While glass-based probes are currently under development, they require specialized handling and fabrication processes.
The Tapered Polymer Optical Probe (TPOP) is a state-of-the-art light probe that collects light from very small, localized areas. It is a small loop of a thin plastic "string" that collects light from a localized area near the loop into a fiber optic for signal testing. The probe is made of a durable polymer, and fabrication is facile and customizable using commercially available two-photon lithography direct laser write systems.