Photonic-chip-on-tip: compound photonic devices fabricated on optical fibers

Just like nanometer-scale conductive paths in an electronic chip at some point end up connected to macroscopic wires of the printed circuit board, photonic integrated circuits often need light in/out coupling from/to external devices, such as light sources or detectors. In the optical domain, these connections are challenging due to the scale mismatch and alignment precision required. At the same time, there is more than 24,500 μm² of space available on two cleaved single mode optical fiber tips. We demonstrate that this space can be used to fabricate compound photonic assembly - Photonic-chip-on-tip - directly integrated with the fibers. As an example, we present a simple setup consisting of in- and out-coupling prisms, tapered waveguide, and a whispering gallery micro-resonator, all made in a single process with two-photon laser photolithography. Temperature sensing is demonstrated as an example of application. This approach to photonic circuit design intrinsically addresses the problems of scale mismatch, fiber alignment, light coupling, and packaging.