Space Qualification of Ultrafast Laser-Written Integrated Waveguide Optics

Satellite-based quantum technologies represent a possible route for extending the achievable range of quantum communication, allowing the construction of worldwide quantum networks without quantum repeaters. In space missions, however, the volume available for the instrumentation is limited, and footprint is a crucial specification of the devices that can be employed. Integrated optics could be highly beneficial in this sense, as it allows for the miniaturization of different functionalities in small and monolithic photonic circuits. This article reports on qualification of waveguides fabricated in glass by femtosecond laser micromachining for their use in a low Earth orbit space environment. In particular, different laser-written integrated devices, such as straight waveguides, directional couplers, and Mach-Zehnder interferometers, are exposed to suitable proton and gamma-ray irradiation. This experiment shows that no significant changes have been induced to their characteristics and performances by the radiation exposure. These results, combined with the high compatibility of laser-written optical circuits to quantum communication applications, pave the way for the use of laser-written integrated photonic components in future satellite missions.