Demonstration of atom interrogation using photonic integrated circuits anodically bonded to ultra-high vacuum envelopes for epoxy-free scalable quantum sensors

Reliable integration of photonic integrated circuits (PICs) into quantum sensors has the potential to drastically reduce sensor size, ease manufacturing scalability, and improve performance in applications where the sensor is subject to high accelerations, vibrations, and temperature changes. In a traditional quantum sensor assembly, free-space optics are subject to pointing inaccuracies and temperature-dependent misalignment. Moreover, the use of epoxy or sealants for affixing either free-space optics or PICs within a sensor vacuum envelope leads to sensor vacuum degradation and is difficult to scale. In this paper, we describe the hermetic integration of a PIC with a vacuum envelope via anodic bonding. We demonstrate utility of this assembly with two proof-of-concept atom-interrogation experiments: (i) spectroscopy of a cold-atom sample using a grating-emitted probe; (ii) spectroscopy of alkali atoms using an evanescent field from an exposed ridge waveguide. This work shows a key process step on a path to quantum sensor manufacturing scalability.