Cryogenic and hermetically sealed packaging of photonic chips for optomechanics

TL;DR

This paper presents a hermetically sealed cryogenic packaging system for integrated photonic devices that enables controlled gas encapsulation, thermalization, and superfluid coverage, enhancing quantum optomechanics and photonics applications.

Contribution

The authors introduce a novel hermetic packaging method for photonic chips at cryogenic temperatures with plug-and-play functionality and optimized fiber-to-chip integration.

Findings

NOA 86H adhesive performs best under cryogenic conditions.

The packaging system effectively encapsulates superfluid helium for optomechanics.

Thermal cycling tests validated fiber-to-chip optical stability.

Abstract

We demonstrate a hermetically sealed packaging system for integrated photonic devices at cryogenic temperatures with plug-and-play functionality. This approach provides the ability to encapsulate a controlled amount of gas into the optical package allowing helium to be used as a heat-exchange gas to thermalize photonic devices, or condensed into a superfluid covering the device. This packaging system was tested using a silicon-on-insulator slot waveguide resonator which fills with superfluid $^4$He below the transition temperature. To optimize the fiber-to-chip optical integration 690 tests were performed by thermally cycling optical fibers bonded to various common photonic chip substrates (silicon, silicon oxide and HSQ) with a range of glues (NOA 61, NOA 68, NOA 88, NOA 86H and superglue). This showed that NOA 86H (a UV curing optical adhesive with a latent heat catalyst) provided the best performance under cryogenic conditions for all the substrates tested. The technique is relevant to superfluid optomechanics experiments, as well as quantum photonics and quantum optomechanics applications.