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Stage M2 : Rare-earth doped oxide thin films for on-chip optical quantum technologies

Rare-earth ions (REI) present a strong interest for quantum technologies due to their ability to
show long-lived quantum superposition states both in their optical and spin transitions. The
perspective of using them for applications such as quantum information processing, quantum
memories and indistinguishable photon sources, however, relies on developing host materials
in which their outstanding quantum properties are preserved, while enabling integration into
nanophotonic devices. Several proof-of-concept experiments based on rare-earth doped oxide
crystals have been reported [1], [2], yet, integration into practical and scalable quantum devices
has still not been stablished. In particular, specific designs compatible with both optical cavities and
MW architectures are generally needed [3], [4]. In this context, the ability to host REI into thin oxide
films deposited on a scalable substrate such as silicon would greatly facilitate the development of
such resonators. A thin film architecture also allows flexibility in material composition or dopant
spatial localization and offers integration perspectives with silicon photonic chips by standard clean
room processing technologies[5], [6]. As a drawback, the obtention of high-crystalline quality oxide
films on silicon is very challenging with most deposition techniques. Moreover, the optical and spin
properties of REIs in thin films tend to lag behind that of their bulk counterpart, mainly due to the
close proximity of surface and the presence of interfacial defects. To overcome these challenges,
we have developed a hybrid thin film fabrication approach combining MBE [5] and CVD [7]
deposition techniques to obtain epitaxial rare-earth oxide thin films on silicon (Fig. 1). The optical
properties of europium ions embedded in this film matrix have already shown promising results
with sub-MHz homogeneous linewidths measured.

This internship will have two main objectives:

(i) the optimisation of the thin-film deposition conditions towards the reproducible obtention of smooth epitaxial Y2O3 thin films doped with REI.
(ii) the fabrication of Y2O3 membranes by both dry and wet chemical etching techniques. The Gd2O3 200 nmSi Y2O3 200 nm 1 μm deposited thin films, and membranes quality and eligibility for quantum technology applications will be assessed by the candidate using different morphological and optical characterizations.