Rare Earth - Diamond Hybrid Materials for Photonics

Project Information

RareDiamond

Grant agreement ID: 101019234

DOI

10.3030/101019234

EC signature date 5 July 2021

Start date 1 January 2022

End date 30 June 2027

Funded under

• EXCELLENT SCIENCE - European Research Council (ERC)

Total cost

€ 2 499 013,00

EU contribution

€ 2 499 013,00

Coordinated by

CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE CNRS
France

Periodic Reporting for period 2 - RareDiamond (Rare Earth - Diamond Hybrid Materials for Photonics)

Reporting period: 2023-07-01 to 2024-12-31

Summary of the context and overall objectives of the project

Hybrid materials associate distinct components to achieve new functionalities. The key challenge in these composite systems is to harness new effects that cannot be obtained by a single material while preserving the necessary underlying properties of each component - a tremendously difficult task in materials science. The fantastic achievements of micro-electronics in this field have boosted similar developments in optics, and especially in the infrared range, where integrated optical chips combine a variety of functionalities like light sources, modulators, and detectors in circuits based on low-loss waveguides. In particular, silicon-integrated optics have witnessed impressive scientific and technological progress as well as industrial production, since this architecture offers seamless integration between optics and electronics.

Among optically active materials, NV- color centers in diamond and rare earth doped crystals have both exceptional properties that are separately used in, or investigated for, a broad range of applications such as lasers, lighting, fluorescence-based sensing and imaging, and quantum technologies like quantum processing, sensing, and communications.

The overall objective of RareDiamond is to design and grow hybrid materials in which rare earth ions and NV- centers can interact on the nanoscale while preserving their outstanding properties. This will open the way to diamond NV- integration with photonic chips and telecom fibers, for unprecedented functionalities in sensing, quantum processing, and quantum communications.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The first part of RareDiamond activities has focused on material development. Y2O3 thin films of 500 nm thickness were deposited using Direct Liquid Injection Chemical Vapor Deposition on diamond substrates. The thin films were doped with erbium, a rare earth element, which has an optical transition at 1.5 µm compatible with optical fiber networks and photonic chips. A study in which substrate temperature was varied during deposition was carried out, showing well-crystallized films with a cubic crystal structure for deposition between 550 and 1000 ºC. Growth took place along a preferential direction that depends on deposition temperature, as determined by X-Ray diffraction and electron microscopy. Photoluminescence (PL) of erbium ions was then recorded at room and low (10 K) temperatures and in different spectral ranges, from the visible to the infrared. Narrow lines similar to those obtained in bulk crystals were observed, evidencing the high crystalline quality of the thin films. PL decays were also measured and found to be close to bulk values which indicates that the films have a low concentration of defects. Y2O3 thin films were also deposited on diamond substrates containing NV- color centers close to the surface. This was achieved by localized implantation at low energy resulting in NV- a few nm under the surface. The optical and spin properties of these NV- centers were probed and did not show significant changes after the oxide film deposition.
In the work's second part, we investigated hybrid structures that include ultra-thin rare earth doped thin films to maximize interactions with shallow NV centers and facilitate their observation. Samples showing PL comparable to thicker films could be obtained and were analyzed to model interaction mechanisms.
In the third part, we developed a low-temperature microscopy experimental setup to explore hybrid structures' quantum properties. A new technique was designed to measure the optical quantum state lifetimes of rare earth ions, a key property for the envisioned applications of the hybrid structures.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The hybrid materials developed so far in RareDiamond demonstrate, for the first time, that erbium ions have bulk-like photoluminescence (PL) properties in 500 nm thick oxide thin films deposited on diamond substrates. Similar PL properties were also found in ultra-thin films of only 15 nm that have been designed to enhance interactions with NV- centers. Moreover, we demonstrated, also for the first time, that NV- color centers located a few nm from the surface are unaffected by the deposition of an oxide thin film at high temperatures. Indeed, optical and spin properties remain the same before and after deposition. Rare earth and NV- PL and spin properties are thus preserved in our thin film based hybrid structures, a fundamental requirement for achieving enhanced functionalities through rare earth-NV interactions. We also developed a new technique to measure optical quantum state lifetimes in nanomaterials such as the project's hybrid structures. It was demonstrated on several erbium doped crystals and is expected to have broad applicability in terms of materials and emitters.
The expected results until the end of the project are 1) the growth of complex, high-quality structures with extreme localization of active centers, 2) the interfacing of diamond NV- centers with infrared light, and 3) innovative demonstrations in magnetometry, fluorescent imaging, and quantum light-matter processes.
RareDiamond hybrid materials target the exploitation of strong interactions between two remarkable systems: rare earth ions and NV- centers. The radically new functionalities of these systems could greatly impact sensing and quantum light-matter interfacing, as well as the broader field of photonics. Indeed, RareDiamond's concept can be extended to other RE, color centers, and materials for developing properties that are out of range with a single system. RareDiamond is expected to influence materials science as its demonstrations will use hybrid materials with ultra-low levels of defects. RareDiamond will provide this topic with unique insights in growth, processing, and characterization and will thus impact developments in a large range of materials, especially for emerging nano-technologies.