Second-Order Nano-Oxides for Enhanced Nonlinear Photonics

Project Information

Chi2-Nano-Oxides

Grant agreement ID: 714837

DOI

10.3030/714837

Project closed

EC signature date 30 November 2016

Start date 1 February 2017

End date 31 January 2022

Funded under

• EXCELLENT SCIENCE - European Research Council (ERC)

Total cost

€ 1 500 000,00

EU contribution

€ 1 500 000,00

Coordinated by

EIDGENOESSISCHE TECHNISCHE HOCHSCHULE ZUERICH
Switzerland

Periodic Reporting for period 4 - Chi2-Nano-Oxides (Second-Order Nano-Oxides for Enhanced Nonlinear Photonics)

Reporting period: 2021-08-01 to 2022-01-31

Summary of the context and overall objectives of the project

The field of nonlinear optics skyrocketed after the invention of laser in 1961 with an experiment of light conversion, a phenomenon called second-harmonic generation (SHG). Many applications from microsurgery light sources to boosting signals in telecommunication fibers have emerged in the last 60 years using nonlinearities of bulk materials. However, applying nonlinear effects at the nanoscale generates very tiny signal and finding materials with high nonlinearities is an open challenge to avoid high power and large interaction length in the material.
Here, I proposed to overcome low nonlinear signal by using Mie scattering resonances in a broad light window spanning from near ultraviolet to the near infrared. I focued on materials rarely used at the nanoscale, namely quadratic (Chi2) nano-oxides as barium titanate and lithium niobate.
We demonstrated that Chi2 materials can be used as single nanoresonators, random assemblies and solution processed with imprint lithography to overcome the complicated fabrication of ultrafast nonlinear photonic crystal cavities. And we also realized top-down nanostructures for integrated modulators, spectrometers and supercontinuum sources.
The impact of these quadratic materials is interdisciplinary since it involves material sciences, photonics and nanotechnology with applications in integrated optics, information technology, and quantum engineering.
The key idea was to demonstrate original strategies to enhance the optical nonlinearities of Chi2 nano-oxides, with the material itself and without involving any hybrid structure such as metals by addressing the following questions:
(1) How is it possible to enhance SHG signal within a single Chi2 nanoparticle?
(2) How to fabricate nonlinear photonic crystal cavity with Chi2 nano-oxides that are very difficult to etch?
(3) How to realize (even commercialize) compact devices with Chi2 nanomaterials?

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

We succeeded in answering those questions, published our work in several peer-reviewed articles, patents and press releases.
First, we demonstrate multiple Mie resonances in different Chi2 materials: lithium niobate nanocubes [1], III-V nanostructures [2], [3] and assembly of barium titanate with gold nanoparticles[4]. For each samples, we mastered the fabrication and the full linear and nonlinear optical characterization of the system. We published some details about the automatization of this setup using autofocusing algorithms [5], and we also patented part of the setup. Finally, I obtained an ERC proof-of-concept grant to study a commercial prototype of this powerful microscope.
Second, we elaborated several process flows to assemble nanoparticles and we fabricated nonlinear 3D photonic crystals [6]. We also demonstrated electro-optic structure based on nanoparticles [7]. Assemblies of nanoparticles were also pushed towards more fundamental studies of the random quasi phase matching in transparent and opaque medium [8], [9].
Third, we became expert in the fabrication of lithium niobate on insulator, which is not as standard as etching semiconductors. We applied this expertise to create and test state-of-the-art applications with outstanding characteristics. We demonstrated a highly broadband spectrometer on a chip with more than 500 nm bandwidth [10]. We developed electro-optic modulators that maximize the electro-optic signal [11] and allows for 100 Gbit/s speed [12]. We also showed supercontinuum generation down to the ultra-violet range in a 14 mm long lithium niobate on insulator waveguide [13]. Finally, in January 2021, we founded a start-up based on this technology that will commercialize above 70 GHz lithium niobate on insulator modulators (https://versics.com/).


References:
1. Timpu, F. et al. ACS Photonics 6, 545–552 (2019).
2. Timofeeva, M. et al. Nano Letters 18, 3695–3702 (2018).
3. Xu, L. et al. ACS Nano (2019) doi:10.1021/acsnano.9b07117.
4. Renaut, C. et al. Nano Letters 19, 877–884 (2019).
5. Saerens, G. et al. Optics Express 27, 19915 (2019).
6. Vogler-Neuling, V. V. et al. physica status solidi (b) 257, 2070024 (2020).
7. Karvounis, A. et al. Advanced Optical Materials 8, 2000623 (2020).
8. Savo, R. et al. Nature Photonics 14, 740–747 (2020).
9. Müller, J. S., Morandi, A., Grange, R. & Savo, R. Phys. Rev. Applied 15, 064070 (2021).
10. Pohl, D. et al. Nature Photonics 14, 24–29 (2020).
11. Escalé, M. R., Pohl, D., Sergeyev, A. & Grange, R. Optics Letters 43, 1515 (2018).
12. Pohl, D. et al. IEEE Photonics Technology Letters 33, 85–88 (2021).
13. Reig Escalé, M., Kaufmann, F., Jiang, H., Pohl, D. & Grange, R. APL Photonics 5, 121301 (2020).

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)

In each part of the project (work packages: WP 1-3), we reached very original results that are summarized below, together with possible perspectives.
In WP1, the demonstration of Mie resonances down to the ultraviolet (UV), with a material system (lithium niobate nanocubes) that was never used before is opening the possibility to develop a UV resonator using a compact and cost-effective material. The first demonstration of anapoles in III-V nanowires is also very promising for the further development of antenna for beam steering. In pursuing more fundamental theoretical and experimental studies, we demonstrated quasi phase matching mechanism in nanoscale particles that can be exploited in laser material suffering from complex crystal growth and size control.
In WP2, the progress in mastering the material for nanoimprint lithography is a major step for the realization of large surface area photonic structure at a low cost, and even disposable. Beyond the passive structure, we also designed and fabricated active photonic structure using electro-optic effect that can very efficiently tune the optical path in such material. We showed that the electro-optic effect in barium titanate nanoparticle assemblies is as strong as lithium niobate bulk structures.
In WP3, the development of a viable process flow for the lithium niobate waveguides fabrication was key to start fabricating devices. The modulator and the spectrometer performances are outstanding and beyond the current state-of-the-art. Moreover, with this advanced fabrication skills, we can now design and produce many other devices with low losses and electro-optic properties that can be further exploited for photonic integrated chip and quantum sensing.

Overview of Chi2 materials buildings blocks for bottom up assembly and integrated devices.

Example of a lithium niobate on insulator integrated photonic chip