DOCTORAL CANDIDATE
David-Gabriel Lange

SUPERVISORS
Dr. Christian Grillet, École Centrale de Lyon (EC Lyon)
Prof. Christelle Monat, École Centrale de Lyon (EC Lyon)
Regis Orobtchouk, École Centrale de Lyon (EC Lyon)
Sébastien Cueff, École Centrale de Lyon (EC Lyon)
Dist. Prof. Arnan Mitchell, RMIT University (RMIT)

Photonics, Integrated Nonlinear Optics, Mid-IR photonics

The Mid-infrared (Mid-IR) wavelength range – from 2.5 to 13 µm – is currently experiencing a huge surge of interest for an enormous range of applications that affect almost every aspect of our society, from compact and highly sensitive biological and chemical sensors, to imaging, defence and astronomy.

Despite their recognized potential, Mid-IR technologies are still limited in their range of applications, largely because of the bulky size of the Mid-IR devices and the prohibitive costs of the instruments used. Compact Mid-IR optical devices are indeed currently lacking and despite recent breakthroughs related to integrated mid-IR supercontinuum sources, compact and broadband sources in particular are critically missing. Our strategy is therefore based on the development of an integrated hybrid Mid-IR platform, involving the miniaturization of optical components and their integration on a planar substrate made of materials with remarkable optical properties (particularly in terms of transparency and non-linearities) at MIR wavelengths like thin film lithium niobate but also III-V semi- conductors like GaP and GIV material platform like SiGe alloys. The student’s project will
focus on one of the fundamental issues of integrated Mid-IR, namely efficient, broadband and highly tuneable MIR sources and their integration into an optical circuit in particular with an electro-optic modulator. In this thesis, we will exploit nonlinear-phenomena (both X2 and X3-based) over an unprecedented wavelength range (from visible to Mid-IR).

The PhD objectives will be to design and realize highly efficient nonlinear devices with anomalous dispersion for comb generation (microcomb and supercontinuum approaches), to experimentally demonstrate the integration of electro-optical modulators with high Q resonators on a single chip, where the modulation frequency of the modulator can be tuned to match the free spectral range of the ring resonator, for improving the efficiency of optical frequency comb generation, explore the alternative path offered by nonlinear optics via quasi-phase matching
for the generation of optical frequency combs via cascaded nonlinear effects, and exploit hybrid material integration to realize tuneable nonlinear functions, e.g. through combining the response of lithium niobate or the tuneable properties of Phase Change Materials with more traditional nonlinear devices.

The work will have elements of: (i) theory (ii) waveguide and resonator design and (iii) optical chip characterization and device benchmarking using both experimental and numerical tools.