All Positions

Optical physics

Integrated nonlinear optics

EC Lyon and SUT
Écully (FR) and Hawthorn (AU)

Proposed projects

Option 1

Mid-IR Integrated Nonlinear Optics

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 SiGe alloys, LiNbO3 or emerging III-V semi-conductors like GaP.

The student’s project will focus on one of the fundamental issues of integrated Mid-IR, namely efficient and broadband MIR sources and their integration into an optical circuit. In this thesis, we will exploit nonlinear-phenomena over an unprecedented wavelength range (from visible to Mid-IR). The aim will be to develop an on-chip supercontinuum (and potentially combs) that can cover a broad wavelength span, from the visible to the mid-IR.

There will be opportunities to travel and interact with our partners on a national and international level (both Europe/France and Australia) including European industry (CEA-LETI and others).

Option 2

Mid-IR Frequency Microcombs

Research conducted at the beginning of the millennium on optical frequency comb generation was crowned in 2005 by the Nobel Prize in Physics awarded to John Hall and Theodore Hansch. The need for more compact, robust, and energy efficient sources offering high repetition rates (> 1 GHz) has favored the emergence of a different approach to comb generation, based on nonlinear chip-based microresonators [1,2] that are manufactured by leveraging microelectronics processes and infrastructure. These “MicroCombs” have recently led to an explosion of record demonstrations, e.g. optical clocks on a chip [3], LIDAR [4], data transmission [5], neural networks [6], mostly using the Si3N4 or Hydex platform. INL/ CEA-Leti contributed to these efforts, with the development of Si3N4 dispersion engineered waveguides with very low loss [7], making possible the co-integration of combs with silicon optoelectronics [8] and the demonstration of an integrated Si3N4 comb source pumped by a butt-coupled DFB III-V laser (InGaAsP/InP) [9]. All these demonstrations are mainly centred around 1550 nm at telecom wavelength whereas many applications such as spectroscopy, gas detection, environmental surveillance, free space communication etc require combs in the mid-infrared (mid-IR – in the molecular fingerprint region beyond 3 um).

Our first objective is to demonstrate the first “Micro-comb” on a CMOS compatible platform to cover the actual mid-IR region. We will exploit the SiGe and Ge platform to create highly nonlinear resonators in the mid-IR with high Q-factor, suitable dispersion and repetition rate (from tens GHz to few GHz FSR as required for direct gas sensing). The initial focus will be to determine the best trade-off architecture, in terms of nonlinear enhancement, dispersion engineering, coupling strategy and loss reduction.

Our second objective is to demonstrate an on-chip dual-comb spectrometer operating in the mid-IR. We will aim at demonstrating the usefulness of these compact spectrometers for sensing applications such as pollution monitoring, breath analysis.
There will be opportunities to travel and interact with our partners on a national and international level (both Europe/France and Australia) including European industry (CEA-LETI and others).

Option 3

Integrated nonlinear optics with 2D materials

Chip-based nonlinear optical devices at around 1,55um wavelength have been successfully developed in the past two decades using silicon photonics, so as to open new technologies for all-optical signal processing devices that could sustain, for example, a new generation of fast and compact optolectronic routing devices for datacom/ telecom applications. Yet, silicon is intrinsically limited at telecom wavelenths, since this material is plagued by two-photon absorption and free carrier penalty, which both restrict the speed and power consumption of the resulting devices. With the advent of graphene and other 2D materials late 2010, hybrid integration of material platforms appears as a new and promising solution for creating more efficient nonlinear devices, with both compact size and low power consumption, while still benefiting from the mature fabrication of the underlying dielectric material platform. Following this route, several demonstrations of graphene and graphene oxide hybrid devices with enhanced nonlinear properties have been reported in the last few years [1-5].

The goal of the present PhD topic will be to move beyond the simple integration of 2D materials and Si or SiN waveguides that have been mainly reported so far, so as to create more efficient nonlinear devices. Resonant structures, for instance, will be designed and fabricated, so as to increase the interaction between light and 2D material deposited on top. Additionally, novel functionalities such as frequency comb generation or broadband supercontinuum will be demonstrated with hybrid devices coated with 2D materials. The unique properties of the 2D material (graphene, graphene oxide…) will be adjusted to provide the best trade-off in terms of their nonlinear properties, so as to achieve optimized nonlinear devices.

There will be opportunities to travel and interact with our partners on a national and international level (both Europe/France and Australia) including European industry (CEA-LETI and others).

Research Areas

Physics, Photonics, Nonlinear Optics