Nonlinear Optics

Feedback, Amplification and Loss baLancing In Nematics for briGht Soliton Transmission And Redirection (FALLING STAR)

Problem statement

Recently, various fields of photonics have been developed to fill the need for fast optical communications, biomedical imaging, sensing devices, tunable lasers, etc. These devices are rated on their power consumption, channel bandwidth and tunability and are particularly interesting since all optical technologies present a power consumption that does not scale with the channel bandwidth. These optical signals can be manipulated by light by means of optical nonlinearities. When they are properly combined with diffraction, dispersion and feedback, nonlinearities can lead to the formation of physical objects called solitons, which retain their spatial or temporal intensity profile during propagation or interactions with each other.

 

Details of the project

Solitons can be used in various ways to handle light in applications that require, for example, reconfigurable fast optical channels. However, these objects lose most of their appealing properties when propagating in media with losses.In our project we propose to build on recent advances of liquid crystal lasers to make a medium that amplifies light in order to compensate for the losses. Liquid crystals are selected for their easy manufacturing, high optical nonlinearities and versatile optoelectronic tuning. Our work will first concentrate on designing the appropriate pumping geometry to obtain a medium in which true solitons (called nematicons in nematic liquid crystals) can propagate and interact over long distances. This will allow to verify and adapt the modeling of nematicons.

We will then investigate the positive gain regime in various feedback conditions. For a weak feedback, we expect to observe complex spatial and/or temporal dynamics similar to that of the fiber ring lasers described by a Cubic Quintic Ginzburg-Landau equation. The unavoidable random feedback induced by scattering should also lead to random lasing. We aim to support all the experiments by proper modeling and numerical simulations.

 

Scientific partners

UGent, Liquid Crystal Group (Jeroen Beeckman and Kristiaan Neyts)

 

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Nonlinear optics in graphene : from basic characterization to observation of solitons.

Problem statement

In order to increase data transmission rates in telecommunication networks, one solution is to replace electronic devices by their optical counterpart. In order to process light by light at low power and in a compact device, the use of highly nonlinear material is mandatory. Those materials are generally working near a resonance which make the device intrinsically narrowband. Due to its zero-gap, graphene can at the same time be broadband and highly nonlinear.

 

Details of the project

This project aims to demonstrate that third order nonlinear optical response of graphene can be used for photonic applications. We will first complete the existing experimental characterization of the nonlinear optical properties of graphene, with the intent to provide a clear and complete picture of the third order optical nonlinearity in monolayer and multilayer graphene. The second aim is to verify experimentally that light propagation in a graphene-structure can be modeled by a well-know equation which is called Nonlinear Schrödinger Equationthe (NLSE). This equation predicts the existence of solitons, which are spatial beam that do not spread during the propagation, the natural diffraction being compensated for by the nonlinearity. Results of this project should be an important step towards the realization of compact and low-power all-optical devices based on graphene.

 

Scientific partners

THALÈS R&T, France (Daniel Dolfi)

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Photonic in integrated structures

Problem statement

Photonic in silicon based nanowires is today one of the most exciting scientific challenge. Numerous laboratories, institute and companies such as Intel or IBM are making research in this field thanks to the great progress of silicon nano-processing. As a result, low loss silicon nanowires were developed leading to new all-optical functions that benefit from high optical nonlinearities.

 

Contributions

Our laboratory's interests are dedicated to the low power and high power nonlinear behavior of those structures. Our recent works include

• The generation of supercontinuum (SC) at telecommunication wavelengths with low pump pulse energy, in amorphous and crystalline silicon chips. The study of the properties of the SC and the comparisons with numerical simulations aim at exploring the potential of these structures for applications of on chip generated SC.
• The study of all-optical logic gate in silicon-based platform based on third-order nonlinearities.
• The demonstration of new highly efficient sources of photon pairs in silicon photonic nanowires.

 

Scientific partners

• Photonic Research Group, Ghent University-IMEC (Pr. G. Roelkens, Pr. R. Baets)
• Laboratoire d’Information Quantique, ULB (Pr. S. Massar)

 

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