Projects proposed by the NAM

During their curriculum, EPFL students must conduct several research projects (Semester projects) as well as a main research project (Master thesis) at the end of their study. The Nanophotonics & Nanophotonics Laboratory (NAM) proposes a variety of projects to the students belonging to most EPFL sections.

The following list gives our current offer, but we always welcome suggestions from the students. So if you have a great idea in the field of photonics or modelling that you would like to tackle, please come talk with us!

Bien que nous donnions cette liste en anglais, le Laboratoire de Nanophotonique & Métrologie (NAM) parle évidemment aussi le français et nous sommes heureux d'accueillir des étudiants francophones!


Electrodeposition of plasmonic nanomaterials (semester or master project)

Electrodeposition of plasmonic nanomaterials Plasmonic nanostructures (PNs) have been proved to enhance the efficiency of conventional semiconductor (SC) to harvest solar energy to generate electric current or drive chemical reactions. PNs concentrate light near SC surface and enhance hot carrier generation through antenna effect and surface plasmon resonance (SPR). Patterning PNs on SC is crucial, receiving high attention to fabricate facile and inexpensive photocatalysts. Though electron beam lithography (EBL) is common to generate such nanostructures on the scale of tens to hundreds of microns, the time and cost required to fabricate arrays over larger areas using EBL is prohibitive. Alternatively, nanochannel glass replica membranes (mask technology), colloidal lithography, and evaporative self-assembly have been used to fabricate patterned nanostructures. In this project, electrochemical deposition technique will be used to deposit noble metal nanoparticles over large surface of SC. PNs such as Au and Ag will be electrodeposited through direct deposition or template assisted deposition, later will give more uniform structures. Plasmonic properties of the electrodeposited photoelectrode will be characterized using UV-Vis. spectrometer and electrochemical potentiostat. This project will show the potential of electrodeposition technique to be a better alternative to fabricate plasmonic nanomaterials modified substrates.

An ideal candidate has preferentially a solid background in chemistry or physics.

What you will learn in this project:
  • Electrodeposition of Au and Ag nanoparticles
  • Optical and electrochemical characterization

Contact: Dr. Madasamy Thangamuthu

Electrochemical investigation of hot electron dynamics(semester or master project)

Electrochemical investigation of hot electron The outstanding light-trapping and electromagnetic-field-concentrating properties of surface plasmons open up a wide range of applications in the field of plasmonics. Recent investigations have shown that plasmonic nanostructures can also directly convert the collected light into electrical energy by generating hot electrons. Investigation of these hot electrons dynamics is highly useful for solar energy conversion to realize photovoltaic and photocatalytic devices. In this project, hot electrons dynamics will be investigated electrochemically to understand the mechanism and life time of this process. The metal–semiconductor Schottky junction will be configured by putting the plasmonic nanostructures in contact with semiconductor and then hot electrons generated photocurrent will be observed using photoelectrochemical cell. In addition transfer of these hot electrons into nearby electron acceptor molecules will also be investigated by employing cyclic voltammetry or amperometry techniques. Further, to correlate the visible-light activity of the photoanode to the optical properties of the Au NPs, the open-circuit voltage (Voc) will be monitored as a function of incident photon energy.

An ideal candidate has preferentially a solid background in chemistry or physics.

What you will learn in this project:
  • Fabrication of plasmonic photoelectrode
  • Optical and electrochemical characterization
  • Hot electron dynamics

Contact: Dr. Madasamy Thangamuthu

Fabrication of metallic nanoaperture by combing electron beam lithography and ion etching techniques and its application in amplification of spontaneous emission(semester or master project)

Fabrication of nanoaperture Metallic nanoaperture as called negative nanoantenna has been attracting intention over the last three decays due to its fundamental research interests [1] and potential applications [2]. Focusing ion beam (FIB) is a popular way to fabricate metallic nanoaperture. However, it is time and effort consuming to fabricate large area nanoaperture with FIB. It is not easier to achieve small nanogaps for complex nanostructures with FIB. In this project we propose using a method that combines e-beam lithography and ion etching techniques to fabricate metallic nanoaperture. The fabricated metallic nanoaperture could be used for fluorescence, Raman, or surface plasmon lasing study.

What you will learn in this project:
  • Clean room (CMI) techniques, such as thermal evaporation, e-beam lithography, reactive ion etching;
  • NAM laboratory: visible range far field spectroscopy for spectrum measurement, confocal fluorescence spectroscopy for fluorescence lifetime measurement.
  • Development of a method to fabricate metallic nanoaperture and the application of the fabricated nanoaperture for amplifying spontaneous mission.

References:
  • [1] T.W. Ebbesen, H.J. Lezec, H.F. Ghaemi, T. Thio, P.A. Wolff, Extraordinary optical transmission through sub-wavelength hole arrays, Nature, 391 (1998) 667-669.
  • [2] F. van Beijnum, P.J. van Veldhoven, E.J. Geluk, M.J.A. de Dood, G.W. ’t Hooft, M.P. van Exter, Surface Plasmon Lasing Observed in Metal Hole Arrays, Physical Review Letters, 110 (2013) 206802.

Contact: Xiaolong Wang

Plasmonic simulations with light beams (semester or master project)

plasmonic simulations with light beams The Surface Integral Equation (SIE) formulation developed at NAM can simulate the optical response of realistic plasmonic nanostructures with complicated geometries. The SIE program can be used to study various features such as scattering and absorption from these structures, as well as the forces and torques induced on them by electromagnetic fields.

The goal of this project is to extend the SIE program to deal with illumination conditions commonly used in optical trapping studies, such as Gaussian and Bessel beams. The project involves three stages. In the first stage, the student will learn the use of SIE through hands-on simulations. They will then proceed to understanding the existing SIE code and extending it to special illuminations. Finally, they will utilise the updated code to study the effects of such illuminations on scattering from and forces and torques on nanostructures.

During the course of the project, the student will:
  • Utilise SIE to study exciting physical effects in plasmonics
  • Learn more about optical forces and torques at the nanoscale
  • Gain expertise in understanding and writing scientific code

Prerequisites:
  • Understanding of basic electrodynamics and Maxwell's equations
  • Basic mathematical physics and linear algebra
  • C++ programming knowledge

Contacts: Raziman Thottungal Valapu

Photonic spin Hall effect from single nanostructure (semester or master project)

Photonic spin Hall effect Light wave exhibits three fundamental characteristics: color (or wavelength), polarization, and direction. These properties of light can be modified using artificial nanostructures that support plasmonic resonances. In case of noble metal nanostructure, its surface electron cloud oscillates coherently respect to the incident EM field and enables strong light-matter interaction at nanoscale.

In this project, we will focus on experimental realization of photonic spin Hall effect, i.e. a separation in momentum space of spin-polarized localized plasmons. The targeting nanostructure allows control over the light propagation direction as well as the degree of circular polarization. These properties are important for encoding more information and provide superior information security of optical signals.

What you will learn in this project:

The candidate will understand the relation between localized surface plasmons (LSP) and the far-field properties of light. The main parts of the project involve fabrication of nanostructure in CMi and their optical characterization in the laboratory. Experimentally, the polarization state of light will be characterized by measuring a set of Stokes parameters in different propagation directions. Student who has strong enthusiasm or experiences in nanofabrication and optical measurements is appreciated.


Contact: Chen Yan

Nonlinear plasmonics (semester or master project)

SHG in a plasmonic nanostructure During the last decades, nanophotonics and, in particular, plasmonics have emerged as vivid fields of research, triggered by the promises of new applications and supported by recent technologic developments. Indeed, plasmonic nanostructures have the unique ability to localize electromagnetic fields in nanoscale volumes, far-beyond the limit established by the diffraction, permitting to control the properties of light at dimension much smaller than its wavelength. The optical properties of plasmonic nanostructures are explained by a physical phenomenon called localized surface plasmon resonances (LSPR), which corresponds to the collective oscillations of the conduction electrons over a static ionic background. The combination of the strong near-field intensity close to plasmonic systems with the intrinsic nonlinearities of metals results in different nonlinear optical processes giving rise to a new research field called nonlinear plasmonics.

What you will learn in this project:

The candidate will work in close interaction with PhD students and post-docs and will be involved in our recent developments in nonlinear plasmonics. The project can be tailored following the wishes of the student, with emphasis either on nanofabrication, numerical simulation or optical measurements based on femtosecond lasers. Come discuss with us, so we can find the topic that interest you most.


Contact: Dr. Jeremy Butet

Fabrication and optical characterisation of metallic nanocubes
(semester or master project)

Fabrication and optical characterisation of metallic nanocubes Precious metal nanoparticles exhibit unique optical properties which pave the way for many applications in material science, physics, chemistry, and biology. Due to there beneficial properties gold and silver are the most prominent metals for the fabrication of metallic nanoparticles. Such nanoparticles are, for instance, used as active substrates for Surface-Enhanced Raman Spectroscopy (SERS), enhanced near-field optical probes, and biological imaging. Size and shape of the particles are of crucial importance for those types of applications. Control of those parameters, however, remains a challenging task.
The present project aims (1) the fabrication of monodisperse silver nanocubes of specific size. (2) hydrophilic or hydrophobic surface functionalisation using self assembled monolayers (SAMs) (3) modelling of optical properties, and (4) experimental verification of the model.
An ideal candidate has preferentially a solid background either in near-field optics, physics, chemistry, or chemical physics.

Les nanoparticules constituées de métaux précieux possèdent des propriétés optiques uniques qui ouvrent de nombreuses possibilités pour des applications dans des domaines aussi divers que les sciences de matériaux, la physique, la chimie et la biologie. Grâce à ces propriétés particulièrement avantageuses, l’or et l’argent sont les matériaux les plus couramment utilisés répandus pour la fabrication de ces nanoparticules. Ils trouvent des applications, par exemple, dans le domaine de la spectroscopie Raman exaltée de surface (SRES), de la microscopie de champ proche et l’imagerie biologique. La taille et la forme de ces nanoparticules ont une importance cruciale pour ce genre d’applications cependant leur contrôle reste un défi.

Le but de ce projet est (1) la fabrication des nanocubes de une taille spécifique et uniforme. (2) Fonctionnalisation des surfaces afin d’obtenir des propriétés hydrophobiques et hydrophiliques en utilisant des techniques d’autoassemblage. (3) Modélisation des propriété optiques et (4) vérification expérimentale du modèle.
Un candidat idéal dispose, avec préférence, des connaissances en physique, optique de champs proche, chimie ou chimie-physique.
 

Contact: Dr. Christian Santschi (photo: Y. Sun et al., Science 298, 2176, 2002)


Advanced visualization for computational optics (semester or master project)

Advanced visualization for computational optics One sometimes forgets that scientific work is much more than the collection of data. Aesthetic representation of measured or calculated results can not only influence the success and impact of a scientific publication, but can also improve the comprehension of one's own work. While many experimental and simulation user interfaces offer graphic representation of results, the produced images seldom allow accurate interpretation and often do not appeal to the eye.

The goal of this semester project is to investigate the application scope of existing visualization packages such as the open-source Visualization ToolKit (VTK) and the possibility to combine these with other graphical representation programs such as Blender or POV-Ray to allow the accurate, meaningful and appealing graphical representation of experimental and simulation data produced in our group. In particular, the visualization of three-dimensional field distributions in combination with measured or simulated geometries will be the focus of this project.

A taste for working with computer graphics is essential to this project, as are a sense of proportion and appreciation for aesthetics. Experience in one of the aforementioned programs is beneficial but not required.
 
On oublie parfois que le résultat du travail scientifique est bien plus qu'une collection de données. La représentation esthétique de résultats mesurés ou calculés peut certes influencer l'impact d'une publication scientifique; mais avant tout, une représentation de graphique de qualité peut aider à comprendre les phénomènes physiques sous-jacents. Malheureusement, beaucoup de programmes de traitement des données ne produisent que des représentations médiocres et imprécises.

L'objectif de ce travail de semestre est d'étudier la combinaison de différents programmes de visualisation, tel par exemple le Visualization ToolKit (VTK) open-source, avec des programmes de rendu graphique, comme Blender ou POV-Ray. Cette combinaison doit permettre d'obtenir des représentations graphiques attrayantes pour les résultats de simulations produits dans notre groupe. Un accent particulier sera mis sur la visualisation de champs optiques 3D en combinaison avec des géométries mesurées ou simulées. Un goût pour le travail graphique avec ordinateur est essential pour ce projet, ainsi qu'un sens des proportions et de l'esthétique. Des connaissances avec l'un des programmes mentionnés serait un avantage.
 
Contacts: Dr. Raziman Thottungal Valapu