OIST Optics Seminars 2023

Past Seminars

Tuesday 28th March 2023: 3-4pm on Zoom

Title:  Levitodynamics: Optomechanics with a levitated nanoparticle

Speaker: Prof. Romain Quidant

Professor, Nanophotonic Systems Laboratory, Department of Mechanical and Process Engineering, ETH Zürich, Switzerland

Levitodynamics—the trapping and control of nano- and micro-objects in vacuum—has established itself as an exciting research field by combining several ingredients from other fields in a single platform. When compared with other levitation platforms, two features stand out: (i) the large mass and density (and hence complexity) of the levitated object, as compared with the mass and density of trapped atoms; (ii) the high degree of control over both conservative dynamics and coupling to the environment, as compared with the degree of control for levitated meter-scale objects. The combination of these two features provides a springboard to many applications and branches of physics.
In this talk we first introduce the audience to the field of levitodynamics, highlighting its advantages over other clamped optomechanical platforms. We then present the different strategies developed to gain control over the center-of-mass motion of levitated objects. This includes the implementation of hybrid levitation platforms combining optical and RF potentials. Finally, we discuss the latest advances from our laboratory related to engineering of quantum states and force sensing.

[1] Carlos Gonzalez-Ballestero, Markus Aspelmeyer, Lukas Novotny, Romain Quidant, Oriol Romero-Isart, Science 374, 6563 (2021)
[2] Johannes Piotrowski, Dominik Windey, Jayadev Vijayan, Carlos Gonzalez-Ballestero, Andrés de los Ríos Sommer, Nadine Meyer, Romain Quidant, Oriol Romero-Isart, René Reimann, Lukas Novotny, Nature Physics, https://doi.org/10.1038/s41567-023-01956-1 (2023)
[3] J Gieseler, B Deutsch, R Quidant, L Novotny, Physical review letters 109 (10), 103603 (2012)

Tuesday 14th March 2023: 4-5pm on Zoom

Title:  Ultrafast measurements, extreme events, and fifty years of solitons in nonlinear fibre optics

Speaker: Prof. John Dudley
Professor, Institut FEMTO-ST, Université de Franche-Comté-CNRS, France

The year 2023 represents fifty years since the first prediction of solitons in optical fibres. This opened up an entirely new field of nonlinear fibre optics, and many results from the fibre platform have been successfully transferred into other areas of science including plasma and atomic physics.   One area of recent interest has focused on extreme nonlinear pulse propagation in optical fibre and fibre lasers where experiments have revealed a rich landscape of complex interactions due to the interplay of nonlinearity, dispersion and dissipation. In the past, however, these dynamics have not been able to be measured completely because of experimental limitations, but new techniques have now opened up the possibility to analyze a range of novel nonlinear processes, including the generation of spontaneous “rogue wave” events with analogies to the giant and destructive waves on the surface of the ocean.  After giving a general introduction to the field and an overview of the measurement techniques used, we will discuss a range of results in both fibre propagation and fibre laser systems. We will also describe how tools from artificial intelligence such as neural networks are providing exciting new methods to study and understand such complex dynamics. Even though sixty years have passed, the study of solitons in fibre is more active than ever.  

Related publications:
Rogue waves and analogies in optics and oceanography, 2019
Intracavity incoherent supercontinuum dynamics and rogue waves in a broadband dissipative soliton laser, 2021



Tuesday 7th March 2023: 4:30- 5:30pm on Zoom

Title:  Exploiting light scattering for imaging and computing

Speaker: Prof. Sylvain GIGAN

Professor, Physics department, Sorbonne Université, Kastler-Brossel Laboratory (ENS, Sorbonne U., CNRS, Collège de France)

Light propagation in complex media, such as paint, clouds, or biological tissues, is a very challenging phenomenon, encompassing fundamental aspects in mesoscopic and statistical physics. It is also of utmost applied interest, in particular for imaging. Wavefront shaping has revolutionized the ability to image through or in complex media.
In this seminar, I will discuss how computational tools and machine learning allows to develop further wavefront shaping for imaging applications, and conversely discuss how the same complexity can be leveraged for optical computing tasks.


Tuesday 28th February 2023: 4 - 5pm on Zoom

Title:  Surfing an optical potential slope by using a phase transition and the spin of light  

Speaker: Prof. Christophe Pin
Assistant Professor, Research Institute for Electronic Science, Hokkaido University, Japan

Phase transitions often cause dramatic change of material properties. The insulator-to-metal phase transition of vanadium dioxide (VO2) drastically modifies its optical properties at temperatures above 341 K. This temperature-dependent permittivity switching was found to induce the reversal of the optical trapping force acting on VO2 particles in the vicinity of a focused infra-red laser beam. The trapped VO2 particles are thus locked on a contour line of the beam intensity profile. The orbital rotation direction of the particle can be controlled by using a circularly polarized laser beam. Like dielectric particles trapped by the evanescent field around a tapered optical fiber, the local electric field intensity gradient enables spin-to-orbital angular momentum coupling via the directional scattering of light. In this seminar, I will discuss the possible mechanisms at the origin of right- and left-handed optical torques acting on VO2 particles trapped in orbit around a focused laser beam.

[1]Yoshito Y. Tanaka, Pablo Albella, Mohsen Rahmani, Vincenzo Giannini, Stefan A. Maier, and Tsutomu Shimura, “Plasmonic linear nanomotor using lateral optical forces,” Science Advances 6, eabc3726 (2020), DOI: 10.1126/sciadv.abc372

[2]Yoshito Y. Tanaka and Tsutomu Shimura, “Tridirectional Polarization Routing of Light by a Single Triangular Plasmonic Nanoparticle,” Nano Letters 17, 5, 3165–3170 (2017), DOI:10.1021/acs.nanolett.7b00672

Tuesday 21st February 2023: 4:30 - 5:30pm on Zoom

Title:  Optical tweezers: from space to the nanoscale… and back 

Speaker: Prof. Onofrio M. Maragò
Director of CNR-IPCF, Istituto Processi Chimico-Fisici (Messina), Italy

Optical tweezers are powerful tools based on focused laser beams. They are able to trap, manipulate and investigate a wide range of micro and nanoscopic particles in different media, such as liquids, air, and vacuum. After an introduction to optical forces, I will give an overview of results on optical trapping and characterization of particles at the nanoscale. Furthermore, I will describe how optical tweezers can be used to trap and characterize extraterrestrial particulate matter. 

Related publications:

Tuesday 7th February 2023: 4- 5pm on Zoom

Title:  Finding Knowledge: Adventures Using the Shape of Light

Speaker: Dr. Mary Jacquiline Romero
Reader and Westpac Research Fellow, School of Mathematics and Physics, University of Queensland, Australia
Chief Investigator, Australian Research Council Centre of Excellence for Engineered Quantum Systems (EQUS) 

The transverse shape of light has emerged in recent years as a promising platform for encoding quantum information, for the multiple levels that it affords and the ease with which shape can be controlled. To demonstrate, I will discuss high-dimensional quantum state tomography.  
We used a tomographic technique inspired by machine learning to track a quantum state as the state changes. The method is computationally efficient and also robust—it converges to a good estimate even in the presence of strong noise.   Developing techniques like this is especially important for systems that are of high dimensionality, where making tomographically complete measurements become impractical.

Related publications:

Tuesday 24th January 2023: 4:30 - 5:30pm on Zoom

Title:  Measurement of optical forces and torques acting on trapped particles

Speaker: Prof. Monika Ritsch-Marte
Professor, Director of the Institute of Biomedical Physics, Department of Physiology and Medical Physics, Medical University of Innsbruck, Austria

Optical tweezers have become so widespread in micro-manipulation, because their application goes beyond simple confinement of a particle in an optical trap: They provide quantitative information on the optical forces in action.
It will be shown how the local forces acting on trapped particles can be inferred from a single interference pattern created by the incident trapping beam and the scattered light. Our method is based on accounting for changes of the optical momentum by refraction or scattering of light by the particles, and therefore can be applied to objects of arbitrary shape, in contrast to many other force-measurement approaches, which only work for spherical particles. Moreover, it allows one to simultaneously measure all components of the force applied to an individual particle in a trapped ensemble [1].
For force measurements we exploit the conservation of optical momentum, but the approach can be modified to measure also optical torque, based on conservation of optical angular momentum [2]. Again, local torques acting on individual particles are accessible, as well as separate spin or orbital parts of the total torque.
Micron-size objects in liquid solution will be discussed as demonstration examples, yet the technique is not limited to typical biomedical contexts, but may also be used in air or vacuum.

Tuesday 17 January 2023: 4-5pm on Zoom

Title: Nonlinear nanocrystals for electro-optic and quantum devices

Speaker: Prof. Rachel Grange
Associate Professor, ETH Zurich, Department of Physics, Institute for Quantum Electronics, Optical Nanomaterial Group, Switzerland

Nonlinear and electro-optic devices are present in our daily life with many applications: light sources for microsurgery, green laser pointers, or modulators for telecommunication. Most of them use bulk materials such as glass fibres or high-quality crystals, hardly integrable or scalable. Even the fast developments of thin film lithium niobate face the challenging etching of metal-oxides1. Therefore, the quest for a non-centrosymmetric material system, easy to fabricate and to scale up while maintaining its functionality is still ongoing2. Here we will present our recent advances in top-down fabrication of lithium niobate devices and bottom-up assemblies of randomly oriented nanocrystals to produce electro-optic, nonlinear and parametric down conversion signals. First, barium titanate metalenses synthesized by a sol-gel technique will be demonstrated. Then, we will show how the electro-optic response in assembled nanostructures can be as strong as certain other perfect crystalline structure. Finally, we will generate photon pairs from free-standing lithium niobate microcubes3 and III-V nanowires at the telecommunication wavelength through the spontaneous parametric down-conversion process.

(1) Pohl, D.; Messner, A.; Kaufmann, F.; Escalé, M. R.; Holzer, J.; Leuthold, J.; Grange, R. 100-GBd Waveguide Bragg Grating Modulator in Thin-Film Lithium Niobate. IEEE Photonics Technol. Lett. 2021, 33 (2), 85–88. https://doi.org/10.1109/LPT.2020.3044648.
(2) Vogler-Neuling, V. V.; Karvounis, A.; Morandi, A.; Weigand, H.; Dénervaud, E.; Grange, R. Photonic Assemblies of Randomly Oriented Nanocrystals for Engineered Nonlinear and Electro-Optic Effects. ACS Photonics 2022, 9 (7), 2193–2203. https://doi.org/10.1021/acsphotonics.2c00081.
(3) Duong, N. M. H.; Duong, N. M. H.; Duong, N. M. H.; Saerens, G.; Saerens, G.; Timpu, F.; Buscaglia, M. T.; Buscaglia, V.; Morandi, A.; Müller, J. S.; Maeder, A.; Kaufmann, F.; Solntsev, A. S.; Grange, R.; Grange, R. Spontaneous Parametric Down-Conversion in Bottom-up Grown Lithium Niobate Microcubes. Opt. Mater. Express 2022, 12 (9), 3696–3704. https://doi.org/10.1364/OME.462981.

Since 2021, Rachel Grange is an associate professor in integrated optics and nanophotonics in the Department of Physics at ETH Zurich. She has been assistant professor at ETH Zurich since 2015. From 2011 to 2014, she was junior group leader at the Friedrich Schiller University in Jena, Germany. Her research covers material investigations at the nanoscale, top-down and bottom-up fabricated nanostructures with metal-oxides, mainly lithium niobate and barium titanate.