Invited Speakers
We are keeping on inviting worldwide scientists and engineers to share with us the
latest research and development on laser interaction with partilces.
Keynote Lecture 01: Microsphere Lens System for
Large Area Laser Parallel Nano-fabrication and Super-resolution Imaging
Prof. Lin Li, FREng
Associate Dean (Business Engagement and Development) of Faculty of Engineering and Physical Sciences, Director of Laser Processing Research Centre, The University of Manchester, Manchester, UK
ABSTRACT:
Nano-fabrication of user defined periodic nano-patterns over a large area needs to overcome optical diffraction limit of the laser beam as well as achieve high production rate for it to be practically feasible for engineering applications. This presentation summarizes the recent work by the author’s research team in the development of a scanning particle lens array system for parallel laser fabrication of user defined periodic micro/nano patterns at a over 100 million “identical” patterns simultaneously over a large area on both flat and curved surfaces as well as below transparent surfaces. Furthermore, a direct imaging method has been applied to producing user-defined patterns. By reversing the optical path, super-resolution imaging of nano-structures has been realized and applied to both engineering and biomedical imaging based on virtual imaging, 50 nm resolution for white light optical imaging and 25 nm resolution of confocal imaging have been demonstrated. The light interactions with microsphere lenses and associated fundamental physics phenomena are discussed.
Biography of Professor Lin Li:
Professor Lin Li, Associate Dean (Business Engagement and Innovation) of Faculty of Engineering and Physical Science, The University of Manchester, is an elected Fellow of Royal Academy of Engineering, International Academy for Production Engineering (CIRP), International Academy of Photonics and Laser Engineering (IAPLE), Institute of Engineering and Technology (IET), and Laser Institute of America (LIA). He obtained a BSc degree in Control Engineering from Dalian University of Technology in 1982 and a PhD degree in Laser Engineering from Imperial College, London in 1989. He worked at University of Liverpool during 1988-1994 as a postdoctoral Research Associate in high power laser engineering. He started his academic career (Lecturer) at UMIST in 1994 and was promoted to a full professor in 2000. He set-up the first high power laser processing research laboratory at UMIST (University of Manchester Science and Technology) and founded the Laser Processing Research Centre in 2000 as its Director since then. He served as Director of Research and Deputy Head of School of Mechanical, Aerospace and Civil Engineering during 2009-2013, and Head of Manufacturing Research Group during 2004-2014. He has over 600 publications in peer reviewed journals and conference proceedings and 47 patents related to laser processing and photonic engineering.
Externally, he serves on the editorial boards of 11 international journals and is President of Laser Institute of America (2016), President of International Academy of Photonics and Laser Engineering (IAPLE, 2013-2015), and Vice President of Association of Laser Users (AILU – 2015-2016). He has been the chairman of 36th, 37th and 38th MATADOR international conferences on advanced manufacturing.
Professor Li received Arthur Charles Main Award from the Institute of Mechanical Engineers in 2001 for work in laser based nuclear decommissioning technology. He received the prestigious Sir Frank Whittle Medal from the Royal Academy of Engineering in 2013 for his outstanding and sustained achievements in engineering innovations in manufacturing that has led to worldwide commercial applications. In 2014 he received Wolfson Research Merit Award from the Royal Society for his research on laser nano-fabrication and nano-imaging, and received the Distinguished Achievement Medal as the Researcher of the Year medal in Engineering and Physical Sciences at The University of Manchester in 2014. He is an inventor of microsphere lens super-resolution optical nanoscope virtual imaging, published in Nature Communications and reported worldwide including BBC and New York Times.
Keynote Lecture 02: Single beam acoustical tweezers
Dr. Jean-Louis Thomas
Research director C.N.R.S. (National Center of Scientific Research, France)
Institut of NanoSciences of Paris, University Pierre et Marie Curie, Paris, France http://www.insp.jussieu.fr
ABSTRACT: Today, remote handling of tiny objects is efficiently performed by optical tweezers. The object is trapped by the radiation pressure at the intensity maximum of a laser beam focused by a high numerical aperture lens. As the wave focus can easily be steered and the beam focus creates a single potential well, such a device can pick, push and pull, control both the position and the force on a single object selected among others. Optical tweezers have become the tool of reference for contactless manipulation with radiation pressure and led to many applications in biology for instance. They are quite efficient to handle particles ranging in size from a few micrometers to hundreds of nanometers and apply forces in the range of tens of picoNewton. However, for larger forces or larger objects, heating or photo-toxicity is recognized issues. At equal incident beam power acoustical forces overtake by five orders of magnitude optical ones since radiation pressure is inversely proportional to the speed of propagation of the field. Furthermore, the large spectrum of frequencies covered by coherent ultrasonic sources provides a wide variety of manipulation possibilities from macro- to microscopic scales. Thus acoustical levitation is an efficient technique for container-less processing and transportation of macroscopic matter in air, while acoustophoresis has provided a powerful strategy for on-chip manipulation, sorting and mixing of many microscopic particles and living organisms. All these ultrasonic techniques are based on standing waves schemes and this has prohibited accurate manipulations of a single particle in three dimensions. The single-beam concept of optical tweezers is fascinating but challenging since one expects and in most situation, observes, that the radiation pressure tends to push a scatterer in the beam propagation direction. This pushing force can be understood as an exchange of wave momentum when the incident beam is partially backscattered. In the single beam scheme of optical tweezers, another component of the radiation pressure force, called “gradient force”, is able to pull a scatterer located downstream from the focus. I will present the trapping of elastic particles by the large radiation force of a single acoustical beam in the three dimensions. As its optical counterpart, it can push, pull and accurately control the position of a unique particle. Various features are promising for the development of a large variety of systems in biology, chemistry and physics where small particles play an important role, in particular, for single particle biophysical essays.
INTRODUCTION: Dr. Jean-Louis Thomas research activity deals with wave propagation in linear or non linear regime and is mostly centered on acoustics. Development of several experimental set-up in the domain of ultrasound based on large array of piezo-electric sources like for instance, first time reversal mirrors, design of a system for HIFU (High Intensity Focused Ultrasound) of brain tissues through skull, facility to study acoustical shock waves for sonic boom at laboratory scale, amplification of the Single Bubble Sonoluminescence phenomenon by acoustics pulses, propagation in suspension of nanoparticles. Recently, Dr. Jean-Louis Thomas worked on acoustical vortices and acoustic radiation pressure.
Keynote Lecture 03: Quantum effects related to optical tweezers
Dr. Samuel Deleglise
CNRS Research Associate in Laboratoire Kastler Brossel, Team "Measure-ment and Fundamental Noises".
http://www.lkb.ens.fr/Deleglise-Samuel?lang=en
ABSTRACT: TBD
INTRODUCTION: Dr. Sammuel Deleglise research activity deals with quantum optics, quantum optomechanics, quantum information, and high-precision measurement. His main scientific achievements include: first observation of the quantum jumps of light, preparation of non-classical cavity-field states and their decoherence, observation of quantum zeno effect in cavity quantum electrodynamics, first observation of optomechanically induced transparence, and quantum coherent coupling of a mechanical resonator to a cavity mode. Dr. Sammuel Deleglise is in the team of the head of the Kastler-Brossel laboratory (antoine.heidmann) and participated to the Haroche Nobel Prize experiments in 2012.
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Keynote Lecture 04: Measuring forces with/in optical tweezers
Prof. Timo Nieminen
School of Mathematics and Physics,The University of Queensland,Australia
ABSTRACT: Since their inception in 1986, optical tweezers have made many and varied contributions to many branches of science from physics to biology. One such constibution that was revolutionary and game-changing is the use of optical tweezers for the minimally-invasive non-contact measurement of forces in the femtonewton and piconewton range. Measurement of forces using optical tweezers is often conceptualised as similar to a spring balance: an external force which we wish to measure displaces a probe particle from the centre of the trap, until there is an equilibrium between the external force and the optical restoring force of the trap. Observation of the position of the particle, coupled with knowledge of the trap obtained through calibration, typically expressed as the spring constant of the trap, yields the force. While this picture is indeed simple, in a strict sense it is untrue. Notably, the probe particle is not in mechanical equlibrium, but rather in thermodynamic equilibrium. This difference between these two is important when measuring very small forces, as the thermal motion of the probe particle is no longer small compared to the displacement from the trap centre.
A weakness of this approach is the dependence on using a known probe particle such as a polystyrene or silica microsphere. Since it is not always possible to introduce probe particles without excessively disturbing the system being measured - for example, if measuring forces inside a living cell - methods for measuring forces without prior calibration of the trap, or for calibrating a trap with an unknown particle in an unknown environment are needed.
Both approaches can be used. Since the optical forces result from the transfer of momentum from the trapping beam to the particle, if the momentum of the transmitted trapping beam can be measured, the optical force can be found. This can be done, for example, by measuring the deflection of the trapping beam by the particle using a position-sensitive detector (PSD) or camera.
The second approach is to calibrate the trap. With an unknown particle in an unknown environment, it is not possible to use methods that require knowledge of the viscous drag force acting on the particle (e.g., measuring the corner frequency of power spectrum of the trap). One method that can be used is to observe the thermal motion of the trap. The probability of finding the particle at some position in the trap can be determined from the thermal motion, and since this probability is related to the potential energy in the trap by the Boltzmann distribution, the trapping potential and hence the force as a function of position can be found.
One might at first consider these two approaches as different roads leading to the same result. However, they are fundamentally different measurements. The first, measurement of the beam deflection, gives the optical force. The second, on the other hand, gives all of the forces that influence the position of the particle in the trap. This can include external forces that act on the particle during the calibration procedure.
The combination of these two methods can give both the optical and the non-optical forces acting in the trap, allowing measurement of the forces acting on an arbitrary particle without prior calibration of the trap. We will present simulations and experimental results demonstrating this method.
INTRODUCTION:Timo Nieminen is a Senior Lecturer in Computational Science in the School of Mathematics and Physics in The University of Queensland. His main research interests can be broadly classified as electromagnetic theory and computational electromagnetics. The main focus of this work is the theory and modelling of optical trapping, and the scattering of electromagnetic waves by particles. This work includes the development of the Optical Tweezers Toolbox, a freely available Matlab toolbox for the computational modelling of optical tweezers, which is available at
http://www.physics.uq.edu.au/people/nieminen/software.html.
Other interests include physics education, the history of physics and the physics of history, photonics, biological applications of optics, astrophysics, and the cross-disciplinary application of research methodology and tools.
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Keynote Lecture 05: Holographic optical tweezers with specific beam generation
Prof. Baoli Yao
State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi’an 710119, China
ABSTRACT: Optical trapping and manipulation of micro/nano objects play important roles in the studies of atom physics, fluid physics, colloid chemistry, cell biology and so forth. Single trap of tightly focused Gaussian beam is the simplest way for high refractive index particles manipulation, but lacks of the efficiency for multiple objects operation, absence of the utilization of optical angular momentum (OAM) of light exerting torque on the particle. Thanks to the advent of spatial light modulators (SLMs), it makes it possible to generate or shape dynamically arbitrary flexible beams by addressing computer generated holograms (CGHs) on the SLM. In this talk, we present the development of a holographic optical tweezers (HOT) based on a reflective phase-only spatial light modulator in our lab. A specially designed 96°-apex-prism is employed to couple the input collimated beam onto the SLM, and then guide out the retro-reflected modulated beam to the relay optics, which minimizes the system in a compact size of 400×450×450 mm3. A modified Gerchberg-Saxton (GS) algorithm is proposed to reduce the computation cost of CGHs for the generation of 3D structures of optical fields, e.g., 3D array of optical traps or vortexes, with high efficiency and high quality. The aberration of wavefront caused by the SLM itself and other optical elements is elaborately corrected by imposing an additional phase mask on the SLM to obtain the highest possible accuracy in field reconstruction. It is demonstrated that silica beads and polystyrene beads are trapped and dynamically manipulated by various 2D and 3D structures of optical fields produced by the designed CGHs. Trapping and rotating of low index particles such as hollow glass spheres are also implemented by adopting Laguerre-Gaussian (LG) beams or high-order Bessel (HB) beams. Compared with the single optical trapping, HOTs enable multiple optical traps in 2D and 3D arbitrary movement simultaneously or independently, as well as rotation control induced by the OAM of LG or HB beams, which greatly extend the application scopes of optical tweezers.
INTRODUCTION:Prof. Baoli Yao obtained the Ph.D. degree at Xi'an Institute of Optics and Precision Mechanics, CAS in 1997, and pursued the postdoctoral work in Technical University of Munich, Germany during 1997-1998. He is currently the deputy director of State Key Laboratory of Transient Optics and Photonics. His research areas include: super-resolution optical microscopy, digital holographic microscopy, optical micro-manipulation and micro-fabrication, optical data storage and information processing. He invented the DMD-based LED-illumination structured illumination microscope (SIM) and got the 90nm lateral resolution. He designed and developed an optical tweezers system, which has been successfully commercialized and exported to
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