From Nonlinear Optics to High-Intensity Laser Physics

The laser increased the intensity of light that can be generated by orders of magnitude and thus brought about nonlinear optical interactions with matter. Chirped pulse amplification, also known as CPA, changed the intensity level by a few more orders of magnitude and helped usher in a new type of lasermatter interaction that is referred to as high-intensity laser physics. In this talk, I will discuss the differences between nonlinear optics and high-intensity laser physics. The development of CPA and why short, intense laser pulses can cut transparent material will also be included. I will also discuss future applications.

Silica and the Global Internet

The internet is perhaps the most important and life-changing invention of the 20th century. It required the invention of a new global communication medium capable of carrying vast quantities of information across trans-oceanic distances, reliably, cheaply and efficiently. Unpredictably, this turned out to be optical fibres made from the two most common elements of the earth’s crust, silicon and oxygen (silica). As the internet traffic grows by some estimates at 60%/annum there is constant pressure to find more fibre capacity, although at $8/km the option remains to simply install more fibre, rather than find better fibres. However, in some applications where small volume, reduced transit time or better phase stability is critical, there will be a role for advanced designs such as hollowcore or multi-core fibres. Transit time and stability is becoming increasingly important for global timing, time-stamping for financial trading, 5G wireless (where the density of masts is determined by the delay between them) and autonomous vehicles.

With the huge increase in data traffic comes a headache in how to store the information for the requisite period of time that is often mandated by banks and government – up to several hundred years. A new storage medium based once again on silica appears a leading contender to replace today’s tape units. The technique, known as 5D storage because of the way each bit can be written and read, provides both high storage density and the extraordinary lifetime estimated at 1020 years.

The parallel field of high-power fibre lasers also relies on silica fibre. This field has seen a revolution in industrial laser processing and the market has grown to several $B/annum. Because of its robust, monolithic nature and its efficiency, the fibre laser is finding favour in defence applications as well. With its extraordinary combination of low expansion coefficient and high optical damage, silica is the unassailable material of choice for this hugely important industrial market.

Light, Lasers and the Nobel Prize

John M Dudley

Department of Optics, Institut FEMTO-ST, CNRS-University of Franche-Comté
15B Avenue des Montboucons, Besançon, France   email: john.dudley@univ-fcomte.fr

The Year 2020 represents the 60th anniversary of the first successful operation of the laser, and is a timely reminder of how basic science has the power to impact dramatically on society. Indeed, the United Nations now recognizes the date of first laser operation as the International Day of Light, celebrated annually on 16 May. The 60th anniversary of the laser provides an ideal occasion to reflect on the many ways that lasers have revolutionized the world. Moreover, from a fundamental perspective, light science and technologies are key components of basic research, and are regularly recognized at the highest level by award of the Nobel Prize. This talk will review some elements from the history of the laser, which will take us on a tour of 120 years of Nobel Prize history, allowing us to appreciate how the study of light has allowed us to understand the world around us - from the fundamental properties of atoms to the cosmological scale and the study of new exoplanets orbiting distant stars.

From Quantum Cascade Lasers to Compact Widely Tunable Molecular Lasers Spanning the THz-gap

Federico Capasso

John A. Paulson School of Engineering and Applied Sciences, Harvard University,
Cambridge, MA 02138, USA   email: capasso@seas.harvard.edu

Quantum Cascade Lasers have become in the last ten years the dominant source of mid-IR radiation with a wide range of applications in the molecular fingerprint region. The THz region (100 GHz to 3 THz) has on the other hand been conspicuously devoid of suitable efficient compact and tunable lasers. We have realized compact, widely frequency-tunable, bright THz lasers: gas-phase molecular laser based on rotational population inversions optically pumped by a quantum cascade laser. By identifying the essential parameters that determine the suitability of a molecule for a terahertz laser, almost any rotational transition of almost any molecular gas can be made to lase. Nitrous oxide is used to illustrate the broad tunability over 37 lines spanning 0.251 to 0.955 terahertz, each with kilohertz linewidths. Our analysis shows that laser lines spanning more than 1 terahertz with powers greater than 1 milliwatt are possible from many molecular gases pumped by quantum cascade lasers. We expect a wide range of scientific and technological applications to be opened by such lasers.

Semiconductor Nanowires for Optoelectronics and Energy Applications

Semiconductors have played an important role in the development of information and communications technology, solar cells, solid state lighting. Nanowires are considered as building blocks for the next generation electronics and optoelectronics. In this talk, I will introduce the importance of nanowires and their potential applications and discuss about how these nanowires can be synthesized and how the shape, size and composition of the nanowires influence their structural and optical properties. I will present results on axial and radial heterostructures and how one can engineer the optical properties to obtain high performance lasers, THz detectors, solar cells and to engineer neuronal networks. Future prospects of the semiconductor nanowires will be discussed.

Nonlinear Optics and Femtosecond Lasers Power Non-invasive Vision Correction

Wayne H. Knox

Professor of Optics, Physics, Materials Science and Vision Science
University of Rochester, and Chief Science Officer Clerio Vision, Inc. Rochester NY 14627
email: wknox@optics.rochester.edu

The field of femtosecond micro-machining has rapidly grown from early observations of laser induced damage in various materials to an important application area today. In this talk, I discuss one specific application area: vision correction. We have demonstrated that focused femtosecond laser pulses over a wide range of laser parameters such as wavelength, repetition rate, power, pulse width and numerical aperture can produce strongly localized refractive index changes in important ophthalmic materials such as human cornea and hydrogels for custom contact lens and adjustable intraocular lens applications. We discuss a nonlinear optics-based photochemical model that we have developed. It has been successfully applied over a wide range of parameters. We also discuss device results sand applications.

Optical Fibre Sensors: Better Solutions for Challenging Industrial Measurement Problems

Optical Fibre Sensors have been developed extensively now over some four decades – created to address a range of challenging industrial applications where conventional sensors often are badly conditioned for important monitoring needs. Systems are required to enhance safety, to allow assets to be used for longer, to schedule repair and maintenance better and to create a more cost effectively and improve the working environment for us all. As an example, the demands of electric and autonomous transport, be it on land, sea or air, as well as energy generation and distribution and robotics make enormous demands for better sensor systems.

This talk will review the essential background to and history of optical fibre sensors and then look at how a range of optical fibre-based techniques can be applied to problems such as those highlighted and offer alternative, and better solutions to those from current technologies be they electronic, hydraulic, electrochemical, and analogue or digital – revealing solutions which have the potential readily to be adopted by industry. The work will review a number of ‘case studies’, where working in collaboration with industry and researchers across the world, new and practical solutions to key problems have been found and implemented in-the-field, not just as laboratory demonstrations.

Unravelling Dance of Electrons and Atoms in Solids Using Ultrafast Spectroscopy

In recent years, ultrafast time-resolved spectroscopies have proved to be excellent probes to understand photo-physics of quantum materials - be it in bulk or in nano-dimensions. Ultrafast lasers offer unique possibilities to control and probe transient processes in nano materials. Following photoexcitation by a femtosecond laser pulse, the carrier dynamics includes many important processes like thermalization, energy relaxation, exciton formation and spin dynamics which are impacted by dimensionality. Their understanding is crucial not only for many optoelectronic applications, but also to gain a deeper understanding of physical processes in nanomaterials.

My talk will discuss our recent work on a novel system, namely an excitonic insulator (EI) which hosts a condensate of electron-hole pairs in its ground state. We use a spatially resolved pump-probe microscopy technique to investigate the propagation of photoinduced excitations in a proposed EI, Ta2NiSe5. Below the critical temperature for the EI phase (328 K), we observe the propagation, for distances of up to 1 􀀀m, of coherent oscillatory modes at velocities typical of electronic excitations [1]. We show that the origin of this effect is the mixing between the phonon mode and the phase mode, which supports the excitonic origin of the ordered state in Ta2NiSe5.

[1] Paolo Andrich, Hope M. Bretscher, Yuta Murakami, Denis Gole, Benjamin Remez, Prachi Telang, Anupam Singh, Luminita Harnagea, Nigel R. Cooper, Andrew J. Millis, Philipp Werner, A. K. Sood, and Akshay Rao, arXiv:2003.1079902 (March25,2020)