Director

Director NAM Chang Hee

Prof. Chang Hee Nam received his Ph. D. in plasma physics from Princeton University. He has worked on ultrafast laser science through Coherent X-ray Research Center at KAIST (1999-2012) and on ultrahigh intensity laser science through Center for Relativistic Laser Science of IBS, based on the PW laser facility at GIST, since 2012. He has been actively involved with the ultrahigh intensity laser community, in part by serving the scientific advisory committees of ELI-ALPS in Hungary and of ELI-NP in Romania. He is a fellow of the American Physical Society and also of Optical Society of America.

Introduction

Understanding superintense lasermatter interactions in the relativistic regime

• - Developing cutting-edge technologies in the field of ultra-high intensity lasers
• - Exploring laser-matter interactions under extreme conditions
• - Investigating laboratory astrophysics with PW lasers
• - Exploring attosecond and zeptosecond phenomena in atoms, molecules, solids and nano-structures

Main research activities

The Center for Relativistic Laser Science (CoReLS) was established in December 2012 to explore novel physical phenomena in the relativistic laser intensity regime. The electron motion enters the relativistic regime at a laser intensity of 10¹⁸W/cm², while protons behave relativistically at 10²⁴W/cm². To tackle the underlying physics of relativistic laser-matter interactions, the center utilizes a 30-fs petawatt (PW) laser facility developed at Gwangju Institute of Science and Technology (GIST). It is a challenging task to reveal the physics of relativistic and ultra-relativistic laser-matter interactions. We examine the fundamental physical processes in atoms, molecules, plasmas, we explore subatomic entities occurring in an ultra-fast timescale (atto- to zepto-second), and we develop high-energy, ultra-short particle (electron, proton, and ion) beams and radiation (X-ray and γ-ray) sources. Sophisticated methods of controlling the spatio-temporal structure of ultra-intense laser pulses are to be developed to precisely manipulate relativistic laser-matter interactions. Such developments will allow us to achieve our goals by steering the interaction processes (e.g., relativistic harmonic generation at extreme orders, mono-energetic electron acceleration over GeV, energetic proton generation with narrow bandwidths; strong X-ray and γ-ray generation).

In order to achieve the aims of the center, research topics have been divided into five subjects:

1. Super-Intense Laser Research: Formation of Super-Intense Laser Intensity over 10²²W/cm²

The current PW laser system will be upgraded to obtain laser intensity greater than 10²²W/cm². Achieving such a high intensity is a challenging task that requires cutting-edge laser technologies, such as highly efficient broadband amplification for super-intense laser pulses, contrast-ratio enhancement for temporally-well-defined pulses, and tight focusing techniques to obtain a diffraction-limited focal spot. The ongoing development of laser technologies is essential for sustaining excellence in research activities.

2. Relativistic Laser-Gas Interaction Research: Generation and Application of High-Energy Electron Beams

We investigate the interactions between super-intense laser pulses and under-dense plasma to accelerate electrons up to tens of GeV through Laser Wakefield Acceleration (LWFA). The high-energy electron beams can be used to generate unique (highly bright, ultra-short, spectrally narrow) high-energy radiation sources (X-ray or γ-ray), which can be powerful tools for nanomaterial and biomaterial research in ultra-fast timescales.

3. Relativistic Over-Dense Plasma Research: Generation and Application of Energetic Proton/Ion Beams

 We conduct research into the generation of protons/ions with the energy of several hundred MeV by applying super-intense laser pulses and exploring underlying physical mechanisms. The realization of radiation pressure acceleration for protons/ions is important because energetic proton/ion beams can be produced in an efficient way. Energetic proton/ion beams can be used as new imaging tools for matter in extreme conditions and for novel laser cancer-therapy machines.

4. Attosecond Science

Attosecond (10^-18s) light pulses can be produced from gaseous and solid targets irradiated by ultra-intense laser pulses. The physical conditions for extending high harmonic orders to support attosecond and even zeptosecond (10^-21s) pulses are being investigated. Ultra-fast physical processes in atoms, molecules, and plasmas can be explored using attosecond pulses. In addition, the generation of zeptosecond pulses makes it possible to investigate nuclear dynamics. Such research should expand new horizons in ultra-fast optical science and advance our understanding of ultra-fast phenomena.

5. Theory and Simulation of Relativistic Laser-Matter Interactions

Ultra-intense laser-plasma interactions are characterized by non-local material responses, extremely high energy density, and serious radiation reactions, all of which result from the ultra-high irradiance of laser pulses and the relativistic nonlinearity of interactions. To fully understand the unprecedented combination of characteristics inherent in physical processes, the theory group has developed a theory and model of relativistic laser-plasma interactions, and an ab initio simulation code (relativistic particle-in-cell code). Using the theory, model, and simulation, the group fully supports the experimental groups in designing experiments and in interpreting their results. As the available radiation irradiance increases, the group will investigate the physical processes in extreme environments, such as the direct drive of nuclear dynamics by intense fields, and the optical responses of quantum vacuums.