A GIST Research Team Led by Prof. Jongmin Lee

Found Principles of X-ray Laser Amplifier

Released in the February Issue of the “Physical Review Letters”, a Renowned Journal of Physics

 

Professor Jongmin Lee, Doctor Chul Min Kim, Professor Karol A. Janulewicz from the Left

 

Professor Jongmin Lee, Doctor Chul Min Kim and Professor Karol A. Janulewicz in the Advanced Photonics Research Institue (APRI) of GIST (Gwangju Institute of Science & Technology, headed by Dr. Jung-Ho SUNO) released its research result that the team succeeded in discovering principles and features of the X-ray laser amplifier expected to take a leap in nano-bio technology.

This result was released in the “Physical Review Letters”, the most authoritative journal in the field of physics.

 

http://link.aps.org/doi/10.1103/PhysRevLett.104.053901

 

□ An X-ray light source with high-order harmonics is a device which enables to watch movements of electrons in atoms or molecules at nanometer (1/100 million meter) and femtosecond (1/1000 trillion seconds) levels.

This source comes from the light by radiating ultrashort visible laser pulse to atoms and has very excellent coherence and pulse width less than a femtosecond. However, the light source is not strong enough to be utilized in various fields. Many research groups in the world have tried to intensify the light source by radiating high-order harmonic pulse to the laser amplifier.

□ The meaning of this research is to clearly discover principles how to work the X-ray laser amplifier. Although existing theories ignore noise from the amplifier and wave features, the research team proposes a theory considering the factors above and explained how the noise affect the X-ray and which conditions are needed to intensify the source with maintaining its excellent features.

 

The research results up to now are expected to be understood more and realize an intensified ultrashort X-ray light source. A project in the ELI (Extreme Light Infrastructure), a large-scale laser project organized by the EU, has planned to develop a multi-level X-ray light source amplifier and the results from professor Lee’s team may significantly contribute to designing this amplifier.

□ Professor Lee who led this research added “Our team is developing a ultrashort coherent X-ray light source in the water window by utilizing ‘the ultrashort photon beam facilities” in the APRI. This will accelerate our development.”

※ Terms

1. High-order Harmonic X-ray

When a strong laser in the visible light area radiates the air, the strong electromagnetic field from the laser violently shakes electrons in the atoms of the air and an X-ray is generated. Unlike previous X-ray from X-ray tubes or synchrotron radiations, the new X-ray shows excellent coherence and the time is less than a femtosecond. Also, it is useful to investigate movements of electrons in atoms or molecules.

2. Coherence

It is a feature of a wave. The water waves from a stone fallen into a calm pond show excellent coherence owing to well-defined shapes. However, the shapes will become bad when some stones are fallen into the pond at random. Two waves with good coherence show clear interference.

3. Ultrashort Laser Pulse

It is a laser pulse with pulse width less than a picosecond (1/1 trillion second), a femtosecond (1/1000 trillion second) or an atosecond (1/100 zillion second). This pulse makes it possible to investigate natural phenomena with ultrahigh speed and movements of atoms or molecules by enabling to measure and control super-speed natural phenomena.

4. Water WIndow

 

It is an X-ray light source area with wavelengths between 2.3 and 4.3㎚. The area is called the water window because an X-ray in this area absorbs nitrogen, oxygen and hydrogen 10 times higher than that of water. An X-ray in the water window penetrates water and is absorbed in living organisms. This means that it is possible to make an X-ray microscope with the X-ray to watch living cells.