Study Defines Fast and Slow Light Within Plasma

Jun, 2021 - By SMI

The research defines the way a system of laser-plasma could be tuned for producing measurable and large changes in light’s group velocity.

Fast and Slow light, or massive changes within the light’s group velocity, has been noticed in several optical media, however fine control on its refractive index vital for inducing a noticeable effect hasn’t been achieved yet in plasma. In a research published in Physical Review Letters, researchers at Lawrence Livermore National Laboratory (LLNL) along with Laboratory for Laser Energetics (LLE), defines the way a system of laser-plasma could be tuned for producing measurable and large changes in light’s group velocity. Titled "Slow and Fast Light in Plasma Using Optical Wave Mixing," the paper’s lead author Clément Goyon, said that team attained both fast and slow light inside plasmas, hence demonstrating ability for tailoring the laser-plasma system’s refractive index.

"Being able to predict and use plasma properties to our advantage is critical for high-energy laser experiments in high-energy density physics and inertial confinement fusion." explains Mr. Goyon. The energy transfer of cross beam used on National Ignition Facility depends on correct prediction of optical properties that are nonlinear of plasma with the use of linear theory. Moreover, replacements based on plasma for series of standard optical components will enable manipulating light at great fluencies.

This experiment was performed at Jupiter Laser Facility, where probe beam of low-energy and energetic pump beam were passing inside He/H plasma. Through tuning the difference between wavelength among two beams, researchers were successful in changing the group velocity of pulsed light from 0.995c to 0.12c and -0.34c (c refers to light’s speed in vacuum, or around 300,000 km/second. Pierre Michel whose group supported the funding of this project stated that interaction between laser-plasma is particularly difficult for controlling and predicting. This helps in accelerating the case of using plasma as medium in future generation designs of lasers with high-power.