Manufacturing Bits: Nov. 7

Making a superbeam; new states of light.

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Making a superbeam
Lawrence Livermore National Laboratory (LLNL) has combined several lasers to create what it calls a superbeam.

The move represents a possible breakthrough in the arena. In theory, lasers can be combined. But the laser beams tend to pass through each other, thereby making a combined laser or a superbeam nearly impossible.

With the help of plasma optics, however, LLNL has combined nine of 192 laser beams within its National Ignition Facility (NIF) to produce a directed pulse of light or a superbeam. The NIF is a laboratory that consists of a 10-meter-diameter target chamber. In the chamber, 192 laser beams converge on different targets to produce temperatures, pressures, and densities that are similar to those of stars and giant planets.

LLNL’s superbeam, which is referred to as a plasma beam combiner, produces a directed pulse of light that is nearly four times the energy of any one beam. Going forward, researchers plan to combine up to 20 beams into one. This, in turn, could be used to advance the study of X-ray sources and physics.

Beamlines entering the lower hemisphere of the National Ignition Facility’s target chamber. (Photo credit: Damien Jemison/LLNL)

“Beam combining has recently been done with solid-state lasers, but was limited by typical standard optics,” said Scott Wilks, a researcher a LLNL. “Because of this plasma optic, we can put a huge amount of energy into a very small space and time–serious energy, in a well-collimated (focused) beam.”

New states of light
The Harvard John A. Paulson School of Engineering and Applied Sciences has made an advancement in a material that creates new states of light.

The material is called a metasurface. Typically, metsurfaces refer to an artificial sheet material, which has sub-wavelength and electromagnetic properties. In simple terms, metasurfaces modulate the behaviors of electromagnetic waves.

These materials create exotic beams and light structures. In the past, using metasurfaces, other researchers have used the polarization of light to control the size and shape of these beams. But the applications are limited with this technology.

In comparison, Harvard’s metasurface material connects two aspects of light–orbital angular momentum and circular polarization. As a result, the polarization can create any kind of light shapes and structures, such as spirals, corkscrews and vortices.

A metasurface uses circularly polarized light to generate and control new and complex states of light. (Image courtesy of Second Bay Studio/Harvard SEAS)

There are several potential applications. Imaging is one application. Another one is the development of optical tweezers, which use light to move molecules. “We have developed a metasurface which is a new tool to study novel aspects of light,” said Federico Capasso, the Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering at SEAS. “This optical component makes possible much more complex operations and allows researchers to not only explore new states of light but also new applications for structured light.”

Noah Rubin, a researcher, added: “These particular beams are first and foremost of fundamental scientific interest. There is interest in these beams in quantum optics and quantum information. On the more applied side, these beams could find application in free-space optical communication, especially in scattering environments where this is usually difficult. Moreover, it has been recently shown that similar elements can be incorporated into lasers, directly producing these novel states of light. This may lead to unforeseen applications.”



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