For many practical applications involving lasers, it’s important to be able
to control the direction of the laser beams. Researchers from North Carolina
State Univ. have come up with a very energy-efficient way of steering laser
beams that is precise and relatively inexpensive.
“In many cases, it is much easier to redirect a laser beam at a target than
to steer the laser itself. We intended to develop a way to do this efficiently
and without moving anything,” says Dr. Michael Escuti, an associate professor
of electrical engineering at NC State and co-author of a paper on the research. “We also wanted to be able to steer the beams over a wide range of angles,
which is important for practical applications.”
The key to the Escuti team’s success was the use of “polarization gratings,”
which consist of a thin layer of liquid crystal material on a glass plate. The
researchers created a device that allows a laser beam to pass through a stack
of these polarization gratings. Researchers manipulated the optical properties
of each grating, and were able to steer the laser beams by controlling how each
individual grating redirects the light. “Because each individual grating is
very good at redirecting light in the desired directions with almost no
absorption, the stack of gratings do not significantly weaken the laser power,”
Escuti says.
Another advantage of the system, Escuti explains, is that “every grating
that we add to the stack increases the number of steerable angles
exponentially. So, not only can we steer lasers efficiently, but we can do it
with fewer components in a more compact system.
“Compared to other laser steering technologies, this is extremely
cost-effective. We’re taking advantage of materials and techniques that are
already in widespread use in the liquid crystal display sector.”
The technology has a variety of potential applications. For example, free
space communication uses lasers to transfer data between platforms—such as
between satellites or between an aircraft and soldiers on the battlefield. This
sort of communication relies on accurate and efficient laser-beam steering.
Other technologies that could make use of the research include laser weapons
and LIDAR, or laser radar, which uses light for optical scanning applications—such
as mapping terrain.
Escuti’s team has already delivered prototypes of the technology to the U.S.
Air Force, and is currently engaged in additional research projects to
determine the technology’s viability for a number of other applications.
The paper, “Wide-angle, nonmechanical beam steering with high-throughput
utilizing polarization gratings,” was co-authored by Escuti; NC State PhD
student Jihwan Kim; former NC State PhD student Chulwoo Oh; and Steve Serati of
Boulder Nonlinear Systems, Inc. The paper is published in the journal Applied
Optics. The research was funded by the U.S. Air Force Research Laboratory.
