ARLINGTON, Va. - In a recent release, the United States DARPA reveals that its Short-range Wide-field-of-view Extremely agile Electronically steered Photonic EmitteR (SWEEPER) program has successfully integrated non-mechanical, phased-array optical scanning technology onto a microchip. The SWEEPER technology, , freed from the traditional architecture of gimbaled mounts, lenses, and servos, has demonstrated the ability to non-mechanically sweep a laser back and forth more than 100,000 times per second. DARPA says that this is 10,000 times faster than current state-of-the-art mechanical systems. SWEEPER, the release notes, can steer its laser precisely about a 51° arc, the widest field of view ever achieved by a chip-scale optical scanning system. These accomplishments will likely open the door to a new class of miniaturized, extremely low-cost, robust laser-scanning technologies for LIDAR and other uses.
Artistic Depiction of Potential SWEEPER Technology Uses
Source: U.S. DARPA
Many essential military capabilities-including autonomous navigation, chemical-biological sensing, precision targeting and communications-increasingly rely upon laser-scanning technologies such as LIDAR (light detection and ranging; similar to the RF-based radar (radio detection and ranging)). These technologies provide amazing high-resolution information at long ranges but have a common Achilles heel in the mechanical assemblies required to sweep the laser back and forth. These large, opto-mechanical systems are both temperature- and impact-sensitive while often costing tens of thousands of dollars each. The combination of these factors has, to date, limited widespread adoption of current high-end EO technologies for military and commercial use.
Phased arrays-engineered surfaces that control the direction of selected electromagnetic signals by varying the phase across many small antennas-have revolutionized radio-frequency (RF) technology by allowing for multiple beams, rapid scanning speeds and the ability to shape the arrays to curved surfaces. DARPA pioneered radar phased array technologies in the 1960s and has repeatedly played a key role in advancing them in the decades since.
DARPA explains that transitioning phased-array techniques from radio frequencies to optical frequencies has proven exceptionally difficult, because optical wavelengths are thousands of times smaller than those used in radar. This means that the array elements must be placed within only a few microns of each other and that manufacturing or environmental perturbations as small as 100 nanometers can hurt performance or even sideline the whole array. The SWEEPER technology sidesteps these problems by using a solid-state approach built on modern semiconductor manufacturing processes.
Four teams of DARPA-funded researchers from the Massachusetts Institute of Technology, the University of California, Santa Barbara, the University of California, Berkeley, and HRL Laboratories have used the semiconductor manufacturing techniques to successfully demonstrate optical phased array technology.
SWEEPER technology is now to be developed further through DARPA's Electronic-Photonic Heterogeneous Integration (E-PHI) program. DARPA says that it has already successfully integrated billions of light-emitting dots on silicon to create an efficient silicon-based laser under the E-PHI program.
"By finding a way to steer lasers without mechanical means, we've been able to transform what currently is the largest and most expensive part of laser-scanning systems into something that could be inexpensive, ubiquitous, robust and fabricated using the same manufacturing technology as silicon microchips," said Josh Conway, DARPA program manager. "This wide-angle demonstration of optical phased array technology could lead to greatly enhanced capabilities for numerous military and commercial technologies, including autonomous vehicles, robotics, sensors and high-data-rate communications."
DARPA is now seeking potential transition partners as the SWEEPER program draws to a close.