Lidar is a remote-sensing technology that measures distance by illuminating a target with a laser and analyzing the reflected light. It is used by autonomous vehicles to perceive their surroundings and is also applicable to several essential military capabilities—including chemical-biological sensing, precision targeting and communications, which increasingly rely upon laser-scanning technologies.
One drawback of Lidar systems is that they require mechanical assemblies to sweep the laser back and forth and as a result these systems are expensive.
Now, however, DARPA has come up with a non-mechanical approach that could open the door to a new class of miniaturized, extremely low-cost, robust laser-scanning technologies for military and commercial use. DARPA’s Short-range Wide-field-of-view Extremely agile Electronically steered Photonic EmitteR (SWEEPER) program has successfully integrated non-mechanical optical scanning technology onto a microchip.
Freed from the traditional architecture of gimbaled mounts, lenses and servos, SWEEPER technology has demonstrated that it can sweep a laser back and forth more than 100,000 times per second, 10,000 times faster than current state-of-the-art mechanical systems. It can also steer a laser precisely across a 51-degree arc, the widest field of view ever achieved by a chip-scale optical scanning system.
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 played a key role in advancing them in the decades since.
Transitioning phased-array techniques from radio frequencies to optical frequencies has proven exceptionally difficult, however, 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 as such 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.
SWEEPER technology is being developed further through DARPA’s Electronic-Photonic Heterogeneous Integration (E-PHI) program, which has already successfully integrated billions of light-emitting dots on silicon to create an efficient silicon-based laser.
Under SWEEPER funding, four teams of DARPA-funded researchers have used advanced manufacturing techniques to successfully demonstrate optical phased array technology. These performers include the Massachusetts Institute of Technology; the University of California, Santa Barbara; the University of California, Berkeley; and HRL Laboratories.
SWEEPER research is drawing to a close and DARPA is seeking potential transition partners.