A new chip-based beam steering device with a smaller, cheaper Lidar

The new chip-based beam steering technology offers low-cost, high-performance lidar. The Lidar acquires 3D information using laser pulses. Free-space optical communications, autonomous driving, 3D holography, and biomedical sensing benefit from it.

Key technology for lidar systems is optical beam steering, but conventional mechanical beam steering systems are bulky, expensive, sensitive to vibration, and slow, said Hao Hu, the team leader.

The chip-based optical phased array can steer light in a non-mechanical way, but so far it has had poor beam quality and a small field of view. Yong Liu and Hu discuss their new chip-based OPA in Optica, Optica Publishing Group's journal for high-impact research.

The device generates high beam quality while eliminating an optical artifact called aliasing across a wide field of view. Combining these two technologies could greatly improve lidar systems.

The results we achieved in optical beam steering are groundbreaking, said Hu. 'This development will allow lidar to be widely used for a variety of applications, including the development of low-cost, compact, OPA-based lidar to assist drivers and park safely.'

The purpose of OPAs is to steer light by electronically controlling its phase profile to form specific patterns of light. OPAs emit many beams of light through an array of waveguides, and then interference is applied in the far field to create the pattern.

The fact that these waveguide emitters are typically spaced far apart from each other and produce multiple beams in the far field results in an optical artifact known as aliasing.

The emitters must be close together to avoid aliasing error and achieve a 180° field of view, but this causes strong crosstalk between adjacent emitters and degrades the beam quality. Thus, until now, the quality of the beam and the field of view of OPA have been traded off.

A slab grating was used to create a single emitter in place of traditional OPAs' multiple emitters. The slab grating setup eliminates aliasing error because adjacent channels can be very close to each other.

A slab grating's coupling between adjacent channels is not detrimental because it enables interference and beam formation in the near field. Using the desired angle, light can be emitted to the far field. Researchers also applied additional optical techniques to reduce background noise and side lobes.

The scientists designed a special imaging system to measure the optical power along the horizontal plane over a 180° field of view. Although some beam degradation was observed, they demonstrated aliasing-free beam steering in this direction.

The researchers plan to decrease the beam width for higher resolution and a longer steering range. “This new chip-based OPA achieves both aliasing-free 2D beam steering with low side lobe levels and high beam quality,” Hu said.