Small silicon-photonics-based optical scanner could work well for automotive lidar

April 1, 2019
A nonmechanical chip-based optical scanner containing multiple optical switches and outcoupling gratings is small and rugged for lidar.

A simple, small, and very compact optical beam scanner that is potentially useful for automotive lidar systems has been designed and fabricated by researchers at Toyota Central Research and Development Labs (Nagakute, Japan). The device consists of an imaging lens along with a photonic integrated circuit with numerous optical switches and grating arrays. Light at a 1551 nm wavelength fiber-coupled into the photonic circuit is optically switched from one grating array to another in a sequence—the grating arrays are placed in a line and couple the beam out of the plane of the circuit so that the beam is linearly translated. After passing through the lens, the sequentially scanned beams all converge at a focal point and then angularly diverge into the far field, resulting in a field scanning angle of 6°. The chip size of the circuit is only 7 × 12 mm.

The researchers designed the grating shape so that the gratings could be packed as densely as possible to minimize gaps in the field—they determined that a diamond shape worked best. The pitch, duty cycle, efficiency, and overall size of each grating are 0.62 μm, 0.5, 35%, and 14 μm, respectively. The optical switches, which have a response time of 0.3 μs, are each made up of a ring resonator, a waveguide, and a thin-film heater. When the thermally controlled resonator’s optical path length equals a multiple of the input light wavelength, the light exits the output port—otherwise, the output port is dark, achieving switching. The resonators’ bandwidth is about 0.3 nm. The experimental setup was very “preliminary,” with the lens held in front of the scanning circuit with a pair of pliers. In addition, the singlet lens had some aberration, which could be corrected in the future by use of a doublet. Lenses with 3 or 4 mm focal lengths produced a 6° or 4.6° scanned field, respectively, with a resolution of 0.3° or 0.23°, respectively. The researchers are also working on a 2D version of the scanner. Future versions of this device, which could have thousands of individual emitters, will require refinements to the driver circuit and other parts, as well as the addition of intensity monitors for the resonator switches. Reference: D. Inoue et al., Opt. Express (2019);

About the Author

John Wallace | Senior Technical Editor (1998-2022)

John Wallace was with Laser Focus World for nearly 25 years, retiring in late June 2022. He obtained a bachelor's degree in mechanical engineering and physics at Rutgers University and a master's in optical engineering at the University of Rochester. Before becoming an editor, John worked as an engineer at RCA, Exxon, Eastman Kodak, and GCA Corporation.

Sponsored Recommendations

Request a free Micro 3D Printed sample part

April 11, 2024
The best way to understand the part quality we can achieve is by seeing it first-hand. Request a free 3D printed high-precision sample part.

How to Tune Servo Systems: The Basics

April 10, 2024
Learn how to tune a servo system using frequency-based tools to meet system specifications by watching our webinar!

Motion Scan and Data Collection Methods for Electro-Optic System Testing

April 10, 2024
Learn how different scanning patterns and approaches can be used in measuring an electro-optic sensor performance, by reading our whitepaper here!

How Precision Motion Systems are Shaping the Future of Semiconductor Manufacturing

March 28, 2024
This article highlights the pivotal role precision motion systems play in supporting the latest semiconductor manufacturing trends.

Voice your opinion!

To join the conversation, and become an exclusive member of Laser Focus World, create an account today!