A Chip-Based Nonmechanical Beam Steerer

Steerable electro-evanescent optical refractor (SEEOR) chips take laser light in the mid-wavelength infrared as an input and steers the beam at the output in two dimensions without the need for mechanical devices. (Source: J. Myers, NRL)

Scientists at the U.S. Naval Research Labora­tory have recently demonstrated a new non­mechanical chip-based beam steering tech­nology that offers an alter­native to costly, cumbersome and often unreliable and ineffi­cient mecha­nical gimbal-style laser scanners. The chip, a steerable electro-evanescent optical refractor – SEEOR, takes laser light in the mid-wave­length infrared (MWIR) as an input and steers the beam in two dimen­sions at the output without the need for mechanical devices – demon­strating improved steering capability and higher scan speed rates than conven­tional methods.

“Given the low size, weight and power consumption and continuous steering capability, this tech­nology represents a promising path forward for MWIR beam-steering techno­logies,” said Jesse Frantz, research physicist, NRL Optical Sciences Division. “Mapping in the MWIR spectral range demon­strates useful potential in a variety of applications, such as chemical sensing and moni­toring emissions from waste sites, refineries, and other industrial faci­lities.”

The SEEOR is based on an optical waveguide. Laser light enters through one facet and moves into the core of the waveguide. Once in the waveguide, a portion of the light is located in a liquid crystal layer on top of the core. A voltage applied to the LC through a series of patterned electrodes changes the refrac­tive index in portions of the wave­guide, making the waveguide act as a variable prism. Careful design of the wave­guides and electrodes allow this refrac­tive index change to be translated to high speed and continuous steering in two dimensions.

SEEORs were origi­nally developed to mani­pulate shortwave infrared (SWIR) light and have found appli­cations in guidance systems for self-driving cars. “Making a SEEOR that works in the MWIR was a major challenge,” Frantz said. “Most common optical materials do not transmit MWIR light or are incom­patible with the waveguide archi­tecture, so developing these devices required a tour de force of materials engi­neering.”

To accom­plish this, the researchers designed new waveguide structures and LCs that are trans­parent in the MWIR, new ways to pattern these materials, and new ways to induce alignment in the LCs without absorbing too much light. The resulting SEEORs were able to steer MWIR light through an angular range of 14°×0.6°. The researchers are now working on ways to increase this angular range and to extend the portion of the optical spectrum where SEEORs work even further. (Source: NRL)

Reference: J. A. Frantz et al.: Chip-based nonmechanical beam steerer in the midwave infrared, JOSA B 35, C29 (2018); DOI: 10.1364/JOSAB.35.000C29

Link: Optical Sciences Division, Naval Research Laboratory, Washington, DC, USA

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