Mechanical devices like laser-beam steering systems will eventually fail, as is the case with the family automobile. Mid-infrared laser beam scanning, particularly for chemical sensing and lidar applications, must be fast and reliable—and beam-steering mechanisms such as moving mirrors and rotating prisms are slow and power-hungry.
A group of researchers created a non-mechanical chip-based steering device for mid-infrared laser beams. The chip moves beams with wavelengths of 3 to 5 m in two dimensions at higher scan-speed rates than gimbal-powered mirrors and comparable technology.
The chip is a solid-state device known as a steerable electro-evanescent optical refractor (SEEOR). These chips have already shown promise in steering light beams at telecommunications wavelengths and may one day be used in self-driving cars. The researchers believe their SEEOR is the first to use a mid-infrared laser.
A SEEOR resembles a small sandwich of layered thin films atop a faceted substrate—a chunk of silicon from the side resembles a trapezoid. The sandwich comprises a 1.2-m-thick chalcogenide glass passive waveguide core, a liquid-crystal layer, and a cover glass with patterned electrodes. The overall dimensions of the chip are 48.5 mm long, 14.5 mm wide, and 2.75 mm deep.
Collimated light from a 4.6-m-wavelength quantum cascade laser enters the SEEOR at one end. The voltage applied to the electrodes reorients the liquid crystal molecules in a controlled pattern, changing their refractive index.