Recognizing that electro-optical beam scanners/deflectors based on diffractive techniques are limited to small angles because grating efficiency drops as scan angle increases, engineers at Vescent Photonics (Golden, CO) have developed a liquid crystal (LC) waveguide approach that scans a 30° × 5° field of view with low power consumption at a frame rate of less than 50 ms/frame.
The scannable electro-evanescent optical refractor (SEEOR) uses LCs that possess an electro-optic response more than 105 times larger than lithium niobate as a cladding layer in a LC-waveguide architecture, whereby the evanescent field of the guided wave extends into an adjustable-refractive-index LC cladding. Rather than transmitting the beam directly through a thin LC layer, the evanescent approach decouples the interaction length from the thickness of the LC layer, creating a well-ordered LC-surface region that provides low insertion losses (as little as 3 dB) and fast response times (in the range of 10 to 500 μs). Circumventing the historic LC limitations of a short interaction length and slow relaxation times, the truly continuous analog scanner does not suffer from 2π reset gaps and is housed in a compact package measuring less than 3.5 in3. In lab experiments, devices that scan as much as 270º in a single plane have been demonstrated. Reference: www.vescent.com/wp-content/uploads/2015/04/LS3.2.pdf.