A new type of non-mechanical beam steering device, based on liquid crystal (LC) cladding waveguide, is the Steerable Electro-Evanescent Optical Refractor (SEEOR), which has attracted widespread attention due to its large angle, continuous steering, and fast response time. However, a comprehensive theory on how to design SEEOR coupling structures with high coupling efficiency is still unclear.

In a study published in Optics Express, a research group led by Prof. MU Quanquan from Changchun Institute of Optics, Fine Mechanics and Physics (CIOMP) of the Chinese Academy of Sciences (CAS) proposed an extended prism coupling theory, which optimized the design of anisotropic LC cladding prism coupling structure and successfully applied to high-speed SEEOR.

Considering the optical reciprocity principle, the researchers used the wave optics method to calculate the optical field distribution Ω* that can perfectly match the coupling structure and achieve 100% coupling efficiency.

A structure that could achieve 100% coupling efficiency for a Gaussian beam was optimized based on the expression of Ω*. Through analyzing the requirements for the Gaussian beam to achieve high coupling efficiency by numerical simulation, they concluded that the coupling structure had large tolerance for the waist radius and center position of the Gaussian beam, but was very sensitive to the incident angle.

Based on the above finding, the researchers developed a SEEOR device with a size of 39 mm×25 mm×6 mm and tested its coupling efficiency.

The experimental results showed that the device achieved a coupling efficiency of 91% and a coupling angle FWHM of about ±0.02°, confirming the validity of the proposed theory. Moreover, the device exhibited 28°×5° continuous 2D steering and a response time of less than 0.5 ms at large angle.

These important results provide theoretical support and experimental guidance for developing a reliable and robust coupling structure of SEEOR.