High-speed optical phased array based on giant electro-optic coefficient KTN crystals

In this paper, we report a high-speed optical phased array based on giant electro-optic coefficient KTN crystals, which is composed of a KTN crystal and an array of electrode. Each electrode corresponds to one phase element. The optical phase delay of each element can be individually controlled by the applied electric field. Due to the giant quadratic electrooptic coefficient of KTN crystal (5.4x10^-14 m² / V²), a reasonable high driving voltage (⁓200) can be used to achieve a half-wave phase modulation for a large optical throughput aperture (5 mm x 5 mm). A high frequency driving voltage source with a frequency >100 kHz and a voltage >200 V can be readily realized. Furthermore, the electro-optic effect itself is very fast (< 1 ns). Thus, a high-speed (>100 kHz) and high optical throughput (5 mm x 5mm or higher) optical phased array can be realized by harnessing giant electro-optic coefficient KTN crystals. Both quantitative theoretical analysis and experimental investigations are conducted. The experimental result confirms that a 100 kHz modulation speed can be achieved at 200 V driving voltage for a 5 mm x 5 mm optical throughput aperture. This high-speed optical phased array can play a key role in variety of applications such as high speed LiDAR used in autonomous driving, reconfiguration free space optical communications, and high-speed adaptive optics system against high-speed turbulence.