Optical beam scanner with phase-variable waveguides-improvement on deflection characteristics

An optical beam scanner with a variable phase waveguide can perform a high-speed scanning into an arbitrary angle. Monolithic integration of the scanner with a light source can be realized by means of fabrication with semiconductor materials. However, in principle, the scanned beam has multiple peaks so that the maximum scanning angle and the power efficiency are limited. To relax the limitations and to improve the characteristics, the following methods are investigated in this paper: (1) a method to suppress the subbeams; (2) a method to increase the angle between the main beam and the subbeams; and (3) a method in which the entire envelope is scanned. The following results were obtained. (1) By chirping the waveguide spacing, the limitation of the scan angle due to the existence of the subbeams is removed. (2) By reducing the waveguide spacing and varying the widths of the adjacent waveguides so that the mode coupling between the waveguides is eliminated, the scan angle is increased. (3) Although the fabrication is difficult, the wavefront in the waveguide is tilted so that the envelope itself is scanned and the inherent limitation of the scan angle is eliminated.