Selective excitation of the LP11 mode in step index fiber using a phase mask

Abstract

We present a novel mode selective coupling technique for step index fiber. This technique utilizes phase matching for excitation of higher-order modes while suppressing the fundamental mode. Using this technique, a phase element is fabricated and tested to demonstrate the high coupling efficiency to the $LP11$ mode. In addition, we derive an analytical expression of the coupling efficiency of the $LP11$ using a single phase element.