Efficient integrated tri-modal coupler for few-mode fibers
Julian L. Pita Ruiz, Lucas G. Rocha, Jun Yang, Şükrü Ekin Kocabaş, Ming-Jun Li, Ivan Aldaya, Paulo Dainese, Lucas H. Gabrielli
Abstract
This paper demonstrates a high-efficiency vertical grating coupler for the LP 01 x , LP 11 ax , and LP 11 bx modes of a graded-index few-mode fiber. The coupler is composed of a non-uniform straight bidirectional grating that was inverse-designed to address the desired fiber modes, combined with two mode-selective directional couplers and two tapers. The device was fabricated by e-beam lithography with a minimum feature size of 100 nm and presented coupling efficiencies of −3.0 dB, −3.6 dB, and −3.4 dB for the LP 01 x , LP 11 ax , and LP 11 bx modes, respectively. The high efficiency of the proposed CMOS-compatible coupler demonstrates its potential as a key device for high-capacity networks exploiting space division multiplexing on few-mode fibers.