Phase-matched second-harmonic generation in a four-layer 2-methyl-4-nitroaniline waveguide with grating couplers

A four-layer 2-methyl-4-nitroaniline (MNA) crystal waveguide device with grating couplers is fabricated. Second-harmonic generation is observed under phase-matching conditions using the mode dispersion curves of the optical waveguide. A second-harmonic generation conversion efficiency in the waveguide of 0.71% is obtained with a grating coupling efficiency of 11.4% and a decoupling efficiency of 43.2%. The MNA single crystal is never damaged mechanically, and it has been kept stable for nine months.