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

Area of Science:

• Nonlinear Optics
• Materials Science
• Integrated Photonics

Background:

• Nonlinear optical (NLO) materials are crucial for frequency conversion technologies.
• Organic crystals offer unique NLO properties but often face challenges in device fabrication and stability.
• Waveguide devices enable efficient light-matter interaction for enhanced NLO effects.

Purpose of the Study:

• To fabricate and characterize a novel waveguide device using a 2-methyl-4-nitroaniline (MNA) crystal.
• To investigate and demonstrate second-harmonic generation (SHG) in the MNA crystal waveguide.
• To evaluate the performance metrics including conversion efficiency and grating coupling efficiency.

Main Methods:

• Fabrication of a four-layer MNA crystal waveguide device incorporating grating couplers.
• Utilizing mode dispersion curves of the optical waveguide to achieve phase-matching conditions for SHG.
• Experimental measurement of SHG conversion efficiency, grating coupling efficiency, and decoupling efficiency.

Main Results:

• Successful fabrication of the MNA crystal waveguide device.
• Observation of second-harmonic generation under phase-matching conditions.
• Achieved a SHG conversion efficiency of 0.71% within the waveguide.
• Measured grating coupling efficiency of 11.4% and decoupling efficiency of 43.2%.
• Demonstrated mechanical stability and long-term (nine months) operational stability of the MNA crystal.

Conclusions:

• The MNA crystal waveguide device is a viable platform for efficient nonlinear optical frequency conversion.
• The demonstrated SHG performance and material stability highlight the potential of MNA for integrated photonic devices.
• Further optimization of grating couplers and waveguide design could lead to even higher efficiencies.