Difference frequency generation in the mid-infrared with orientation-patterned gallium phosphide crystals.

Area of Science:

• Nonlinear Optics
• Solid-State Physics
• Materials Science

Background:

• Mid-infrared (mid-IR) radiation is crucial for spectroscopy and sensing applications.
• Efficient generation of mid-IR light often requires specialized nonlinear optical materials.
• Orientation-patterned (OP) semiconductors offer promising nonlinear optical properties.

Purpose of the Study:

• To demonstrate mid-infrared radiation generation via difference frequency generation (DFG) in an OP-GaP crystal.
• To characterize the linear, thermo-optic, and nonlinear optical properties of OP-GaP in a DFG setup.
• To determine the effective nonlinear coefficient of first-order quasi-phase-matched OP-GaP.

Main Methods:

• Difference Frequency Generation (DFG) using a continuous-wave Nd:YAG laser (1064 nm) and a diode laser (1301 nm).
• Utilized an orientation-patterned gallium phosphide (OP-GaP) nonlinear crystal.
• Characterized material properties and compared experimental efficiency with Gaussian beam DFG theory.

Main Results:

• Successfully generated coherent mid-infrared radiation centered at 5.85 μm.
• Provided the first comprehensive characterization of OP-GaP's linear, thermo-optic, and nonlinear properties in a DFG configuration.
• Derived an effective nonlinear coefficient (d) of 17(3) pm/V for first-order quasi-phase-matched OP-GaP.

Conclusions:

• OP-GaP is a viable material for efficient mid-infrared generation via DFG.
• Experimental results align with theoretical predictions for tuning curves.
• The derived effective nonlinear coefficient provides crucial data for future OP-GaP device design.