High-efficiency THz generation in optically contacted GaAs with near-Brewster angle pumping

Area of Science:

• Optics and Photonics
• Terahertz (THz) Science and Technology
• Nonlinear Optics

Background:

• Quasi-phase matching (QPM) is crucial for efficient nonlinear optical processes.
• Gallium arsenide (GaAs) is a promising material for THz generation.
• Reducing pump reflection losses enhances overall conversion efficiency.

Purpose of the Study:

• To numerically investigate high-efficiency THz generation in quasi-phase matched optically contacted GaAs (OC-GaAs).
• To explore the impact of near-Brewster angle pumping on THz generation efficiency.
• To analyze the role of effective nonlinear coefficients and air-gap spacing.

Main Methods:

• Numerical simulation of THz generation in OC-GaAs.
• Investigation of effective nonlinear coefficients (d(eff)) for varying incident angles and polarizations.
• Calculation of optimal QPM periods and THz generation efficiency based on air-gap spacing.

Main Results:

• Pump propagation at a near-Brewster angle (66.92?) significantly reduces reflection losses.
• The number of optimal QPM periods increased from 12 (normal incidence) to 25 (near-Brewster angle).
• THz generation efficiency was enhanced by more than 16 times using near-Brewster angle pumping.

Conclusions:

• Near-Brewster angle pumping is a highly effective strategy for enhancing THz generation efficiency in OC-GaAs.
• Optimizing QPM periods and minimizing reflection losses are key to maximizing THz output.
• This approach offers a significant improvement over traditional normal incidence methods.