Efficient, low-threshold collinear and noncollinear beta-barium borate optical parametric oscillators

Area of Science:

• Nonlinear Optics
• Laser Physics
• Materials Science

Background:

• Optical parametric oscillators (OPOs) are crucial for generating tunable laser light.
• Barium borate (BBO) crystals are widely used in OPOs due to their nonlinear properties.
• Understanding the optimal configuration (collinear vs. noncollinear) is key for maximizing OPO performance.

Purpose of the Study:

• To analyze and compare the performance of collinear and noncollinear BBO OPOs.
• To investigate the influence of tangential phase matching and pump walk-off compensation.
• To determine the optimal configuration based on pump parameters like divergence and spot size.

Main Methods:

• Theoretical analysis of collinear and noncollinear OPO configurations.
• Experimental investigation using third-harmonic Nd:YAG laser pumping.
• Evaluation of parameters including slope efficiency, threshold, pump divergence, and crystal aperture.

Main Results:

• Tangential phase matching and pump Poynting vector walk-off compensation enhance noncollinear operation but are mutually exclusive in Type I BBO OPOs.
• Tangential phase matching is the dominant effect for Type I BBO OPOs.
• Noncollinear operation is optimal for pump divergence of 4 mrad, yielding 37% slope efficiency and 5 mJ threshold with near-perfect tangential phase matching.
• Collinear operation is optimal for pump divergence < 2 mrad, yielding 33% slope efficiency and 3.2 mJ threshold.

Conclusions:

• The choice between collinear and noncollinear configurations depends critically on pump beam characteristics.
• Optimized phase matching is essential for achieving high performance in BBO OPOs.
• This study provides valuable insights for designing and operating efficient BBO OPOs for various applications.