Efficiency signal conversion parameter to evaluate astigmatic femtosecond-optical parametric oscillator cavities

Area of Science:

• Nonlinear Optics
• Laser Physics
• Optical Engineering

Background:

• Femtosecond-Optical Parametric Oscillators (fs-OPO) are crucial for generating tunable ultrashort laser pulses.
• Evaluating fs-OPO cavity efficiency, especially considering optical aberrations like astigmatism, is essential for performance optimization.
• Existing methods may not fully capture the complex interplay of parameters affecting fs-OPO efficiency.

Purpose of the Study:

• To define and validate a novel numerical parameter, V_eff, for evaluating fs-OPO cavity efficiency.
• To introduce a new metric, pump energy threshold per crystal unit length (ζ_p,th), for characterizing fs-OPO performance.
• To experimentally demonstrate high-efficiency fs-OPO cavities with tunable output.

Main Methods:

• Development of the V_eff parameter based on ABCD matrix Gaussian beam propagation.
• Incorporation of astigmatism effects into the beam propagation model to calculate pump-signal mode coupling.
• Experimental fabrication and testing of singly resonant fs-OPO ring cavities using MgO:PPLN crystals.

Main Results:

• The V_eff parameter was successfully defined and validated through experimental measurements.
• Demonstrated high-efficiency fs-OPO cavities with signal tunability from 1.1 µm to 1.6 µm.
• Achieved a record low pump threshold of 142 mW (ζ_p,th = 2.10 nJ/mm) by optimizing V_eff.

Conclusions:

• The V_eff parameter provides a reliable method for evaluating and optimizing fs-OPO cavity efficiency, including astigmatism.
• The developed ABCD matrix model accurately predicts mode coupling and cavity performance.
• The study presents a pathway to achieving lower pump thresholds and higher efficiencies in fs-OPO systems.