Measurement of third-order optical nonlinear susceptibility using four-wave mixing in a single-mode ridge waveguide

Area of Science:

• Nonlinear optics
• Quantum well physics
• Semiconductor device characterization

Background:

• Third-order nonlinear susceptibility (χ(3)) is crucial for nonlinear optical phenomena.
• Accurate measurement of both the imaginary (Im χ(3)) and absolute magnitude (|χ(3)|) components is challenging.
• AlGaAs/GaAs quantum-well waveguides are promising for integrated photonic devices.

Purpose of the Study:

• To develop a simultaneous measurement technique for Im χ(3) and |χ(3)|.
• To apply this technique to AlGaAs/GaAs quantum-well waveguides.
• To investigate the nonlinear optical properties and identify dominant absorption mechanisms.

Main Methods:

• Utilizing nondegenerate four-wave mixing in a single-mode ridge waveguide.
• Measuring pump-induced probe power loss to determine Im χ(3).
• Deriving |χ(3)| from Stokes wave generation efficiency.

Main Results:

• Simultaneous measurement of Im χ(3) and |χ(3)| achieved with high precision.
• For AlGaAs/GaAs waveguides and picosecond pulses (photon energy ~1.43 eV): Im χ(3) = (6.1 ± 0.5) × 10⁻¹¹ esu and |χ(3)| = (7.6 ± 1.7) × 10⁻¹¹ esu.
• The ratio Im χ(3)/|χ(3)| = 0.8 ± 31%, indicating significant two-photon absorption.

Conclusions:

• The demonstrated four-wave mixing technique enables precise simultaneous measurement of nonlinear susceptibility components.
• Two-photon absorption is a dominant nonlinear process in these AlGaAs/GaAs quantum-well waveguides.
• This method offers a robust approach for characterizing nonlinear optical materials and devices.