Random quasi-phase-matching in bulk polycrystalline isotropic nonlinear materials

Area of Science:

• Nonlinear optics
• Materials science

Background:

• Three-wave mixing in nonlinear materials generates new optical frequencies but suffers from poor conversion yield due to phase mismatch.
• Phase mismatch arises from optical dispersion, limiting the efficiency in isotropic nonlinear materials.

Purpose of the Study:

• To demonstrate an effective strategy for achieving efficient phase matching in isotropic nonlinear materials.
• To introduce and characterize the 'random quasi-phase-matching' approach.

Main Methods:

• Exploiting the random motion of relative phases in highly transparent polycrystalline materials.
• Investigating the properties of random quasi-phase-matching in isotropic media.

Main Results:

• Achieved efficient phase matching in isotropic materials using random quasi-phase-matching.
• Demonstrated a linear dependence of conversion yield with sample thickness.
• Showed the absence of requirements for preferential material orientation or specific polarization rules.

Conclusions:

• Random quasi-phase-matching is an effective strategy for enhancing optical conversion efficiency in isotropic nonlinear materials.
• This approach offers advantages such as thickness-dependent conversion yield and relaxed material/polarization constraints.
• The polycrystalline grain size exhibits a wavelength-dependent resonance, influencing the process.