Linear and nonlinear optical properties of co-sputtered Ge-Sb-Se amorphous thin films

Area of Science:

• Materials Science
• Optics and Photonics
• Condensed Matter Physics

Background:

• Amorphous chalcogenide thin films are explored for nonlinear optical applications.
• Understanding the relationship between composition and nonlinear optical properties is crucial for device development.

Purpose of the Study:

• To investigate the linear and nonlinear optical properties of amorphous Ge-Sb-Se thin films.
• To determine optimal film compositions for future nonlinear optical integrated platforms.

Main Methods:

• Co-sputtering of GeSe4 and Sb2Se3 targets to create amorphous Ge-Sb-Se thin films.
• Ellipsometry was used to study linear optical properties.
• Sheik-Bahae's formalism was applied to estimate the Kerr coefficient and two-photon absorption coefficient.

Main Results:

• The Kerr coefficient was found to be in the range of 4.9–21 × 10⁻¹⁸ m²/W.
• Compositions of Ge7Sb25Se68 and Ge9Sb20Se71 exhibited high Kerr coefficients (10.1–13.4 × 10⁻¹⁸ m²/W).
• These compositions, near the (GeSe4)50(Sb2Se3)50 pseudo-binary, balance high nonlinearity with low optical losses.

Conclusions:

• Amorphous Ge-Sb-Se thin films, particularly Ge7Sb25Se68 and Ge9Sb20Se71, are promising candidates for nonlinear optical integrated platforms.
• The studied compositions offer a favorable trade-off between a high nonlinear Kerr coefficient and minimal two-photon absorption losses.
• These findings pave the way for advanced photonic devices utilizing chalcogenide materials.