Characterization of thermally poled germanosilicate thin films

Area of Science:

• Materials Science
• Photonics
• Nonlinear Optics

Background:

• Germanosilicate films are promising for electro-optic devices.
• Thermal poling is used to induce nonlinear optical properties in silica-based materials.
• Understanding nonlinearity profiles is crucial for device optimization.

Purpose of the Study:

• To measure and analyze the nonlinearity profile of thermally poled germanosilicate films.
• To investigate the effect of germanium on the nonlinearity profile and magnitude.
• To demonstrate a record nonlinear coefficient for potential electro-optic applications.

Main Methods:

• Deposition of germanosilicate films on fused-silica substrates using Plasma-Enhanced Chemical Vapor Deposition (PECVD).
• Thermal poling of the films under various conditions.
• Measurement of the nonlinearity profile using techniques to probe nonlinear optical coefficients.
• Optimization of poling parameters to maximize the nonlinear coefficient.

Main Results:

• The films exhibited a sharp peak in nonlinearity near the anode surface, followed by a pedestal.
• No sign reversal in nonlinearity was observed, unlike in undoped fused silica.
• A record peak nonlinear coefficient of approximately 1.6 pm/V was achieved.
• The results suggest slowed positive ion injection during poling.

Conclusions:

• Thermally poled germanosilicate films offer significantly enhanced nonlinear optical properties compared to undoped fused silica.
• The observed nonlinearity profile is advantageous for device fabrication and performance.
• These films represent a significant advancement for electro-optic device technology.