Infrared optical glasses for applications in 8-12-microm thermal imaging systems.

Area of Science:

• Materials Science
• Solid State Chemistry
• Optical Materials

Background:

• Chalcogenide glasses, specifically Germanium-Arsenic-Selenium (Ge-As-Se) systems, are crucial for infrared optical applications.
• Understanding their thermophysical and optical properties is essential for material selection and device fabrication.
• Oxide impurities can significantly degrade the optical performance of these glasses.

Purpose of the Study:

• To measure and analyze key physical properties of Ge-As-Se glasses, including glass transition temperature, thermal expansion coefficient, and refractive index.
• To investigate the relationship between these properties and the reciprocal dispersive power in the mid-infrared range (8-12 microm).
• To identify suitable Ge-As-Se glass compositions for bulk synthesis and assess the impact of oxide impurities on optical transmission.

Main Methods:

• Synthesis of Ge-As-Se glasses using advanced preparation techniques to achieve low oxide content (<1 ppm wt).
• Characterization of thermophysical properties: glass transition temperature (Tg) and thermal expansion coefficient (CTE).
• Measurement of optical properties: refractive index (n) and reciprocal dispersive power (Vd) in the 8-12 microm range.
• Analysis of oxide impurity levels using gamma photon activation analysis (GPAA).
• Spectroscopic analysis to determine the influence of oxide impurities on optical transmission.

Main Results:

• Comprehensive data on glass transition temperature, thermal expansion coefficient, and refractive index for various Ge-As-Se compositions.
• A defined range of reciprocal dispersive power (110-159) between 8-12 microm, correlated with basic physical properties.
• Identification of specific Ge-As-Se compositions suitable for bulk synthesis.
• Demonstration of the detrimental effect of oxide impurities on the optical transmission of Ge-As-Se glasses, exemplified by Ge2O-Se80, As40-Se60, and Ge30-As15-Se55.

Conclusions:

• The study successfully characterized Ge-As-Se glasses, providing valuable data for material selection in optical applications.
• Optimal compositions for bulk synthesis were identified based on the relationship between physical properties and optical performance.
• Minimizing oxide impurities is critical for achieving high optical transmission in Ge-As-Se based infrared materials.