Ultraviolet characterization of integrating spheres

Area of Science:

• Optical Engineering
• Materials Science
• Environmental Science

Background:

• Integrating spheres are crucial for optical measurements, particularly in the ultraviolet (UV) spectrum.
• Polytetrafluoroethylene (PTFE) is commonly used for integrating sphere coatings due to its reflective properties.

Purpose of the Study:

• To evaluate the performance of PTFE integrating spheres in the UV region (down to 200 nm).
• To identify and characterize contaminants affecting UV performance.
• To assess remediation strategies for contaminated integrating spheres.

Main Methods:

• Spectral throughput analysis of a PTFE integrating sphere using a deuterium lamp and monochromator.
• Investigation of UV laser-induced fluorescence within the integrating sphere.
• Analysis of contaminant effects and the efficacy of thermal baking for remediation.

Main Results:

• Significant absorption and fluorescence features were observed in the UV spectra of PTFE integrating spheres.
• Contamination by environmental pollutants, such as polycyclic aromatic hydrocarbons (PAHs), was identified as the cause.
• Thermal baking partially reversed the effects of contaminants but did not fully restore the sphere's original performance.

Conclusions:

• PTFE integrating spheres are susceptible to contamination by common environmental pollutants, impacting UV measurements.
• Baking can mitigate some contamination effects, but complete restoration of performance is not guaranteed.
• Careful consideration of potential contamination and its impact is essential for accurate UV measurements using integrating spheres.