Optical constants of far infrared materials. 3: plastics

Area of Science:

• Materials Science
• Optics
• Polymer Science

Background:

• Accurate optical constants are crucial for designing optical systems and understanding material interactions with electromagnetic radiation.
• Plastic materials are increasingly used in optical applications, necessitating detailed characterization.
• Data for many polymers in the far-infrared spectral range (50-350 cm⁻¹) is limited.

Purpose of the Study:

• To measure and report the room temperature optical constants (refractive index and absorption coefficient) of several plastic materials.
• To provide a dataset for high-density polyethylene, TPX, Aclar, Kapton, Surlyn, and Mylar in the 50-350 cm⁻¹ spectral range.
• To investigate the influence of manufacturing processes (e.g., stretching leading to birefringence) on optical properties.

Main Methods:

• Optical constants were measured at room temperature over the 50-350 cm⁻¹ spectral range.
• Refractive index was determined using reflection measurements and analyzing channeled spectra.
• Absorption coefficients were derived from transmission measurements for most materials, with polyethylene being an exception.

Main Results:

• Room temperature optical constants were successfully measured for high-density polyethylene, TPX, Aclar, Kapton, Surlyn, and Mylar.
• Birefringence was observed in sheet materials (except TPX) due to manufacturing-induced stretching.
• Average optical constants are reported for each material, accounting for birefringence.

Conclusions:

• The study provides valuable optical constant data for common plastic materials in the far-infrared region.
• The reported data can aid in the selection and application of these polymers in optical devices.
• Understanding the impact of manufacturing processes on optical properties is essential for material characterization.