Terahertz characterization Microcellular Polyethylene Terephthalate (MCPET) across broad temperature range

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Abstract The optical properties of Microcellular Polyethylene Terephthalate (MCPET) towards light and terahertz waves were compared. Within the measurement range of 0.3–1.3 THz and 30 K to room temperature, the refractive index remained nearly constant at approximately 1.15, close to 1. It was observed that MCPET with a thickness of 0.5 mm transmits over 70% of terahertz waves, while blocking more than 99.9% of light in the 300–2000 nm range. These findings present significant advantages for the design of optical devices using MCPET, highlighting its potential for selective transparency and high opacity in specific applications.