Refractive index database

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Optical constants of (C10H8O4)n (Polyethylene terephthalate, PET)
Zhang et al. 2020: n,k 0.4–20 µm

Wavelength: µm

Complex refractive index (n+ik)[ i ]

n   k   LogX   LogY   eV

Derived optical constants

Conditions & Spec sheet

n_is_absolute: true
wavelength_is_vacuum: false


Normal temperature and pressure. Manufacturer: Chenghang plastic material, China.


1) X. Zhang, J. Qiu, X. Li, J. Zhao, L. Liu. Complex refractive indices measurements of polymers in visible and near-infrared bands, Appl. Opt. 59, 2337-2344 (2020) (0.4-2 µm)
2) X. Zhang, J. Qiu, J. Zhao, X. Li, L. Liu. Complex refractive indices measurements of polymers in infrared bands, J. Quant. Spectrosc. Radiat. Transf. 252, 107063 (2020) (2-20 µm)


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Polyethylene terephthalate (PET), (C10H8O4)n

Polyethylene terephthalate (PET, (C10H8O4)n) is a widely-used thermoplastic polymer that manifests as a clear, strong, and lightweight material. Recognized for its transparency, PET is predominantly employed in the manufacture of plastic bottles for beverages and other liquids, as well as in packaging films for food. Beyond its vast presence in the packaging sector, PET's inherent strength and ease of molding make it a prime candidate for textile fibers, known commercially as "polyester". In optical applications, PET’s clarity, combined with its ability to be precisely molded, lends itself to the production of optical films and lenses. Its excellent barrier properties against oxygen and carbon dioxide also mean that PET is highly favored in the food and beverage industry to maintain product freshness. Moreover, its high mechanical strength, dimensional stability, and resistance to moisture further cement PET's reputation as a versatile and reliable material in diverse applications. The refractive properties of PET can be attributed to its molecular structure, where the repeating units play a significant role in determining its optical characteristics.

Other names

  • PETE
  • poly(ethylene terephthalate)
  • poly(oxyethyleneoxyterephthaloyl)
  • PETP (obsolete abbreviation)
  • PET-P (obsolete abbreviation)


  • Terylene
  • Lavsan
  • Dacron

External links