An anti-reflection coating for silicon optics at terahertz frequencies

Author

Gatesman, A.J. ; Waldman, J. ; Ji, M. ; Musante, C. ; Yagvesson, S.

Author_Institution

Submillimeter Wave Technol. Lab., Massachusetts Univ., Lowell, MA, USA

Volume

10

Issue

7

fYear

2000

fDate

7/1/2000 12:00:00 AM

Firstpage

264

Lastpage

266

Abstract

A method for reducing the reflections from silicon optics at terahertz frequencies has been investigated. In this study, we used thin films of parylene as an anti-reflection (AR) layer for silicon optics and show low-loss behavior well above 1 THz. Transmittance spectra are acquired on double-sided-parylene-coated, high-resistivity, single-crystal silicon etalons between 0.45 THz and 2.8 THz. Modeling the optical behavior of the three-layer system allowed for the determination of the refractive index and absorption coefficient of parylene at these frequencies. Our data indicate a refractive index, n, of 1.62 for parylene C and parylene D, and a reasonably modest absorption coefficient make these materials a suitable AR coating for silicon at terahertz frequencies. Coatings sufficiently thick for AR performance reduced the average transmittance of the three-layer system by <10% compared to a lossless AR coating with an ideal refractive index

Keywords

antireflection coatings; electromagnetic wave interferometers; microwave photonics; organic compounds; refractive index; silicon; submillimetre wave devices; thin films; 0.45 to 2.8 THz; Si; THF Si optics; absorption coefficient; anti-reflection coating; double-sided-parylene-coated Si etalons; high-resistivity Si etalons; low-loss behavior; optical behavior modelling; parylene AR layer; parylene C; parylene D; parylene thin film; refractive index; single-crystal Si etalons; terahertz frequencies; three-layer system; Absorption; Coatings; Frequency; Optical films; Optical reflection; Optical refraction; Optical variables control; Refractive index; Semiconductor thin films; Silicon;

fLanguage

English

Journal_Title

Microwave and Guided Wave Letters, IEEE

Publisher

ieee

ISSN

1051-8207

Type

jour

DOI

10.1109/75.856983

Filename

856983