Romanian Journal of Information Science and Technology (ROMJIST)

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ROMJIST is a publication of Romanian Academy,
Section for Information Science and Technology

Editor – in – Chief:

Academician Dan Dascalu

Secretariate (office):
Adriana Apostol
Adress for correspondence: romjist@nano-link.net (after 1st of January, 2019)

Editing of the printed version: Mihaela Marian (Publishing House of the Romanian Academy, Bucharest)

Technical editor
of the on-line version:
Lucian Milea (University POLITEHNICA of Bucharest)

Sponsors:
• National Institute for R & D
in Microtechnologies
(IMT Bucharest), www.imt.ro
• Association for Generic
and Industrial Technologies (ASTEGI), www.astegi.ro

ROMJIST Volume 24, No. 2, 2021, pp. 233-243, Paper no. 691/2021
 

R. REBIGAN, A. AVRAM, R. TUDOR, M. KUSKO, D. URSU, G. SOROHAN, C. KUSKO
Fabrication of Fresnel lenses operating as image correcting optical components for long infrared imaging systems

ABSTRACT: We present the technological processes required to fabricate silicon Fresnel lenses with sixteen discrete depth levels operating as corrector optical components for long infrared imaging systems. In order to configure the discrete surface of the lenses, four separated photolithographic processes each one of them followed by deep reactive ion etching were used. In order to detach the configured lenses presenting a disk like shape from the wafer, a DRIE Bosch deep etching process was employed. Finally, an antireflective layer consisting of a nanostructured surface was configured on both sides of the lenses in order to improve the transmission in LWIR spectral range. The geometrical parameters of the fabricated Fresnel lenses were determined by white light interferometry method and it was found that they are in good agreement with the design specifications. The optical and scanning electron microscopy measurements reveal a high quality of the optical surface with a low value of roughness. The spectral characteristics of the lenses in the LWIR spectral region reveal a transmission of above 70%.

KEYWORDS: Fresnel lens, long infrared optics, silicon microfabrication, photolithographic processes, reactive ion etching

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