Open AccessHybrid micro-optical elements by laser-based fabrication of Fresnel lenses on the end face of gradient index lenses
Author(s) -
Thomas Fricke-Begemann,
J. Ihlemann
Publication year - 2018
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.26.023751
Subject(s) - optics , materials science , lens (geology) , gradient index optics , laser , numerical aperture , fabrication , focal length , fresnel lens , fresnel zone , wavelength , refractive index , physics , diffraction , medicine , alternative medicine , pathology
Fresnel lenses are fabricated directly upon the end face of gradient index (GRIN) lenses by F 2 -laser machining at 157 nm wavelength. The employed laser processing technique combines a mask projection configuration at 25-x demagnification with a rotation of the structured lens. The ablation characteristics of the GRIN materials require very high pulse fluences with typical values above 7 J/cm 2 . Topography measurements on the Fresnel lenses reveal a good contour accuracy with residual deviations from the design profile well below 100 nm. Such hybrid optical elements, combining GRIN lenses with diffractive lenses in one element, can serve as the basis for high-performance micro-optical imaging systems with diameters up to 2 mm. Examples of possible applications include imaging sensors like proximity sensors or color-corrected microscope objectives with high numerical aperture for endoscopy applications.