Open AccessInfluence of diffraction by a rectangular aperture on the aspect ratio of femtosecond direct-write waveguides
Author(s) -
K. J. Moh,
Yun Tan,
Xiaocong Yuan,
D. K. Y. Low,
Z.L. Li
Publication year - 2005
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/opex.13.007288
Subject(s) - optics , diffraction , femtosecond , numerical aperture , aperture (computer memory) , curvature , radius of curvature , focus (optics) , focal length , ptychography , radius , materials science , gaussian , physics , wavelength , lens (geology) , laser , geometry , mathematics , computer science , acoustics , mean curvature , computer security , mean curvature flow , quantum mechanics
Rectangular apertures have been used as a simple means to approximate elliptical Gaussian beams in femtosecond direct writing systems to correct for the elongated focus inherent in low numerical aperture (NA) systems. In this work it is recognized that the rectangular aperture, more accurately functions as a diffractive element and hence redistributes the intensity gradient around the focus in accordance to the physical effects of diffraction. A diffractive model for the technique was proposed and confirmed experimentally to investigate the effects of diffraction and the extent of its influence on the focus shape over different conditions. It was found that because of diffraction, the radius of curvature for the leading edge of the focal spot is dissimilar from its trailing edge. However this effect is mitigated when lower processing energy is used and circular waveguides can be obtained.