International Journal of Optics and Photonics
IJOP
Basic Sciences
http://ijop.ir
1
admin
1735-8590
2538-4007
10.52547/ijop
1735-8590
en
jalali
1399
9
1
gregorian
2020
12
1
14
2
online
1
fulltext
en
Fresnel Diffraction from Phase Steps and Its Applications
عمومى
General
پژوهشي
Research
The well-established Fresnel diffraction occurs as an opaque object partially obstructs the passage of a coherent beam of light. In this process, the amplitude of the optical wave experiences a discontinuous change that leads to peculiar bright and dark fringes near the ray optics border of the beam. The fringe pattern varies very slowly by distance from the object and away from the beam border the diffraction effect is negligible. These behaviors have limited the applications of the conventional Fresnel diffraction very severely. In this article, we introduce a new kind of Fresnel diffraction that occurs due to discontinuous change in phase or phase gradient, in a part of a coherent beam of light. The change splits the beam into two diffracting wavefronts with common border that interfere with each other. In this kind of diffraction, the fringes may appear in the central part of the beam and their locations and visibilities are very sensitive to the phase change. Therefore, the researchers have utilized the effect in the measurements of different physical quantities, with high accuracy, using modest equipment. In this article, we use the Fresnel diffraction from the semi-infinite opaque screen (knife- edge) as the building block to describe the introduced effect, diffraction from the phase steps, and discuss its different aspects. We simulate the implied diffraction patterns, investigate the patterns by experiments, elaborate on the unique features of the effect, and present some interesting applications.
Fresnel diffraction, phase step, physical optics, metrology,
195
208
http://ijop.ir/browse.php?a_code=A-10-738-1&slc_lang=en&sid=1
Mohammad Taghi
Tavassoly
Tavassoly@ut.ac.ir
10031947532846003484
10031947532846003484
Yes
Department of Physics, College of Science, University of Tehran, Kargar Shomali Avenue, Tehran 14399-55961, Iran
Hamid
Salvdari
salvdari@ut.ac.ir
10031947532846003485
10031947532846003485
No
Department of Physics, Ilam branch, Islamic Azad University, Ilam, Iran