Comparison of the vectorial diffraction theory and Fraunhofer approximation method on diffractive images of Fresnel zone plates

AbstractFocusing systems with high numerical aperture can be used to convert spin angular momentum into orbital angular momentum with efficiencies of 50%, while for low numerical apertures this conversion vanishes. In this paper, based on the properties of binary Fresnel zone plates, we propose a structure that is achieved by making an accurate selection of the width and the depth of the rings. This allows us to obtain a large increase in the spin to orbital angular momentum conversion of the resulting focusing fields, and it also has the special characteristic that the obtained conversion is higher for low numerical aperture structures, where standard focusing systems do not work. The ability of the system to perform this extraordinary conversion is demonstrated by FDTD methods and an analytical model developed using a combination of guided mode theory for the structure and Stratton–Chu diffraction theory.

Download Full-text

Extraordinary Spin to Orbital Angular Momentum Conversion on Guided Zone Plates

10.21203/rs.3.rs-190268/v1 ◽

2021 ◽

Author(s):

Pablo Acebal ◽

Luis Carretero ◽

Salvador Blaya

Keyword(s):

Angular Momentum ◽

Orbital Angular Momentum ◽

Fresnel Zone ◽

Numerical Aperture ◽

Diffraction Theory ◽

Fresnel Zone Plates ◽

Zone Plates ◽

Guided Mode ◽

Fdtd Methods ◽

Selection Of

Abstract Focusing systems with high numerical aperture can be used to convert spin angular momentum into orbital angular momentum with efficiencies of 50%, while for low numerical apertures this conversion vanishes. In this paper, based on the properties of binary Fresnel zone plates, we propose a structure that is achieved by making an accurate selection of the width and the depth of the rings. This allows us to obtain a large increase in the spin to orbital angular momentum conversion of the resulting focusing fields, and it also has the special characteristic that the obtained conversion is higher for low numerical aperture structures, where standard focusing systems do not work. The ability of the system to perform this extraordinary conversion is demonstrated by FDTD methods and an analytical model developed using a combination of guided mode theory for the structure and Stratton-Chu diffraction theory.

Download Full-text

Diffraction Theory of Fresnel Zone Plates

Journal of the Optical Society of America ◽

10.1364/josa.58.001536 ◽

1968 ◽

Vol 58 (11) ◽

pp. 1536 ◽

Cited By ~ 10

Author(s):

Henri Arsenault

Keyword(s):

Fresnel Zone ◽

Diffraction Theory ◽

Fresnel Zone Plates ◽

Zone Plates

Download Full-text

Nanometer focusing properties of Fresnel zone plates described by dynamical diffraction theory

Physical Review B ◽

10.1103/physrevb.73.245331 ◽

2006 ◽

Vol 73 (24) ◽

Cited By ~ 39

Author(s):

F. Pfeiffer ◽

C. David ◽

J. F. van der Veen ◽

C. Bergemann

Keyword(s):

Fresnel Zone ◽

Diffraction Theory ◽

Fresnel Zone Plates ◽

Dynamical Diffraction ◽

Zone Plates ◽

Focusing Properties

Download Full-text

Analysis of Predistortion Techniques on Fresnel Zone Plates in Ultrasound Applications

Sensors ◽

10.3390/s21155066 ◽

2021 ◽

Vol 21 (15) ◽

pp. 5066

Author(s):

José Miguel Fuster ◽

Sergio Pérez-López ◽

Francisco Belmar ◽

Pilar Candelas

Keyword(s):

Intensity Distribution ◽

Fresnel Zone ◽

Focal Depth ◽

Acoustic Intensity ◽

Fresnel Zone Plates ◽

Therapeutic Applications ◽

Zone Plates ◽

Ultrasound Applications

In this work, we analyze the effect of predistortion techniques on the focusing profile of Fresnel Zone Plates (FZPs) in ultrasound applications. This novel predistortion method is based on either increasing or decreasing the width of some of the FZP Fresnel rings by a certain amount. We investigate how the magnitude of the predistortion, as well as the number and location of the predistorted rings, influences the lens focusing profile. This focusing profile can be affected in different ways depending on the area of the lens where the predistortion is applied. It is shown that when the inner area of the lens, closer to its center, is predistorted, this technique allows the control of the focal depth at the main focus. However, when the predistortion is applied to an area farther from the center of the lens, the acoustic intensity distribution among the main focus and the closest adjacent secondary foci can be tailored at a certain degree. This predistortion technique shows great potential and can be used to control, modify and shape the FZP focusing profile in both industrial and therapeutic applications.

Download Full-text