Today, reminder: STI Seminar IN PERSON & online: Tuesday. 6 September 2022 at 3 pm (Rome time)

[STI Secretariat]

_____________

STI seminar
___________


You are most cordially invited to a seminar organized by the ICTP 
Science Technology and Innovation Unit (STI Unit)

** * * Tuesday, 6 September 2022 at 15:00 (Rome/CEST time) *** * *

*- in person: Fibonacci Lecture Room, ICTP Galileo Guesthouse, entrance 
level

- via Zoom: Link to advanced 
registrationhttps://zoom.us/meeting/register/tJUtf-GsrT4oGNfSqZQwev-izOAh_FVpFubT/
/After registering, you will receive a confirmation email containing 
information about joining the seminar.


Speaker: *Saifollah RASOULI, *Institute for Advanced Studies in Basic 
Sciences (IASBS), Zanjan, Iran

Title:***Radial carpet and combined half-integer Bessel-like beams: 
generation, properties, and applications*


_Abstract_
Structured beams, whose intensity, phase, or polarization profiles have 
very complex structures, are attracting major attention and presenting 
various applications in many areas of optics. We have recently reported 
the observation of a new class of accelerating, self-healing, 
non-diffracting, and shape invariant beams, have numerous phase 
anomalies and unprecedented patterns, and can be feasibly tuned. In the 
diffraction of a plane wave from radial amplitude/phase gratings such 
beams are generated, and due to the beauty and structural complexity of 
the generated beams, we named them “radial carpet beams” (RCBs). In this 
talk, a report on the recent studies we have done on the RCBs will be 
presented. In the diffraction of a plane wave from an amplitude radial 
grating we have shown that the boundaries of geometric shadow, near- and 
far-field diffraction regimes to be curved. It is also shown that the 
Talbot carpet can be generated at the transverse plane in the 
diffraction of a plane wave from an amplitude radial grating. In 
addition, we introduce "diffraction-based rainbow" in the diffraction of 
a collimated white light wavefront from a radial grating, and formation 
of colorful radial Talbot carpet at the transverse plane is also 
investigated. An exceptional sample for the spectrum-invariant 
propagation is also presented. An azimuthally-modified linear phase 
grating is also introduced and generation of varied radial carpet beams 
over the different diffraction orders with controlled intensity sharing 
among the generated beams is presented. Existence of the self-imaging in 
the polar coordinates for the azimuthally periodic Bessel-based 
structures is proved. We also consider a family of solutions of the 
homogeneous free-space scalar wave equation, and we named them “combined 
half-integer Bessel-like beams” which are determined by linear 
combinations of the half-integer order Bessel functions. It is shown 
that, this family of beams satisfies a “radial structured” boundary 
condition at z = 0 plane, therefore they can be produced by the 
diffraction of a plane wave from suitable “radial structures.” The use 
of RCBs for "multiple particle trapping" is presented. This type of 
trapping is very versatile, yet cheap and simple. We also investigate 
and compare the propagation of Laguerre-Gaussian (LG) and RCBs through 
an indoor convective air turbulence and atmospheric turbulence under 
weak to strong turbulence conditions. We show that, under the same 
turbulence conditions, the RCB experiences less disturbance and is more 
resilient to the turbulence, especially when it has a complicated 
structure. It is also shown that a set of RCBs having different values 
of the main intensity spots can be used as an orthogonal bases for the 
free-space optical communication. Finally, the strength of the 
self-healing of RCBs is quantified in terms of the beams’ specifications.


-- 
Nicoletta Ivanissevich (Ms.)
Secretariat,
STI - Science, Technology and Innovation Unit
The Abdus Salam International Centre for Theoretical Physics
Strada Costiera, 11
I-34151 Trieste
Italy

Phone: +39-040-2240.383
STI Webpage:https://www.ictp.it/research/sti.aspx
Email:sti at ictp.it

--