arXiv subjects

Mo Mojahedi

Publications and source records attributed to Mo Mojahedi.

7 recordsLinked to original sources

arXiv2026

Structured light sheets

In this work, we present a simple, exact, and fully analytical method for generating light sheets parallel to the propagation direction, with amplitude and phase envelopes structured on demand. We validate the approach theoretically and experimentally by imprinting images onto light sheets, and we compare the theoretical performance with that obtained using an alternative strategy based on arrays of Frozen Waves (FWs). In this context, the proposed method provides a more direct and flexible control of the field envelopes on the light sheets, resulting in higher-fidelity reconstructions than those achieved with FW-based approaches. The method thus offers a versatile framework for structured light-sheet generation, with potential applications in optical manipulation, microscopy, and 3D holographic imaging.

physics.optics↗

arXiv2023

Creating Light-Made Waveguides with Structured Optical Beams in Nonlinear Kerr Media

While in linear optics the subject of structured light has been a fruitful field of both theoretical and applied research, its development in the arena of nonlinear optics has been underexplored. In this paper, we construct Frozen-Wave-type structured optical beams in Kerr nonlinear media, emphasizing the self-defocusing case, and use them to guide and control Gaussian optical beams. The results presented in this study support the expectation that structured light in nonlinear media can open new venues of theoretical research and applications, particularly in the realms of light controlling light and for all-optical photonics.

physics.optics↗

arXiv2018

Fusion Between Frozen-Wave-Type Beams and Airy-Type Pulses: Diffraction-Dispersion-Attenuation Resistant Vortex Pulses in Absorbing Media

In this paper we perform a fusion between two important theoretical methodologies, one related to the Frozen Wave beams, which are non-diffracting beams whose longitudinal intensity pattern can be chosen a priori in an medium (absorbing or not), and the other related to the Airy-Type pulses, which are pulses resistant to dispersion effects in dispersive materials. As a result, a new method emerges, capable of providing vortex pulses resistant to three concomitant effects, i.e.: diffraction, dispersion and attenuation; while concurrently the spatial variation of the wave intensity along its axis of propagation can be engineered at will. The new approach can be seen as a generalization of the Localized Waves theory in the paraxial regime and the new pulses can have potential applications in different fields such as optics communications, nonlinear optics, micromanipulation, and so on.

physics.optics↗

arXiv2018

Evolution of orbital angular momentum in three-dimensional structured light

Light beams with an azimuthal phase dependency of $e^{i\ellϕ}$ have helical phase fronts and thus carry orbital angular momentum (OAM), a strictly conserved quantity with propagation. Here, we engineer quasi three-dimensional (3D) structured light fields and demonstrate unusual scenarios in which OAM can vary locally in both sign and magnitude along the beam's axis, in a controlled manner, under free-space propagation. To reveal the underlying mechanisms of this phenomenon, we perform full modal decomposition and reconstruction of the generated beams to describe the evolution of their intrinsic OAM and topological charge with propagation. We show that topological transition and the associated variation in local OAM rely on the creation, movement, and annihilation of local vortex charges without disturbing the global net charge of the beam, thus conserving the global OAM while varying it locally. Our results may be perceived as an experimental demonstration of the Hilbert Hotel paradox, while advancing our understanding of topological deformations in general.

physics.optics↗

arXiv2017

Arbitrary control of the polarization and intensity profiles of diffraction-attenuation-resistant beams along their propagation direction

We report on the theory and experimental generation of a class of diffraction-attenuation-resistant beams with state of polarization (SoP) and intensity that can be controlled on demand along the propagation direction. This is achieved by a suitable superposition of Bessel beams, whose parameters are systematically chosen based on closed-form analytic expressions provided by the Frozen Waves (FWs) method. Using an amplitude-only spatial light modulator, we experimentally demonstrate three scenarios. In the first, the SoP of a horizontally polarized beam evolves to radial polarization and is then changed to vertical polarization, with the beam intensity held constant. In the second, we simultaneously control the SoP and the longitudinal intensity profile, which was chosen such that the beam's central ring can be switched-off over predefined space regions, thus generating multiple foci with different SoP and at different intensity levels along the propagation. Finally, the ability to control the SoP while overcoming attenuation inside lossy fluids is shown experimentally for the first time in the literature (to the best of our knowledge). Therefore, we envision our proposed method to be of great interest for many applications, such as optical tweezers, atom guiding, material processing, microscopy, and optical communications.

physics.optics↗

arXiv2016

An Efficient and Compact Excitation of Surface Plasmons Using a Si Gable Tip

We propose a novel technique to efficiently excite a surface plasmon polariton (SPP) mode at a gold-glass interface by exploiting the near field excitation of an engineered high index (silicon) gabled tip at the telecom wavelengths. The proposed structure can theoretically convert 49% of the input optical power to a SPP mode. The device is compact, it will facilitate the on-chip excitation of the SPP, its fabrication is compatible with the standard Si fabrication processes, and as such, it is expected to be useful in the design of future integrated sensors.

physics.optics↗

arXiv2016

Longitudinal patterning of twisted light

Light beams with azimuthal phase dependence [$exp(i \ellϕ)$] carry orbital angular momentum (OAM) which differs fundamentally from spin angular momentum (SAM) associated with polarization. Striking difference between the two momenta is manifested in the allowable values: where SAM is limited to $\hbar k_0$ per photon, the OAM has unbounded value of $\ell\hbar$ per photon ($\ell$ is integer), thus dramatically exceeding the value of SAM \cite{Ref1,Ref2, Ref3}. OAM has thus been utilized in optical trapping \cite{Ref4}, imaging\cite{Ref2}, and material processing \cite{Ref5}. Furthermore, the unbounded degrees-of-freedom in OAM states have been deployed in data communications \cite{Ref6}. Here, we report an \textit{exceptional} behavior for a class of light beams---known as Frozen Waves (FWs)---whose intensity and azimuthal phase profiles can be controlled along the propagation direction, at will. Accordingly, we generate rotating light patterns that can change their sense of rotation and order of phase twist with propagation. Manipulating OAM along the beam axis can open new directions in optical science and its applications.

physics.optics↗