Orbital angular momentum sidebands in second harmonic generation of a vortex beam by a nonlinear crystal with inhomogeneous refractive index

Sabouri, Saeed Ghavami

doi:10.1088/2040-8986/ac6960

Cited by 3 publications

(2 citation statements)

References 39 publications

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“…The fork element should be an array of positive numbers in the range of [0, 1] and be able to produce superposed vortex beams with high fidelity. First of all, the hologram h(x, y) of each LG basis mode of a superposition, is designed in the form of [31]: (8) where, a(x, y) is the normalized amplitude distribution, and (u 0 , v 0 ) are the spatial frequencies of the periodic grating. Secondly, to associate the phase of modal coefficient θ ℓ with the related basis LG mode, we develop equation (8) which is given by:…”

Section: Resultsmentioning

confidence: 99%

“…They carry orbital angular momentum (OAM) with a phase of the form e iℓφ , where φ is the azimuthal angle, and ℓ is the helicity or topological charge [3,4]. They have found numerous applications in a variety of optical systems, such as material processing [5], optical tweezers [6], micromanipulation [7], nonlinear frequencyconversion processes [8,9], and optical communications [10,11]. Multiplexing OAM modes enables high-capacity optical communication.…”

Section: Introductionmentioning

confidence: 99%

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The measurement of complex modal coefficients of a superposed vortex beam based on intensity sampling methods

Mohagheghian,

Ghavami Sabouri

2024

J. Opt.

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In recent years, extracting information from superposed vortex beams has been a topic of intense study. In this paper, complex coefficients of various superpositions are measured in both simulation and experiment by proposing and implementing four different sampling methods. Superposed vortex beams are experimentally generated using a digital micromirror device, and recorded on a 2 f optical imaging setup. To extract both amplitude and phase values of modal coefficients, a single intensity frame of the beam is sampled in the form of concentric circles, sectors, random circles, and random squares. Considering just specified parts of the intensity instead of the whole to sample the pattern increases the speed of the modal coefficient extraction. Besides, a linear set of coherent equations is solved, and achievements are compared together. As a consequence, measuring both the amplitude and phase values of coefficients simultaneously can pave the way to enable high-capacity optical communication which is carried out in this research with better than 99% and 96% accuracy, respectively.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The measurement of complex modal coefficients of a superposed vortex beam based on intensity sampling methods

Mohagheghian,

Ghavami Sabouri

2024

J. Opt.

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A perspective on the manipulation of orbital angular momentum states in nonlinear optics

Chen

et al. 2023

Applied Physics Letters

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Orbital angular momentum (OAM) of light has been widely investigated in optical manipulation, optical communications, optical storage, and precision measurement. In recent years, the studies of OAM are expanded to nonlinear and quantum optics, paving a way to high-quality nonlinear imaging, high-capacity quantum communication, and many other promising applications. In this Perspective, we first summarize the fundamental research on OAM in nonlinear optics. Then, we introduce its recent applications in nonlinear imaging (including nonlinear spiral imaging and OAM-multiplexing nonlinear holography) and high-dimensional quantum entanglement. In particular, we highlight the manipulations of OAM through various functional nonlinear photonic crystals. Finally, we discuss the further developments of OAM-based nonlinear and quantum techniques in the near future.

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Harnessing physics-guided neural networks for tailoring the orbital angular momentum spectrum in second harmonic generation

Ghavami Sabouri,

Sadat Hashemi

2024

Appl. Opt.

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The management of orbital angular momentum (OAM) in frequency conversion processes is essential for numerous applications such as quantum and classical optical communications. This paper presents a wavefront modulation approach for the fundamental beam in second harmonic generation (SHG) to efficiently control the OAM spectrum. We employ an inverse design method to derive the necessary wavefront shape of the fundamental beam for achieving a desired SHG OAM spectrum. Specifically, we introduce an efficient inverse design technique based on physics-guided neural networks (PGNNs) that incorporates the coupled equations governing SHG, aimed at tailoring the OAM spectrum of SHG. Utilizing the proposed PGNN, we design the phase pattern for a spatial light modulator (SLM) to shape the wavefront of the fundamental beam. Furthermore, we present a novel loss function, to our knowledge, that effectively links the OAM of the SHG spectrum and efficiency to the SLM phase pattern and crystal temperature, independent of empirical weight coefficients. The proposed PGNN facilitates the purification of the SHG OAM spectrum, even when the fundamental beam comprises mixed Laguerre–Gaussian (LG) modes. Additionally, we demonstrate the generation of desired SHG spectra using the proposed PGNN framework. This study introduces what we believe to be a groundbreaking inverse design method for developing photonic devices with customized functionalities, addressing challenges associated with traditional data-driven deep learning techniques.

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Orbital angular momentum sidebands in second harmonic generation of a vortex beam by a nonlinear crystal with inhomogeneous refractive index

Cited by 3 publications

References 39 publications

The measurement of complex modal coefficients of a superposed vortex beam based on intensity sampling methods

The measurement of complex modal coefficients of a superposed vortex beam based on intensity sampling methods

A perspective on the manipulation of orbital angular momentum states in nonlinear optics

Harnessing physics-guided neural networks for tailoring the orbital angular momentum spectrum in second harmonic generation

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