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3 pages, 155 KiB

Open AccessEditorial

Introduction to the Special Issue on Coherent and Polarization Optics

by Yongtao Zhang and Jiayi Yu

Photonics 2024, 11(1), 50; https://doi.org/10.3390/photonics11010050 - 3 Jan 2024

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Abstract

Both coherence and polarization are important inherent properties of light [...] Full article

(This article belongs to the Special Issue Coherent and Polarization Optics)

Research

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18 pages, 4634 KiB

Open AccessArticle

Powerful Elliptically Polarized Terahertz Radiation from Oscillating-Laser-Driven Discharge Surface Currents

by Egor Dmitriev, Nikolai Bukharskii and Philipp Korneev

Photonics 2023, 10(7), 803; https://doi.org/10.3390/photonics10070803 - 11 Jul 2023

Cited by 3 | Viewed by 1585

Abstract

This work presents a general concept of an intense laser-driven source of strong electromagnetic waves, which can be used for obtaining powerful terahertz radiation with controlled polarization. It is shown that the irradiation of a solid target surface by short relativistic laser pulses [...] Read more.

This work presents a general concept of an intense laser-driven source of strong electromagnetic waves, which can be used for obtaining powerful terahertz radiation with controlled polarization. It is shown that the irradiation of a solid target surface by short relativistic laser pulses at small angles provides the excitation of strong compact relativistic discharge current pulses, propagating in a certain direction. For elliptical targets, this current emits elliptically polarized electromagnetic radiation at a given frequency with the ellipticity and the spectra defined by the target geometry. The proposed setup allows reaching extreme THz intensities and provides easy control of the radiation parameters, making it attractive for various scientific and technological applications. Full article

(This article belongs to the Special Issue Coherent and Polarization Optics)

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11 pages, 2153 KiB

Open AccessArticle

Two-Dimensional Polarization Holographic Gratings in Azopolymer Thin Films: Polarization Properties in the Presence or Absence of Surface Relief

by Georgi Mateev, Lian Nedelchev, Ludmila Nikolova, Branimir Ivanov, Velichka Strijkova, Elena Stoykova, Kihong Choi, Joongki Park and Dimana Nazarova

Photonics 2023, 10(7), 728; https://doi.org/10.3390/photonics10070728 - 26 Jun 2023

Cited by 3 | Viewed by 1625

Abstract

During polarization holographic recording in azopolymer thin films, usually together with the volume anisotropic grating, a surface relief grating (SRG) is also formed. By using two consecutive exposures, it is possible to obtain a two-dimensional (2D) grating. To the best of our knowledge, [...] Read more.

During polarization holographic recording in azopolymer thin films, usually together with the volume anisotropic grating, a surface relief grating (SRG) is also formed. By using two consecutive exposures, it is possible to obtain a two-dimensional (2D) grating. To the best of our knowledge, the polarization properties of such gratings have not been studied yet. To determine the influence of the surface relief on the polarization selectivity of the 2D gratings, we propose two methods to suppress the SRG formation: by varying the recording conditions or varying the sample structure. In these experiments we have used the commercially available azopolymer PAZO, poly[1-4-(3-carboxy-4-hydrophenylazo) benzene sulfonamido]-1,2-ethanediyl, sodium salt] to perform the polarization holographic recording using a 442 nm He-Cd laser. As indicated by our results, when the surface relief is present, it strongly dominates the response of the 2D grating and it behaves almost as a scalar polarization insensitive grating. Conversely, when the SRG formation is suppressed, the polarization properties of the 2D grating in all four diffracted orders are very well pronounced. In this way, we demonstrate that we can easily control SRG formation and, if desired, obtain 2D grating with high surface relief modulation, or alternatively record polarization-selective 2D gratings with virtually no surface relief. Full article

(This article belongs to the Special Issue Coherent and Polarization Optics)

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13 pages, 2898 KiB

Open AccessArticle

Study of the Interference Color with Nomarski Prism Wedge Angle in a Differential Interference Contrast Microscopy System

by Fei Li and Tingyu Zhao

Photonics 2023, 10(6), 678; https://doi.org/10.3390/photonics10060678 - 11 Jun 2023

Viewed by 2044

Abstract

Differential interference contrast microscopy systems demonstrate the phase (optical path) rather than the amplitude of a sample. Previous studies have usually approximated the optical path difference produced by the Normarski prism. We derive the mathematical expression for the optical path difference produced by [...] Read more.

Differential interference contrast microscopy systems demonstrate the phase (optical path) rather than the amplitude of a sample. Previous studies have usually approximated the optical path difference produced by the Normarski prism. We derive the mathematical expression for the optical path difference produced by the incident light at any position of the Nomarski prism. As a result, the optical path difference introduced by the differential interference contrast microscope can be calculated. Moreover, the optical path difference is linearly related to the position of the incident light. In addition, the differential interference contrast microscopy system uses a composite light source, while previous studies were basically performed at a single wavelength. The standard wavelengths d (656 nm), F (587 nm), and C (486 nm) are taken as examples to analyze the relationship between the interference color change of the observation surface under the superposition of different wavelengths and the prism wedge angle when the prism moves. When the prism moves the same distance, the larger the prism wedge Angle is, the faster the interference color change is. The analysis based on practical considerations in this paper is believed to provide a method for studying Nomarski prisms. Full article

(This article belongs to the Special Issue Coherent and Polarization Optics)

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15 pages, 21221 KiB

Open AccessArticle

Generalized Asymmetric Hermite–Gaussian and Laguerre–Gaussian Beams

by Eugeny G. Abramochkin, Victor V. Kotlyar, Alexey A. Kovalev and Sergey S. Stafeev

Photonics 2023, 10(6), 606; https://doi.org/10.3390/photonics10060606 - 23 May 2023

Cited by 3 | Viewed by 2419

Abstract

We derive analytical formulae for the complex amplitudes of variants of generalized Hermite–Gaussian (HG) and Laguerre–Gaussian (LG) beams. We reveal that, at particular values of parameters of the exact solution of the paraxial propagation equation, these generalized beams are converted into conventional elegant [...] Read more.

We derive analytical formulae for the complex amplitudes of variants of generalized Hermite–Gaussian (HG) and Laguerre–Gaussian (LG) beams. We reveal that, at particular values of parameters of the exact solution of the paraxial propagation equation, these generalized beams are converted into conventional elegant HG and LG beams. We also deduce variants of asymmetric HG and LG beams that are described by complex amplitudes in the form of Hermite and Laguerre polynomials whose argument is shifted into the complex plane. The asymmetric HG and LG beams are, respectively, shown to present the finite superposition of the generalized HG and LG beams. We also derive an explicit relationship for the complex amplitude of a generalized vortex HG beam, which is built as the finite superposition of generalized HG beams with phase shifts. Newly introduced asymmetric HG and LG beams show promise for the study of the propagation of beams carrying an orbital angular momentum through the turbulent atmosphere. One may reasonably believe that the asymmetric laser beams are more stable against turbulence when compared with the radially symmetric ones. Full article

(This article belongs to the Special Issue Coherent and Polarization Optics)

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10 pages, 8807 KiB

Open AccessCommunication

Radially Phased-Locked Hermite–Gaussian Correlated Beam Array and Its Properties in Oceanic Turbulence

by Peiying Zhu, Guiqiu Wang, Yan Yin, Haiyang Zhong, Yaochuan Wang and Dajun Liu

Photonics 2023, 10(5), 551; https://doi.org/10.3390/photonics10050551 - 9 May 2023

Cited by 2 | Viewed by 1201

Abstract

The descriptions of a radially phased-locked Hermite–Gaussian correlated beam array are introduced, the equation of this beam array in oceanic turbulence is derived, and the intensity profiles of this beam array are shown and analyzed. The results imply that the evolutions of the [...] Read more.

The descriptions of a radially phased-locked Hermite–Gaussian correlated beam array are introduced, the equation of this beam array in oceanic turbulence is derived, and the intensity profiles of this beam array are shown and analyzed. The results imply that the evolutions of the sub-beam of this beam array in free space are the same as the Hermite–Gaussian correlated beam, while the intensity of this beam array can be adjusted by controlling the initial beam radius

R

and the coherence length. The intensity profiles of this beam array in free space have multiple spots during propagation, while the same beam array in oceanic turbulence can become a beam spot due to the influences of

R

and oceanic turbulence. The beam array with smaller coherence length in oceanic turbulence retains the splitting properties better during propagation. Full article

(This article belongs to the Special Issue Coherent and Polarization Optics)

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13 pages, 25808 KiB

Open AccessCommunication

Statistical Properties of Partially Coherent Higher-Order Laguerre-Gaussian Power-Exponent Phase Vortex Beams

by Zhiyuan Ma, Yuqi Pan, Jiantai Dou, Jiang Zhao, Bo Li and Youyou Hu

Photonics 2023, 10(4), 461; https://doi.org/10.3390/photonics10040461 - 17 Apr 2023

Cited by 2 | Viewed by 1682

Abstract

In this paper, partially coherent radially polarized (RP) Laguerre-Gaussian (LG) rotationally symmetrical power-exponent phase vortex (RSPEPV) beams with the LG-correlated Schell-model (LGSM) were introduced. The statistical properties of the tightly focused beams, including intensity distribution, degrees of polarization and coherence, and Stokes vector, [...] Read more.

In this paper, partially coherent radially polarized (RP) Laguerre-Gaussian (LG) rotationally symmetrical power-exponent phase vortex (RSPEPV) beams with the LG-correlated Schell-model (LGSM) were introduced. The statistical properties of the tightly focused beams, including intensity distribution, degrees of polarization and coherence, and Stokes vector, were studied based on vectorial Richards-Wolf diffraction integral theory. Moreover, when the distance between focal plane and the observation plane z = 0, the relationships between the tight-focusing properties of RP-LG-RSPEPV beams with LGSM and the order of LGSM p’, topological charges l, power exponent n, spatial correlation δ, and radial index p were investigated. The results show that by changing the order of LGSM, topological charge, power exponent, spatial correlation length, and radial index, the focal spot distribution of various shapes can be obtained. This work provides ideas for the application of partially coherent beams in particle capture and optical tweezers. Full article

(This article belongs to the Special Issue Coherent and Polarization Optics)

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14 pages, 5943 KiB

Open AccessCommunication

Influence of Off-Axis Noncanonical Vortex on the Dynamics of Energy Flux

by Xinying Zhao, Huijian Liang, Gaofeng Wu and Xiaoyan Pang

Photonics 2023, 10(3), 346; https://doi.org/10.3390/photonics10030346 - 22 Mar 2023

Cited by 2 | Viewed by 1389

Abstract

In this article, we analyze the impact of the off-axis noncanonical vortex on the dynamics of 3D energy flux. The results reveal that the properties of energy flux are significantly influenced by the anisotropy parameter

σ_{c}

of the off-axis noncanonical vortex. It [...] Read more.

In this article, we analyze the impact of the off-axis noncanonical vortex on the dynamics of 3D energy flux. The results reveal that the properties of energy flux are significantly influenced by the anisotropy parameter

σ_{c}

of the off-axis noncanonical vortex. It is demonstrated that by adjusting the anisotropy parameter, we can control the transverse energy flux, from the position of the transverse energy tornado and the distribution of the transverse energy strength to the rotation direction of the transverse energy flux as the beam propagates. The interesting phenomenon, the reversed energy flux, is also closely related to the anisotropy parameter. The position and size of the reversed energy flux region, as well as the production of two energy tornadoes with opposite rotating directions, resembling a Chinese “Taiji” pattern, can be controlled by varying the anisotropy parameter. This result will potentially provide a new freedom for tailoring the 3D optical field and be useful in optical manipulation and processing. Full article

(This article belongs to the Special Issue Coherent and Polarization Optics)

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12 pages, 5571 KiB

Open AccessCommunication

Second-Order Statistics of Self-Splitting Structured Beams in Oceanic Turbulence

by Liming Liu, Yulu Liu, Hao Chang, Jifei Huang, Xinlei Zhu, Yangjian Cai and Jiayi Yu

Photonics 2023, 10(3), 339; https://doi.org/10.3390/photonics10030339 - 22 Mar 2023

Cited by 8 | Viewed by 1359

Abstract

Free-space optical communication is restricted by random media-stimulated beam degradation. However, partially coherent structured beams modulated by the coherence structure can potentially mitigate this negative effect. By employing the extended Huygens–Fresnel integral, we provide an examination of the second-order statistical features of a [...] Read more.

Free-space optical communication is restricted by random media-stimulated beam degradation. However, partially coherent structured beams modulated by the coherence structure can potentially mitigate this negative effect. By employing the extended Huygens–Fresnel integral, we provide an examination of the second-order statistical features of a common type of partly coherent structured beams, self-splitting structured beams, in a turbulent ocean. The implications of turbulence parameters relating to the ocean and beginning beam parameters corresponding to the progression of such beam propagation attributes are fully investigated. Our numerical outcomes show that, for turbulence with a low-dissipation kinetic energy rate per unit mass of fluid, small Kolmogorov inner scale, large relative strength of temperature to salinity undulations, and large dissipation rate of mean-square temperature has a greater negative effect on the structured beams. In addition, we suggest an effective approach, enhancing the order of the beam and reducing the coherence length of the beams, to lower the oceanic turbulence-induced negative effects, and thus have future extensive possibilities in free-space optical communication. Full article

(This article belongs to the Special Issue Coherent and Polarization Optics)

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12 pages, 6637 KiB

Open AccessArticle

Effect of Twisting Phases on Linear–Circular Polarization and Spin–Orbital Angular Momentum Conversions in Tightly Focused Vector and Scalar Beams

by Shu-Dan Wu, Khian-Hooi Chew and Rui-Pin Chen

Photonics 2023, 10(2), 151; https://doi.org/10.3390/photonics10020151 - 1 Feb 2023

Cited by 3 | Viewed by 1782

Abstract

We theoretically investigated the effect of a new type of twisting phase on the polarization dynamics and spin–orbital angular momentum conversion of tightly focused scalar and vector beams. It was found that the existence of twisting phases gives rise to the conversion between [...] Read more.

We theoretically investigated the effect of a new type of twisting phase on the polarization dynamics and spin–orbital angular momentum conversion of tightly focused scalar and vector beams. It was found that the existence of twisting phases gives rise to the conversion between the linear and circular polarizations in both scalar and vector beams during focusing. The linear–circular polarization conversion further leads to an optical spin–orbital angular momentum transformation in the longitudinal component (LC). Therefore, even in a scalar optical field with a uniform linear polarization distribution, a circular polarization (spin angular momentum), and an orbital angular momentum (OAM) can appear in the cross-section and the longitudinal component, respectively, while being tightly focused. The novel distributions of the optical field, state of polarization (SOP) and OAM in the focal region are sensitively dependent on the twisted strength of the twisting phase. These results provide a more flexible manipulation of a structured optical field in the aspects of the optical field, SOP, and OAM. Full article

(This article belongs to the Special Issue Coherent and Polarization Optics)

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11 pages, 7082 KiB

Open AccessArticle

Propagation of a Lorentz Non-Uniformly Correlated Beam in a Turbulent Ocean

by Dongmei Wei, Ke Wang, Ying Xu, Qian Du, Fangning Liu, Juan Liu, Yiming Dong, Liying Zhang, Jiayi Yu, Yangjian Cai and Xinlei Zhu

Photonics 2023, 10(1), 49; https://doi.org/10.3390/photonics10010049 - 3 Jan 2023

Cited by 4 | Viewed by 1862

Abstract

We study the propagation characteristics (spectral intensity and degree of coherence) of a new type of Lorentz non-uniformly correlated (LNUC) beam based on the extended Huygens–Fresnel principle and the spatial power spectrum of oceanic turbulence. The effects of the oceanic turbulence parameters and [...] Read more.

We study the propagation characteristics (spectral intensity and degree of coherence) of a new type of Lorentz non-uniformly correlated (LNUC) beam based on the extended Huygens–Fresnel principle and the spatial power spectrum of oceanic turbulence. The effects of the oceanic turbulence parameters and initial beam parameters on the evolution propagation characteristics of LNUC beams are studied in detail by numerical simulation. The results indicate that such beams exhibit self-focusing propagation features in both free space and oceanic turbulence. Decreasing the dissipation rate of kinetic energy per unit mass of fluid and the Kolmogorov inner scale, or increasing the relative strength of temperature to salinity undulations and the dissipation rate of mean-square temperature of the turbulent ocean tends to increase the negative effects on the beams. Furthermore, we propose a strategy of increasing the beam width and decreasing the coherence length, to reduce the negative effects of the turbulence. Full article

(This article belongs to the Special Issue Coherent and Polarization Optics)

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14 pages, 14620 KiB

Open AccessArticle

Manipulation of Energy Flow with X-Type Vortex

by Han Zhang, Tianhu Zhang, Xinying Zhao and Xiaoyan Pang

Photonics 2022, 9(12), 998; https://doi.org/10.3390/photonics9120998 - 17 Dec 2022

Viewed by 1535

Abstract

In this study, a new method for manipulating energy flow in a 3D vector field is proposed. In this method, an azimuthally-polarized beam with a noncanonical vortex, the X-type vortex, is focused in a high-numerical aperture system. It is found that, instead of [...] Read more.

In this study, a new method for manipulating energy flow in a 3D vector field is proposed. In this method, an azimuthally-polarized beam with a noncanonical vortex, the X-type vortex, is focused in a high-numerical aperture system. It is found that, instead of the invariance of the energy flow which is characteristic of the traditional vortex (i.e., canonical vortex), both the longitudinal and the transverse energy flows in virtue of the X-type vortex rotate around the beam center as the beam propagates, and this rotational behavior (including the maxima location and the rotational angle) can be adjusted by the anisotropic parameter and the order the X-type vortex. Through defining a complex transverse Poynting field and applying the equivalence principle, the transverse energy flow and its topological reactions are discussed in the focal plane. Our result shows that, by changing the anisotropic parameter of the X-type vortex, rich topological reactions will occur, resulting in various distribution patterns of the energy flow, such as multi vortex-type singularities around the beam center. Our research demonstrates newly-observed features of the X-type vortex and also provides a simple method to manipulate energy flows both along longitudinal and transverse directions, which will be useful in optical manipulations. Full article

(This article belongs to the Special Issue Coherent and Polarization Optics)

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10 pages, 2008 KiB

Open AccessCommunication

Poincaré Beams at the Tight Focus: Inseparability, Radial Spin Hall Effect, and Reverse Energy Flow

by Victor V. Kotlyar, Sergey S. Stafeev, Vladislav D. Zaitsev and Alexey M. Telegin

Photonics 2022, 9(12), 969; https://doi.org/10.3390/photonics9120969 - 11 Dec 2022

Cited by 4 | Viewed by 2437

Abstract

The family of Poincaré beams has three parameters, including two real-valued angular parameters, which specify a definite polarization state on the Poincaré sphere, and a third integer parameter n specifying the beam singularity order. We show theoretically and through a numerical simulation that, [...] Read more.

The family of Poincaré beams has three parameters, including two real-valued angular parameters, which specify a definite polarization state on the Poincaré sphere, and a third integer parameter n specifying the beam singularity order. We show theoretically and through a numerical simulation that, while being inseparable and not allowing for the separation of polarization and orbital degrees of freedom in the general case, the Poincaré beams display remarkable properties when tightly focused. We find that at n = 2, a reverse energy flow occurs near the optical axis, which is mathematically expressed as the negative projection of the Poynting vector. We also reveal that given certain parameters of the Poincaré beams, the energy flow rotates around the optical axis due to spin–orbital conversion. We also reveal a radial optical Hall effect that occurs at the tight focus of Poincaré beams, when the on-axis components of the spin angular momentum vector have different signs on certain different-radius circles centered at the focal spot center. Full article

(This article belongs to the Special Issue Coherent and Polarization Optics)

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11 pages, 2912 KiB

Open AccessCommunication

Tight Focusing Properties of Ring Pearcey Beams with a Cross Phase

by Chaoqun Yu, Zhimin He, Cheng Huang, Fuchang Chen, Jun Zeng, Yan Li, Yongtao Zhang, Jixiong Pu and Huichuan Lin

Photonics 2022, 9(12), 964; https://doi.org/10.3390/photonics9120964 - 10 Dec 2022

Cited by 5 | Viewed by 1981

Abstract

We theoretically investigated the properties of tightly focused ring Pearcey beams with a cross phase (CPRPB). The expressions of the distributions of both electric field and magnetic field in the focal region of an objective were first derived from the vectorial Debye theory, [...] Read more.

We theoretically investigated the properties of tightly focused ring Pearcey beams with a cross phase (CPRPB). The expressions of the distributions of both electric field and magnetic field in the focal region of an objective were first derived from the vectorial Debye theory, and then numerical calculations were carried out to obtain the focused intensity distribution and the Poynting vector of CPRPB near the focus. Numerical calculations indicate that as CPRPB is focused on an objective of high numerical aperture (NA), two nonuniform self-focusing spots occur at both sides of the geometrical focus of the objective symmetrically, and the angle between their directions is 90 degrees. The stronger is the strength of cross-phase modulation, the flatter are the ellipses of the self-focusing spots, and the smaller is the intensity at the geometrical focus of the objective. Numerical calculations also demonstrate that the optical gradient force produced by tightly focused CPRPB in the focal region can be manipulated in magnitude and in direction by tuning the strength of cross-phase modulation. Due to these properties of tightly focused CPRPB, they might find applications in the manipulation of micro- and nanoparticles and so on. Full article

(This article belongs to the Special Issue Coherent and Polarization Optics)

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13 pages, 7558 KiB

Open AccessArticle

Evolution Properties of a Partially Coherent Twisted Laguerre-Gaussian Pulsed Beam Propagating through Anisotropic Atmospheric Turbulence

by Ying Xu, Yonggen Xu and Tiejun Wang

Photonics 2022, 9(10), 707; https://doi.org/10.3390/photonics9100707 - 28 Sep 2022

Cited by 6 | Viewed by 1642

Abstract

Analytical expressions for the cross-spectral density matrix of a partially coherent twisted Laguerre-Gaussian pulsed (PCTLGP) beam in anisotropic atmospheric turbulence are derived based on the extended Huygens–Fresnel principle. Numerical results indicate that the atmospheric turbulence induces the degeneration of the spectral intensity distribution [...] Read more.

Analytical expressions for the cross-spectral density matrix of a partially coherent twisted Laguerre-Gaussian pulsed (PCTLGP) beam in anisotropic atmospheric turbulence are derived based on the extended Huygens–Fresnel principle. Numerical results indicate that the atmospheric turbulence induces the degeneration of the spectral intensity distribution of the PCTLGP beam, and the PCTLGP beam also shows different evolution properties on propagation in weaker turbulence and stronger turbulence. The PCTLGP beam with a negative twisted factor exhibits an advantage over the Laguerre-Gaussian pulsed beam for reducing the atmospheric turbulence-induced degeneration, and this advantage is further strengthened with increasing the topological charge, mode order and absolute value of the twisted factor. In addition, we also find that the pulse duration will affect the spectral intensity of the PCTLGP beam in turbulence. This kind of beam will show potential application value in free-space optical communications and remote sensing. Full article

(This article belongs to the Special Issue Coherent and Polarization Optics)

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