Photonics

14 pages, 8494 KiB

Open AccessArticle

Design of Cascaded DOEs for Focusing Different Wavelengths to Different Points

by Leonid L. Doskolovich, Daniil V. Soshnikov, Georgy A. Motz, Egor V. Byzov, Evgeni A. Bezus, Dmitry A. Bykov and Nikolay L. Kazanskiy

Photonics 2024, 11(9), 791; https://doi.org/10.3390/photonics11090791 (registering DOI) - 23 Aug 2024

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Abstract

We propose a task-specific method for calculating cascaded phase diffractive optical elements (DOEs) for focusing Q incident beams with different wavelengths to Q given points. Due to the utilization of a special optimization criterion, the proposed method makes it possible to calculate the [...] Read more.

We propose a task-specific method for calculating cascaded phase diffractive optical elements (DOEs) for focusing Q incident beams with different wavelengths to Q given points. Due to the utilization of a special optimization criterion, the proposed method makes it possible to calculate the elements of the cascaded DOE in a sequential way. In addition, the calculation of the diffractive microrelief of each DOE in the cascade is reduced to solving a set of independent and computationally simple “pointwise” optimization problems. Using the proposed method, cascades of two DOEs were designed to focus radiation of 11 different wavelengths to 11 different points. The presented numerical simulation results demonstrate good performance of the method. The chosen operating wavelengths correspond to a set of widely used vegetation indices enabling monitoring the vegetation status conditions and tracking the environmental stresses. This makes the obtained results promising for the application in remote sensing and smart agriculture. Full article

(This article belongs to the Special Issue Recent Advances in Diffractive Optics)

13 pages, 1250 KiB

Open AccessArticle

Super-Oscillating Diffractive Optical Spot Generators

by Markus E. Testorf, Praneeth Gadamsetti, Paolo Batoni and Menelaos K. Poutous

Photonics 2024, 11(9), 790; https://doi.org/10.3390/photonics11090790 (registering DOI) - 23 Aug 2024

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Abstract

The prior discrete Fourier transform (PDFT) is applied to the design of super-oscillating diffractive optical elements with rotational symmetry. Numerical simulations of the filter response are used to demonstrate the potential of the PDFT-based approach, which includes a regularization method for improved numerical [...] Read more.

The prior discrete Fourier transform (PDFT) is applied to the design of super-oscillating diffractive optical elements with rotational symmetry. Numerical simulations of the filter response are used to demonstrate the potential of the PDFT-based approach, which includes a regularization method for improved numerical and functional stability of the filter design. For coherent monochromatic illumination, the Strehl ratio of spot generators as a function of the spot radius is compared to the theoretical upper bound. It is shown that the performance of the PDFT design varies significantly depending on the aperture function and the encoding as a phase-only diffractive element. Experimental results are in good agreement with simulations and demonstrate the moderate demands to implement super-oscillating diffractive optical elements. Full article

(This article belongs to the Special Issue Recent Advances in Diffractive Optics)

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11 pages, 533 KiB

Open AccessArticle

Gold Nanoparticles at a Liquid Interface: Towards a Soft Nonlinear Metasurface

by Delphine Schaming, Anthony Maurice, Frédéric Gumy, Micheál D. Scanlon, Christian Jonin, Hubert H. Girault and Pierre-François Brevet

Photonics 2024, 11(9), 789; https://doi.org/10.3390/photonics11090789 (registering DOI) - 23 Aug 2024

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Abstract

Optical second-harmonic generation (SHG) is achieved using adsorbed gold nanoparticles (AuNPs) with an average diameter of 16 nm at the aqueous solution–air interface in reflection. A detailed analysis of the depth profile of the SHG intensity detected shows that two contributions appear in [...] Read more.

Optical second-harmonic generation (SHG) is achieved using adsorbed gold nanoparticles (AuNPs) with an average diameter of 16 nm at the aqueous solution–air interface in reflection. A detailed analysis of the depth profile of the SHG intensity detected shows that two contributions appear in the overall signal, one arising from the aqueous solution–air interface that is sensitive to the AuNP surface excess and one arising from the bulk aqueous phase. The latter is an incoherent signal also known as hyper-Rayleigh scattering (HRS). The results agree with those of an analysis involving Gaussian beam propagation optics and a Langmuir-like isotherm. Discrepancies are revealed for the largest AuNP concentrations used and indicate a new route for the design of soft metasurfaces. Full article

(This article belongs to the Special Issue Recent Advances in Nonlinear Optics: From Fundamentals to Applications)

13 pages, 1073 KiB

Open AccessArticle

Controlling the Shape of a Double DNA-Like Helix as an Element of Metamaterials

by Igor V. Semchenko, Ivan S. Mikhalka, Andrey L. Samofalov and Sergei A. Khakhomov

Photonics 2024, 11(9), 788; https://doi.org/10.3390/photonics11090788 (registering DOI) - 23 Aug 2024

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Abstract

The aim of the article is to study the forces arising in a conductive DNA-like double helix in the field of a microwave electromagnetic wave. These forces must be considered for both actual DNA molecules and double DNA-like helices that serve as components [...] Read more.

The aim of the article is to study the forces arising in a conductive DNA-like double helix in the field of a microwave electromagnetic wave. These forces must be considered for both actual DNA molecules and double DNA-like helices that serve as components of metamaterials and metasurfaces. The helix comprises twenty-and-a-half turns and has geometric parameters proportional to the size of an actual DNA molecule. The forces acting on the strands of a double helix, both in the central region and at the edges of the helix, are investigated. It has been demonstrated that the aforementioned forces induce a change in the shape of the helix, specifically the mutual repulsion of the strands, as well as their stretching and twisting in the field of electromagnetic waves. Consequently, exposure to an electromagnetic wave under half-wave resonance can damage the double helix. Conversely, the impact of electromagnetic waves has the potential to introduce novel avenues for controlling the shape of the double helix. Full article

(This article belongs to the Special Issue Emerging Trends in Metamaterials and Metasurfaces Research)

10 pages, 1452 KiB

Open AccessCommunication

From Text to Hologram: Creation of High-Quality Holographic Stereograms Using Artificial Intelligence

by Philippe Gentet, Matteo Coffin, Yves Gentet and Seung Hyun Lee

Photonics 2024, 11(9), 787; https://doi.org/10.3390/photonics11090787 (registering DOI) - 23 Aug 2024

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Abstract

This study simplified the creation of holographic stereograms using AI-generated prompts, overcoming the conventional need for complex equipment and professional software. AI enabled the generation of detailed perspective images suitable for various content styles. The generated images were interpolated, upscaled, and printed using [...] Read more.

This study simplified the creation of holographic stereograms using AI-generated prompts, overcoming the conventional need for complex equipment and professional software. AI enabled the generation of detailed perspective images suitable for various content styles. The generated images were interpolated, upscaled, and printed using a CHIMERA holoprinter to obtain high-quality holograms. This method significantly reduces the required time and expertise, thereby making holographic content creation accessible. This approach demonstrated that AI can effectively streamline the production of high-fidelity holograms, suggesting exciting future advancements in holographic technology. Full article

(This article belongs to the Special Issue Advances in Holography and Its Applications)

33 pages, 3041 KiB

Open AccessArticle

A Framework for Iterative Phase Retrieval Technique Integration into Atmospheric Adaptive Optics—Part I: Wavefront Sensing in Strong Scintillations

by Mikhail A. Vorontsov and Ernst Polnau

Photonics 2024, 11(9), 786; https://doi.org/10.3390/photonics11090786 (registering DOI) - 23 Aug 2024

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Abstract

The objective of this study, which is divided into two parts, is twofold: to address long-standing challenges in the sensing of atmospheric turbulence-induced wavefront aberrations under strong scintillation conditions via a comparative analysis of several basic scintillation-resistant wavefront sensing (SR-WFS) architectures and iterative [...] Read more.

The objective of this study, which is divided into two parts, is twofold: to address long-standing challenges in the sensing of atmospheric turbulence-induced wavefront aberrations under strong scintillation conditions via a comparative analysis of several basic scintillation-resistant wavefront sensing (SR-WFS) architectures and iterative phase retrieval (IPR) techniques (Part I, this paper), and to develop a framework for the potential integration of SR-WFS techniques into practical closed-loop non-astronomical atmospheric adaptive optics (AO) systems (Part II). In this paper, we consider basic SR-WFS mathematical models and phase retrieval algorithms, tradeoffs in sensor design and phase retrieval technique implementation, and methodologies for WFS parameter optimization and performance assessment. The analysis is based on wave-optics numerical simulations imitating realistic turbulence-induced phase aberrations and intensity scintillations, as well as optical field propagation inside the SR-WFSs. Several potential issues important for the practical implementation of SR-WFS and IPR techniques, such as the requirements for phase retrieval computational grid resolution, tolerance with respect to optical element misalignments, and the impact of camera noise and input light non-monochromaticity, are also considered. The results demonstrate that major wavefront sensing requirements desirable for AO operation under strong intensity scintillations can potentially be achieved by transitioning to novel SR-WFS architectures, based on iterative phase retrieval techniques. Full article

(This article belongs to the Special Issue Challenges and Future Directions in Adaptive Optics Technology)

20 pages, 14645 KiB

Open AccessArticle

Research on Electro-Optic Hybrid Multidigit Digital Multiplier Based on Surface Plasmon Polariton Technology

by Zhixun Liang, Yunying Shi, Yunfei Yi, Zhirong Wei and Peng Tang

Photonics 2024, 11(9), 785; https://doi.org/10.3390/photonics11090785 (registering DOI) - 23 Aug 2024

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Abstract

Digital multipliers are the core components of digital computers, and improving the speed of transistor electronic computers during computation has almost reached its limit, with high power consumption. In this paper, we proposed an electro-optic hybrid multidigit digital multiplier based on SPP technology, [...] Read more.

Digital multipliers are the core components of digital computers, and improving the speed of transistor electronic computers during computation has almost reached its limit, with high power consumption. In this paper, we proposed an electro-optic hybrid multidigit digital multiplier based on SPP technology, which has the advantages of high speed and low power consumption in optical logic, as well as flexible electrical operation and easy storage. The electro-optic hybrid digital multiplier mainly consists of an electrical AND logic gate, an electro-optic hybrid half adder, and an electro-optic hybrid full adder. The optical logic unit is controlled by activated ITO materials to achieve optical-domain operations, and then the multiplication calculation results are converted into electrical signals through photoelectric conversion. The experimental results show that when the scale is 64 × 64 bits, compared with transistor digital multiplication, the energy consumption is reduced by 48.8%; the speed is increased by a factor of 28; and the volume of the electro-optic hybrid digital multiplier device is larger than that of the transistor multiplier, saving 59.9% of the area. For optical transmission loss, a single adder outputs 0.31 dB at different device scales, while the carry output continuously increases with device scale. At scales of 8 × 8 bits, 16 × 16 bits, and 64 × 64 bits, the insertion losses at the sum output ports are 1.03 dB/μm and 1.87 dB/μm, respectively. Full article

(This article belongs to the Special Issue Silicon-Based Integrated Optics: From Design to Applications)

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14 pages, 4511 KiB

Open AccessArticle

Photonic Crystal Fiber Based on Surface Plasmon Resonance Used for Two Parameter Sensing for Magnetic Field and Temperature

by Tiantian Dai, Yingting Yi, Zao Yi, Yongjian Tang, Yougen Yi, Shubo Cheng, Zhiqiang Hao, Chaojun Tang, Pinghui Wu and Qingdong Zeng

Photonics 2024, 11(9), 784; https://doi.org/10.3390/photonics11090784 (registering DOI) - 23 Aug 2024

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Abstract

This paper presents a photonic crystal fiber (PCF) sensor that can be used to measure the temperature and magnetic field simultaneously, and to monitor the changes in them in the environment. When we designed the fiber structure, two circular channels of the same [...] Read more.

This paper presents a photonic crystal fiber (PCF) sensor that can be used to measure the temperature and magnetic field simultaneously, and to monitor the changes in them in the environment. When we designed the fiber structure, two circular channels of the same size were added to the fiber to facilitate the subsequent addition of materials. A gold film is added to the upper channel (ch1), and the channel is filled with a magnetic fluid (MF). The sensor can reflect changes in the temperature and magnetic field strength. The two channels containing MF and PDMS in the proposed fiber are called ch1 and ch2. The structure, mode and properties (temperature and magnetic field) were analyzed and discussed using the finite element method. By using the control variable method, the influence of Ta₂O₅ or no Ta₂O₅, the Ta₂O₅ thickness, the diameter of the special air hole, the distance from the fiber core and the distance between them in the displacement of the loss spectrum and the phase-matching condition of the coupling mode were studied. The resulting maximum temperature sensitivity is 6.3 nm/°C (SPR peak 5), and the maximum magnetic field sensitivity is 40 nm/Oe (SPR peak 4). Because the sensor can respond to temperature and magnetic field changes in the environment, it can play an important role in special environmental monitoring, industrial production and other fields. Full article

(This article belongs to the Special Issue Thermal Radiation and Micro-/Nanophotonics)

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30 pages, 13607 KiB

Open AccessArticle

Grating Coupler Design for Low-Cost Fabrication in Amorphous Silicon Photonic Integrated Circuits

by Daniel Almeida, Paulo Lourenço, Alessandro Fantoni, João Costa and Manuela Vieira

Photonics 2024, 11(9), 783; https://doi.org/10.3390/photonics11090783 (registering DOI) - 23 Aug 2024

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Abstract

Photonic circuits find applications in biomedicine, manufacturing, quantum computing and communications. Photonic waveguides are crucial components, typically having cross-section orders of magnitude inferior when compared with other photonic components (e.g., optical fibers, light sources and photodetectors). Several light-coupling methods exist, consisting of either [...] Read more.

Photonic circuits find applications in biomedicine, manufacturing, quantum computing and communications. Photonic waveguides are crucial components, typically having cross-section orders of magnitude inferior when compared with other photonic components (e.g., optical fibers, light sources and photodetectors). Several light-coupling methods exist, consisting of either on-plane (e.g., adiabatic and end-fire coupling) or off-plane methods (e.g., grating and vertical couplers). The grating coupler is a versatile light-transference technique which can be tested at wafer level, not requiring specific fiber terminations or additional optical components, like lenses, polarizers or prisms. This study focuses on fully-etched grating couplers without a bottom reflector, made from hydrogenated amorphous silicon (a-Si:H), deposited over a silica substrate. Different coupler designs were tested, and of these we highlight two: the superimposition of two lithographic masks with different periods and an offset between them to create a random distribution and a technique based on the quadratic refractive-index variation along the device’s length. Results were obtained by 2D-FDTD simulation. The designed grating couplers achieve coupling efficiencies for the TE-like mode over −8 dB (mask overlap) and −3 dB (quadratic variation), at a wavelength of 1550 nm. The coupling scheme considers a 220 nm a-Si:H waveguide and an SMF-28 optical fiber. Full article

(This article belongs to the Special Issue Progress in Integrated Photonics and Future Prospects)

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15 pages, 2434 KiB

Open AccessArticle

Resolving the Refractive Indices of Transparent and Translucent Liquids from the Spacings, Spatial Frequencies, and Directions of Interference Fringes

by Qingli Jing, Jiajian Wang, Jianglong Lei, Qi Wang, Jialing Chen, Jun Liu, Minglin Zhao, Jiantai Dou, Yuanxiang Wang and Youyou Hu

Photonics 2024, 11(9), 782; https://doi.org/10.3390/photonics11090782 (registering DOI) - 23 Aug 2024

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Abstract

In this work, we present a novel approach to resolve the refractive indices of transparent and translucent liquids from straight interference fringes. The optical path difference between the two arms of the Mach–Zehnder interferometer is first derived by assuming a reference plane wave [...] Read more.

In this work, we present a novel approach to resolve the refractive indices of transparent and translucent liquids from straight interference fringes. The optical path difference between the two arms of the Mach–Zehnder interferometer is first derived by assuming a reference plane wave interfering with a plane wave passing through a rectangular cuvette. The analytic expressions for the liquid refractive indices are then deduced, describing how the refractive index is related to the fringe spacings, spatial frequencies, and directions. The structure coefficients in the above formulas are determined from the fringe spacings and directions of the interference patterns of the empty cuvette and the cuvette filled with a liquid of a known refractive index. The NaCl solution and Coca Cola are adopted as the test examples to show experimentally the validity of the proposed method. There is good agreement between the refractive indices obtained from the fringe spacings and direction of a single interference pattern. The sensitivity and resolution of this method are dependent on the structure of the experimental systems and thus can be adjusted in a controlled manner. The proposed method is simple to implement and can be easily extended to other high precision optical interferometer systems. Full article

(This article belongs to the Section Lasers, Light Sources and Sensors)

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Photonics, Volume 11, Issue 9 (September 2024) – 10 articles

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