Modulation of Non-diffracting Hermite Gaussian Beams and Nonlinear Optical Microscopy for Nanoscale Sulfur Imaging

Author(s):

Navarro, Gilberto

Abstract:

“Hermite Gaussian beams are the solutions of the scalar paraxial wave equation in Cartesian coordinates. A method was developed to modulate the intensity profile of non-diffracting Hermite Gaussian (HG) beams. The original HG beams intensity profile consists of high intense corner lobes and low intense central lobes which is not ideal for structured illumination in light-field microscopy. The modulated HG beams were generated by multiplying the original HGâ??s beam envelope by a super-Gaussian envelope to modify the intensity profile to attain equal intensity lobes. The propagation of the original HG beam and modulated HG beam were compared to determine that the non-diffracting properties of the modulated HG beam were held.

Two-photon absorption (TPA) is a nonlinear optical process in which the absorption coefficient depends on the optical intensity. In the process of two-photon absorption, an atom makes a transition from its ground state to an excited state by the simultaneous (  1 fs) absorption of two photons. In the second project, two-photon microscopy was used to detect the root uptake and determine the biodistribution of nanoscale sulfur. Characterization of pristine, stearic acid coated, and bulk sulfur was done to determine their fluorescent signal properties. Tomatoes that were grown in nano-sulfur treated soils to enhance crop nutrition and suppress disease, were imagined under the two-photon microscope to detect the root uptake of the nanoscale sulfur.”

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Publication: University of Texas at El Paso, Thesis
Issue/Year: , 2022
URL: https://scholarworks.utep.edu/open_etd/3706

Simultaneously sorting vector vortex beams of 120 modes

Author(s):

Jia, Qi; Zhang, Yanxia; Shi, Bojian; Li, Hang; Li, Xiaoxin; Feng, Rui; Sun, Fangkui; Cao, Yongyin; Wang, Jian; Qiu, Cheng-Wei & Ding, Weiqiang

Abstract:

“Polarization (P), angular index (l), and radius index (p) are three independent degrees of freedom (DoFs) of vector vortex beams, which have been widely used in optical communications, quantum optics, information processing, etc. Although the sorting of one DoF can be achieved efficiently, it is still a great challenge to sort all these DoFs simultaneously in a compact and efficient way. Here, we propose a beam sorter to deal with all these three DoFs simultaneously by using a diffractive deep neural network (D^2NN) and experimentally demonstrated the robust sorting of 120 Laguerre-Gaussian (LG) modes using a compact D^2NN formed by one spatial light modulator and one mirror only. The proposed beam sorter demonstrates the great potential of D^2NN in optical field manipulation and will benefit the diverse applications of vector vortex beams.”

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Publication: arXiv
Issue/Year: arXiv, 2022
DOI: 10.48550/ARXIV.2212.08825

Pixel super-resolution quantitative phase imaging based on modulation diversity

Author(s):

Gao, Yunhui & Cao, Liangcai

Abstract:

“Quantitative phase imaging with high resolution remains a long-term pursuit of many biomedical applications. However, the performance of coherent imaging systems is challenged by the intensity-only measurement mechanism and the sampling limit of the pixels. In this work, we introduce an imaging system that achieves pixel super-resolution quantitative phase imaging based on modulation diversity. A programmable phase-only spatial light modulator is used to generate various phase modulation patterns to the wavefront, providing data diversity for phase recovery at subpixel resolution. The system requires no mechanical displacements, enabling high-speed image acquisition, providing a competitive approach to high-throughput quantitative phase imaging applications.”

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Publication: Proc. SPIE 12318
Issue/Year: Proc. SPIE 12318, Holography, Diffractive Optics, and Applications XII, 123180Q, 2022
DOI: 10.1117/12.2642054

Three-dimensional wide-field fluorescence microscopy for transcranial mapping of cortical microcirculation

Author(s):

Zhou, Quanyu; Chen, Zhenyue; Liu, Yu-Hang; El Amki, Mohamad; Glück, Chaim; Droux, Jeanne; Reiss, Michael; Weber, Bruno; Wegener, Susanne & Razansky, Daniel

Abstract:

“Wide-field fluorescence imaging is an indispensable tool for studying large-scale biodynamics. Limited space-bandwidth product and strong light diffusion make conventional implementations incapable of high-resolution mapping of fluorescence biodistribution in three dimensions. We introduce a volumetric wide-field fluorescence microscopy based on optical astigmatism combined with fluorescence source localization, covering 5.6×5.6×0.6 mm^3 imaging volume. Two alternative configurations are proposed exploiting multifocal illumination or sparse localization of point emitters, which are herein seamlessly integrated in one system. We demonstrate real-time volumetric mapping of the murine cortical microcirculation at capillary resolution without employing cranial windows, thus simultaneously delivering quantitative perfusion information across both brain hemispheres. Morphological and functional changes of cerebral vascular networks are further investigated after an acute ischemic stroke, enabling cortex-wide observation of concurrent collateral recruitment events occurring on a sub-second scale. The reported technique thus offers a wealth of unmatched possibilities for non- or minimally invasive imaging of biodynamics across scales.”

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Publication: Nature Communications
Issue/Year: Nature Communications, Volume 13; Number 1; Pages 1–11; 2022
DOI: 10.1038/s41467-022-35733-0

Coupled two-core integrated waveguides modal analysis

Author(s):

Benedicto, David; Collados, M. Victoria; Martín, Juan C.; Jesú s Atencia & Vallés, Juan A.

Abstract:

“We present a modal analysis of coupled two-core integrated waveguides fabricated by femtosecond laser writing as a function of the core-to-core distance, illuminating position and input light wavelength. In order to do that we use the correlation filter method, implementing the computer generated holograms in a phase-only spatial light modulator. Due to the two-core waveguide symmetry, we prove it is not necessary to encode the complex amplitude in a phase-only device as long as the cores are not strongly coupled. A comparison between experimental and numerical modal weights is presented, showing that simple phase-only match filters allow the modal decomposition of two-core waveguides output beams”

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Publication: Journal of Physics: Conference Series
Issue/Year: Journal of Physics: Conference Series, Volume 2407; Number 1; Pages 012016; 2022
DOI: 10.1088/1742-6596/2407/1/012016

Simulated LCSLM with Inducible Diffractive Theory to Display Super-Gaussian Arrays Applying the Transport-of-Intensity Equation

Author(s):

Arriaga-Hernandez, Jesus; Cuevas-Otahola, Bolivia; Oliveros-Oliveros, Jacobo; Morin-Castillo, Maria; Martinez-Laguna, Ygnacio & Cedillo-Ramirez, Lilia

Abstract:

“We simulate a liquid crystal spatial light modulator (LCSLM), previously validated by Fraunhofer diffraction to observe super-Gaussian periodic profiles and analyze the wavefront of optical surfaces applying the transport-of-intensity equation (TIE). The LCSLM represents an alternative to the Ronchi Rulings, allowing to avoid all the related issues regarding diffractive and refractive properties, and noise. To this aim, we developed and numerically simulated a LCSLM resembling a fractal from a generating base. Such a base is constituted by an active square (values equal to one) and surrounded by eight switched-off pixels (zero-valued). We replicate the base in order to form 1 ×N-pixels and the successive rows to build the 1024×1024 LCSLM of active pixels. We visually test the LCSLM with calibration images as a diffractive object that is mathematically inducible, using mathematical induction over the N×N-shape (1×1, 2×2, 3×3, …, n×n pixels for the generalization). Finally, we experimentally generate periodic super-Gaussian profiles to be visualized in the LCSLM (transmission SLM, 1024×768-pixels LC 2012 Translucent SLM), modifying the TIE as an optical test in order to analyze the optical elements by comparing the results with ZYGO/APEX.”

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Publication: Photonics
Issue/Year: Photonics, Volume 10; Number 1; Pages 39; 2022
DOI: 10.3390/photonics10010039

Functional pixels: a pathway towards true holographic displays using today’s display technology

Author(s):

Falldorf, Claas; Rukin, Ilja; Müller, André F.; Kroker, Stefanie & Bergmann, Ralf. B.

Abstract:

“Today’s 3D dynamic holographic display techniques suffer from severe limitations due to an available number of pixels that is several orders of magnitude lower than required by conventional approaches. We introduce a solution to this problem by introducing the concept of functional pixels. This concept is based on pixels that individually spatially modulate the amplitude and phase of incident light with a polynomial function, rather than just a constant phase or amplitude. We show that even in the simple case of a linear modulation of the phase, the pixel count can be drastically reduced up to 3 orders of magnitude while preserving most of the image details. This scheme can be easily implemented with already existing technology, such as micro mirror arrays that provide tip, tilt and piston movement. Even though the individual pixels need to be technologically more advanced, the comparably small number of such pixels required to form a display may pave the way towards true holographic dynamic 3D displays.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 30; Number 26; Pages 47528; 2022
DOI: 10.1364/oe.474589

Optical classification and reconstruction through multimode fibers

Author(s):

Kürekci, Şahin

Abstract:

“When a light beam travels through a highly scattering medium, two-dimensional random intensity distributions (speckle patterns) are formed due to the complex scattering within the medium. Although they contain valuable information about the input signal and the characteristics of the propagation medium, the speckle patterns are difficult to unscramble, which makes imaging through scattering media an extremely challenging task. Multimode fibers behave similarly to scattering media since they scramble the input information through modal dispersion and create speckle patterns at the distal end. Because multimode fibers are compact and low-cost structures with the ability to transmit large amounts of data simultaneously for long distances, decoding the speckle patterns formed by a multimode fiber and reconstructing the input information has great implications in a wide range of applications, including fiber optic communication, sensor technology, optical imaging, and invasive biomedical applications such as endoscopy. In this thesis, we decode the speckle patterns and reconstruct the input information on the proximal end of a multimode fiber in three different scenarios. Our choice of input signals consists of numbers encoded as binary digits, handwritten letters, and optical frequencies. We train a deep learning model to classify and reconstruct the handwritten letters, while for the rest of the cases, we construct a transmission matrix between the input signals and the output speckle patterns, and solve the inverse propagation equation algebraically. In all cases, the relation between a speckle pattern and the corresponding input signal is learned with low error rates; thus, the signals are classified and reconstructed successfully using the speckle patterns they created. Classifying digits, letters, or images with speckle information aims to build useful systems in optical imaging, communication, and cryptography, while the classification of optical frequencies paves the way for building novel spectrometers. In addition to replicating the currently existing compact, low-budget, and high-resolution multimode fiber spectrometer, we also build a single-pixel fiber spectrometer in order to increase the compactness on the detection side and expand the application areas of the system. The single-pixel spectrometer we offer is based on the integrated intensity measurements of a fixed target region, where the light is focused by shaping the wavefront with a spatial light modulator. Spatial light modulators and wavefront shaping techniques are also utilized in other classification tasks in this thesis to generate the desired input signals.”

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Publication: Middle East Technical University, Thesis
Issue/Year: Graduate School of Natural and Applied Sciences, Thesis, 2022
DOI: https://hdl.handle.net/11511/101287

Binocular holographic display based on the holographic optical element

Author(s):

Qin, Xiujuan; Sang, Xinzhu; Li, Hui; Yu, Chongxiu; Xiao, Rui; Zhong, Chongli; Sun, Zhi; Dong, Yu & Yan, Binbin

Abstract:

“Due to the limited pixel pitch of the spatial light modulator (SLM), the field of view (FOV) is insufficient to meet binocular observation needs. Here, an optimized controlling light method of a binocular holographic threedimensional (3D) display system based on the holographic optical element (HOE) is proposed. The synthetic phase-only hologram uploaded onto the SLM is generated with the layer-based angular spectrum diffraction theory, and two different reference waves are introduced to separate the left view and the right view of the3Dscene. The HOE with directional controlling light parameters is employed to guide binocular information into the left-eye and the right-eye viewing zones simultaneously. Optical experiments verify that the proposed system can achieve binocular holographic augmented reality 3D effect successfully with real physical depth, which can eliminate the accommodation-vergence conflict and visual fatigue problem. For each perspective, the FOV is 8.7 when the focal length of the HOE is 10 cm. The width of the viewing zone is 2.3 cm when the viewing distance is 25 cm.”

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Publication: Journal of the Optical Society of America A
Issue/Year: Journal of the Optical Society of America A, Volume 39; Number 12; Pages 2316; 2022
DOI: 10.1364/josaa.473989

Accommodation through simulated multifocal optics

Author(s):

Vedhakrishnan, Shrilekha; de Castro, Alberto; Vinas, Maria; Aissati, Sara & Marcos, Susana

Abstract:

“We evaluated the interaction of multifocal patterns with eye’s accommodation. Seven patterns were mapped on the spatial light modulator and the deformable mirror of an adaptive optics visual simulator, and projected onto the subjects eyes, representing different contact lens designs: NoLens, Bifocal Center Distance (+2.50D), Bifocal Center Near (+2.50D) and Multifocal Center Near-MediumAdd (+1.75D) and Center Near HighAdd (+2.50D), positive and negative spherical aberration (±1µm). The change in spherical aberration and the accommodative response to accommodative demands were obtained from Hartmann-Shack measurements. Positive spherical aberration and Center Distance designs are consistent with a higher accommodative response (p=0.001 & p=0.003): steeper shift of SA towards negative values and lower accommodative lag.”

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Publication: Biomedical Optics Express
Issue/Year: Biomedical Optics Express, Volume 13; Number 12; Pages 6695; 2022
DOI: 10.1364/boe.473595
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