Encoding the Intensity and Phase Gradient of Light Beams with Arbitrary Shapes

Author(s):

Serrano-Trujillo, Alejandra; Ruiz-Cortés, Victor

Abstract:

“We present an approach for engineering the intensity trajectory and phase gradient of light beams with arbitrary shapes by estimating their parametric equations using Freeman chain code and by applying the fast Fourier transform. The analysis of the electric field distribution expected for a given curve allows the phase extraction over each local coordinate, generating a phase pattern to be displayed over a spatial light modulator. The intensity and phase gradient of eight different shapes is encoded during our experiments. The far field intensity profiles are captured and compared in shape to those designed, while the encoded phase is demonstrated by implementing a common path interference setup with a pair of beams from the spatial light modulator. The designed beams, initially drawn either by hand or generated with software, exhibit both the intensity and phase profiles encoded onto them.”

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Publication: Applied Sciences
Issue/Year: Applied Sciences, Volume 13; Number 5; Pages 3192; 2023
DOI: 10.3390/app13053192

Modeling of laser beam shaping by volume holographic phase masks

Author(s):

Vashchenko, Elena Shirshneva; Mohammadian, Nafiseh; Divliansky, Ivan & Glebov, Leonid

Abstract:

“Laser material processing applications often require the flat-top beam profile within focal spots ranged below 100 μm. For high power applications, volume phase masks recorded in photo- thermo-refractive glass (PTR) are promising. The problem is how to achieve simultaneously a high-quality shape and a small size of the beam. The commercial phase masks usually show large power losses in the beam wings, only about 40% of the energy was concentrated under the 95% level. By applying a gray phase mask instead of binary mask, one can reduce losses in the wings of the beam. In this work, a spatial light modulator (SLM) with designed computer generated holograms (CGHs) was used as a beam converter. Using the SLM with programmed gray mask allows obtaining flexible laser beam shaping, but beam quality is limited by imposed parameters of the SLM. The requirements for obtaining a square flat-top beam with energy lost in wings less than 10% is described. It was found that for sharp edges of the square flat-top beam, it is necessary that the size of the output beam contains at least 16 pixels of SLM. This fact is a consequence of the Fourier transform, where high spatial frequencies are responsible for the shape. The concept design of the scanning progressive mechanism of the master volume phase mask recording to exclude the influence of SLM work area dimensions is discussed.”

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Publication: Proc. SPIE 12402
Issue/Year: Proc. SPIE 12402, Components and Packaging for Laser Systems IX, 124020A, 2023
DOI: 10.1117/12.2651281

Solid-state 360° optical beamforming for reconfigurable multicast optical wireless communications

Author(s):

Zeng, Shihao; Zhang, Yanfeng; Liu, Junyi; Lin, Zhenrui; Lin, Zhongzheng; Chen, Hongjia; Liu, Jie & Yu, Siyuan

Abstract:

“Optical wireless communication is an attractive technique for data center interconnects due to its low latency line-of-sight connectivity. Multicast, on the other hand, is an important data center network function that can improve traffic throughput, reduce latency, and make efficient use of network resources. To enable reconfigurable multicast in data center optical wireless networks, we propose a novel 360° optical beamforming scheme based on the principle of superposition of orbital angular momentum modes, emitting beams from the source rack pointing towards any combination of other racks so that connections are established between the source and multiple destination racks. We experimentally demonstrate the scheme using solid state devices for a scenario where racks are arranged in a hexagonal formation in which a source rack can connect with any number of adjacent racks simultaneously, with each link transmitting 70 Gb/s on-off-keying modulations at bit error rates of <10−6 at 1.5-m and 2.0-m link distances.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 31; Number 6; Pages 10070; 2023
DOI: 10.1364/oe.477553

Highly transparent wave front printed volume holograms realized by amplitude-modulated incoherent pre-illumination

Author(s):

Wilm, Tobias; Wieland, Max; Fiess, Reinhold & Stork, Wilhelm

Abstract:

“We present highly transparent, wave front printed volume holographic optical elements (vHOEs), realized with a new recording method based on the pre-illumination of incoherent light patterns. The introduced amplitudemodulated pattern illuminates a distinct area on the unexposed, photopolymer-based holographic recording material prior to the hologram recording sequence. The incoherent pre-illumination scheme enables a precise tuning of the material’s local photosensitivity without the formation of a holographic volume diraction grating. As a consequence, the pre-illumination exposure signicantly suppresses the formation of transparency diminishing structures in the material that are formed concurrently with the volume diraction grating during the hologram recording sequence. The pre-illumination component is integrated in an extended immersion-based wave front printing setup, which realizes vHOEs by sequentially recording single holographic elements in an array-like structure. A wide range of dierent recording congurations is enabled by our recording setup due to independent modulation of both wave fronts and the possibility to realize large o-axis recording angles. We introduce two hologram characterization methods, based on a diraction eciency and a slanted-edge method analysis, which are used to evaluate the implemented pre-illumination method and demonstrate signicant improvements to the see-through quality of the presented wave front recorded vHOEs.”

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Publication: Proc. SPIE 12445
Issue/Year: Proc. SPIE 12445, Practical Holography XXXVII: Displays, Materials, and Applications, 124450S, 2023
DOI: 10.1117/12.2647361

Generation of high-dimensional caustic beams via phase holograms using angular spectral representation

Author(s):

Sun, Zhuo; Hu, Juntao; Wang, Yishu; Ye, Wenni; Qian, Yixian & Li, Xinzhong

Abstract:

“Using angular spectral representation, we demonstrate a generalized approach for generating high-dimensional elliptic umbilic and hyperbolic umbilic caustics by phase holograms. The wavefronts of such umbilic beams are investigated via the diffraction catastrophe theory determined by the potential function, which depends on the state and control parameters. We find that the hyperbolic umbilic beams degenerate into classical Airy beams when the two control parameters are simultaneously equal to zero, and elliptic umbilic beams possess an intriguing autofocusing property. Numerical results demonstrate that such beams exhibit clear umbilics in 3D caustic, which link the two separated parts. The dynamical evolutions verify that they both possess prominent self-healing properties. Moreover, we demonstrate that hyperbolic umbilic beams follow along a curve trajectory during propagation. As the numerical calculation of diffraction integral is relatively complex, we have developed an effective approach for successfully generating such beams by using phase hologram represented by angular spectrum. Our experimental results are in good agreement with the simulations. Such beams with intriguing properties are likely to be applied in emerging fields such as particle manipulation and optical micromachining.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 31; Number 5; Pages 7480; 2023
DOI: 10.1364/oe.483169

Optical Bottle Shaping Using Axicons with Amplitude or Phase Apodization

Author(s):

Khonina, Svetlana N.; Ustinov, Andrey V.; Kharitonov, Sergey I.; Fomchenkov, Sergey A. & Porfirev, Alexey P.

Abstract:

“We investigate the formation of single and multiple optical bottle beams on the optical axis using a diffractive axicon with amplitude or phase apodization. The proposed approach allows one to control the location and the contrast of the boundaries of the generated dark intensity regions on the optical axis. Experimental results obtained using a spatial light modulator are in good agreement with numerically obtained ones. We successfully used the designed and experimentally formed set of three optical bottle beams for trapping light-absorbing agglomerations of carbon nanoparticles in air under the action of photophoretic forces. This confirms the efficiency of the proposed approach for optical manipulation applications.”

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Publication: Photonics
Issue/Year: Photonics, Volume 10; Number 2; Pages 200; 2023
DOI: 10.3390/photonics10020200

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

Ultrafast Transverse Modulation of Free Electrons by Interaction with Shaped Optical Fields

Author(s):

Madan, Ivan; Leccese, Veronica; Mazur, Adam; Barantani, Francesco; LaGrange, Thomas; Sapozhnik, Alexey; Tengdin, Phoebe M.; Gargiulo, Simone; Rotunno, Enzo; Olaya, Jean-Christophe; Kaminer, Ido; Grillo, Vincenzo; de Abajo, F. Javier Garcia; Carbone, Fabrizio & Vanacore, Giovanni Maria

Abstract:

“Spatiotemporal electron-beam shaping is a bold frontier of electron microscopy. Over the past decade, shaping methods evolved from static phase plates to low-speed electrostatic and magnetostatic displays. Recently, a swift change of paradigm utilizing light to control free electrons has emerged. Here, we experimentally demonstrate arbitrary transverse modulation of electron beams without complicated electron-optics elements or material nanostructures, but rather using shaped light beams. On-demand spatial modulation of electron wavepackets is obtained via inelastic interaction with transversely shaped ultrafast light fields controlled by an external spatial light modulator. We illustrate this method for the cases of Hermite-Gaussian and Laguerre-Gaussian modulation and discuss their use in enhancing microscope sensitivity. Our approach dramatically widens the range of patterns that can be imprinted on the electron profile and greatly facilitates tailored electron-beam shaping.”

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Publication: ACS Photonics
Issue/Year: ACS Photonics, 2022
DOI: 10.1021/acsphotonics.2c00850

High-Flexibility Control of Structured Light with Combined Adaptive Optical Systems

Author(s):

Grunwald, Rüdiger; Jurke, Mathias; Bock, Martin; Liebmann, Max; Bruno, Binal Poyyathuruthy; Gowda, Hitesh & Wallrabe, Ulrike

Abstract:

“Combining the specific advantages of high-resolution liquid-crystal-on-silicon spatial light modulators (LCoS-SLMs) and reflective or refractive micro-electro-mechanical systems (MEMS) presents new prospects for the generation of structured light fields. In particular, adaptive self-apodization schemes can significantly reduce diffraction by low-loss spatial filtering. The concept enables one to realize low-dispersion shaping of nondiffracting femtosecond wavepackets and to temporally switch, modulate or deflect spatially structured beams. Adaptive diffraction management by structured illumination is demonstrated for piezo-based and thermally actuated axicons, spiral phase plates (SPPs) and Fresnel bi-mirrors. Improved non-collinear autocorrelation with angular-tunable Fresnel-bi-mirrors via self-apodized illumination and phase contrast of an SLM is proposed. An extension of the recently introduced nondiffractive Talbot effect to a tunable configuration by combining an SLM and a fluid lens is reported. Experimental results for hexagonal as well as orthogonal array beams are presented.”

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Publication: Photonics
Issue/Year: Photonics, Volume 9; Number 1; Pages 42; 2022
DOI: 10.3390/photonics9010042

Electro-Optic Modulation of Higher-Order Poincar’e Beam Based on Nonlinear Optical Crystal

Author(s):

Han, Lu; Li, Zhan; Chen, Chao; Sun, Xin; Zhang, Junyong & Liu, Dean

Abstract:

“Vector beams (VBs) have spatially inhomogeneous polarization states distribution and have been widely used in many fields. In this paper, we proposed a method to modulate polarization states of higher-order Poincaré (HOP) beams and designed a system based on Mach-Zehnder interferometers, in which polarization state (include azimuth and ellipticity) of generated HOP beams were modulated by linear electro-optic (EO) effect of nonlinear optical crystals. Using this method, the polarization state of generated HOP beams could be controlled by voltage signal applied on EO crystals, which makes the process of the polarization state change with no optical element moving and mechanical vibrations. Besides, due to the flexibility of the voltage signal, the polarization state could be switched directly and immediately.”

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Publication: Photonics
Issue/Year: Photonics, Volume 9; Number 1; Pages 41; 2022
DOI: 10.3390/photonics9010041
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