Diffraction Of Light Beams Research Articles

Diffraction of displaced Gaussian light beams on ultrasound in paratellurite crystals

The Bragg diffraction of displaced Gaussian light beams on a slow shear ultrasonic wave in paratellurite crystals, in which the beam energy is efficiently transferred from the zero diffraction order to the first, is investigated. It is established that circularly polarized light beams should be used to optimize the energy exchange of diffracted light beams in the considered geometry of acousto-optic interaction. It is shown that the diffracted beams have the form of displaced Gaussian beams, the spatial structure of which is determined by the displacement parameter of the incident beam and the ultrasound power.

Fluid-responsive tunable metasurfaces for high-fidelity optical wireless communication.

Optical wireless communication (OWC), with its blazing data transfer speed and unparalleled security, is a futuristic technology for wireless connectivity. Despite the significant advancements in OWC, the realization of tunable devices for on-demand and versatile connectivity still needs to be explored. This presents a considerable limitation in utilizing adaptive technologies to improve signal directivity and optimize data transfer. This study proposes a unique platform that utilizes tunable, fluid-responsive multifunctional metasurfaces offering dynamic and unprecedented control over electromagnetic wave manipulation to enhance the performance of OWC networks. We have achieved real-time, on-demand beam steering with vary-focusing capability by integrating the fabricated metasurfaces with different isotropic fluids. Furthermore, the designed metasurfaces are capable of polarization-based switching of the diffracted light beams to enhance overall productivity. Our research has showcased the potential of fluid-responsive tunable metasurfaces in revolutionizing OWC networks by significantly improving transmission reliability and signal quality through real-time adjustments. The proposed methodology is verified by designing and fabricating an all-dielectric metasurface measuring 500 μm × 500 μm and experimentally investigating its fluid-responsive vary-focal capability. By incorporating fluid-responsive properties into spin-decoupled metasurfaces, we aim to develop advanced high-tech optical devices and systems to simplify beam-steering and improve performance, adaptability, and functionality, making the devices suitable for various practical applications.

Polarization Conversion of Light Diffracted from InP Nanowire Photonic Crystal Arrays

AbstractThis work investigates the polarization state of light diffracted from uncoated and gold‐coated InP nanowire photonic crystal arrays grown by selective area epitaxy. Experimental data and finite‐difference time‐domain simulations show that both the intensity and the ellipticity of the polarization state of the diffracted light beam can be controlled by the nanowire dimensions and gold coating, while the diffracted angle remains unchanged with respect to variations of these parameters. A nominally 10 nm‐thick gold film deposited around the nanowires enhances the diffraction intensity by plasmonic effects. These results demonstrate that the controlled conversion of incident linearly polarized light to circularly polarized or rotated linearly polarized diffracted light can find applications in photonic integrated circuits. The high sensitivity of the polarization state with respect to alterations of the nanowire dimension opens new prospects in the areas of semiconductor metrology and microchip inspection as well as for submicron particle detection.

Transmission functions of transmissive multilayer inhomogeneous holographic photopolymer liquid crystal diffraction structures

A new analytical model of diffraction of quasimonochromatic light beams on spatially inhomogeneous multilayer diffraction structures formed in photopolymer material with nematic liquid crystals having smooth optical inhomogeneity in the thickness of layers is presented. It is shown that when an applied electric field isapplied to diffraction layers containing a photopolymer composition with a high proportion of liquid crystalline component, a transformation of the selective response with a significant shift in angular selectivity occurs

Acousto-optical modulation of airy light beams in crystals

The non-collinear diffraction of Airy light beams on ultrasound in the regime of weak and strong acousto-optical (AO) interaction is investigated. Expressions are obtained for the complex amplitudes of diffracted waves in the general case of an anisotropic medium. It is shown that with an increase in the dimensionless parameter of the Airy beam, the efficiency of Bragg diffraction decreases. At the same time, however, the shape of the modulation curve remains unchanged. It is established that the greatest efficiency of anisotropic Bragg diffraction is achieved for a case when the diffracted Airy beam propagates along the front of the ultrasonic wave. It is shown that the efficiency of AO diffraction of Airy beam on an amplitude-modulated wave is determined by the diffraction efficiencies of constant components in a diffracted beam.

Nanometer-scale displacement measurement using a simple diffraction grating with a quadrature detection technique.

A phase-sensitive transparent grating interferometer is proposed to measure small displacements. A transparent grating is inserted between a light source and a reflective mirror. The diffracted light beams of the forward and backward propagation are superposed to form the interference pattern. When two detectors are placed at two different positions of the interference fringe in such a way that the signals have quadrature phase difference, the phase variation can infer the displacement of the reflected mirror. This simple setup can measure the displacement of the mirror at nanometer scale with 98.2% accuracy, high precision with 10 nm in standard deviation, and lowest bound of 0.4 nm resolution.

Grating-based 2D displacement measurement with quadruple optical subdivision of a single incident beam.

We propose a new symmetrical heterodyne grating displacement measurement method, based on 2D grating and single diffraction quadruple subdivision method. Using a dual-frequency laser with a wavelength of 632.8 nm, output power of 2.2 mW, and a 1200 l/mm 2D grating, eight diffracted light beams interfere in pairs in the X and Y directions through a turning element. The detection system's measurement accuracy was assessed experimentally. The system measurement resolution in the X and Y directions is better than 3 nm; the grating displacement measurement errors within a 10 mm range are better than ±30 nm and ±40 nm, and the repeatability error is better than ±25 nm. The method is not only applicable to nanoscale 2D displacement measurement technology but also can be used for ultra-precision positioning and ultra-precision processing, with the potential for picometer-level improvement.

Optical Vortices: 3D Optical Vortex Lattices (Ann. Phys. 7/2021)

In article number 2100114, Denis Ikonnikov and co-workers report the results of Fresnel diffraction of light beams with a topological charge on a 2D regular amplitude transparency mask. The cover illustrates the complex optical field behind the grating, representing all 3D lattice of optical vortices, which is formed owing to the Talbot effect. These results are confirmed by the experimental reconstruction of all 3D optical vortex lattices. It is shown that the optical vortices are created and annihilated during light propagation behind the mask with the preservation of the total topological charge. The 3D optical vortex lattices are considered to be promising for transport and manipulation of multiple micro-objects.

3D Optical Vortex Lattices

AbstractFresnel diffraction of light beams with a topological charge on a 2D regular amplitude transparency mask is studied. Numerical predictions show that the 3D optical lattices of optical vortices can be formed using the Talbot effect, with these predictions confirmed by the experimental reconstruction of all 3D optical vortex lattices. The periodicity of the 3D optical vortex lattices is determined by the light wavelength and periodicity of a transparency mask. Furthermore, it is shown that the optical vortices are created and annihilated during light propagation behind the mask with the preservation of the total topological charge. The 3D optical vortex lattices are considered to be tolerant to the perturbations induced by trapped particles caused by the features of the Talbot effect. The 3D optical vortex lattices open new possibilities for light–matter interactions and the related applications.

Diffraction of quasimonochromatic light beams on multilayer inhomogeneous photopolymer holographic diffraction structures

A theoretical model of quasimonochromatic light beams diffraction by spatially inhomogeneous transmitting multilayer diffraction structures formed in a photopolymer material by a holographic method is presented in this work. This model takes into account the heterogeneity of the amplitude profile of the first harmonic of the refractive index of each layer of the multilayer structure. The model is presented using method of transfer matrixes whose components are the solutions of the coupled waves equations of partial derivates.

Interaction between Light and Transmission Multi-Layered Heterogeneous Photopolymer Holographic Diffraction Structures

An analytical model of the diffraction of quasi-monochromatic light beams on spatially inhomogeneous multilayer diffraction structures formed in a photopolymer material by holographic means is presented. This model allows for inhomogeneities in the amplitude profile of the first harmonic of the refractive index of each layer of the multilayer structure.

Peculiarities of the acousto-optical interactions of Bessel light beams in crystals

The noncollinear acousto-optical filtration of diffracted Bessel light beams in uniaxial paratellurite crystals has been investigated. With the use of the method of overlap integrals it is shown that independently on the order of Bessel light beams in the conditions of transverse phase-matching of diffracted waves in the range of optical spectrum of 0.4-1.1 nm in paratellurite crystals the bandwidth of transmission of ∼0.52 nm is reached due to detuning from Bragg’s synchronism only. It is shown that in uniaxial gyrotropic crystals polarization-independent diffraction of Bessel light beams is possible, i.e. Bragg diffraction efficiency is independent of the polarization state of the incident beam. It has been stated that the physical reason of such diffraction is simultaneous realization of two processes of anisotropic scattering under which the Bragg synchronism conditions are realized for the orthogonally polarized elliptical Bessel beams.

Holographic formation of photon structures by Bessel-like and Gaussian light fields in photopolymer materials taking into account two-beam interaction and small contrasts

This paper presents a theoretical model of the holographic formation of photon structures (PS) in a photopolymer material (PPM) by Bessel-like and Gaussian light beams, taking into account the self-diffraction of recording light beams in areas of low contrast of the interference pattern. It was demonstrated by numerical simulation and experiment that the influence of the self-diffraction effect leads to an increase in the level of the side maxima of the diffracted light beam.

Holographic formation of diffractive optical elements in photopolymer with two-beam interactions taken into account

This work presents the theoretical model of holographic formation of the diffraction optical element (DOE) in photopolymer material (PPM). DOE allows transforming Gaussian light fields to Bessel-like. Self-diffraction of writing light beams at low contrasts is taken into account. It is experimentally shown that influence of effect of self-diffraction in areas of low contrast leads to amplification of level of side’s maxima of diffracted light beam.

Diffraction of a Gaussian beam near the beam waist

The behavior of the light field near the beam waist has attracted considerable attention due to the studies of the light spin-orbit interaction: it’s manifestation as well as potential applications. Similarly, the light beam diffraction can reveal new light particularities. We have studied the far-field diffraction of a Gaussian beam by a half-plane edge placed near the beam waist. We have solved numerically the Helmholtz equation using the spectral method. We have found symmetric penetration of the light energy into the shadow region if we placed the half-plane edge exactly in the beam waist region. The symmetry gets broken down as the edge moves along the optical axis toward or away from the lens at a distance more than 0.01% of the focal length. Experimental verification has been obtained using a Gaussian beam focused by a lens of 4 cm focal length.The results can be used for precise determination of the beam waist position while investigating the effects of the light spin-orbit interaction in focused Gaussian beams.

Measurement of thickness of thin film by fitting to the intensity profile of Fresnel diffraction from a nanophase step.

Diffraction of light beams from the phase steps due to abrupt/sharp changes in the boundary of the steps leads to Fresnel fringes whose visibility and intensity profile depend on the change of the step height or light incident angle. The visibility has been utilized in measurements of different physical quantities. In this paper, for the first time to our knowledge, by introducing the fitting method as a fast method, we show that by fitting the theoretical intensity distributions on the experimental intensity profiles of the light diffracted from a step at different incident angles, one can specify the step height with precision of a few nanometers. In addition, we show that this approach provides accurate film thickness in a broad range of thicknesses using modest instrumentation. Furthermore, based on Fresnel diffraction from the phase step, we have manufactured and trademarked an optical device for measuring the thickness of thin films.

Double Bragg Diffraction of Bessel Light Beams on Ultrasound in Uniaxial Gyrotropic Crystals

Noncollinear double acousto-optical diffraction of Bessel light beams on ultrasound in uniaxial gyrotropic crystals is studied theoretically and experimentally. It is found that when a Bessel light beam propagates along the optic axis of a crystal, the diffracted light beams of the ±1 order are symmetric relative to the incident beam and have roughly the same intensity. Double Bragg diffraction is also observed when a Bessel light beam is incident at the Bragg angle and near the optic axis, but the intensities of the +1 and +2 order diffracted beams are significantly different.

Spatial solitons supported by graphene/hexagonal boron nitride heterostructures

In this paper, we show how the diffraction of light beams is balanced by the nonlinearity of graphene/hexagonal boron nitride heterostructures, which discretely occurs in the very thin graphene layers, forming spatial solitons. We also discuss the effects of the layer number and the peak E-field amplitude on the soliton width.

Polarizer-Free Acousto-Optic Monochromators

Monochromators based on a noncollinear acousto-optic filter without external polarizers have been studied. As an element to select an operating diffracted light beam, (1) a spatial filter-telescope and (2) an output plane of a filter crystal rotated in a diffraction plane have been used. In the latter case, dispersion of the acousto-optic filter crystal is compensated using a correcting prism made from the same crystal and placed behind an output filter plane along a path of a filtered light beam. As a result, the transmission coefficient of the monochromator is increased upon an effective compensation of the angular drift of the filtered light beam, the monochromator design is simplified, and its sizes are decreased.

Development of acousto-optic spatial light modulator unit for effective control of light beam intensity and diffraction angle in 3D holographic display applications

An acousto-optic (AO) based holographic display unit was developed using surface acoustic wave (SAW) with different wavelength to modulate the diffraction angles, intensities, and phases of light. The new configurations were employed to control two beams simultaneously by using a single chirp inter-digital transducer (IDT), and a micro-lens array was integrated at the end of the waveguide layer to focus the diffracted light on to the screen. Two incident light beams were simultaneously modulated by using different refractive grating periods generated from chirp IDT. A diffraction angle of about 5° was obtained by using a SAW with a frequency of 430 MHz. The increase in the SAW input power enhances the diffraction efficiency of the light beam at the exit. The obtained maximum diffraction efficiency is ~70% at a frequency of 430 MHz. The sloped shape of the waveguide entrance and a tall rounded Ni poles help in coupling the incident light to the waveguide layer. The diffracted beam was collected through the lens, which increased the intensity of light in the viewing plane. COMSOL multi-physics and coupling of mode (COM) modeling were performed to predict the device performance and compared with the experimental results.