Light Wave Propagation Research Articles

16-channel photonic solver for optimization problems on a silicon chip

A programmable photonic solver for quadratic unconstrained binary optimization (QUBO) problems is demonstrated with a hybrid optoelectronic scheme, which consists of a photonic chip and an electronic driving board. The photonic chip is employed to perform the optical vector-matrix multiplication (OVMM) to calculate the cost function of the QUBO problem, while the electronic processor runs the heuristic algorithm to search for the optimal solution. Due to the parallel and low-latency propagation of lightwave, the calculation of the cost function can be accelerated. The photonic chip is fabricated on the silicon on insulator (SOI) substrate and integrates 16 high-speed electro-optic modulators, 88 thermo-optic phase shifters, and 16 balanced photodetectors. The computing speed of the photonic chip is 1.66 TFLOP/s. As a proof of principle, two randomly generated 16-dimensional QUBO problems are solved with high successful probabilities. These results present the potential of fast solving optimization problems with integrated photonic systems.

EXPERIMENT TO DETECT THE ABSOLUTE VELOCITY OF EARTH IN THE UNIVERSE

A number of experiments have been carried out to measure the velocity of earth in the space but absolute velocity of earth could not be detected. One of the most famous Michelson and Morley experiment was conducted in the year 1887 to detect the motion of earth with reference to luminiferous aether a supposed medium permeating space that was thought to be the carrier of light waves but unexpected results were obtained. The experiment has given negative results, MMX type experiments have been repeated so many times with steadily increasing sensitivity from 1902 to 1930 and more recently in the year 2009 by optical resonator but all the experiments confirmed the negative results of MMX. Albert Einstein submitted his special theory of relativity in the year 1905 and stated that there is no medium like aether for propagation of light waves and there is no absolute velocity in the universe, all the motions are relative. Relative velocity of earth has been measured by various methods and observations such as stellar parallax, position of stars and planets, satellite laser ranging, GPS and CMB radiation. Second postulate of STR states that velocity of light is constant in all inertial frames of reference, there is no effect of motion of source of light or observer on the speed of light. As the velocity of light is a universal Constant hence any velocity with reference to speed of light will be absolute velocity. On the basis of second postulate of STR absolute velocity of earth in the universe can be determined by experiment based on the laser light beams. A laser beam may be directed on the fixed screen and movement of laser spot due to motion of earth may be observed. The displacement of laser spot with passage of time may be observed to determine the velocity of earth. In the present article it is explained how the velocity of earth may be detected by measuring displacement of laser spot. The displacement of laser spot from its normal position will determine the absolute velocity of earth in the universe.

Mathematical analysis of bent optical waveguide eigenvalue problem

Abstract This work investigates a mathematical model of the propagation of lightwaves in bent optical waveguides. This modeling leads to a non-self-adjoint eigenvalue problem for differential operator defined on the unbounded domain. Through detailed analysis, a relationship between the real and imaginary parts of the complex-valued propagation constants was constructed. Using this relation, it is found that the real and imaginary parts of the propagation constants are bounded, meaning they are limited within certain region in the complex plane. The orthogonality of these bent modes is also proved. By the asymptotic analysis of these modes, it is proved that as r → ∞ the behavior of the eigenfunctions is proportional to 1 / r .

On-demand photonic Ising machine with simplified Hamiltonian calculation by phase encoding and intensity detection

The photonic Ising machine is a new paradigm of optical computing that takes advantage of the unique properties of light wave propagation, parallel processing, and low-loss transmission. Thus, the process of solving combinatorial optimization problems can be accelerated through photonic/optoelectronic devices, but implementing photonic Ising machines that can solve arbitrary large-scale Ising problems with fast speed remains challenging. In this work, we have proposed and demonstrated the Phase Encoding and Intensity Detection Ising Annealer (PEIDIA) capable of solving arbitrary Ising problems on demand. The PEIDIA employs the heuristic algorithm and requires only one step of optical linear transformation with simplified Hamiltonian calculation by encoding the Ising spins on the phase term of the optical field and performing intensity detection during the solving process. As a proof of principle, several 20 and 30-spin Ising problems have been solved with high ground state probability (≥0.97/0.85 for the 20/30-spin Ising model).

On the distinction between corpuscular and wave processes and the arbitrariness in the basis of special relativity theory

This article is devoted to the criticism of the wave-particle dualism and the provisions of the special theory of relativity (SRT). The fallacy of accepting the extended principle of relativity and identifying particles and waves is shown. The substantiation is given that the own fields of physical objects, which are material substances and spatially connect physical objects with each other, are the medium of propagation of light waves. The causal and visual picture of the propagation of light waves is considered, and the features of the mechanism of their propagation in comparison with other types of waves are described. On the basis of an alternative method for obtaining the relativistic law of velocities addition, the inconsistency of the principle of invariance of the interval adopted in the framework of SRT is shown. The inconsistency of the SRT positions and conclusions regarding the so-called relativistic effects—time dilation, mass increase, length decrease, as well as the energy of relativistic particles is shown. The presence of the clock paradox is shown by a simple example. The conclusion is made about the incorrectness of using mathematical transformations of Lorentz and the four-dimensional continuum in the physical representation.

Propagation of light wave around planets in cosmic space

The propagation of light wave around planets is studied in this paper. There are planets having an atmosphere with permittivity which is high close to the planet surface and gradually decreases with elevation. Based on the results of our investigations when the light beam propagates parallel to the layers of atmosphere, its propagation direction is gradually deviating from the straight line toward higher permittivity layers. This way the light wave follows a curved route. The aim of the paper is to provide a qualitative picture for the phenomenon of light wave propagation bending around cosmic planets.Some planets have no atmosphere. Their surface is not smooth, in addition to plains there are hills and mountains with varying heights. Therefore, dielectric layers parallel to the planet surface can be considered by an equivalent average permittivity which is high at the planet surface and gradually decreases with the elevation. As its consequence the light beam tangentially incident to the planet surface deviates from the straight line and follows a curved route.Based on the results of present investigations, it is not necessary to assume that the cosmic space is curved close to a planet containing a huge mass.

Advances in light transverse momenta and optical lateral forces

Harnessing linear and angular momenta of light is one of the cornerstones in modern optics and has found tremendous applications in optical circuits, particle manipulation, metrology, quantum information processing, etc. Emerging theoretical protocols and experimental explorations have created a surge of interest in light lateral momenta and forces, which are perpendicular to the light wave propagation direction. However, there is yet a lack of a comprehensive and holistic overview of transverse momenta (both linear and angular) as well as of optical lateral forces (OLFs). In this article, we first review the most recent transverse momenta including the transverse spin angular momentum, optical skyrmions, as well as lateral momenta from directional side scattering, spin–orbit interaction, and surface plasmon polaritons. Since optical forces result from the momentum exchange between light and matter, the transverse momentum consequently gives rise to intriguing OLFs, which is the second topic of this article. Additional non-trivial lateral forces that combine optics with other effects from thermodynamics, electricity, and microfluidics, are also discussed. It should be emphasized that these momenta and forces ubiquitously exist in a broad range of optical phenomena and have often been neglected due to their unpredicted underlying physics and shortage of experimental means, especially prior to the last decade.

Light wave propagation and diffraction inhibition in three-dimensional photonic quasicrystal lattices

We have investigated the linear propagation of light wave in three-dimensional photonic quasicrystal lattices by numerical simulation. The diffraction characteristics of the light waves in the longitudinal non-modulated, in-phase modulated and out-of-phase modulated quasicrystal lattices have been compared and discussed. We have demonstrated the diffraction inhibition of light wave in three-dimensional photonic quasicrystals. Linear transverse light localization has been realized in the longitudinal out-of-phase modulated three-dimensional quasicrystal lattices by adjusting the structural parameters appropriately. Furthermore, the results also show that the longitudinal out-of-phase modulated photonic quasicrystals are easier to produce diffraction inhibition than the longitudinal out-of-phase modulated periodic lattices under low transverse refractive index contrast. Distortionless dot image transmission has numerically demonstrated in out-of-phase modulated photonic quasicrystals array. It provides a new way for distortion-free image transmission, which has promising applications in optical information transmission and all-optical signal processing.

Deep compression network for enhancing numerical reconstruction quality of full-complex holograms.

The field of digital holography has been significant developed in recent decades, however, the commercialization of digital holograms is still hindered by the issue of large data sizes. Due to the complex signal characteristics of digital holograms, which are of interferometric nature, traditional codecs are not able to provide satisfactory coding efficiency. Furthermore, in a typical coding scenario, the hologram is encoded and then decoded, leading to a numerical reconstruction via a light wave propagation model. While previous researches have mainly focused on the quality of the decoded hologram, it is the numerical reconstruction that is visible to the viewer, and thus, its quality must also be taken into consideration when designing a coding solution. In this study, the coding performances of existing compression standards, JPEG2000 and HEVC-Intra, are evaluated on a set of digital holograms, then the limitations of these standards are analyzed. Subsequently, we propose a deep learning-based compression network for full-complex holograms that demonstrates superior coding performance when compared to the latest standard codecs such as VVC and JPEG-XL, in addition to JPEG2000 and HEVC. The proposed network incorporates not only the quality of the decoded hologram, but also the quality of the numerical reconstruction as distortion costs for network training. The experimental results validate that the proposed network provides superior objective coding efficiency and better visual quality compared to the existing methods.

Influence of Free Motion of Atoms on Atomic Density-Dependent Effects in Nonlinear Laser Spectroscopy of Resonant Gas Media

We develop a nonlinear theory of propagation of a monochromatic light wave in a gas of two-level atoms under the condition of inhomogeneous Doppler lineshape broadening, while considering a self-consistent solution of the Maxwell–Bloch equations in the mean-field approximation using a single atom density matrix formalism. Our approach shows a significant deformation of the Doppler resonant lineshape (shift, asymmetry), which depends on the atomic density. These effects are a consequence of only the free motion of atoms in a gas and is not associated with interatomic interaction. In particular, the frequency shift of the field-linear contribution to the transmission signal is more than an order of magnitude greater than the shift due to the interatomic dipole–dipole interaction, and the first nonlinear correction has an even stronger deformation, which exceeds the effect of the interatomic interaction by three orders of magnitude. The found effects caused by the free motion of atoms require a significant revision of the existing picture of spectroscopic effects, which depend on the atomic density in a gas.

Modelling light wave propagation and interaction and dynamical regimes analysis using the Lyapunov exponents method in ring fibre cavities

The ‘Cabaret’ finite differences method allows the performance of fast and conclusive modelling of the microcavity temporal dynamics with group velocity dispersion, cross- and self- phase modulation included. The proposed scheme and model allow us to study the dynamics of a cavity with two counter-propagating pulses, second order dispersion, modulation instability, Rayleigh scattering and other effects along the cavity roundtrips number up to 106…7. The possibility of Lyapunov exponents mapping for the Raman and SBS fibre lasers and cavities is discussed.

Numerical investigations of 2-D optical free-form couplers for surface connections of photonic integrated circuits

Two-dimensional (2-D) connections and couplers play a key role in the design of computational, highly compact integrated circuits and optical communication circuits. 2-D designs allow for very large-scale optical integration (VLSOI) within photonic chips. In this paper, optimized parabolic 2-D couplers are presented for 2-D or surface connection of two parts of a photonic integrated circuit (PIC). Dimensions and structure optimization has been done by Nelder-Mead method through several design parameters, simultaneously. In addition, the light waves propagation is simulated in the optimized designs for different cases via the Finite Element Method (FEM) and the transmittance diagrams are reported for different design cases. Investigation of coupling rate is shown about 90–95 % for coupling at a 90-degree angle for the wavelength range 800–920 nm and about 80–90 % for the light coupling to the other part of optical chip for the same wavelength range. By comparing the light coupling rate in these 2-D designs with the 3-D samples, it has been found that despite the reduction of dimensions, the light coupling performance is still acceptable. Also, the simulation of the design and the results related to the integration of these couplers are given.

The Analysis of FSO Link Performance in Ulaanbaatar

Recently, developed countries are leading in telecommunications technology, and many studies are being conducted to transmit information through the free space (FSO) or atmosphere using optical frequency light waves. The natural factors that most affect the propagation of optical light waves are fog, rain, and snow. Ulaanbaatar is the capital of Mongolia and has an extreme and variable climate. This paper is devoted to analyzing FSO link performance during data transmission in Ulaanbaatar during heavy rain months (July-August) and simulation using OptiSystem software. Marshall and Palmer's model was used for data transmission using FSO link performance to estimate the rainfall reduction, and several factors such as BER rate and Q factor were investigated. We have made a detailed assessment of the result of rainfall on the FSO system in Mongolia based on the technical data on the weather in Ulaanbaatar in 2018, 2019, and 2020 for the three meteorological station servers of the world weather online site www.worldweatheronline.com.

A 3D indoor positioning system based on common visible LEDs

We propose a realistic 3D positioning system for indoor navigation that exploits visible Light Emitting Diodes (LEDs), placed on the ceiling. A unique frequency tone is assigned to each lamp and modulates its intensity in periodic time slots. The Time Difference of Arrival (TDOA) is measured without the need of a synchronization system between the sources and the receiver, then it is used to accurately estimate the receiver position. We first describe the theoretical approach, then propose the model and characterize the possible sources of noise. Finally, we demonstrate the proof-of-concept of the proposed system by simulation of lightwave propagation. Namely, we assess its performance by using Montecarlo simulations in a common room and estimate the impact of the different implementation parameters on the accuracy of the proposed solution. We find that, in realistic conditions, the technique allows for centimeter precision. Pushing the device requirements, the precision can be further increased to a sub-centimeter accuracy.

Phase retrieval using hologram transformation with U-Net in digital holography

Digital holography is a method of recording light waves emitted from an object as holograms and then reconstructing the holograms using light wave propagation calculations to observe the object in three dimensions. However, a problem with digital holography is that unwanted images, such as conjugate images, are superimposed as the hologram is reconstructed to create an observed image. In particular, the superimposition of conjugate light on the observed image is caused by the imaging device’s ability to record just the intensity distribution of light rather than the phase distribution of light. In digital holography, it has been shown that unwanted light can be eliminated by the phase-shift method. However, it is difficult to apply the phase-shift method to digital holographic microscopy (DHM), which takes only one shot of light intensity. Alternatively, machine learning methods called deep learning have been actively studied in recent years for image-related problems, with image transformation as an example. Furthermore, a method that combines digital holography and deep learning has been proposed to perform image transformation to remove conjugate images using deep learning on the reconstructed image of a hologram. In this study, we generated a pair of holograms with only light intensity distribution and holograms with complex amplitude by simulating light wave propagation, trained U-Net to perform image transformation that adds phase information to the hologram with only light intensity distribution, and proposed a method for phase retrieval and conjugate image removal for holograms using the learned U-Net. To verify the effectiveness of the proposed method, we evaluated the image quality of the reconstructed image of holograms before and after processing by U-Net. Results showed that the peak signal-to-noise ratio (PSNR) increased by 8.37 [dB] in amplitude and 9.06 [dB] in phase. The amplitude and phase of the structural similarity index (SSIM) increased by 0.0566 and 0.0143, respectively. Furthermore, the results of applying the proposed method to holograms captured by actual digital holography optics showed the effectiveness of the proposed method in eliminating conjugate images in the reconstructed images. These results show that the proposed method is capable of phase retrieval of holograms in a single shot without the need for a complex optical system. This is expected to contribute to the field of portable DHMs and other applications that require compact and simple optical systems.

Analytical study of perturbed chirped solitons with triple-power law nonlinearity

In this work, a novel class of analytical chirped soliton solutions of the triple-power law nonlinear Schrödinger equation with perturbations are constructed. This model is used to describe the propagation of light waves in a nonlinear medium with the higher-order nonlinear optical effects including the triple-power law nonlinearity, self-frequency shift and self-steepening. The results shown that exact chirped plane wave, bright and kink solitons can exist in this physical setting when the degree of nonlinearity satisfy 2m=3n.

Impact of arrangement, length and chemical potential on the robustness of graphene induced photonic bandgap in photonic crystals

The study of photonic crystals, artificial materials whose dielectric properties can be tailored according to the stacking pattern of their constituents, remains an attractive research area. Very recently, the propagation of light waves in periodic and quasiperiodic graphene embedded dielectric multilayers has also been considered. The presence of graphene between consecutive layers induces the emergence of the so-called graphene induced photonic bandgap. In this article, we employ a transfer-matrix treatment to study the effects of (i) random arrangement of the layers, (ii) length of the multilayer and (iii) chemical potential of graphene on the robustness of the graphene induced photonic bandgap (GIPBG) in one dimensional graphene-embedded photonic crystals. The photonic crystals considered here are composed of two dielectric materials, namely, silicon dioxide (layer A=SiO2) and titanium dioxide (layer B=TiO2). Our numerical results quantitatively show that the random arrangement and length of the multilayers cause minor changes in the bandgap edge of the low frequency GIPBG, i.e., the low frequency GIPBG is robust regarding composition and length of the structures. On the other hand, the chemical potential strongly affects the robustness of the low frequency GIPBG. In fact, the low frequency GIPBG is strongly dependent on the properties of graphene, reinforcing that it is possible to adjust its width and bandgap edge by tuning the chemical potential via a gate voltage.

Visualization and quantum control of light-accelerated condensates by terahertz multi-dimensional coherent spectroscopy

Characterizing and controlling high-order correlation of quantum systems is key for developing quantum devices and switching technologies. Although conventional static and ultrafast spectroscopy gives access to collective excitations characterizing quantum states, more exotic correlations cannot be easily separated from other contributions. Here we develop density matrix simulations to show that seventh-order-wave-mixing peaks with distinct temperature and field dependences in two-dimensional terahertz nonlinear spectra reveal light-induced correlations in non-equilibrium superconducting states. Above critical terahertz driving, these emerging peaks split from conventional peaks along the second axis introduced by pump-probe relative phase in two-dimensional frequency space. They are photo-generated by correlations between two-photon fluctuations and interacting quasi-particle and quasi-particle/Higgs superconductor excitations. By photo-inducing persistent symmetry breaking via light-wave propagation, we also demonstrate seventh-order-wave-mixing sensing of Higgs collective modes. Our theory suggests to use multi-dimensional spectroscopy for quantum sensing of light-driven superconductivity and paves a path for quantum operations by few-cycle-THz-periodic photocurrent modulation.

Controlling the Bandgaps of One-Dimensional TiO<sub>2</sub>/SiO<sub>2</sub>, TiO<sub>2</sub>/SnO<sub>2</sub>, and SiO<sub>2</sub>/SnO<sub>2</sub> Photonic Crystals Using the Transfer Matrix Method

One-dimensional photonic crystals (1D PhCs) have a unique ability to control the propagation of light waves, however certain classes of 1D oxides remain relatively unexplored for use as PhCs. Specifically, there has not been a comparative study of the three different 1D PhC structures to compare the influence of layer thickness, number, and refractive index on the ability of the PhCs to control light transmission. Herein, we use the transfer matrix method (TMM) to theoretically examine the transmission of 1D PhCs composed of layers of TiO2/SiO2, TiO2/SnO2, SiO2/SnO2, and combinations of the three with various top and bottom layer thicknesses to cover a substantial region of the electromagnetic spectrum (UV to NIR). With increasing layer numbers for TiO2/SiO2 and SiO2/SnO2, the edges became sharper and wider and the photonic bandgap width increased. Moreover, we demonstrated that PhCs with significantly thick TiO2/SiO2 layers had a high transmittance for a wide bandgap, allowing for wide-band optical filter applications. These different PhC architectures could enable a variety of applications, depending on the properties needed.

Experimental Study of Light Wave Propagation for Underwater Optical Wireless Communication (UOWC)

Underwater Optical Wireless Communication (UOWC) is identified as a promising technology because it offers higher bandwidth than acoustics and radio frequency techniques. This paper investigates the performance of light wave propagation for UOWC through experimental approach. An experimental set-up is developed consists of a transmitter, receiver and a glass chamber to emulate the water channel. Three types of water including clear, sea and cloudy are used to investigate their interaction with the light emitted by light emitting diode (LED) and laser diode. The geometrical loss (GL) analysis shows the white LED suffered a severe GL (GL<<1) as the transmission link increases due to the wide viewing angle while green and yellow LED obtained an equal GL due to the same size of viewing angle. However, red laser does not experience any GL. Therefore, the received power by red laser is 35% higher than by green LED. The analysis deduces that the estimated attenuation coefficient c had an increase of 15% and 55% for green LED and red laser respectively when the UOWC medium changed from clear water to sea water. This study contributes to identify the potential and limitations of different parameter design in order to optimize UOWC performance.