Beam Propagation Analysis Research Articles

A 1 × 8 Optical Splitter Based on Polycarbonate Multicore Polymer Optical Fibers.

Visible light communication (VLC) is becoming more relevant due to the accelerated advancement of optical fibers. Polymer optical fiber (POF) technology appears to be a solution to the growing demand for improved transmission efficiency and high-speed data rates in the visible light range. However, the VLC system requires efficient splitters with low power losses to expand the optical energy capability and boost system performance. To solve this issue, we propose an effective 1 × 8 optical splitter based on multicore polycarbonate (PC) POF technology suitable for functioning in the green-light spectrum at a 530 nm wavelength. The new design is based on replacing 23 air-hole layers with PC layers over the fiber length, while each PC layer length is suitable for the light coupling of the operating wavelength, which allows us to set the right size of each PC layer between the closer PC cores. To achieve the best result, the key geometrical parameters were optimized through RSoft Photonics CAD suite software that utilized the beam propagation method (BPM) and analysis using MATLAB script codes for finding the tolerance ranges that can support device fabrication. The results show that after a light propagation of 2 mm, an equally green light at a 530 nm wavelength is divided into eight channels with very low power losses of 0.18 dB. Additionally, the splitter demonstrates a large bandwidth of 25 nm and stability with a tolerance range of ±8 nm around the operated wavelength, ensuring robust performance even under laser drift conditions. Furthermore, the splitter can function with 80% and above of the input signal power around the operated wavelength, indicating high efficiency. Therefore, the proposed device has a great potential to boost sensing detection applications, such as Raman spectroscopic and bioengineering applications, using the green light.

Simulation and analysis of high-brightness tapered ridge-waveguide lasers

In this work, a simulation-based analysis of a CW-driven tapered ridge-waveguide laser design is presented. Measurements of these devices delivered high lateral brightness values of {4}{hbox {W}cdot hbox {mm}^{-1} hbox {mrad}^{-1}} at {2.5},hbox {W} optical output power. First, active laser simulations are performed to reproduce these results. Next, the resulting complex valued intra-cavity refractive index distributions are the basis for a modal and beam propagation analysis, which demonstrates the working principle and limitation of the underlying lateral mode filter effect. Finally, the gained understanding is the foundation for further design improvements leading to lateral brightness values of up to {10}{hbox {W}cdot hbox {mm}^{-1} hbox {mrad}^{-1}} predicted by simulations.

Axial effect analysis of relativistic electron beam propagation in vacuum

In geostationary orbits and other quasi-vacuum environments, relativistic electron beams are affected by the initial emittance and space charge effects during the propagation process, resulting in beam quality degradation. Furthermore, axial energy distribution change in the beam and the axial transient electromagnetic effect caused by current changes in the head and tail regions of the beam also cause the beam to expand and affect its quality. In this study, the particle-in-cell method was used to construct a long-range propagation model of a relativistic electron beam in a vacuum environment. By calculating and simulating the axial energy distribution of the beam and the changes in the transient electromagnetic field, the axial effect during the propagation process was analyzed, and the parameter change law of the effective propagation of the beam was explored. This provided a theoretical reference for a more accurate assessment of the beam quality during propagation.

Electron Optical Optimisation of an Imaging Energy Analyser: Real Model Field- and Trajectory Simulations Applied to k-Space Visualisation of Electronic States

In this report we present a new numerical approach and complex analysis of electron beam propagation based on a realistic model of an optimised imaging spherical deflector analyser. Electron beam trajectory simulations, carried out for real experimental boundaries, enabled us to reveal and explain the unique optical properties which were employed in the instrumental optimisation followed by empirical, spectromicroscopic applications. In terms of numerical treatment, it was possible to verify the low-aberration imaging in reciprocal and real spaces at π and 2π, respectively, and the advantage of energy-selective visualisation of the k-space. Furthermore, this unique feature has been proven and confirmed experimentally by implementing the HeI/HeII monochromatic photon source into our improved spectromicroscopic system and by the energy-selective visualisation of an electronic state projection in the reciprocal plane. A clear correlation between a numerically simulated electronic projection and an experimentally-obtained k-space imaging has been demonstrated.

Efficient Scalar Bidirectional Beam Propagation Analysis for Photonic Devices With Circular Symmetry

In this letter, a scalar non-iterative bi-directional finite element based beam propagation method (NI-BiBPM) is proposed for the analysis of light propagation in photonic devices with circular symmetry. We adopt the Blocked Schur algorithm (BSA) for calculating the square root of the characteristic matrix in order to achieve fast and stable results and to avoid the complications and limitations of other computational modeling techniques such as Taylor or Pade approximations. The suggested NI-BiBPM approach does not only offer reduction in execution time and memory requirements but also guarantees the numerical stability.

Vortex dynamics and applications to gaseous optical elements

Experimental studies of the optical properties of compressible, viscous, and rapidly rotating gas flows (vortices) are presented. Gas vortices can function as optical elements such as lenses or waveguides. The optical properties are determined from direct interferometric phase measurements and beam propagation analysis. Output beams are analyzed in terms of Zernike polynomials for a range of gas flow parameters, including choked flow. The absolute radial gas density distribution is measured, and a technique for adjusting it is demonstrated.

Geometrical analysis of Kerr-lens mode-locking for high-peak-power ultrafast oscillators

Ultrashort pulses from Kerr-lens mode-locked oscillators have inspired a variety of applications. The design and alignment of these laser resonators have thus far been theoretically supported by the conventional analysis of beam propagation. However, the well-established theoretical framework is sometimes beyond the scope of high-peak-power oscillators. In this paper, we analyze the geometry of ring resonators by extending the ABCD-matrix method to a high-peak-power regime. The guidelines to achieving stable Kerr-lens mode-locking is provided for high-peak-power pulses.

Temporal analysis of Airy beam propagation in photorefractive media

We theoretically examine the temporal behavior of Airy beams and their interactions in photorefractive medium with the split-step Fourier method. Simulations indicate that Airy beam propagations are effectively controlled by the illumination time. Under saturated nonlinearity, the beam intensity maintains the soliton profile at the output section, and its propagation direction is modulated by the beam amplitude. Moreover, the temporal behavior of Airy beam interactions varies greatly with illumination time, especially for the in-phase case. Breathing solitons and parallel soliton pairs are produced in-phase and out-of-phase, respectively. These results are potentially useful in all-optical device applications.

Polarimetric laser beam diffraction in a tokamak plasma

In this paper the method of complex geometrical optics (CGO) is applied to the analysis of polarimetric laser beam propagation and diffraction in tokamak plasma. The paraxial CGO reduces the problem of beam diffraction in inhomogeneous medium to the set of ordinary differential equations, which significantly simplifies calculation as compared with full-wave approach. Numerical simulations for Gaussian beam, propagating in the poloidal plane of the inhomogeneous thermonuclear plasma, reveal differences in beam parameters evolution (beam path, width and phase front curvature) in comparison with homogeneous media. Such additional distortion of the beam must be taken into account in polarimetric system modelling. The presented approach may also be applied in other measurement techniques that use electromagnetic beams, like interferometry or refractometry – with limitations discussed in the text.

Beam propagation analysis of optical activity and circular dichroism in helically twisted photonic crystal fiber

Transmission characteristics of a helically twisted photonic crystal fiber (PCF) are theoretically investigated by a recently developed beam propagation method for a helicoidal system. Experimentally reported features of the twisted PCF, such as periodical transmission dips, optical activity discontinuity, and circular dichroism, are successfully reproduced in a simulation. We reveal unique properties related to circular dichroism and optical activity in the twisted PCF. Through Stokes parameter evaluation, the polarization state of the input light in the twisted PCF is investigated in detail and the transition from linearly polarized that to circularly polarized light is demonstrated. Furthermore, the optical activity discontinuity is confirmed near the transmission dip.

Ultra-compact all-optical phase-controlled NAND, OR, XOR, XNOR, and NOT multi-function logic gate

We propose a novel multi-function logic gate in order to attain all NAND, OR, XOR, XNOR, and NOT logic functions in a single structure with controlling the phase of input lights. Beam propagation analysis illustrates that the highest insertion loss of structure is − 0.05 dB in whole C-band. The output on–off logic level contrast ratio for NAND, OR, XOR, XNOR, and NOT logic functions are 28.2, 28.2, 30.2, 30.2, and 30.2 dB, respectively. The structure which is composed of one multimode interference region with ultra-small size of 1.5 µm × 12.2 µm is a promising candidate for ultra-compact systems.

Finite element steady periodic beam propagation analysis of mode instability in high power fiber amplifiers.

A finite element steady periodic scalar beam propagation method suited to treating mode instability in amplifiers incorporating fibers with complicated design features is presented and demonstrated on test cases. These incorporate large pitch photonic crystal fibers with confined and down-doped cores in co-pumped and counter-pumped configurations. Seed power fluctuations and slight launch misalignment are proposed and implemented as a noise source to seed the instability. Down doping the confined core by -7.0E-5 was found to increase the instability threshold by 25% in the co-pumped case and 9% in the counter-pumped case. The increase in threshold is correlated with the suppression of higher frequency components of intensity gratings associated with the instability.

Experimental measurement of the atmospheric turbulence effects and their influence on performance of fully photonic wireless communication receiver

The new generation of Free-Space Optical systems utilizes photonic components used in optical fiber communications which demand high precision and complexity of the system. We present an analysis of the laser beam propagation in the context of fully photonic free space optical links. The experimental data is presented and used for the estimation of single-mode (SM) fiber coupling loss.

Analysis of Plane-Parallel Electron Beam Propagation in Different Media by Numerical Simulation Methods

Simulation by the Monte Carlo method is widely used to calculate the character of ionizing radiation interaction with substance. A wide variety of programs based on the given method allows users to choose the most suitable package for solving computational problems. In turn, it is important to know exactly restrictions of numerical systems to avoid gross errors. Results of estimation of the feasibility of application of the program PCLab (Computer Laboratory, version 9.9) for numerical simulation of the electron energy distribution absorbed in beryllium, aluminum, gold, and water for industrial, research, and clinical beams are presented. The data obtained using programs ITS and Geant4 being the most popular software packages for solving the given problems and the program PCLab are presented in the graphic form. A comparison and an analysis of the results obtained demonstrate the feasibility of application of the program PCLab for simulation of the absorbed energy distribution and dose of electrons in various materials for energies in the range 1–20 MeV.

Beam propagation in an inhomogeneous medium of a static gas cesium diode pumped alkali laser: three-dimensional wave optics and fluid dynamics simulation

Analysis of beam propagation and kinetic and fluid dynamic processes in static Cs diode pumped alkali lasers (DPALs), using the wave optics model and gasdynamic code, is reported. The analysis is based on a three-dimensional, time-dependent computational fluid dynamics (3D CFD) model. The gas flow conservation equations in the DPAL cell are coupled to a fast-Fourier-transform algorithm for the laser beam transverse modes’ propagation to obtain a solution of the scalar paraxial wave equation where the gain and refractive index in the DPAL medium affect the wave amplitude and phase. Using the CFD and beam propagation models, the gas flow pattern and spatial distributions of the pump and laser intensities and the laser beam phase in a plano-concave resonator were calculated for end-pumped Cs DPAL. The DPAL medium temperature and refractive index, along with the laser power and laser beam quality factor M2, were calculated as a function of pump power. The results of the theoretical model for laser power were compared to experimental results of Cs DPAL. In addition, the pump and laser induced thermal effects in the DPAL cell on the laser beam quality were studied for Cs DPAL with hydrocarbon only as a buffer gas. For methane it was found that the temperature and the resulting refractive index gradients in the DPAL cell are larger than for He rich buffer gas. The large radial gradient of the refractive index in the heated gain medium, achieved for the present resonator and wide-aperture pump beams, along with the fact that in gases the thermo-optic coefficient is negative, results in improvement of M2 as compared to a gain medium with a uniform refractive index. This counterintuitive conclusion is contrary to the behavior of the beam quality of solid-state lasers, which deteriorates when the gain medium is heated by the pump beams.

Wavefront Analysis of Annular Beam Propagation in Random Media Using Geometric Optics Approximation

Wavefront Analysis of Annular Beam Propagation in Random Media Using Geometric Optics Approximation

Analysis of the joint impact of atmospheric turbulence and refractivity on laser beam propagation

A laser beam propagation model that accounts for the joint effect of atmospheric turbulence and refractivity is introduced and evaluated through numerical simulations. In the numerical analysis of laser beam propagation, refractive index inhomogeneities along the atmospheric propagation path were represented by a combination of the turbulence-induced random fluctuations described in the framework of classical Kolmogorov turbulence theory and large-scale refractive index variations caused by the presence of an inverse temperature layer. The results demonstrate that an inverse temperature layer located in the vicinity of a laser beam’s propagation path may strongly impact the laser beam statistical characteristics including the beam wander and long-exposure beam footprint, and be a reason for refractivity-induced spatial anisotropy of these characteristics.

Coupling Characteristics of Fused Optical Fiber Coupler Formed with Single-Mode Fiber and Photonic Crystal Fiber Having Air Hole Collapsed Taper

Fused coupler forming with a single-mode fiber (SMF) and a photonic crystal fiber (PCF) is one of the solutions for optical coupling from a light source to a PCF. In this paper, we presented coupling characteristics of a fused fiber coupler formed with an ordinary SMF and a PCF having air hole collapsed taper. A prototype of SMF-PCF coupler with air hole collapsed taper was fabricated using CO2 laser irradiation. The coupling efficiency from SMF to PCF was −6.2 dB at 1554 nm wavelength in the fabricated coupler. The structure of the SMF-PCF coupler to obtain high coupling efficiency was theoretically clarified by beam propagation analysis using an equivalent model of the coupler with simplification. It was clarified that appropriately choosing the prestretched or etched SMF diameter and the length of air hole collapsed region was effective to obtain high coupling efficiency that was a result of high extinction ratio at cross port and low excess loss. We also demonstrated that the diameter of prestretched SMF to obtain high coupling efficiency was insensitive to the air hole diameter ratio to pitch of the PCF in the air hole collapsed SMF-PCF coupler.

Large deflection angle, high-power adaptive fiber optics collimator with preserved near-diffraction-limited beam quality.

We report on the development of a monolithic adaptive fiber optics collimator, with a large deflection angle and preserved near-diffraction-limited beam quality, that has been tested at a maximal output power at the 300 W level. Additionally, a new measurement method of beam quality (M2 factor) is developed. Experimental results show that the deflection angle of the collimated beam is in the range of 0-0.27 mrad in the X direction and 0-0.19 mrad in the Y direction. The effective working frequency of the device is about 710 Hz. By employing the new measurement method of the M2 factor, we calculate that the beam quality is Mx2=1.35 and My2=1.24, which is in agreement with the result from the beam propagation analyzer and is preserved well with the increasing output power.

WITHDRAWN: Beam propagation analysis on thickness measurements in quantitative phase microscopy

WITHDRAWN: Beam propagation analysis on thickness measurements in quantitative phase microscopy