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The transient current technique (TCT) is widely used in the field of silicon particle detector development. So far, only laser wavelengths with a photon energy larger than or similar to the silicon bandgap (single photon absorption) were used. Recently, measurements using two-photon absorption (TPA) for silicon detector testing have been carried out for the first time. Excess carriers are only created at the focal point of the laser beam and thus resolution in all three spatial directions could be achieved. The resolution perpendicular to the incident laser beam could be increased roughly by a factor of 10. First measurements using this new method were performed at the Singular Laser Facility of Universidad del País Vasco (UPV)/Euskal Herriko Unibertzitatea (EHU). Following the initial success of the method, a compact TPA-TCT setup is under development. A first description of the setup and laser system is presented in this article., This work was supported in part by the Spanish Ministry of Economy and Competitiveness (MINECO) under Grant FPA2013-48387-C6-1-P and in part by the Wolfgang Gentner Programme of the German Federal Ministry of Education and Research under Grant 05E15CHA.

A brief review of works devoted to theoretical and experimental studies of structural and polarization transformations of laser beams in anisotropic crystals is presented. Generation of laser beams with a complex polarization-phase state is shown. It is demonstrated that adaptive tuning of structural and polarization-phase states can be carried out by relatively slow changes in the parameters of the optical system and by fast electro-optical modulations with a high response rate.

we discuss state-of-the-art techniques to generate on-demand structured light and their application to quantum light-matter interactions, especially in the generation and control of charged-particle beams and X-ray light sources.

We review the fundamentals of electron beam generation in self-modulated laser wakefield acceleration (SM-LWFA) using laser pulses with peak powers on the TW and sub-TW scale. The results of several new particle-in-cell simulations for λ = 0.8 µm and a thin H2 gas target are shown. By scanning the peak gas density and peak power values of the incident laser, we discuss the resulting acceleration processes, as well as the characteristics of the electron beams generated for different conditions. Our approach provides a method to optimize these beams with lasers operating at kHz repetition rates.

The main workhorse of the production of coherent XUV attosecond pulses, and therefore a tool of choice for atomic and molecular physics applications, is the high-order harmonic generation technique (HHG). The HHG technique, however, has its limits: it cannot deliver high-energy XUV pulses. The HHG's problem is fundamental: the HHG process is very inefficient, which strongly limits XUV applicability. We propose to use a recently demonstrated powerful alternative technique of XUV generation, based on the high-order parametric processes. We discuss the results and the feasibility at the unique ELI Beamlines laser facility.

Vision impairment caused by degenerative retinal pathologies such as age-related macular degeneration can be treated using retinal implants. Such devices receive power and data using cables passing through a permanent surgical incision in the eye wall (sclera), which increases the risk to patients and surgical costs. A recently developed retinal implant design eliminates the necessity of the implant cable using a photonic power converter (PPC), which receives optical power and data through the pupil and is directed by an ellipsoidal reflector and micro-electromechanical mirror. We present a misalignment compensation algorithm model that accounts for rigid-body motions of the reflector relative to the eye and applies the correction to the mirror coordinates in the presence of angular misalignment of the reflector. We demonstrate that up to 85% of the nominal optical power can be delivered to the implant with axial reflector misalignments up to 30 deg using the compensation algorithm.

We demonstrate efficient interaction of hard x-ray single photons with a beam splitter for the first time and use it to show the nonclassical behavior of x-ray heralded photons.

Single photon holographic methods would aid several applications that raised with recent advances in quantum technologies. Our method records single photon holograms without detecting the photon itself thanks to the concept of induced coherence. ©2021 Marta Gilaberte Basset, Sebastian Topfer, Jorge Fuenzalida, Juan P. Torres, Fabian Steinlechner and Markus Grafe.

We present a novel real-time frequency-encoded spatiotemporal (FEST) focusing technology using a programmable two-dimensional optical frequency comb. This technique enables, for the first time, simultaneous spatial and temporal focusing at microseconds through thick scattering media.

We propose and experimentally demonstrate a liquid crystal-assisted coherent fiber laser combining system for tailoring orbital angular momentum (OAM) beam arrays. Spatially-distributed multiple OAM beams with synchronously tunable OAM modes can be efficiently generated. © 2020 The Author(s)

We present a numerical simulation technique for short laser pulse amplification in solid-state crystals. It takes into account the full spatial pumping profile by solving the 3-dimensional photon transport and allows to calculate pulse energy accurately.

We discuss a novel use of photonic metasurfaces and metamaterials for mechanical stabilization of freestanding objects. Self-restoring optical forces and torques can arise from asymmetric scattering of the metasurface unit cell.

This paper presents a method of improving the accuracy of a circular laser system in fabrication of large-diameter diffractive optical elements by means of a polar coordinate system and the results of their use. An algorithm for correcting positioning errors of a circular laser writing system developed at the Institute of Automation and Electrometry, SB RAS, is proposed and tested. Highprecision synthesized holograms fabricated by this method and the results of using these elements for testing the 6.5 m diameter aspheric mirror of the James Webb space telescope (JWST) are described..

A method is developed to ensure precise alignment of the origin of a polar coordinate system in which the laser beam position is defined in writing diffractive optical elements with the optical workpiece rotation axis. This method is used to improve the accuracy of a circular laser writing system in writing large-scale diffractive optical elements in a polar coordinate system. Results of studying new algorithms of detection and correction of positioning errors of the circular laser writing system in the course of writing are reported.

21st International Conference on Transparent Optical Networks, ICTON ( 2019: Angers, France ), In this study, we propose and experimentally demonstrate spatial filtering of light by the photonic wavy structures designed to be operated in a Bragg regime. The proposed configuration is designed, optimized and analyzed by 3D finite-difference time-domain (FDTD) method. Both incidence angle variation and wavelength dependency are examined in detail. The multilayered photonic structure with preselected structural parameters is fabricated by physical vapour deposition on the microstructured substrate. The numerical results as well as experimental measurements of the angle/wavelength transmission of the proposed structure indicate the evidence of the angular filtering based on the selective diffraction of light. © 2019 IEEE., The study is supported by the EUROSTARS Project E!10524 HIP-Lasers, Spanish Ministerio de Ciencia e Innovación, and European Union FEDER through project FIS2015-65998-C2-1-P, also from “FOKRILAS” (Project No. P-MIP-17-190) from Research Council of Lithuania. Authors are grateful to dr. Algirdas Selskis from State research institute Center for Physical Sciences and Technology for SEM measurements.

Glass poses unique challenges for additive manufacturing. A Laser-Heated Filament-Fed process has been developed to deposit transparent glass for both refractive free-form optics and free-standing light-guiding structures. The process is discussed with examples of capabilities.

Bioinspired structural colors are attracting increasing attention in photonics, display, labeling and so forth. High-resolution and stable coloration is significant but is challenging to be fabricated in a facile and low-cost way. Herein, multilayer architecture containing an internal nanocavity as the structural color unit is obtained conveniently by direct nanosecond laser printing in atmosphere condition. Arbitrary colorful patterns with submicron accuracy can be realized only by a single step. And such structural colors induced by inner structures in the interlayer are antipollutive, antioxidative and easy to clean.

A novel design of a two-axis fast steering mirror (FSM) with piezoelectric actuators is proposed for incoherent laser beam combination. The mechanical performance of the FSM is tested. The results show that the tilting range of the mirror is about 4 mrad, and the 1st-order resonance frequency is about 250 Hz. A self-designed grating encoder is taken as the sensor, which ensures the optimal precision of 10 μrad. The novel mechanical design can meet the requirement of engineering in incoherent laser beam combination.

Results of an experimental study of spatial parameters of the region of multiple filamentation of gigaand terawatt pulses of a Ti:Sapphire laser in glass and water are described. The pulse-power dependencies of the coordinates of the filamentation region, the number of filaments, their distribution along the laser beam axis, and the mean length of the filaments are presented. It is shown that the spatial parameters of the filamentation region are qualitatively similar in water and glass. It is found that the number of filaments along the region of multiple filamentation is a unimodal distribution. When increasing the radiation power, the length of individual filaments in the region of multiple filamentation is reduced, and their diameters are quasi-constant at all power values implemented in the experiment. When attaining a certain power of laser pulses with a Gaussian energy-density distribution, the filamentation region takes the shape of a hollow cone with the apex directed to the radiation source.

Results of long-term continuous measurements of the atmospheric backscattering amplification coefficient on a 2-km-long near-ground path with the use of a two-channel micropulse lidar based on a waveguide laser are presented. It is shown that the backscattering amplification coefficient has a pronounced daily variation. In the night and in the afternoon, atmospheric backscattering amplification is maximal and the amplification coefficient can exceed 2. The amplification is low or absent in morning and evening hours at neutral temperature stratification in the near-ground layer of the atmosphere. The backscattering amplification coefficient increases with an increase in the structure constant of the air refracting index and variance of the image jitter of the illumination spot created by the probing laser beam on the wall of a 2-km-distant building.

Lasers and anti-lasers (time-reversed counterpart of lasers) are critical for the generation and absorption of coherent light beams. Here we experimentally demonstrate on-chip switchable lasing and anti-lasing in a single photonic cavity using the concept of parity-time symmetry. This opens the door for extreme light control towards the ultimate limit of modulation depth.

We report on the progress of the thermal noise further reduced method via enlarging the equivalent beam size without increasing the cavity length in cavity-stabilized lasers at 1555 nm, which are built as the frequency source for a photonic microwave generation system. In addition, we perform an experiment to evaluate the effect of thermal noise reduced method via estimating the frequency instability of a synthesized new ultrastable laser. The relative frequency instability reaches 5∗10−16 at 1 s averaging time via reducing the thermal noise of the cavity.

We numerically analysis spatiotemporal profile of HHG. A detailed physical picture of HHG over four-dimensional spatiotemporal spaces is studied for the first time, which may benefit potential applications like super-resolution XUV imazing, XUV tweezer.

Straight and bent self-written waveguides (SWWs) are formed within a photomonomer mixture by means of a self-trapping effect when a single laser beam or two laser beams with tilt are propagated inside. These SWWs can be used as optical interconnects in integrated photonic circuits if two laser beams are launched in opposite directions into the photomonomer. In this work, two kinds of photo-polymerization models are implemented to simulate the SWWs. In the phenomenological model, the refractive index increases directly with actinic laser intensity, whereas the diffusion model has a more complex variation of refractive index profile which takes into account the individual redistribution of mixture components. Both these models are linked with a CrankNicholson based Beam Propagation Method (CN-BPM) to simulate the time varying light distribution within the polymer coupling structures. Differences are observed in the numerical simulation results for straight and bent SWWs with respect to the temporal evolution of refractive index within the mixture, corresponding beam intensity profiles and curing time. In addition, we show that a saturation of refractive index change leads to the polymerization of surrounding monomer and, as consequence, to corrupted light guiding. We report on the minimum refractive index modulation that is required for optimal light guiding within the SWW. © 2018 SPIE.

Recently it has been reported that photon anti-bunching can be obtained via second-order interference of mutually incoherent weak lasers under a proper post-selection scheme [Phys. Rev. A 92, 033855 (2015); Opt. Express 24, 19574 (2016)]. Here, we report theoretical analysis on the limits of manipulating conditional photon statistics of lasers via interference and post-selections.

We demonstrate, for the first time, simultaneous generation, transmission and reception of quantum signals and classical signals on a single wavelength. 61.6kbps quantum key and 590kbps classical data rates are estimated.

Laser-induced periodic surface structures (LIPSS) in GaP with high and low spatial frequencies were systematically investigated. We fabricated these structures using a fs laser as a feasible alternative method to realize nonlinear photonic metasurfaces.

We demonstrate that rectangular few-mode dielectric waveguides, fabricated with standard lithographic technique, can support on-chip propagation of optical vortices. We show that specific superpositions of waveguide eigenmodes form quasi-degenerate modes carrying light with high purity states of orbital angular momentum.

Results of the experimental study of filamentation of terawatt femtosecond pulses of a Ti:Sapphire laser along an atmospheric path 106 m long using different spatial focusing and pulse power are presented. The control of filamentation region position and length by means of changing the initial laser beam focusing is shown to be highly effective. Dependencies are derived of filamentation region position and length on the initial degree of focusing, pulse power, and the number of filaments along the filamentation region. The obtained data on the filamentation region length and the number of filaments are compared with the results of our previous experiments and data from other authors.

There are a number of areas in automation technology where precise positioning is necessary. This particularly applies to laser technology. High-precision beam steering and focusing is just as indispensable in ophthalmology as in super-high resolution microscopy, interferometry or photonics where the objective is to align fibers precisely. At the same time, laser beam steering and focusing also requires the drive systems used to be dynamic, reliable, and compactly dimensioned, so that they can be easily integrated into applications. Now, small positioning systems based on piezo inertia drives offer possible new solutions. In miniaturized design, they offer a high resolution at theoretically unlimited travel ranges, are self-locking and on top of that, they are also inexpensive.

Due to the nature of light fields of laser waves and pulses as vector quantities with complex spatial distribution and temporal dependence, the optics and photonics courses have always been difficult to teach and learn without the support of graphical visualization, numerical simulations and hands-on experiments. One of the state-of-the-art method of computational photonics, the finite-difference time-domain(FDTD) method, is applied with MATLAB simulations to model typical teaching cases in optics and photonics courses. The obtained results with graphical visualization in the form of animated pictures allow students to more deeply understand the dynamic process of light interaction with classical optical structures. The discussed teaching methodology is aimed to enhance the teaching effectiveness of optics and photonics courses and arousing the students' learning interest.

The search for new paradigms for all-optical processing plays a pivotal role in current photonics research. In this perspective, light-defined waveguides (LDW) are of central importance. LDW can be roughly divided into two groups: permanent [1] and real-time [2]. In the first case, LDW persist even after the writing beam is shut off; in the second case, the effect requires the presence of an input (writing) beam. The latter corresponds to the formation of a spatial soliton, a shape-preserving wavepacket arising from the balance between diffraction and self-focusing [2]. Here, we show how spatial soliton waveguides in nematic liquid crystals (NLC), namely nematicons [2], can be rendered permanent via UV photo-polymerization.

A polarization-insensitive 2D high index contrast gratings (HCGs) beam splitter based on silicon-on-insulator(SOI) is proposed and demonstrated, which performs two independent functions: transmission focusing and power equalization at the wavelength of 1550 nm.

We experimentally generate multiple orbital angular momentum (OAM) modes with different color in 2D nonlinear photonic crystal. The process is achieved by the cascaded third-harmonic generation using the non-collinear quasi-phase-matching technique.

We report recent advance in coherent polarization beam combining of fiber lasers. Power scaling of all-fiberized linear-polarized fiber amplifier is studied, four channels of kilo-watt level narrow-linewidth linear-polarized fiber amplifiers are coherently polarization combined with 5.02 kW output power.

Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC).-- Date of Conference: 25-29 June 2017.-- Conference Location: Munich, Germany., Networks of photonic elements are a key enabling technology for the realization of multiple next generation photonic systems. Phased beam arrays, coherent beam combining or neuromorphic computing in photonic networks: all these high-impact applications fundamentally require coupling between a large number of photonic components. Recently, a small network of ~20 semiconductor lasers based on coupling via a holographic element was reported [1]. However, the demonstration of large-scale complex photonic networks is lacking.Here, we demonstrate the scalability of holographic coupling, creating a large scale complex network of 1600 opto-electronic oscillators. The network's nonlinear nodes are implemented using a spatial light modulator (SLM) operated in intensity modulation mode. Imaging the SLM-surface through a polarizing beam splitter (PBS) onto a camera and closing the loop between camera and the SLM, we realize a nonlinear iterative map. The state of SLM pixel n is then given by I n (t + 1) = sin 2 (κI n (t) + φ 0 ). Here, I n (t)is the nth pixel intensity at time t, κ the feedback gain and φ 0 a constant phase offset. This equation corresponds to a simplified version of the Ikeda map. Figure 1 (a) schematically illustrates the experimental implementation. An exemplary bifurcation diagram for node (23, 8) is shown in Fig. 1 (b). The route to chaos shown in Fig. 1(b) exhibits the period-doubling behaviour expected from such an Ikeda system.

We experimentally demonstrated the generation of the multiple-order orbital angular momentum modes (± 1st, ± 2nd and ± 3rd order) using an UV-laser inscribed tilted few-mode fiber Bragg grating with mode conversion efficiency of >90%.

We propose and experimentally demonstrate a new complex laser beam with inhomogeneous polarization distributions mapping onto high-order Poincaré spheres (HOPSs). The complex laser mode is achieved by superposition of Laguerre-Gaussian modes and manifests exotic flower-like localization on intensity and phase profiles. A simple optical system is used to generate a polarization-variant distribution on the complex laser mode by superposition of orthogonal circular polarizations with opposite topological charges. Numerical analyses of the polarization distribution are consistent with the experimental results. The novel flower HOPS beams can act as a new light source for photonic applications.

Individual or arrayed microlenses offer remarkable opportunities in optics and photonics. However, their usage is currently limited by the lack of manufacturing technologies capable of tailoring the lens geometry to target devices. Here, we demonstrate how laser catapulting (LCP), a recent laser-based additive manufacturing technique, enables the preparation of microlenses with controlled geometry and curvature. LCP exploits single laser pulses to catapult polymeric microdisks into user-selectable positions on a substrate, which are converted into microlenses following a thermal reflow treatment. By shaping the irradiance distribution of the incident laser beam, we obtained arrays of circular, triangular, and cylindrical microlenses with a radius between 50-250 µm and 100% fill-factor. The good quantitative agreement between beam shape and microlens geometry, combined with the in-situ fabrication capabilities and high-throughput of LCP, can help the consolidation of laser additive methods for micro-optics in scientific and industrial applications.

Surface wave provides unique applications ranging from biological sensing, deep-subwavelength lasing to plasmonic circuits. Seeking new approaches for controlling surface wave is highly desired in future integrated photonic devices. Here, we develop a versatile platform based on metasurfaces for the launch and control of propagating surface wave in the terahertz frequency regime.

Light beams shaped by programmable megapixel spatial light modulators (SLMs) are key to broadening the applications of photonics. In this paper, we consider the application of a SLM for the generation of two mutually coherent white-light continuum optical sources by filamentation of infrared femtosecond pulses in bulk. We demonstrate that the inhomogeneity of the input beam and the longitudinal separation of the generated filaments are crucial parameters that break down the mutual coherence across neighboring filaments. We show that local control over the optical phase enables us to gain fine control over filament interference effects., This work was supported by Generalitat Valenciana through the programme (PROMETEO\2012\021), Spanish Ministry of Science under Grant FIS2013-40666-P) and University Jaume I through the project P1 1B2013-53.

n this paper, we report on a three-dimensional beam splitter monolithically integrated in an Nd:YAG laser crystal wafer by applying the direct femtosecond laser writing technique with the photonic-lattice-like cladding approach, capable of 1 to 2 and 1 to 4 beam splitting. Using the pump at 808 nm, 1064-nm splitting lasers with slope efficiencies of 34% and 22% for 1 to 2 and 1 to 4 configurations were realized. This study paves a way to fabricate direct-pump compact laser devices in a single chip for light guiding and beam dividing in Nd:YAG crystals for various photonic applications., This work was supported by National Natural Science Foundation of China (No. 11274203) and Ministerio de Economía y Competitividad under Project FIS2013–44174-P, Spain.

A technique for constructing an innovative structure of the three dimensional beam splitter with a designable feature is demonstrated. Orthogonal cascaded Y-branch couplers are utilized. Perfect 3D beam splitting results are achieved.

The laser facility for single event effect (SEE) testing at the Saskatchewan Structural Sciences Centre is introduced. Its capabilities of studying SEEs via two photon absorption (TPA) are described. Data on a Virtex-5 FPGA are provided.

International audience; Wide bandgap semiconductors such as silicon carbide, gallium nitride and diamond have been recently investigated in order to replace silicon in the power electronic domain. In this paper, silicon carbide devices are studied using an optical method. It consists on illuminating a reverse biased junction with a laser beam with an appropriate wavelength, and then measuring the induced current due to the photon absorption. According to the wavelength, one- or two-photon absorption is triggered when photon energy is respectively higher or lower than the semiconductor bandgap. In the latter case, the probability of electron hole pair (EHP) generation is very small, which leads to use a powerful incident beam. In this paper, two-photon generation is used in order to determine the lifetime of minority charge carriers in N doped 4H-SiC. The incident beam is a pulsed green source with a wavelength of 532 nm and a high power density that can reach up to 6 GW.cm-2. Test devices are PN diodes protected by a junction termination extension (JTE). Results show a hole's lifetime of 730 ns.

Observing an amplified picosecond pulse, plasma physicists determine the spatial pattern of polarization changes to understand the scattering of intense laser beams in plasma photonics applications.