Single Laser Beam Research Articles

A 100-PW compressor based on single-pass single-grating pair

Abstract A multistep pulse compressor (MPC) based on a single-pass single-grating pair (SSGP) is proposed to simplify the entire multi-petawatt (PW) compressor. Only one grating pair with relatively long perpendicular distance is used to generate the same amount of spectral chirp compared with a four-grating main compressor. As SSGP compressor induces the largest spatial chirp, it can introduce the best beam-smoothing effect to the laser beam on the last grating. When considering the diffraction loss of only two gratings, the total compression efficiency of the SSGP compressor is even larger than that of a four-grating main compressor. Furthermore, the wavefront aberration induced by the SSGP compressor can be better compensated by using deformable mirrors; however, it is difficult or complicated to be well compensated in a four-grating compressor. Approximately 50–100 PW laser pulses can be obtained using this SSGP-based multistage-smoothing MPC with a single laser beam.

Simulation study of quasi-monoenergetic high-energy proton beam based on multiple laser beams driving

High-energy proton beams have extensive and important applications. Traditional proton accelerators are bulky and costly. The high-power laser pulse technology provides a new proton acceleration scheme based on the interaction between laser and plasma, and has the advantage of miniaturization. Furthermore, comparing with traditional proton accelerators, the proton acceleration gradient by high-power laser pulses can be increased by three orders of magnitude. The proton beams with high brightness, narrow pulse width, and good directionality can be generated in theory within a very small effective size, and they are suitable for fields such as nuclear physics and particle physics, ion beam fast ignition, medical treatment, and proton beam detection. In order to realize laser proton acceleration, a great many of researches of different target configurations and acceleration mechanisms have been reported on proton acceleration driven by ultrashort and high-power lasers. However, owing to the limitation of laser intensity, the energy of proton beam driven by a single-beam laser is difficult to improve to meet the needs of medical applications. In this paper, a new method of driving proton acceleration by multiple ultrashort high-power lasers with grazing incidence on both sides of the microstrip target is proposed. A proton beam with an energy divergence of about 3% and energy of about 165 MeV can be obtained by using the two-beam driving setting. The results of two-dimensional particle-in-cell simulation show that a large number of collimated high-energy electron charges are extracted from both sides of the solid target by laser and injected into the back of the target. A longitudinal bunching field is established on the back of the target, which drives protons to accelerate and bunch to form a quasi-monoenergetic high-energy proton beam. The research also shows that the proton beam with an energy divergence of about 2% and energy of about 250 MeV can be obtained by using four grazing ultrashort high-power lasers on both sides of the microstrip target. The mechanism of multi-laser beams driving proton acceleration provides a new idea for the energy enhancement of the proton beam, and the quasi-monoenergetic high-energy proton beam is expected to be applied to the field of medical treatment.

Influence of Spherical Aberration on the SNR in Single-Beam Laser Doppler Velocimeter for Remote Measurement

Influence of Spherical Aberration on the SNR in Single-Beam Laser Doppler Velocimeter for Remote Measurement

Multibeam laser–plasma interaction at the Gekko XII laser facility in conditions relevant for direct-drive inertial confinement fusion

Abstract Laser–plasma interaction and hot electrons have been characterized in detail in laser irradiation conditions relevant for direct-drive inertial confinement fusion. The experiment was carried out at the Gekko XII laser facility in multibeam planar target geometry at an intensity of approximately $3\times {10}^{15}$ W/cm2. Experimental data suggest that high-energy electrons, with temperatures of 20–50 keV and conversion efficiencies of $\eta <1\%$ , were mainly produced by the damping of electron plasma waves driven by two-plasmon decay (TPD). Stimulated Raman scattering (SRS) is observed in a near-threshold growth regime, producing a reflectivity of approximately $0.01\%$ , and is well described by an analytical model accounting for the convective growth in independent speckles. The experiment reveals that both TPD and SRS are collectively driven by multiple beams, resulting in a more vigorous growth than that driven by single-beam laser intensity.

Towards a Practical Implementation of a Single-Beam All-Optical Non-Zero-Field Magnetic Sensor for Magnetoencephalographic Complexes.

We present a single-beam all-optical two-channel magnetic sensor scheme developed for biological applications such as non-zero-field magnetoencephalography and magnetocardiography. The pumping, excitation and detection of magnetic resonance in two cells are performed using a single laser beam with time-modulated linear polarization: the linear polarization of the beam switches to orthogonal every half-cycle of the Larmor frequency. Light with such characteristics can be transmitted over a single-mode polarization-maintaining fiber without any loss in the quality of the polarization characteristics. We also present an algorithm for calculating optical elements in a sensor scheme, the results of measuring the parametric dependences of magnetic resonance in cells, and the results of direct testing of a sensor in a magnetic shield. We demonstrate sensitivity at the level of 20 fT/√Hz in one sensor channel in the frequency range of 80-200 Hz.

Measurement range expansion of single-beam Laser Doppler velocimeter based on a focusing transmitter

The own velocity of a ground vehicle with high precision provided by the single-beam Laser Doppler velocimeters (LDV) promotes the localization accuracy of vehicles efficiently. However, the present LDVs are unable to be mounted on air vehicles for the velocity measurement of vehicles so far because of the restricted working distance. In order to expand the measuring range, a mid-distance LDV is designed in this paper. An optical focusing transmitter that transforms the Gaussian beam waist to the pre-set distance with an appropriate radius is constructed through theoretical simulations. Further experiments show that the mid-distance velocimeter can measure the velocity of moving objects within 50 m and the signal quality of measurement holds at a high level. This improved single-beam LDV with a longer working distance has great potential in acquiring the high-precision velocity of low-altitude air vehicles and many other remote velocity measurement applications.

Frequency shift compensation for single and dual laser beam pass sensors of a coherent population trapping resonance based coupled dark state magnetometer

The Coupled Dark State Magnetometer is an atomic magnetometer designed for magnetic field measurements in space. Its measurement principle is based on the excitation of coupled dark state resonances prepared via the coherent population trapping effect. The coupled dark state resonances enable the compensation of disturbing frequency shifts which degrade the measurement accuracy. Results with a sensor design based on a single laser beam pass through the sensor unit reveal a reduced ability to compensate these disturbing effects compared to theoretical predictions. Therefore, a new sensor design is presented which enables a dual laser beam pass through the sensor unit. For almost all angles between the external magnetic field and the light propagation direction, the dual pass sensor design enables a better compensation of disturbing frequency shifts than the single pass sensor design - up to a factor of nine.

Laser-optics-based method to suppress Mikania micrantha growth

Mikania micrantha is an exotic and aggressive species that can reproduce asexually and sexually through its germinative stem and its featherlike seeds. Present weeding methods cannot effectively or economically control the spread of Mikania micrantha. In this article, we propose a method to suppress the growth and spread of Mikania micrantha by applying a high-energy laser beam to penetrate its stem. The threshold penetrating optical intensity is 3.1 W/mm2. To optimize the damage to the inner tissue of the stem, which includes the vascular bundle and medulla for transporting organic nutrients, water, and inorganic salt, the absorption spectrum of the tissue and laser beam size are analyzed. According to the absorption spectrum of the tissue and growth mechanism of Mikania micrantha, a 455 nm blue laser is used as an irradiated light source. A single beam with two different beam sizes or two laser beams with the same beam size is used to optimize the stem damage. By the time the cumulative energy reaches 15 Joules for a single laser beam with dimensions of 0.81 mm × 0.74 mm, the inner tissue will be damaged 97.5%. We perform laser irradiation on the fresh Mikania micrantha grown hydroponically, with the result that all samples withered in 30 days. Therefore, using the method before the flowering season of Mikania micrantha can effectively inhibit its reproduction.

Phthalocyanine-Based Nanoassembly with Switchable Fluorescence and Photoactivities for Tumor Imaging and Phototherapy.

Switchable theranostics are of great interest for accurate tumor imaging and targeted therapy. Here, we develop smart engineering to construct nanostructured phthalocyanines self-assembled by amphiphilic zinc phthalocyanines (ZnPcs) and hydrophobic copper phthalocyanines (CuPcs) (ZnPc(PEG)5:CuPc-N, where ZnPc(PEG)5 is monosubstituted ZnPcs with pentaethylene glycol as the substituent). The fluorescence and reactive oxygen species generation of ZnPc(PEG)5:CuPc-N can be triggered depending on the membrane of the tumor cells for the imaging and photoactivities. Concerning the stability in blood circulation, the surface of the nanocomplex is coated with polydopamine, which responds to the tumor acidic microenvironment. ZnPc(PEG)5 and CuPc focus on photodynamic and photothermal properties, respectively, and can be stimulated by a single laser beam, endowing ZnPc(PEG)5:CuPc-N a combined antitumor effect from evaluations both in vitro and in vivo. In our study, the mechanism of switchable theranostics, the strategy of combined photodynamic and photothermal therapy, and the smart nanoengineering technology of phthalocyanines with poor water solubility can be applied to other phthalocyanines or phthalocyanine-like phototherapy agents.

Free-space remote detection of a spinning object using the combined vortex beam.

The rotational Doppler effect (RDE) associated with orbital angular momentum (OAM) has been used for remote sensing of a spinning object. However, one of the challenges of long-range detection stems from the low echo signal power. In this paper, we propose a new detection scheme that uses the combined vortex beam (CVB) generated by coherent beam combining (CBC) technology as the probe beam to enhance the echo signal power. Furthermore, we establish a rotational speed remote sensing model based on RDE, the emitted power and emission diameter of the probe beam are investigated in detail. The results show that, compared with the superposition vortex beam (SVB) generated by a single laser beam, the CVB detection scheme can significantly enhance the echo signal intensity and detection distance. The measuring range and accuracy of rotational speed are also studied in detail. And finally, we present the first experimental demonstration of the RDE arising directly from the interaction of the CVB with a rotating rough surface. The scheme proposed in our paper offers a good reference for practical application of the remote detection based on RDE.

An efficient ultrasound-assisted CH3COONa catalyzed synthesis of thiazolidinone molecule: Theoretical and nonlinear optical evaluations of thiazolidinone-Schiff base derivative

Chemical synthesis, structural analysis, theoretical calculations and optical properties exploration of (E)-2-((E)-(4-nitrobenzylidene)hydrazono)-3-phenyl-4-thiazolidinone 7 (C16H12N4O3S) are introduced. The synthesis method involves three steps. The applying of 1H and 13C NMR, infrared radiation (IR), mass and UV–visible spectroscopies and melting point (m.p) confirmed the expected compound structure. Optimization of the compound geometrical structure is carried out via the theoretical calculation and evaluation of its nonlinear optical (NLO) properties. The NLO properties of the synthesized 4-thiazolidinone derivative 7 are studied under the irradiation with visible and single transverse mode laser beam, through the determination of the nonlinear refractive index (NRI) via the diffraction ring patterns (DRPs) and the Z-scan together with optical limiting. Using two visible laser beams, the all-optical switching (AOS) in 4-thiazolidinone derivative 7 is studied too.

Plane-based self-calibration and improvement of three-dimensional multi-beam laser scanning with two-axis-mirror

The geometry and calibration of three-dimensional multi-beam laser scanning (MBLS) is more difficult than single-beam laser scanning, especially for a one laser emitter and multiple laser-echo detection within the same optical path and scanning with a two-axis-mirror. This paper focuses on the influence of the main systematic errors upon the geometric imagery of the MBLS, and presents a plane-based self-calibration method to improve the geometric positioning. First, the model for geometric imaging and systematic errors for the MBLS is presented, and the adjustment of the plane-based self-calibration is developed. Second, the influence of systematic errors upon geometric imagery of the MBLS is simulated and conducted to find the main errors. Third, a strong network configuration based on planar calibration is addressed and implemented, and the improvement of accuracy is examined via qualitative and quantitative analysis. The results show that the rangefinder offset, horizontal direction circle index and vertical circle index are the main systematic errors. The accuracy of distance is corrected from 29.94 cm to 2.86 cm with an improvement of 86.89% for the plane-based calibration, and validation indicates that this is corrected from 25.47 cm to 5.60 cm with an improvement of 88.25%.

Optical Erasure and Reconfiguration of Surface‐Relief‐Gratings of Azo Polymer and Azo Molecular Glass: A Comparative Study on Soft‐Lithographic Duplicates

Surface‐relief‐gratings (SRGs) of azo polymers and azo molecular glasses have attracted considerable interest for their erasable and reconfigurable characteristics. Herein, the optical erasure of soft‐lithographically duplicated SRGs of an azo polymer (BP‐AZ‐CN) and an azo molecular glass (IAC‐4) is investigated to tackle a long‐standing problem from “memory” effect existing in optically inscribed SRGs. The optical erasure is performed by single laser beam irradiation at wavelength of 488 nm with different polarizations, and the erasing behavior is thoroughly investigated by real‐time diffraction efficiency measurement and atomic force microscopy (AFM) observation. Showing no obvious dependence on the light polarizations, the optical erasure of IAC‐4 grating is a relatively fast process, and the original one can be completely erased and recreated. In contrast, the erasure of BP‐AZ‐CN grating is not only much slower, but also strongly correlated with the light polarizations. Upon the p‐polarized light irradiation, the grating profiles are substantially distorted during the erasure with a significant difference in that of the s‐polarized light irradiation. The gratings cannot be completely erased by the lights with all the polarizations. The erasure behavior is found to be determined by the effects of surface tension and mass transfer along the light polarization direction to different extents.

Nano-spheroid formation on YAG surfaces induced by single ultrafast Bessel laser pulses

We report on single pulse ultrafast Bessel laser beam processing of YAG ceramic surfaces as a method for producing contamination-free submicron particles and size adjustable surface hemisphere structures of different curvature signs. The micro-machining process was performed in both air and liquid environments, leading to a variety of surface structures depending on the processing parameters. Particularly, a transformation of the surface structure morphology from micro-hole profiles to hemisphere extrusions was observed. The size of the hemisphere structure is found to be highly sensitive to laser parameters, such as pulse energy, pulse duration and beam focusing position. Through careful analyses of the influence of the laser pulse parameters, a precise regulation of the lateral diameter and height of the hemisphere structure was achieved. Large area hemisphere arrays with low standard deviation in size were fabricated. The detachment of the emerging structures and subsequent particle deposition can be observed in liquid environments when the height-diameter aspect ratio of the hemisphere exceeds a factor of 0.65. The Mechanisms for the formation and detaching of the hemisphere structure are discussed with cross-sectional and morphology imaging via Scanning Electron Microscopy and Atomic Force Microscopy. As a preliminary step towards submicron particle generation in liquid environments, the observation of surface hemispheres has interest in exploring the initial mechanisms of particles formation under laser ablation in liquids. The presented method allows for the fabrication of contamination-free and size adjustable YAG submicron convex structures which have potential applications in integrated optics, biotechnology and other advanced processing techniques.

Self-pulsing and chaos in the asymmetrically driven dissipative photonic Bose-Hubbard dimer: A bifurcation analysis.

We perform a systematic study of the temporal dynamics emerging in the asymmetrically driven dissipative Bose-Hubbard dimer model. This model successfully describes the nonlinear dynamics of photonic diatomic molecules in linearly coupled Kerr resonators coherently excited by a single laser beam. Such temporal dynamics may include self-pulsing oscillations, period doubled oscillatory states, chaotic dynamics, and spikes. We have thoroughly characterized such dynamical states, their origin, and their regions of stability by applying bifurcation analysis and dynamical system theory. This approach has allowed us to identify and classify the instabilities, which are responsible for the appearance of different types of temporal dynamics.

Mode division multiplexing free space optics system with 3D hybrid modulation under dust and fog

Mode division multiplexing (MDM) is an emerging information transmission technique in which multiple data signals can be transmitted simultaneously on different modes of a single wavelength laser beam over a free-space channel. MDM is a potential technique for the realization of high-speed spectral efficient communication links for future generations of wireless networks. We present a novel MDM-based free-space optics (FSO) system. The system integrates a 3D hybrid modulation scheme produced by combining carrier suppressed-non-return-to-zero (CSNRZ), differential quadrature phase-shift keying (DQPSK), and polarization shift keying (PolSK) modulation schemes for beyond 100 Gbps applications. Three unrelated 40 Gbps data signals are modulated and transmitted on one optical carrier utilizing three distinct signal properties: amplitude (CSNRZ), phase (DQPSK), and polarization state (PolSK). The proposed 3D modulation scheme offers a high-capacity system, where each channel transmits 4 Gbps as compared to 1 Gbps in the case of OOK modulation. MDM using distinct Hermite Gaussian modes: (HG00 and HG01) of a laser beam is incorporated to boost the spectral efficiency and information rates of the FSO link. The proposed 120 Gbps single-channel MDM-FSO link performance is examined under the impact of different levels of dust and fog environmental conditions using quality factors and received eye diagrams as the performance metrics. This system achieved optimal performances up to 1250 m (very light dust), 540 m (light dust), 170 m (moderate dust), 750 m (low fog), and 425 m (medium fog). In the worst-case scenario, the system manages to work up to a 67 m range in dense dust with a maximum attenuation of 297.38 dB/km and a 200 m distance in heavy fog with only 90 dB/km attenuation which is less than 1/3rd of the attenuation measured for dense dust event. In addition, our results and the case studies confirm that dust introduces greater signal attenuation than fog. Therefore, an encounter with a dust environment should be considered as the bottleneck issue for FSO links. The creative contribution of this paper is to put forward a bandwidth-efficient MDM-FSO-enabled B5G system that could be deployed in harsh and challenging locations at reduced visibility. This is expected to be further technically sustainable owing to the use of advanced 3D hybrid optical orthogonal modulation and therefore find use in implementing 5G and 6G cellular and data networks.

An Initial Study on Multi-Point Laser Acupuncture Based on 2-D Galvo Mirror.

Currently, the majority of commercially available laser acupuncture instruments are still hand-held and only support single-point stimulation. Simultaneous multi-point stimulation improves the therapeutic efficacy of laser acupuncture by stimulating multiple acupoints at the same time. A "2-dimensional (2-D) galvo mirror" was utilized as a positioning laser acupuncture device for multi-acupoints stimulation. Due to its ability to perform 2-D fast scanning, a single laser beam was reflected by the mirror and stimulated multiple acupuncture points simultaneously. This introduction to the new system, presents its architecture, and shows some initial results. This initial stage of development was focused on the acupoints of the human forearm. This proposed system is the first low-cost, noncontact laser acupuncture system that enables continuous multi-acupoint stimulation with a single laser beam. Notably, it is technically feasible to develop this technique into a whole-body laser acupuncture stimulation system.

Broadband plasmonic half-subtractor and digital demultiplexer in pure parallel connections

Abstract Nanophotonic arithmetic circuits requiring cascaded Boolean operations are difficult to implement due to loss and footprint issues. In this work, we experimentally demonstrate plasmonic half-subtractor and demultiplexer circuits based on transmission-lines. Empowered by the unique polarization selectivity in the surface plasmon modal behaviors, both circuits are realized without cascading. The operations of the half-subtractor and demultiplexer can be performed using a single laser beam with three predefined linear polarizations. All of our experiments are performed using a 56 fs laser providing greater than 12.5 THz optical bandwidth. The experimental results are found in excellent quantitative accordance with numerical calculations. The photonic integrated circuit framework proposed in this work could pave the future avenue towards the realization of highly compact, multi-functional, on-chip integrated photonic processors.

Multi-beam heterodyne laser Doppler vibrometer based on a line-scan CMOS digital camera.

Multi-beam laser Doppler vibrometers (MB-LDVs) have an advantage over scanning single-beam laser Doppler vibrometers (LDVs) due to the reduction in measurement time and their ability to measure non-stationary and transient events. However, the number of simultaneously interrogated points in current MB-LDVs is limited due to the complexity of the electronic hardware, which increases with the number of measurement channels. Recent developments of high-speed line-scan CMOS cameras suggest that their use in MB-LDVs can reduce the hardware complexity and increase the number of measurement channels. We developed a MB-LDV based on a digital line-scan CMOS camera that simultaneously measures vibrations on a linear array of 99 points. The experimental setup and performance of the developed MB-LDV are discussed in this paper.

Performance evaluation of MDM-FSO transmission system for varying atmospheric conditions

Abstract We report the designing of a free-space-optics (FSO) transmission system capable of transmitting high rate information by utilising novel mode division multiplexing (MDM) transmission technique. In the work reported, 2-channels transmitting 10 Gbps data, using either non-return-to-zero (NRZ) encoding scheme or return-to-zero (RZ) encoding scheme are modulated by using different Hermite–Gaussian (HG) modal beams of the single laser beam to realize of 20 Gbps transmission system. The system proposed is simulative analysed under the effect of different weather states. Also, we have compared the bit error rate (BER) and Quality factor (Q Factor) performance for RZ and NRZ encoding schemes in the system for varying weather states. The results reported show that NRZ encoding exhibits a superior performance. Also, we have analysed the system performance by taking into consideration atmospheric scintillation effect and the reported results show notable signal degradation in the presence of scintillation.