- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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LPSE: A 3-D wave-based model of cross-beam energy transfer in laser-irradiated plasmas
摘要： The new component of the “laser–plasma simulation environment” (LPSE) described here is a practical numerical model that solves the coupled vector equations for the propagation of nearly monochromatic, coherent, electromagnetic waves in inhomogeneous unmagnetized plasmas. It operates efficiently in the numerically challenging semiclassical regime where characteristic plasma scale lengths are many times greater than the wavelength of the light and solutions are highly oscillatory. Solutions can be obtained in one, two, or three spatial dimensions and time. The model includes the effects of nonlinear coupling of electromagnetic waves to the low-frequency plasma perturbations (i.e., ion-acoustic response) that are responsible for stimulated Brillouin scattering. Induced plasma perturbations are assumed to be imposed on a prescribed large-scale inhomogeneous background that includes spatially varying plasma density and flow. Our code is directly relevant to the problem of cross-beam energy transfer in laser-driven inertial confinement fusion. It may also be applicable in other areas where eikonal solutions of multicomponent wave equations (or coupled wave equations) are insufficient, such as optical scattering from ultrasound, electron dynamics in quantum devices or in nanoscale light–matter interactions.
关键词： Maxwell solver,Parametric instabilities,Semiclassical,Laser–plasma,Nonlinear scattering problem,Stimulated Brillouin scattering
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Up-Scaling the Power of Pulsed Single Frequency Fibre Amplifiers for Coherent LIDAR Applications
摘要： In optical sensing applications, the laser sources are strongly constrained by the sensing system requirements. In the case of coherent LIDARs, that measure wind speed thanks to the Doppler shift (by means of a coherent detection), highly coherent high power pulsed lasers with good output beam quality are necessary to guarantee a proper measurement over long distances. The pulsed emission ensures the spatial resolution along the line of sight whereas the high coherence accounts for the wind speed resolution (measured in the frequency domain). Thus, the challenge when designing laser sources for such instruments resides in the difficulty of improving the output power while not altering the other characteristics. Fibre lasers and amplifiers have proven their interest in high power laser systems thanks to their compactness and their stability against temperature and mechanical fluctuations. The increase of emitted optical power is currently limited by nonlinear effects due to the intrinsically high confinement of the optical field in fibres. Among all the nonlinear effects, the Stimulated Brillouin Scattering (SBS) predominates in the case of single frequency or narrow spectrum optical fields. In order to increase the power of single frequency fibre lasers, many developments have been done in the past decades to mitigate SBS. We can class the different SBS mitigation techniques in two categories depending on whether they act on the optical field properties or on the optical fibre itself. All the techniques belonging to the first category are based on an active control of the phase or the frequency of the incident optical wave, in order to spread the incident energy in the spectral domain. In the second category, we can maximize the core radius of the fibre, minimize the fibre length, apply temperature gradients, dopant concentrations gradients or strain gradients to broaden the SBS spectrum in a controlled manner and thus lower its effective gain. We review here the different techniques we use to mitigate the SBS in pulsed single frequency fibre amplifiers and discuss their conceptual and technical limitations. Among all the existing mitigation techniques, we present here different realizations of fibre amplifiers designed for coherent LIDAR systems, based on strain gradients [1] and specifically designed highly doped and large core active fibres [2]. Figure 1 presents the typical achievements obtained with our patented tensile and compressive strain gradients techniques when applied to active fibers. We are able to increase the output power by a factor 2 to 3 while keeping a high beam quality on a highly coherent laser emission. We emphasize the robustness of such developments thanks to the absence of active devices that make them suitable for embedded sensing applications.
关键词： coherent LIDAR,high power pulsed lasers,Stimulated Brillouin Scattering,SBS mitigation,single frequency fibre amplifiers
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Extreme Events Generation via Cascaded Stimulated Brillouin Scattering in Self-Pulsing Fiber Lasers
摘要： Extreme-amplitude events and rare instabilities are observed for more than a decade in various optical systems. Specifically in dissipative systems, such as Raman fiber lasers, laser diodes or mode-locked lasers, to name a few, long-tailed statistics and highly-localized temporal structures have been observed [1,2]. Recent studies showed that stimulated Brillouin scattering (SBS) can also trigger the generation of extreme events in various configurations, from self-pulsing fiber lasers [3,4] to Q-switched random fiber lasers [5]. It is indeed known that the stochastic nature of SBS can promote the emergence of randomly distributed giant pulses which can induce irreversible damages in fiber laser systems. In order to understand and open the possibility to harness such extreme events, numerical models have then to be developed and refined. In the context of self-pulsed fiber lasers, a few studies taking into account only one or two fundamental Stokes orders have already been reported [6]. Such models describe well the large pulse-to-pulse intensity fluctuations observed in Erbium-doped fiber lasers Q-switched through SBS but they however did not predict any extreme event [6]. We propose here an extension of the model proposed in Ref. [3] by generalizing it to higher Stokes orders to study their impact on extreme dynamics in a self-pulsing laser. Our model is based on the coupled amplitudes equations describing the spatiotemporal dynamics of both the laser and Brillouin waves with their corresponding acoustic fields, as well as the temporal variations of the gain for each wave. We also consider a matter equation to account for the saturable absorption effect which can occur in the un-pumped segment of the active fiber. We show that increasing the number of SBS orders interacting with the gain medium reveals new dynamics enabling the generation of extreme events which are not predicted by the single SBS order model. Pulses with amplitudes 27 times the so-called significant wave height are indeed predicted, which attest of the presence of extreme-amplitude events, as shown in Fig. 1. Such giant pulses could then reach the threshold of irreversible damage in optical fibers. We also provide a comprehensive study on the different parameters influencing the dynamics, including the number of Stokes orders that strongly affect the laser dynamical behavior and then allow to somehow control the highest intensity of the laser instabilities. The influence of other parameters, such as the input noise, on the system’s dynamics will be discussed and we will show that our simplified model can pave the way towards a better understanding of the complex stochastic dynamics under the influence of SBS.
关键词： stimulated Brillouin scattering,stochastic dynamics,Extreme events,optical systems,self-pulsing fiber lasers
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Coherent Beam Combining of Fiber Amplifiers Seeded by Commercial Low Cost Diode
摘要： Coherent beam combining (CBC) is one of the methods for power scaling of high power lasers. In the scientific literatures a low power narrow linewidth source is used for CBC, however in this report, a low cost diode laser source (spectral bandwidth <10 MHz) is used to fabricate near diffraction-limited 300 W fiber laser with CBC method. The diode laser is amplified by a preamp fiber amplifier and then divided in to three channels. Each channel is amplified to achieve 120W output with homemade power amplifiers. A 1×3 diffractive optical element is used to combine the output of the amplifiers with ~83% efficiency. Active phase locking is achieved with the stochastic parallel gradient descent (SPGD) method. A major obstacle towards high power narrow-linewidth fiber lasers is stimulated Brillouin scattering (SBS). It has been proven that phase modulation is an effective way to suppress SBS in these kind of lasers. Applying phase modulation to a single frequency laser, splits its spectrum to many spectral lines with the same frequency spacing of the modulation frequency. In this work, we use a sinusoidal signal phase modulation (30 MHz frequency and 10 V amplitude) to suppress SBS effect. The result of this modulation on the spectrum of the laser is illustrated. The maximum achievable output power for each channel without modulation is ~40 W. However, by applying modulation SBS threshold power enhances with a factor of 3. The output power of combined beam versus pump diode current (solid line) is shown. Also the backward output power (dashed line) is illustrated. As it can be seen in the figure the maximum backward power is 110 μW which proves the SBS effect is cancelled.
关键词： stimulated Brillouin scattering,diode laser,phase modulation,Coherent beam combining,fiber amplifiers
更新于2025-09-11 14:15:04
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Investigation of the dynamical behaviour of a high-power laser diode subject to stimulated Brillouin scattering optical feedback
摘要： In this work, we propose a new scheme of optical feedback using stimulated Brillouin scattering (SBS). A high-power laser diode emitting at 1450 nm stimulates Brillouin back-scattering in a 4km-long optical fibre and the back-scattered light is injected back into the laser diode for optical feedback. The experimental results with RF spectrum exhibit clearly the Brillouin frequency shift at 11.46 GHz. Although the frequency shift is very large, the laser diode subject to optical feedback using SBS shows abundant dynamics. RF spectrum maps are also established with respect to the laser drive current. The results are compared with the ones for conventional optical feedback and it is clearly shown that the dynamical behaviours for both the con?gurations are very different. The investigation with autocorrelation functions reveals that the time-delay signature vanishes completely using the SBS feedback scheme unlike the conventional feedback one.
关键词： stimulated Brillouin scattering,optical feedback,chaotic laser
更新于2025-09-11 14:15:04
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Optical Smoothing with Reduced FM-to-AM Conversion in High-Power Lasers Using Spectral Distribution
摘要： High-power energetic nanosecond lasers, such as the Laser Mégajoule, require optical smoothing techniques to make their focal spots as homogeneous as possible. This strongly reduces parametric instabilities that occur during laser-plasma interaction, such as stimulated Brillouin scattering. Smoothing by spectral dispersion is one of the most-used techniques. It requires spectral broadening through phase modulation. However, because of propagation impairments, part of the phase modulation is converted into unwanted intensity modulation that induces laser nonlinearities and optical damage. This is called “FM-to-AM conversion.” Taking advantage of the architecture of the Laser Mégajoule, for which each “beam” (quadruplet) is split into four sub-beams, we show that the spectral broadening can be distributed on the sub-beams, reducing FM-to-AM conversion from 30% to 10% while maintaining smoothing performance for mitigation of stimulated Brillouin scattering.
关键词： FM-to-AM conversion,stimulated Brillouin scattering,optical smoothing,spectral distribution,high-power lasers
更新于2025-09-11 14:15:04
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Investigation of the Brillouin effect in highly nonlinear hafnium bismuth erbium doped fiber
摘要： This paper demonstrates the generation of the Brillouin fiber laser (BFL) with 0.5 m long hafnium bismuth erbium doped fiber (HBEDF) as a hybrid gain medium. As the gain medium is pumped by a 980 nm laser diode at the power of 170 mW, a stable Stokes is observed at the output power of ?2.96 dBm with Brillouin pump (BP) power of 3 dBm. The laser operates at wavelength shifted by 0.09 nm from the BP. To the best of the authors’ knowledge, this is the first report of a compact BFL without employing any lengthy SMF, which features a simple cavity configuration.
关键词： hafnium bismuth erbium doped fiber,Brillouin fiber laser,stimulated Brillouin scattering
更新于2025-09-09 09:28:46
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Microwave Photonic Image-Reject Mixer Based on a Tunable Microwave Photonic Filter With High Rejection
摘要： In a heterodyne receiver, the image can interfere with the desired signal and must be eliminated at the mixing stage. This paper presents a ?exible microwave photonic image-reject mixer based on a widely tunable microwave photonic ?lter (MPF), which is used to select the desired signal and suppress the image. The MPF is realized by using stimulated Brillouin scattering, which offers signi?cant advantages of wideband tunability, high selectivity, and large image rejection. In this work, a theoretical model is established to describe the operation principle of the proposed mixer at ?rst. Then, in the experiment, a 7.8-GHz radio frequency (RF) signal is successfully down-converted to an intermediate frequency signal between 0.2 and 1.5 GHz, with an image rejection of larger than 40 dB. Additionally, when the RF frequency is tuned from 1.8 to 19.8 GHz, the image rejection remains above 40 dB.
关键词： microwave photonic ?lter (MPF),image-reject mixer (IRM),Microwave photonics,stimulated Brillouin scattering (SBS)
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE 7th International Conference on Photonics (ICP) - Langkawi, Malaysia (2018.4.9-2018.4.11)] 2018 IEEE 7th International Conference on Photonics (ICP) - Advanced Functions for Signal Processing and Sensing Harnessing On-Chip SBS
摘要： This paper reviews some of the significant SBS-enabled signal processing applications in chalcogenide photonic waveguides and demonstrates a characterization technique to monitor the performance of this platform. an opto-electronic oscillator (OEO) was demonstrated utilizing on-chip SBS. SBS as a narrow- band active filter allows single-mode OEO operation and ultrawide frequency tunability with no signal degeneration [4]. The abovementioned functionalities are based on the high yield of the chalcogenide photonics waveguide, which requires a precise method for characterization against the fabrication variations. In the following section, we describe a method which is used to provide us with such information.
关键词： on-chip RF signal processing,distributed SBS sensing,BOCDA,photonic integrated waveguides,Stimulated Brillouin scattering(SBS)
更新于2025-09-04 15:30:14