The image shows fast object detection and data analysis of high-power high-repetition-rate laserplasma experiment using neural networks. In the petawatt, Hz laser system at the Center for Advanced Laser Applications, Munich, object detection networks are used to rapidly process and visualize various diagnostic data from each frame of the laser’s output images, including electron energy spectra, plasma wave, and laser damage.
Helical laser beams, due to their unique ?eld structure, are ideal optical drivers for producing monoenergetic, pellet-like electron bunches. In contrast to regular laser beams, their ?eld structure close to the axis of the beam is dominated by longitudinal electric and magnetic ?elds. The bunches are generated as a result of two synergetic e?ects that take place when such a beam is re?ected o? a mirror: the longitudinal electric ?eld accelerates electrons after extracting them from the mirror surface; while the magnetic ?eld con?nes them into the central region, allowing for acceleration within the laser over a long duration.
The cover image illustrates the photonic quasicrystal fiber (PQF), which is also named quasiperiodic photonic crystal fiber. The five insets surrounding the PQF end-face provide a simultaneous display of three typical structures and two representative potential applications of PQF. The three white-circled insets (top-left, right, and bottom-left) represent the Stampfli-type, Penrose-type, and Sunflower-type structures, respectively. The two blue-circled insets (left and bottom-right) show applications of the supercontinuum generation and orbital angular momentum mode propagation, respectively.
By harnessing Tamm plasmon coupling, spintronics THz radiation not only achieved a 264% enhancement but guaranteed nearly lossless (~4%) THz transmission. This approach provides the compatible optical structure design and the low energy consumption for ultrafast opto-spintronics devices.
A snapshot full-polarization hyperspectral imaging method based on convolutional neural network (CNN) reconstruction is proposed. In the imaging system, a quarter-wave plate is combined with a liquid crystal tunable filter to encode full-polarization information. Meanwhile, the liquid crystal tunable filter flexibly selects spectral bands of interest. Finally, a CMOS detector captures the total light intensity image after full-polarization encoding. In the reconstructed model, a two-layer CNN reconstructs four full-polarization images from one full-polarization encoded image. The cover image shows the main components of both the full-polarization hyperspectral imaging system and the CNN reconstruction model.
As a successful case of combining deep learning with photonics, the research on optical machine learning has recently undergone rapid development. Among v
As a successful case of combining deep learning with photonics, the research on optical machine learning has recently undergone rapid development. Among various optical classification frameworks, diffractive networks have been shown to have unique advantages in all-optical reasoning. As an important property of light, the orbital angular momentum (OAM) of light shows orthogonality and mode-infinity, which can enhance the ability of parallel classification in information processing. However, there have been few all-optical diffractive networks under the OAM mode encoding. Here, we report a strategy of OAM-encoded diffractive deep neural network (OAM-encoded D2NN) that encodes the spatial information of objects into the OAM spectrum of the diffracted light to perform all-optical object classification. We demonstrated three different OAM-encoded D2NNs to realize (1) single detector OAM-encoded D2NN for single task classification, (2) single detector OAM-encoded D2NN for multitask classification, and (3) multidetector OAM-encoded D2NN for repeatable multitask classification. We provide a feasible way to improve the performance of all-optical object classification and open up promising research directions for D2NN by proposing OAM-encoded D2NN.show less
Breathing solitons, i.e., dynamic dissipative solitons with oscillating pulse shape and energy caused by different mechanisms of spatiotemporal instabilit
Breathing solitons, i.e., dynamic dissipative solitons with oscillating pulse shape and energy caused by different mechanisms of spatiotemporal instabilities, have received considerable interest from the aspects of nonlinear science and potential applications. However, by far, the study of breathing solitons is still limited within the time scale of hundreds of cavity round trips, which ignores the slow dynamics. To fill this lacuna, we theoretically investigate a new type of vector dissipative soliton breathing regime and experimentally demonstrate this concept using mode-locked fiber lasers, which arise from the desynchronization of orthogonal states of polarization (SOPs) in the form of complex oscillations of the phase difference between the states. The dynamic evolution of polarization states of the vector breathings solitons takes the form of a trajectory connecting two quasi-equilibrium orthogonal SOPs on the surface of the Poincaré sphere. The dwelling time near each state is on the scale of a tenth of a thousand cavity round trip times that equals the breathing period, which is up to 2 orders of magnitude longer than that for common breathers. The obtained results can reveal concepts in nonlinear science and may unlock approaches to the flexible manipulation of laser waveforms toward various applications in spectroscopy and metrology.show less
We report a Yb-doped all-fiber laser system generating burst-mode pulses with high energy and high peak power at a GHz intra-burst repetition rate. To acq
We report a Yb-doped all-fiber laser system generating burst-mode pulses with high energy and high peak power at a GHz intra-burst repetition rate. To acquire the uniform burst envelope, a double-pre-compensation structure with an arbitrary waveform laser diode driver and an acoustic optical modulator is utilized for the first time. The synchronous pumping is utilized for the system to reduce the burst repetition rate to 100 Hz and suppress the amplified spontaneous emission effect. By adjusting the gain of every stage, uniform envelopes with different output energies can be easily obtained. The intra-burst repetition rate can be tuned from 0.5 to 10 GHz actively modulated by an electro-optic modulator. Optimized by timing control of eight channels of analog signal and amplified by seven stages of Yb-doped fiber amplifier, the pulse energy achieves 13.3 mJ at 0.5 ns intra-burst pulse duration, and the maximum peak power reaches approximately 3.6 MW at 48 ps intra-burst pulse duration. To the best of our knowledge, for reported burst-mode all-fiber lasers, this is a record for output energy and peak power with nanosecond-level burst duration, and the widest tuning range of the intra-burst repetition rate. In particular, this flexibly tunable burst-mode laser system can be directly applied to generate high-power frequency-tunable microwaves.show less
High-intensity vortex beams with tunable topological charges and low coherence are highly demanded in applications such as inertial confinement fusion (ICF) and optical communication. However, t
High-intensity vortex beams with tunable topological charges and low coherence are highly demanded in applications such as inertial confinement fusion (ICF) and optical communication. However, traditional optical vortices featured with non-uniform intensity distributions are dramatically restricted in application scenarios that require a high-intensity vortex beam owing to their ineffective amplification resulting from the intensity-dependent nonlinear effect. Here, a low-coherence perfect vortex beam (PVB) with a topological charge as high as 140 is realized based on the super-pixel wavefront-shaping technique. More importantly, a globally adaptive feedback algorithm (GAFA) is proposed to efficiently suppress the original intensity fluctuation and achieve the flat-top PVB with dramatically reduced beam speckle contrast. The GAFA based flat-top PVB generation method can pave the way for high-intensity vortex beam generation which is crucial for potential applications in ICF, laser processing, optical communication, and optical trapping.show less
This paper presents the development and experimental utilization of a synchronized off-harmonic laser system designed as a probe for ultra-intense laser-plasma interaction experiments. The syste
This paper presents the development and experimental utilization of a synchronized off-harmonic laser system designed as a probe for ultra-intense laser-plasma interaction experiments. The system exhibits a novel seed-generation design, allowing for a variable pulse duration spanning over more than three orders of magnitude, from 3.45 picoseconds to 10 nanoseconds. This makes it suitable for various plasma diagnostics and visualization techniques. In a side-view configuration, the laser was employed for interferometry and streaked shadowgraphy of a laser-induced plasma while successfully suppressing the self-emission background of the laser-plasma interaction, resulting in a signal-to-self-emission ratio of 110 for this setup. These properties enable the probe to yield valuable insights into the plasma dynamics and interactions at PHELIX and to be be deployed at various laser facilities due to its easy-to-implement design.show less
Mid-spatial frequency wavefront deformation can be deleterious for the operation of high-energy laser systems. When fluid cooled high-repetition rate amplifiers are used, the coolant flow is lik
Mid-spatial frequency wavefront deformation can be deleterious for the operation of high-energy laser systems. When fluid cooled high-repetition rate amplifiers are used, the coolant flow is likely to induce such detrimental mid-spatial frequency wavefront deformations. Here, we describe the design and performance of a 90×90 mm² aperture, liquid-cooled Nd:phosphate split-slab laser amplifier pumped by flash lamps. The performance of the system is evaluated in terms of wavefront aberration and gain at repetition rates down to 1 shot per minute. The results show that this single cooled split-slab system exhibits low wavefront distortions in the medium to large period range, compatible with a focus on target, and despite the use of liquid coolant traversed by both pump and amplified wavelengths. This makes it a potential candidate for applications in large high-energy laser facilities.show less
Fast neutron absorption spectroscopy is widely used in study of nuclear structure and element analysis. However, due to long pulse duration (of the order of nanosecond) of traditional pulsed fas
Fast neutron absorption spectroscopy is widely used in study of nuclear structure and element analysis. However, due to long pulse duration (of the order of nanosecond) of traditional pulsed fast neutron sources, it is difficult to realize a fine absorption spectrum. Here, we present a method of ultra-high energy-resolution absorption spectroscopy via a high repetition rate, pico-second duration fast neutron source driven by a Tera-Watt laser plasma electron accelerator. The technology of single neutron count is used, which results in easily distinguish the width of ∼20 keV at 2 MeV and the asymmetric shape of the neutron absorption peak. The absorption spectroscopy proposed has one order of magnitude higher energy-resolution power than the state-of-art traditional neutron sources, which could be benefit for deep understanding the theoretical model of neutron physics and more precisely measuring the nuclear structure data.show less