- 标题
- 摘要
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- 实验方案
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Signal Acquisition with Photon-Counting Detector Arrays in Free-Space Optical Communications
摘要： The science and art of Spatial Audio is concerned with the capture, production, transmission, and reproduction of an immersive sound experience. Recently, a new generation of spatial audio technology has been introduced that employs elevated and lowered loudspeakers and thus surpasses previous ‘surround sound’ technology without such speakers in terms of listener immersion and potential for spatial realism. In this context, the ISO/MPEG standardization group has started the MPEG-H 3D Audio development effort to facilitate high-quality bitrate-efficient production, transmission and reproduction of such immersive audio material. The underlying format is designed to provide universal means for carriage of channel-based, object-based and Higher Order Ambisonics based input. High quality reproduction is provided for many output formats from 22.2 and beyond down to 5.1, stereo and binaural reproduction—independently of the original encoding format, thus overcoming the incompatibility between various 3D formats. This paper provides an overview of the MPEG-H 3D Audio project and technology and an assessment of the system capabilities and performance.
关键词： channel-based,object-based,audio compression,SAOC,MPEG-H,USAC,Audio coding,spatial audio,MPEG,HOA,higher order Ambisonics
更新于2025-09-16 10:30:52
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Influences of nanosecond pulse pre-irradiation on femtosecond laser damage resistance of gold pulse compression grating
摘要： The gold pulse compression gratings (PCG) used in the Bidirectional Grating Compressor (BGC) suffers a nano- and femtosecond dual pulses irradiation. In the case that the ns pre-pulse comes 10 nanoseconds early before the fs pulse, experiments were conducted to investigate damage behaviors under the dual pulse irradiation. 1-on-1 laser induced damage threshold (LIDT) of the ns–fs dual pulses and fs single pulse were tested and compared. Scanning Electron Microscope (SEM) was employed to capture damage onset and exam the damage macro- and micro-morphologies. The mono-shot method, comparison between the damage zone and spatial distribution of laser pulses, was employed to analyze the difference of the damage onset fluences for the two cases thoroughly. It was found that there is no degradation of laser damage resistance due to the ns pre-pulse. Instead, a slightly increase (～10%) of fs LIDT caused by the ns pre-pulse was found.
关键词： Femtosecond laser damage,Nano- and femtosecond dual beam processing,Nanosecond pre-pulse,Gold-coated pulse compression gratings,Bidirectional grating compressor
更新于2025-09-16 10:30:52
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Quantitative measurements of formaldehyde in the low-temperature oxidation of iso-octane using mid-infrared absorption spectroscopy
摘要： Time-resolved quantitative measurements of formaldehyde (HCHO) in the low-temperature oxidation of iso-octane using a rapid compression machine have been performed with mid-infrared laser absorption spectroscopy. Due to the weak interference of the broadband absorption of iso-octane, a two-color detection scheme was applied to HCHO detection. The cross-sections of HCHO and iso-octane in two colors were measured using the rapid compression machine in the temperature range of 450–737 K and pressure range of 100–700 kPa. The time-resolved quantitative HCHO profiles in the low-temperature oxidation of iso-octane at 0.77 MPa, 645 K, and an equivalence ratio of 1.0 were successfully obtained. The calculated HCHO profiles using the latest chemical kinetic model of iso-octane show the same tendency as the experimental profiles.
关键词： formaldehyde,mid-infrared absorption spectroscopy,iso-octane,low-temperature oxidation,rapid compression machine
更新于2025-09-16 10:30:52
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35 fs, all-polarization-maintaining MOPA laser system
摘要： We have experimentally observed ultrashort pulse in a simple, all-polarization-maintaining fiber, master oscillator and power amplifier laser. A semiconductor saturable mirror (SESAM) module is used as the mode locker. The ultrashort pulse exhibits perfect Gaussian spectrum without any fine structure. The 20 dB pulse spectral width is 28 nm, and the pulse duration directly output from the oscillator is 268.6 fs. Via a two-stage amplifier, the pulse spectrum is greatly broadened to 43 nm, and the pulse duration lengths to 0.9 ps. Moreover, after compression, a typical saddle-shaped spectrum appears and the spectral bandwidth broadens to 121 nm; the pulse duration is compressed to ~35 fs with a pulse peak power of 22.79 kW, which is high enough to stimulate a one-octave supercontinuum spectrum. Due to the polarization-maintaining structure and high reliability of SESAM, the whole system exhibits strong environmental stability. Experimental observation reveals that such a fiber laser with a very simple structure exhibits excellent performance, and could be applied in the area of optical frequency comb.
关键词： ultrafast fiber lasers,pulse propagation and temporal solitons,pulse compression
更新于2025-09-16 10:30:52
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Compression of laser pulses by near-forward Raman amplification in plasma
摘要： We propose a new scheme for compression of ultrashort laser pulses enabled by Near-Forward Raman Ampli?cation (NFRA) in plasma. In contrast to traditional forward Raman ampli?cation in plasma, the seed pulse in NFRA propagates faster than the pump through manipulation of the spatiotemporal properties of the pump beam. A “p-pulse” solution similar to that of stimulated Raman backscattering ampli?cation is obtained, indicating that NFRA can be used for compression of ultrashort laser pulses. NFRA is numerically demonstrated with a 2D simulation using a front-tilt near-forward pump pulse.
关键词： Raman amplification,plasma,laser pulses,pulse compression
更新于2025-09-16 10:30:52
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Ultrafast Pulse Manipulation in Dispersion-Flattened Waveguides With Four Zero-Dispersion Wavelengths
摘要： On-chip formation and manipulation of ultrashort pulses would be of great interest to ultrafast optics and integrated photonics communities. One of key issues is dispersion-assisted nonlinear interactions of broadband frequency components. In this paper, we show for the first time that a bilayer waveguide for quasi-TE mode without using a slot produces a quite flat and saddle-shaped dispersion profile. Different from previously reported TE-mode waveguides with flattened dispersion, the proposed waveguide exhibits a greatly simplified structure with no need for a high-aspect-ratio slot and has quite small group delay difference in a wide spectral range with four zero-dispersion wavelengths (ZDWs). We study supercontinuum generation in hybrid dispersion regime for the first time, in which the broadened spectrum covers a bandwidth with all ZDWs. It is found that one can obtain greatly improved spectral flatness in supercontinuum generation, with a power variation as small as 3 dB over a bandwidth of >500 nm. Moreover, the proposed waveguides are particularly suitable for low-distortion pulse propagation over a long distance, which is important for on-chip ultrashort pulse delivery.
关键词： Dispersion engineering,pulse compression,waveguide,supercontinuum generation
更新于2025-09-12 10:27:22
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[IEEE 2019 International Topical Meeting on Microwave Photonics (MWP) - Ottawa, ON, Canada (2019.10.7-2019.10.10)] 2019 International Topical Meeting on Microwave Photonics (MWP) - Laser ranging with analog all-optical coherent pulse compression
摘要： We propose and demonstrate a simple experimental platform that enables ranging by optical coherent pulse compression. Our system, based on a frequency shifting loop, is particularly simple and involves only a single CW laser and standard telecom components. It does not require fast electronic systems, since the pulse compression is realized in a purely analog way, by the beating between two sequences of optical chirped waveforms with the same chirp rate, but slightly different repetition rates. We demonstrate a range resolution in the centimeter range set by the bandwidth of the optical chirps, 24 GHz, and a time-bandwidth product of 300, with a detection bandwidth of only a few tens of MHz.
关键词： pulse compression,Lidar,ranging,chirps
更新于2025-09-12 10:27:22
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Optimized x-ray sources for x-ray diffraction measurements at the Omega Laser Facility
摘要： The use of x-ray diffraction (XRD) measurements in laser-driven dynamic compression experiments at high-power laser facilities is becoming increasingly common. Diffraction allows one to probe in situ the transformations occurring at the atomic level at extreme conditions of pressure, temperature, and time scale. In these measurements, the x-ray source is generated by irradiation of a solid foil. Under certain laser drive conditions, quasimonochromatic He-α radiation is generated. Careful analysis of the x-ray source plasma spectra reveals that this radiation is not a single line emission and that monochromaticity is highly dependent on the laser irradiance. In this work, we analyze how the spectra emitted by laser-irradiated copper, germanium, and iron foils at the Omega Laser vary depending on different laser drive conditions and discuss the implications for XRD experiments.
关键词： laser irradiance,x-ray diffraction,Omega Laser Facility,quasimonochromatic He-α radiation,laser-driven dynamic compression
更新于2025-09-12 10:27:22
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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) - Joule-Class 500 Hz Cryogenic Yb:YAG Chirped Pulse Amplifier
摘要： A cryogenic solid-state laser (CSSL) based on a chromium-doped gadolinium scandium gallium garnet (Cr:GSGG) crystal has been demonstrated. The laser operates at 1.94 μm with a maximum output power of 1.1 W at 100 K. The output pulses (FWHM 1.24 ns) may be compressed to 31 ps. The current state of art in cryogenic solid-state lasers is presented, and the advantages of the CSSL are discussed.
关键词： solid-state laser,1.94 μm,cryogenic,pulse compression,Cr:GSGG
更新于2025-09-12 10:27:22
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Laser-shock compression experiment on magnesium hydride
摘要： A dynamic high-pressure experiment was performed on magnesium hydride to measure the Hugoniot equation-of-state point using laser-driven shock waves. By measuring the mean shock velocity of MgH2 and the time-resolved shock velocity of the quartz reference, the Hugoniot state of MgH2 at 150 GPa was determined. The reliability of the data is ensured by using another reference material, polystyrene, which is next to the sample and is compressed by the same. This work validates the experimental methodology to obtain further high-pressure data of MgH2 with high accuracy.
关键词： Velocity interferometer,Magnesium hydride,Shock compression,Laser-driven shock,Hugoniot measurement
更新于2025-09-12 10:27:22