Measurement of femtosecond pulse contrast of low-repetition-rate lasers by optical Kerr effect

2014 ◽  
Vol 23 (03) ◽  
pp. 1450031 ◽  
Author(s):  
Dengke Wu ◽  
Junfang He ◽  
Changjun Zhu ◽  
Yishan Wang ◽  
Wei Zhao
Keyword(s):  
Repetition Rate ◽  
Kerr Effect ◽  
Dynamic Range ◽  
Femtosecond Lasers ◽  
Wide Spectrum ◽  
Sampling Interval ◽  
Temporal Sampling ◽  
Optical Kerr Gate ◽  
Scanning Range ◽  
Pulse Contrast

In this paper, pulse contrast was measured for femtosecond lasers with low-repetition-rate (40 Hz) using optical Kerr gate as a sampler. The results show that, without attenuator, dynamic range as high as 104 was achieved, with a scanning range of 126 ps and a temporal sampling interval of 6.3 fs. Moreover, the method suits for measuring laser pulse contrast in wide spectrum range.

scholarly journals Cerebral CT Perfusion in Acute Stroke: The Effect of Lowering the Tube Load and Sampling Rate on the Reproducibility of Parametric Maps

Diagnostics ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1121
Author(s):  
Georgios S. Ioannidis ◽  
Søren Christensen ◽  
Katerina Nikiforaki ◽  
Eleftherios Trivizakis ◽  
Kostas Perisinakis ◽  
...  
Keyword(s):  
Cerebral Blood Volume ◽  
Ct Perfusion ◽  
Sampling Rate ◽  
Volumetric Analysis ◽  
Sampling Interval ◽  
Diagnostic Efficiency ◽  
Temporal Sampling ◽  
Sampling Intervals ◽  
The Mean ◽  
Parametric Maps

The aim of this study was to define lower dose parameters (tube load and temporal sampling) for CT perfusion that still preserve the diagnostic efficiency of the derived parametric maps. Ninety stroke CT examinations from four clinical sites with 1 s temporal sampling and a range of tube loads (mAs) (100–180) were studied. Realistic CT noise was retrospectively added to simulate a CT perfusion protocol, with a maximum reduction of 40% tube load (mAs) combined with increased sampling intervals (up to 3 s). Perfusion maps from the original and simulated protocols were compared by: (a) similarity using a voxel-wise Pearson’s correlation coefficient r with in-house software; (b) volumetric analysis of the infarcted and hypoperfused volumes using commercial software. Pearson’s r values varied for the different perfusion metrics from 0.1 to 0.85. The mean slope of increase and cerebral blood volume present the highest r values, remaining consistently above 0.7 for all protocol versions with 2 s sampling interval. Reduction of the sampling rate from 2 s to 1 s had only modest impacts on a TMAX volume of 0.4 mL (IQR −1–3) (p = 0.04) and core volume of −1.1 mL (IQR −4–0) (p < 0.001), indicating dose savings of 50%, with no practical loss of diagnostic accuracy. The lowest possible dose protocol was 2 s temporal sampling and a tube load of 100 mAs.

GHz femtosecond processing with agile high-power laser

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Eric Audouard ◽  
Guillaume Bonamis ◽  
Clemens Hönninger ◽  
Eric Mottay
Keyword(s):  
High Power ◽  
Repetition Rate ◽  
Thermal Ablation ◽  
Femtosecond Lasers ◽  
Optimal Choice ◽  
Process Conditions ◽  
High Power Laser ◽  
Power Laser ◽  
Ablation Efficiency ◽  
High Power Lasers

Abstract Bursts of GHz repetition rate pulses can significantly improve the ablation efficiency of femtosecond lasers. Depending on the process conditions, thermal mechanisms can be promoted and controlled. GHz ablation therefore combines thermal and non-thermal ablation mechanisms. With an optimal choice of the burst duration, the non-thermal ablation can be highly enhanced by a heating phase due to the first pulses in the burst. The GHz burst mode can be considered as a key function for the “agility” of new high-power lasers.

scholarly journals Detecting gas leakage using high-frequency signals generated by air-gun arrays

Geophysics ◽  
2017 ◽  
Vol 82 (2) ◽  
pp. A7-A12 ◽  
Author(s):  
Martin Landrø ◽  
Fredrik Hansteen ◽  
Lasse Amundsen
Keyword(s):  
High Frequency ◽  
Field Experiments ◽  
Water Layer ◽  
Sampling Interval ◽  
Acoustic Energy ◽  
Storage Site ◽  
High Frequency Signal ◽  
Gas Leakage ◽  
Temporal Sampling ◽  
Air Gun

Recent field experiments have demonstrated that marine air-gun arrays create acoustic energy greater than 1 kHz. We have suggested to use the high-frequency signal as a source to look for gas leakage at, for instance, a producing hydrocarbon field, or a [Formula: see text] storage site in which the field is covered by permanent acoustic sensors at the seabed, often referred to as a permanent reservoir monitoring field. The only needed modification is that the temporal sampling interval for the receivers is decreased to 0.1 ms (in contrast to the normal sampling interval of 1 or 2 ms), to ensure that the system is capable of recording signals up to 5 kHz. We suggest using numerous fixed receivers at the seabed to detect a gas chimney by simple high-pass filtering and subsequent transmission type analysis of the recorded signals. We think this method might serve as an elegant, precise, and very cost-effective way to detect gas leakage into the water layer.

scholarly journals Characterizing Variability of Solar Irradiance in San Antonio, Texas Using Satellite Observations of Cloudiness

2018 ◽  
Vol 10 (12) ◽  
pp. 2016 ◽  
Author(s):  
Shuang Xia ◽  
Alberto Mestas-Nuñez ◽  
Hongjie Xie ◽  
Jiakui Tang ◽  
Rolando Vega
Keyword(s):  
Temporal Variability ◽  
Solar Irradiance ◽  
San Antonio ◽  
Sampling Interval ◽  
Energy Potential ◽  
Ice Clouds ◽  
Similar Frequency ◽  
Temporal Sampling ◽  
Cloud Properties ◽  
High Layer

Since the main attenuation of solar irradiance reaching the earth’s surface is due to clouds, it has been hypothesized that global horizontal irradiance attenuation and its temporal variability at a given location could be characterized simply by cloud properties at that location. This hypothesis is tested using global horizontal irradiance measurements at two stations in San Antonio, Texas, and satellite estimates of cloud types and cloud layers from the Geostationary Operational Environmental Satellite (GOES) Surface and Insolation Product. A modified version of an existing solar attenuation variability index, albeit having a better physical foundation, is used. The analysis is conducted for different cloud conditions and solar elevations. It is found that under cloudy-sky conditions, there is less attenuation under water clouds than those under opaque ice clouds (optically thick ice clouds) and multilayered clouds. For cloud layers, less attenuation was found for the low/mid layers than for the high layer. Cloud enhancement occurs more frequently for water clouds and less frequently for mixed phase and cirrus clouds and it occurs with similar frequency at all three levels. The temporal variability of solar attenuation is found to decrease with an increasing temporal sampling interval and to be largest for water clouds and smallest for multilayered and partly cloudy conditions. This work presents a first step towards estimating solar energy potential in the San Antonio area indirectly using available estimates of cloudiness from GOES satellites.

scholarly journals Single-shot cross-correlator for pulse-contrast characterization of high peak-power lasers

2018 ◽  
Vol 6 ◽  
Author(s):  
Jingui Ma ◽  
Peng Yuan ◽  
Jing Wang ◽  
Guoqiang Xie ◽  
Heyuan Zhu ◽  
...  
Keyword(s):  
Real Time ◽  
Peak Power ◽  
Dynamic Range ◽  
High Dynamic Range ◽  
System Optimization ◽  
High Peak ◽  
High Peak Power ◽  
Single Shot ◽  
High Dynamic ◽  
Pulse Contrast

Pulse contrast is a crucial parameter of high peak-power lasers since the prepulse noise may disturb laser–plasma interactions. Contrast measurement is thus a prerequisite to tackle the contrast challenge in high peak-power lasers. This paper presents the progress review of single-shot cross-correlator (SSCC) for real-time contrast characterization. We begin with the key technologies that enable an SSCC to simultaneously possess high dynamic range ($10^{10}$), large temporal window (50–70 ps) and high fidelity. We also summarize the instrumentation of SSCC prototypes and their applications on five sets of petawatt laser facilities in China. Finally, we discuss how to extend contrast measurements from time domain to spatiotemporal domain. Real-time and high-dynamic-range contrast measurements, provided by SSCC, can not only characterize various complex noises in high peak-power lasers but also guide the system optimization.

Extending the 3D scanning range of DMD-based scanners for femtosecond lasers

2020 ◽  
Vol 45 (24) ◽  
pp. 6639
Author(s):  
Yu Wang ◽  
Huaming Li ◽  
Qinglei Hu ◽  
Ruixi Chen ◽  
Xiaohua Lv ◽  
...  
Keyword(s):  
Femtosecond Lasers ◽  
3D Scanning ◽  
Scanning Range

STUDY ON THIRD-ORDER OPTICAL NONLINEARITY OF BIS(TETRABUTYLAMMONIUM)-Hg(dmit)2 BY FEMTOSECOND OPTICAL KERR GATE TECHNIQUE

2008 ◽  
Vol 22 (16) ◽  
pp. 1573-1577 ◽  
Author(s):  
HONGLIANG YANG ◽  
XINQIANG WANG ◽  
QUAN REN ◽  
FUJUN ZHANG ◽  
GUANGHUI ZHANG ◽  
...  
Keyword(s):  
Response Time ◽  
Kerr Effect ◽  
Reference Signal ◽  
Optical Nonlinearity ◽  
Second Order ◽  
Optical Kerr Effect ◽  
Third Order ◽  
Optical Susceptibility ◽  
Optical Kerr Gate

Bis(tetrabutylammonium)- Hg(dmit) 2 was synthesized and its sample solution's optical Kerr Effect (OKE) signal was measured by the femtosecond optical Kerr gate technique. With the concentration of 9.27 × 10-4 M, the sample solution's third-order optical susceptibility was obtained to be 2.53 × 10-14 esu by using the CS2 OKE signal as reference signal measured under identical conditions. The second-order hyperpolarizability for the bis(tetrabutylammonium)- Hg(dmit) 2 molecular was estimated to be 1.7 × 10-32 esu. Its response time was about 226 fs, which is believed to be the contribution from the delocalized electrons.

High Repetition Rate kJ-class Nanosecond to Femtosecond Lasers

2014 ◽  
Author(s):  
T. Ditmire ◽  
E. Gaul ◽  
M. Martinez ◽  
M. Donovan ◽  
W. White ◽  
...  
Keyword(s):  
Repetition Rate ◽  
Femtosecond Lasers ◽  
High Repetition Rate ◽  
High Repetition

scholarly journals Ultra-High Repetition Rate Terahertz Time-Domain Spectroscopy for Micrometer Layer Thickness Measurement

Sensors ◽  
2021 ◽  
Vol 21 (16) ◽  
pp. 5389
Author(s):  
Kevin Kolpatzeck ◽  
Xuan Liu ◽  
Lars Häring ◽  
Jan C. Balzer ◽  
Andreas Czylwik
Keyword(s):  
Time Domain ◽  
Repetition Rate ◽  
Dynamic Range ◽  
Reference Signal ◽  
Thickness Measurement ◽  
Optical Signal ◽  
High Repetition Rate ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
High Repetition

Terahertz time-domain spectroscopy systems driven by monolithic mode-locked laser diodes (MLLDs) exhibit bandwidths exceeding 1 THz and a peak dynamic range that can compete with other state-of-the-art systems. Their main difference compared to fiber-laser-driven systems is their ultra-high repetition rate of typically dozens of GHz. This makes them interesting for applications where the length of the terahertz path may not be precisely known and it enables the use of a very short and potentially fast optical delay unit. However, the phase accuracy of the system is limited by the accuracy with which the delay axes of subsequent measurements are synchronized. In this work, we utilize an all-fiber approach that uses the optical signal from the MLLD in a Mach–Zehnder interferometer to generate a reference signal that we use to synchronize the detected terahertz signals. We demonstrate transmission-mode thickness measurements of stacked layers of 17μm thick low-density polyethylene (LDPE) films.

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