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[IEEE 2019 PhotonIcs & Electromagnetics Research Symposium - Spring (PIERS-Spring) - Rome, Italy (2019.6.17-2019.6.20)] 2019 PhotonIcs & Electromagnetics Research Symposium - Spring (PIERS-Spring) - Narrow Linewidth Fiber Brillouin Ring Laser for Sensing Applications
摘要： A novel tunable, stable and low-noise Brillouin ring laser layout composed of a doubly-resonant short-cavity Brillouin ring laser (DR-SC) paired with an active wavelength stabilization setup is presented in this work. Measurements of temporal signal stability, relative intensity noise, spectral linewidth and tunability range yielded a marked improvement over the long-cavity version that we have previously reported, making the new layout a promising alternative for applications in fiber sensing and other fields that require highly coherent and stable tunable sources.
关键词： relative intensity noise,fiber sensing,Brillouin ring laser,tunable sources,spectral linewidth
更新于2025-09-23 15:21:01
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Diagnostics of peak laser intensity by pair production from thin foil target
摘要： It is known that in the small quantum parameter regime the Breit-Wheeler electron-positron pair creation cross section is extremely sensitive on the photon energy and on the background field. We present the dependence of positron yield on laser intensity in laser-foil interactions with the help of analytical theory and particle-in-cell simulaitons. These particles are emitted in a relatively narrow range of cone angles close to perpendicular direction relative to the laser beam axis. This allows for establishing an in situ intensity diagnostic by measuring the positron current in experiments where peta-watt class lasers are used.
关键词： high power lasers,QED in plasmas,laser intensity diagnostics
更新于2025-09-23 15:21:01
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Electron-atom potential scattering in a corotating bicircular laser field
摘要： S-matrix theory is used in order to analyze the energy spectra of electron-atom potential scattering assisted by a bicircular (two-component circularly polarized) laser field having corotating field components. The double scattering (rescattering) is also included in the analysis by applying the second Born approximation in the expansion of the S-matrix element. We have investigated how the energy spectrum of scattered electrons is affected by the scattering angle. We have also analyzed the sensitivity of the energy spectrum to the relative phase and intensity ratio of the laser-field components. The calculated energy spectra are characterized by the plateau-like oscillatory structures with abrupt cutoffs. Positions of these cutoffs in the energy spectra are confirmed by a classical analysis. Rescattering effects can be observed in the calculated energy spectra for certain values of the scattering angle. These effects are represented by the second plateau in the energy spectrum. This is different from the process of above-threshold ionization/detachment by a bicircular laser field, where the (re)scattering effects in the photoelectron energy spectra cannot be observed in the case of corotating laser-field components.
关键词： bicircular laser field,relative phase,electron-atom scattering,rescattering effects,intensity ratio
更新于2025-09-23 15:21:01
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Comparison of Time-intensity Curve with Gadobenatedimeglumine and Gadobutrol on Multiphase Contrast-enhanced Breast MRI; 乳腺Dynamic 造影MR 検査におけるtime-intensity-curve のGd-DTPA とGadobutrol 間での比較検討;
摘要： The purpose of this study was to compare the time-intensity curve (TIC) on multiphase contrast-enhanced breast magnetic resonance imaging (MRI) between Gadobenatedimeglumine (Gd-DTPA) and Gadobutrol. We assessed the images of 53 cases obtained from MRI that had malignant findings by pathology from October 2015 to October 2016 in our institute. Gd-DTPA and Gadobutrol were administrated in 16 and 37 cases, respectively. The TIC of the lesion was classified according to the Kuhl’s method (type I: persistent pattern, type II: plateau pattern and type III: washout pattern). Type III was the most common TIC pattern in both the groups (Gd-DTPA, 12 cases; Gadobutrol, 18 cases). Type II was the second common TIC pattern in Gadobutrol group (12 cases). As a result, there was no significant difference in TIC analysis between Gd-DTPA and gadobutrol. In conclusion, the contrast between Gd-DTPA and Gadobutrol contrast media did not differ in TIC pattern of multiphasic contrast-enhanced breast MRI.
关键词： Gadobutrol,Gd-DTPA,time-intensity curve,breast MRI
更新于2025-09-23 15:21:01
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Nonlinear Optics || The Intensity-Dependent Refractive Index
摘要： The refractive index of many optical materials depends on the intensity of the light used to measure the refractive index. In this chapter, we examine some of the mathematical descriptions of the nonlinear refractive index and examine some of the physical processes that give rise to this effect. In the following chapter, we study the origin of optical nonlinearities in molecular systems, in Chapter 6 we study the intensity-dependent refractive index resulting from the resonance response of an atomic system, and in Chapter 7 we study some physical processes that result from the nonlinear refractive index.
关键词： intensity-dependent,atomic system,optical materials,nonlinear refractive index,molecular systems
更新于2025-09-23 15:21:01
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The mean energy transfer and collisional absorption coefficient of high power laser in plasma
摘要： The absorption coefficient of high power laser incident normally onto a plasma medium is studied when electron energy distribution obeys non-extensive function. The variation of the absorption coefficient with the incident laser intensity is investigated for different electron temperatures as well as different non-extensive distribution parameter (q). The variation of the absorption coefficient with plasma density is also investigated for different q values for constant temperature. Furthermore the mean rate of energy absorption is evaluated as function of the incident laser intensity for different electron temperatures and q values. The results are compared with ones obtained in Maxwellian case and differences are shown in the corresponding diagrams.
关键词： Non-extensive distribution,Absorption coefficient,Inverse bremsstrahlung,Laser intensity,Maxwellian distribution
更新于2025-09-23 15:21:01
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Influences of Low Intensity on Diode Parameters of CdTe Solar Cells
摘要： This study deals with the CdS/CdTe solar cells under low illumination intensity, with cell #1 for the shunt resistance exceeding 100,000 ?·cm2 and cell #2 for the shunt resistance above 1000 ?·cm2. The diode parameter variations with the decline of the irradiance intensity are illustrated by dividing 0–100 mW/cm?2 into a number of small intensity ranges for J–V measurements and assuming the diode parameters to be constant within each range, the diode parameters of each range including the series resistance, the shunt resistance, the reverse saturation current density and the ideality factor are then extracted by employing an analytical approach. The mechanism of the cell performance deviations are also investigated by basic theories, reports and experiments. For cell #1 with higher Rsh corresponding to less traps, Rsh shows a upward tendency as the irradiance declines, n and J0 exhibit a rise with the irradiance and keep nearly unchanged at the low irradiance values mainly due to recombination and carrier contributions, Rs shows a slight increase when the irradiance intensity goes down because of the resistance of CdTe absorption layer. For cell #2 with lower Rsh corresponding to more traps, with the decrease of the illumination intensity, Rsh increases sharply only for captured carrier reduction, Rs goes steadily up similarly, n and J0 exhibit a decline with the irradiance due to recombination shift. It should be pointed out that Rs varies much smoother than the traditional approximation of a reciprocal of di?erential at short circuit, and the distribution of Rsh is diverse, and an average Rsh of for each intensity range can re?ect the variation trend.
关键词： solar cell,CdTe,low intensity
更新于2025-09-23 15:21:01
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Efficiency control of high-order harmonic generation in gases using driving pulse spectral features
摘要： The low conversion efficiency of high-order harmonic generation (HHG) in gases is an insurmountable limitation for many applications, where a considerable photon flux is an instrumental prerequisite. We present a study of the HHG conversion efficiency dependence on the driving laser intensity and analyze the conditions for optimal phase-matching in a loose focusing configuration and long generation medium using a Ti:Sapphire laser. Moreover, by determination of the influence of plasma effects on the driving laser pulse, we observe a correlation between the HHG conversion efficiency and the blueshift of the fundamental pulse. The maximal HHG conversion efficiency is achieved just before the driving laser spectrum is considerably affected by the plasma. Similar behavior is observed in HHG for different noble gases. In this respect, the appearance of a plasma-induced spectral shift in the driving laser might serve as an indication of a substantial loss of HHG conversion efficiency. Consequently, our findings can be exploited to obtain essential information about the laser-plasma interaction process during HHG and can pave the way for a more convenient control of optimal HHG conditions.
关键词： plasma effects,high-order harmonic generation,conversion efficiency,driving laser intensity,spectral blueshift,phase-matching
更新于2025-09-23 15:21:01
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HIFU-induced changes in optical scattering and absorption of tissue over nine orders of thermal dose
摘要： The optical properties of tissue change during thermal ablation. Multi-modal methods such as acousto-optic (AO) and photo-acoustic (PA) imaging may provide a real-time, direct measure of lesion formation. Baseline changes in optical properties have been previously measured over limited ranges of thermal dose for tissues exposed to a temperature-controlled water bath, however, there is scant data for optical properties of lesions created by HIFU. In this work, the optical scattering and absorption coefficients from 400–1300 nm of excised chicken breast exposed to HIFU were measured using an integrating sphere spectrophotometric technique. HIFU-induced spatiotemporal temperature elevations were measured using an infrared camera and used to calculate the thermal dose delivered to a localized region of tissue. Results obtained over a range of thermal dose spanning 9 orders of magnitude show that the reduced scattering coefficient increases for HIFU exposures exceeding a thermal dose of CEM43 = 600 ± 81 cumulative equivalent minutes. HIFU-induced thermal damage results in changes in scattering over all optical wavelengths, with a 2.5-fold increase for thermal lesions exceeding 70 °C. The tissue absorption coefficient was also found to increase for thermally lesioned tissue, however, the magnitude was strongly dependent on the optical wavelength and there was substantial sample-to-sample variability, such that the existence of a threshold thermal dose could not be determined. Therapeutic windows, where the optical penetration depth is expected to be greatest, were identified in the near infrared regime centered near 900 nm and 1100 nm. These data motivate further research to improve the real-time AO and PA sensing of lesion formation during HIFU therapy as an alternative to thermometry.
关键词： thermal damage,optical properties,thermal dose,lesion,high-intensity focused ultrasound
更新于2025-09-23 15:21:01
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Generation of N00N-like interferences with two thermal light sources
摘要： Measuring the M th-order intensity correlation function of light emitted by two statistically independent thermal light sources may display N00N-like interferences of arbitrary order N = M/2. We show that via a particular choice of detector positions one can isolate M -photon quantum paths where either all M photons are emitted from the same source or M/2 photons are collectively emitted by both sources. The latter superposition displays N00N-like oscillations with N = M/2 which may serve, e.g., in astronomy, for imaging two distant thermal sources with M/2-fold increased resolution. We also discuss slightly modified detection schemes improving the visibility of the N00N-like interference pattern and present measurements verifying the theoretical predictions.
关键词： resolution,quantum paths,intensity correlation function,thermal light sources,N00N-like interferences,imaging,astronomy
更新于2025-09-23 15:21:01