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Impact of Nonlinear Kerr Effect on the Focusing Performance of Optical Lens with High-Intensity Laser Incidence
摘要： The rapid development of high-energy and high-power laser technology provides an important experimental means for the research of extreme physical state in the laboratory and for the design of large laser facilities for realizing inertial con?nement fusion. However, when the incident laser ?eld is very strong, the Kerr e?ect of materials a?ects the nominal performance of optical elements. In this work, the impact of Kerr e?ect on the focusing performance of an optical lens is studied by calculating and comparing the ?led patterns of focal spots for three di?erent incident laser beams together with three di?erent levels of light intensities. The traditional transfer function of an optical lens is ?rstly modi?ed according to the theory of nonlinear Kerr e?ect. We use the two-dimensional fast Fourier transform algorithm and angular spectrum algorithm to numerically calculate the ?eld distributions of focal spots in the nominal focal plane of lens and its adjacent planes based on the Fresnel di?raction integral formula. The obtained results show that the Kerr e?ect a?ects the focusing characteristics of lens, especially for the incidence of high-order Gaussian beams, such as Hermite-Gaussian beams and Laguerre-Gaussian beams. At the same time, the focal length and refractive index of lens also change the ?eld patterns of focal spots. The presented methodology is of great value in engineering applications where the practical problem with beam size up to 100 mm can be calculated using a common laptop computer. The work provides an e?cient numerical technique for high-intensity incident laser beams focused by lens that takes Kerr e?ect into consideration, which has potential applications in high energy density physics and large laser facilities for inertial con?nement fusion.
关键词： Kerr effect,optical lens,numerical analysis,focal spot,high-intensity laser
更新于2025-09-23 15:21:01
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Short-Term Efficacy Comparison of High-Intensity and Low-Intensity Laser Therapy in the Treatment of Lateral Epicondylitis: A Randomized Double-Blind Clinical Study
摘要： Objectives: This study aims to evaluate and compare the short-term efficacies of high-intensity laser therapy (HILT) and low-intensity laser therapy (LILT) in the treatment of lateral epicondylitis (LE). Patients and methods: Sixty patients (16 males, 44 females; mean age 44.2±9.3 years; range, 18 to 65 years) with unilateral elbow pain were randomized into two groups as 30 patients treated with HILT (9 males and 21 females) and 30 patients treated with LILT (7 males and 23 females). The HILT (1,064 nm) and LILT (904 nm) were administered three times a week for three weeks, and each treatment was combined with an epicondylitis bandage. A visual analog scale (VAS), quick Disabilities of the Arm, Shoulder, and Hand (QDASH) questionnaire, Medical Outcomes Study Questionnaire Short Form 36 Health Survey (SF-36), and hand grip strength test were used to evaluate the patients before and three weeks after treatment. Results: The two groups had similar demographic characteristics, including age, sex, occupation, and body mass index (p>0.05). There were no statistically significant differences between the two groups in terms of the pretreatment VAS, QDASH, hand grip strength, and SF-36 scores (p>0.05). After three weeks, both groups showed significant improvements in all of the parameters (p<0.05). However, in the HILT group, the QDASH, hand grip strength, and SF-36 physical component summary (PCS) scores showed superior improvement compared to the LILT group (p<0.05). Conclusion: Each treatment modality was found to be effective and safe for the short-term treatment of LE. However, the HILT exhibited more significant effects on the hand grip strength, QDASH, and SF-36 PCS scores than the LILT.
关键词： Hand grip strength,low-intensity laser therapy,pain,high-intensity laser therapy,lateral epicondylitis
更新于2025-09-23 15:19:57
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Influence of target curvature on the characteristics of particle beams generated by laser ion acceleration with microstructured enhanced targets at ultra high intensity
摘要： Following the advances in laser science that have been performed recently, the push to improve the quality of the laser generated particle beams has seen a lot of interest in the past decade. The work presented in this paper aims to study the role of target curvature using 2D PIC simulations to ascertain its influence on the angular spread and peak energy for the accelerated proton beam, and the characteristics of the gamma photons produced for potential usage as secondary sources. For the scope of this work we parametrically probed different curvature radii of a microstructured enhanced target impacted by a laser pulse with predetermined parameters. This paper continues past studies (Tatomirescu et al 2017 AIP Conf. Proc. 1796 020013; Tatomirescu et al 2017 AIP Conf. Proc. 1916 030002) and concentrates on determining the target curvature effect when using conical structures for pulse focusing. The results show promising enhanced focus of the accelerated particles and an enhancement of the peak energy of the accelerated particles.
关键词： variable target curvature,particle-in-cell,ultra high intensity laser pulse,microstructured target
更新于2025-09-23 15:19:57
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Ionization and acceleration of multiply charged gold ions in solid film irradiated by high intensity laser
摘要： In this paper, we present the mechanisms of ionization of a thin gold ?lm irradiated by a high-intensity, short-pulse laser in the range of I ? 1020(cid:2)22 W=cm2 and the associated acceleration of multiply charged gold ions. A numerical one-dimensional simulation using an extended particle-in-cell code, which includes atomic and collisional relaxation processes, indicates that two types of acceleration, hole-boring radiation pressure acceleration (RPA) and target normal sheath acceleration (TNSA), contribute to the generation of highly charged ions with kinetic energies on the order of 10 MeV/u. In each acceleration, a longitudinal electrostatic ?eld excited by different mechanisms dominantly ionizes atoms to higher charge states and accelerates them to the vacuum region from the rear surface, which is opposite the front surface irradiated by the laser ?eld. The ?eld ionization process dominantly ionizes high energy ions to the high charge state, while a large number of ions with energy <1 MeV=u are ionized by an electron impact ionization process. In TNSA, a multiply charged ion generated at the rear surface is accelerated to the maximum energy although the ion with the highest charge state is generated at the front surface in RPA. However, the existence of contamination, such as water vapor, suppresses the ion energy of TNSA to less than that of RPA since the sheath ?eld readily accelerates the protons and oxygen prior to the acceleration of the gold ions. Our derived theoretical scaling describes the maximum ion energy for each charge state in the cases with and without contamination using the relationship between the longitudinal electrostatic ?eld pro?le near the rear surface and the classical tunnel ?eld ionization model.
关键词： acceleration,multiply charged gold ions,RPA,TNSA,high-intensity laser,ionization,solid film
更新于2025-09-23 15:19:57
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Imitating the effect of amplified spontaneous emission pedestal at relativistically intense laser interaction with nanostructured solid targets
摘要： We investigated the effect of focusing sub-nanosecond laser radiation with varied fluence onto the surface of different flat and nanostructured targets utilized in ultra-high intensity laser-plasma experiments. Thus, we modeled the action of the prepulse, referred to as an amplified spontaneous emission pedestal, typically present for a relativistic (with peak intensity over 1018 W cm?2) laser pulse with naturally limited contrast. The suppressed melting threshold was detected for the sub-wavelength scale structured material. Local melting leading to distortion of initial structures was detected at a fluence of ~0.2 J cm?2 and below, or 3–5 times lower compared to the flat substrate melting threshold. It is also demonstrated that the threshold lowering is dependent on the production method of the structures, which may be attributed to increased absorption and suppressed heat transfer into the bulk.
关键词： high intensity laser interaction,amplified spontaneous emission pedestal,laser melting,sub-nanosecond pulse,nanostructures
更新于2025-09-19 17:13:59
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Terahertz radiation enhanced by target ablation during the interaction of high intensity laser pulse and micron-thickness metal foil
摘要： When an ultra-intense relativistic laser is irradiated on a solid target, terahertz (THz) pulses can be generated by coherent transition radiation when the laser-driven electron beams cross the rear surface of the target. The radiation energy depends on the number and energy of the electrons. By introducing a milli-joule picosecond ablation laser pulse, an underdense preplasma with a scale length of micrometers is generated at the front surface of the target. Electron beams with more charge and higher energy can be produced during the interaction between the following main laser pulse and the preplasma, which enhance the THz radiation and affect the radiation angle. Two dimensional particle-in-cell simulations demonstrate the improvement of electron beams and a nearly tenfold enhancement of THz radiation energy is observed.
关键词： high intensity laser pulse,particle-in-cell simulations,coherent transition radiation,terahertz radiation,target ablation,micron-thickness metal foil
更新于2025-09-19 17:13:59
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Pulsed Nd:YAG laser: effects on pain, postural stability, and weight-bearing pattern in children with hemophilic ankle arthropathy
摘要： Hemophilic ankle arthropathy features joint pain, impaired postural control, and abnormal weight-bearing pattern. This study was designed to investigate the effects of pulsed Nd:YAG laser on pain, postural stability, and weight-bearing pattern in children with hemophilic ankle arthropathy. Forty children diagnosed with hemophilia type A (age, 8–16 years) were randomly allocated to either the treatment group (n = 20) who received a three-phase active therapy with pulsed Nd:YAG laser thrice/week (total energy was 1500 J) plus a physical exercise program for four consecutive weeks, or the placebo group (n = 20) who received placebo laser plus the physical exercise program. Pain, postural control (i.e., directional control [DC], endpoint excursion [EE], center-of-gravity movement velocity [CoG-MV], and maximum excursion [MXE]), and weight-bearing pattern (i.e., pressure peaks of the hindfoot [PP-HF] and forefoot [PP-FF], and the foot contact area [FCA]) were assessed pre- and post-treatment. The treatment group showed greater improvement in pain (P = .004), DC (P = .02), EE (P = .003), and CoG-MV (P = .003) compared to the placebo group. However, there was no statistically significant difference between both groups regarding the MXE (P = .15). In addition, the treatment group achieved favorable improvements in PP-HF (P = .003), PP-FF (P = .027), and FCA (P = .002) relative to the placebo group. Pulsed Nd:YAG laser is a potentially effective therapy for pain relief, postural control enhancement, and weight-bearing pattern adjustment in children with hemophilic ankle arthropathy.
关键词： Dynamic stability limits,Hemophilia,Plantar pressure,High-intensity laser therapy,Joint inflammation
更新于2025-09-19 17:13:59
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Direct observation of ultrafast electrons generated by high-intensity laser-matter interaction
摘要： High intensity ultrashort laser pulses interacting with thin solid targets are able to produce energetic protons and ions by means of extremely large accelerating fields, generated by escaping electrons. The characterization of such electrons is thus a key factor for the understanding of the accelerating potential temporal evolution. Here, we present temporally resolved measurements of the ultrafast escaping electron component. The charge, electric field, and temporal duration of the emitted ultrafast electron beams are determined using temporal diagnostics with a 100 fs temporal resolution. Experimental evidence of scaling laws for the ultrafast electron beam parameters with respect to the incident laser pulse energy is retrieved and compared with theoretical models, showing an excellent agreement.
关键词： ultrafast electrons,high-intensity laser-matter interaction,scaling laws,temporal diagnostics
更新于2025-09-19 17:13:59
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Application of harmonics imaging to focal spot measurements of the “PETAL” laser
摘要： By using numerical simulations and experimental campaigns on a small-scale laser facility, the concept of the focal spot imaging on harmonics of laser frequency is developed and implemented on the Laser MegaJoule (LMJ)/PETawatt Aquitaine Laser (PETAL) facility. The Two/Three ω Imaging System was activated and validated during the first 2017–2019 interaction campaigns of PETAL on the LMJ. It provides major information on focal spot characteristics on a target. Such an approach could be easily applied to any high-intensity facility in the relativistic intensity regime (>1018 W cm?2).
关键词： PETAL laser,harmonics imaging,high-intensity laser-plasma interaction,focal spot measurements
更新于2025-09-16 10:30:52
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High Intensity Laser Therapy for Treatment of Spinal Disorders
摘要： The aim of this systematic review was to evaluate the effectiveness of high intensity laser therapy (HILT) on pain and function in individuals with spinal disorders. Six Electronic databases were searched up to the end of February 2018. In addition, the reference lists of all included studies were searched for any relevant studies. Studies were eligible for inclusion if they met the following criteria: randomised controlled trials (RCTs) assessing the effectiveness of HILT in adult individuals (<18 years old) with spinal disorders, studies must have at least one primary outcome measure of pain and function, and all included studies must be written in English language. PRISMA guidelines were followed to prepare this review. The number in CRD42018090019. PEDro scale and GRADE system were performed to assess the quality of studies. A meta-analysis was conducted to calculate the overall effect size. A total of ten RCTs met the inclusion criteria, with four studies of the ef?cacy of HILT on neck pain (NP) and six on low back pain (LBP). Forest plots showed that HILT with exercise was signi?cantly more effective than placebo HILT with exercise in terms of pain reduction (SMD -1.42 to -0.80; P<0.00001; I2 0%) and functional improvement (SMD -1.03; 95% CI -1.33 to -0.72; P<0.00001; I2 0%). Meta-analyses also showed that HILT alone or HILT with conventional physiotherapy (CPT) signi?cantly provided better outcomes than CPT alone. HILT is considered as a complementary modality for pain reduction and function improvement in individuals with spinal disorders. However, the quality of the body of evidence was rated from ‘very low’ to ‘low’ quality.
关键词： Neck Pain,Rehabilitation,High Intensity Laser Therapy,Low Back Pain,Spinal Disorders
更新于2025-09-16 10:30:52