Long-pulse Laser Research Articles

Evaluation of combined treatment with long-pulsed neodymium-doped yttrium aluminum garnet laser and potassium hydroxide for the treatment of recalcitrant wart: a prospective comparative study

Background: Lasers have been used for verruca treatment in recent years with successful results in some types. In addition, peeling processes have been used to enhance penetration in some studies.Objectives: This study aimed to evaluate combined treatment with LP Nd:YAG laser and KoH for the treatment of recalcitrant wart.Methods: This study included 132 lesions from 38 patients. Long-pulsed (LP) Nd:YAG laser was applied to 66 lesions with daily 10% KOH application at night, and the remaining 66 lesions underwent LP Nd:YAG laser therapy only.Results: Both groups showed statistically significant regressions in the size of the lesions at the end of the fifth session compared with those present at the onset of therapy (p < .05). Also, complete clearance of the lesions was noticed after 2.2 sessions in the combined therapy group, and after 3.1 sessions in the LP Nd:YAG laser group (p < .05).Conclusions: Although the difference in clearance rate between the combined therapy group and the LP Nd:YAG laser group could not be detected after the fifth session, adding KOH to LP Nd:YAG laser can decrease the number of treatment sessions to a large extent.

Sequential delivery of long-pulsed 755-nm alexandrite laser and long-pulsed 1,064-nm neodymium:yttrium-aluminum-garnet laser treatment for pigmented disorders.

Long-pulsed (LP) lasers at pulse durations of 1-300ms have been used to destroy nests of nevi cells by selectively targeting pigment chromophores. To evaluate dual-wavelength LP laser-induced tissue reactions. The patterns of LP 755-nm alexandrite (Alex) and/or 1064-nm neodymium (Nd):yttrium-aluminum-garnet (YAG) laser-induced tissue reactions were macroscopically evaluated using a tattoo-embedded phantom. Additionally, a pilot in vivo human study was performed for common acquired melanocytic nevus, of which dermoscopic images and high-speed cinematographs were obtained. Combinations of Nd:YAG and Alex laser treatments at interpulse intervals of 10 or 20ms generated round to oval zones of photothermal and photoacoustic injury in two distinctive areas containing disintegrated tattoo particles. Treatment at interpulse intervals of 10 or 20ms between Alex and Nd:YAG pulses elicited lesser degrees of thermal damage to surrounding tissues, compared to treatment at 100 or 200ms. Immediately after combined LP laser treatment of human nevus lesions in vivo, Nd:YAG-Alex treatment at a 20-ms interpulse interval exhibited more remarkable crusting and erosive appearances than Alex-Nd:YAG treatment. For treating pigmented disorders, sequential delivery of LP Nd:YAG and Alex pulses at short interpulse intervals of 10-20ms can effectively destroy nests of pigment chromophores.

Characterization of Ablated Bone and Muscle for Long-Pulsed Laser Ablation in Dry and Wet Conditions.

Smart laser technologies are desired that can accurately cut and characterize tissues, such as bone and muscle, with minimal thermal damage and fast healing. Using a long-pulsed laser with a 0.5–10 ms pulse width at a wavelength of 1.07 µm, we investigated the optimum laser parameters for producing craters with minimal thermal damage under both wet and dry conditions. In different tissues (bone and muscle), we analyzed craters of various morphologies, depths, and volumes. We used a two-way Analysis of Variance (ANOVA) test to investigate whether there are significant differences in the ablation efficiency in wet versus dry conditions at each level of the pulse energy. We found that bone and muscle tissue ablated under wet conditions produced fewer cracks and less thermal damage around the craters than under dry conditions. In contrast to muscle, the ablation efficiency of bone under wet conditions was not higher than under dry conditions. Tissue differentiation was carried out based on measured acoustic waves. A Principal Component Analysis of the measured acoustic waves and Mahalanobis distances were used to differentiate bone and muscle under wet conditions. Bone and muscle ablated in wet conditions demonstrated a classification error of less than 6.66% and 3.33%, when measured by a microphone and a fiber Bragg grating, respectively.

Focus on lasers, imaging, and microscopy

Focus on lasers, imaging, and microscopy

Enhancement of molecular formation in fiber-optic laser ablation with a long nanosecond pulsed laser

Fiber-optic laser-induced breakdown spectroscopy (LIBS) can be used for on-site chemical analysis in harsh environments with a flexible light delivery system. In this work, the use of a long-pulse laser (100 ns) is proposed for the detection of molecular emission signals, instead of a normal-pulse laser (6 ns). We show a significant enhancement of AlO signals using an aluminum metal target in air. We also elucidate the enhancement mechanism of the AlO formation by measuring species-specific images of the emission from aluminum atoms, oxygen atoms, and AlO molecules in the plasma. The internal structure of the plasma suggests that the formation origin of AlO molecules in the long-pulse-produced plasma is essentially different from that in the normal-pulse-produced plasma. The long-pulse laser causes a rise of the ablation plume and facilitates the flow of oxygen from the ambient air. This is a key factor to enhance the molecular emission signals.

Effects of 1064-nm Nd:YAG long-pulse laser on polidocanol microfoam injected for varicose vein treatment: a controlled observational study of 404 legs, after 5-year-long treatment.

Sclerotherapy continues to be the treatment of choice for varicose veins in the legs. However, isolated treatment using microfoam or lasers requires a high number of sessions to eliminate them. In 2013, we published results about the efficacy and safety 3years after the combined treatment with microfoam injections and subsequent application of Nd:YAG laser. The aim of this paper is to clinically evaluate the treatment of varices in a control visit after 5years, when polidocanol microfoam is used and is immediately irradiated in the tissue with 1064-nm Nd:YAG laser beam. The outcome persistence after 5years was studied in the legs that had received combined treatment and had been studied 3years after treatment. Patients were contacted by phone, interviewed, and examined with echo-Doppler. Out of the 259 patients who were contacted, 221 agreed to make the appointment, although in the end, only 202 came, which meant analysing 404 legs. At 5years, the clearance rates were very high: patients were included in class CEAP C1 showing vessels of from 0.5 to 3mm diameter. The patients showed a high level of satisfaction. Regarding adverse effects, only 4 cases of hypopigmentation described in the previous publication persisted. Although the action mechanisms between the microfoam and the Nd:YAG laser must still be elucidated, it is notable that combining microfoam with laser exposure obtained a complete, effective treatment of legs in only 2 sessions, with high clearance rates and high level of satisfaction among patients.

A high-beam-quality Nd:YAG rod laser with a VRM and spherical aberration compensation at 400 Hz

A high-beam-quality and high-energy long-pulse laser has been developed with VRM(variable reflectivity mirror)coupling and spherical aberration compensation. The thermal lens and the thermal birefringence are compensated for by the 10 mm DL rod side-pumped laser module. The output mirror employs VRM coupling with R=35% in the center, which presents a energy of 1.04 J at a pulse width of 195 μs and a repetition rate of 400 Hz with a beam quality of M2≈8.4. The spherical aberration compensation improves the beam quality M2 factor to 2.15; the power stability (RMS) is 0.4% at 5 min, and the optical-optical efficiency is 19.7%.

Sustained Benefit After Treatment of Acne Vulgaris Using Only a Novel Combination of Long-Pulsed and Q-Switched 1064-nm Nd:YAG Lasers

Acne vulgaris remains a challenging disease to treat in many patients. Traditional therapies may have limited successes with potential side effects. Laser and light energy devices may offer a desirable alternative. To evaluate the effectiveness and safety in using a combination laser approach with both long-pulsed (LP) and Q-switched (QS) Nd:YAG lasers in the treatment of active acne. Twenty patients with moderate to severe inflammatory acne were treated with LP YAG laser followed immediately with QS YAG laser. Patients received at least 8 treatments. Follow-up evaluation occurred at a minimum of 12 months. Pre- and post-treatment photographs were graded by blinded physicians. All topical acne medications and oral antibiotics were discontinued throughout the therapy and follow-up period. There was a 81% reduction in acne lesions, with 60% of patients having 90% or greater reduction. Overall appearance was graded at 84% improvement at follow-up. Follow-up occurred at a mean of 22.7 months after completion of therapy. Aside from transient erythema, there were no other adverse effects. Active acne can be treated successfully with a combination of LP and QS YAG lasers with patients remaining off acne medications throughout laser therapy and the follow-up period.

Improved Analysis of Manganese in Steel Samples Using Collinear Long-Short Double Pulse Laser-Induced Breakdown Spectroscopy (LIBS).

A long-short double pulse laser-induced breakdown spectroscopy (long-short DP-LIBS) method was employed to improve the analytical performance of LIBS for the measurement of manganese in steel samples. The long pulse with a duration of 60 μs was generated using a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser which was operated at free-running (FR) mode. To investigate the detection ability without sample preparation, the steel washers were tested using single-pulse LIBS (SP-LIBS) and long-short DP-LIBS, respectively. The measurement results show that long-short DP-LIBS was able to record clear spectra from the steel washers with a surface layer. Through the observation on the laser craters with a scanning electron microscope (SEM), the results suggest that the improvement in detection ability can be attributed to the pre-irradiation effect of long-pulse laser beam. Next, the analytical performance for quantitative measurement of manganese was evaluated employing ten standard steel samples. The results show that the linearity fit (R2) of the calibration curve is 0.988 for long-short DP-LIBS, whereas, R2 is only 0.810 for SP-LIBS under the same measurement conditions. The repeated measurement results show that the average relative standard deviation (RSD) of the tested samples is 29.3% for SP-LIBS and is 10.5% for long-short DP-LIBS. The prediction results also show that the average relative error of prediction (REP) is 94.9% for SP-LIBS and is 4.9% for long-short DP-LIBS.

One‐year follow‐up results of hair removal using an 810 nm diode laser

Laser hair removal is a common light-based aesthetic procedure. Diode lasers and specifically the long-pulse diode laser 810nm are the most popular preference for hair removal due to the deep penetration and targeting of the hair follicle. In a recently published article, we presented our hair removal clinical evaluation results using an 810nm scanning diode laser. Three- and six-month follow-up hair counts demonstrated an average hair reduction of about 70%. In the current article, we demonstrate long-term follow-up hair removal results of 1year after last treatment. Among 11 out of 14 female patients who received three axillary hair removal treatments, 4-6weeks apart, returned to the 1-year follow-up visit. Treatment area photographs and hair count of 1-year follow-up visit were compared to baseline. The average hair count reduction of about 70% at 1year after the last treatment was maintained. The examined 810nm diode laser has been proven to be a safe and effective for hair removal. Results sustain not only for 3 or 6months but also for 1year after last treatment.

Magnetised thermal self-focusing and filamentation of long-pulse lasers in plasmas relevant to magnetised ICF experiments

In this paper, we study the influence of the magnetised thermal conductivity on the propagation of a nanosecond 1014 W cm−2 laser in an underdense plasma by performing simulations of a paraxial model laser in a plasma with the full Braginskii magnetised transport coefficients. Analytical theory and simulations show the shortening of the self-focal length of a laser beam in a plasma as a result of the reduction of the plasma thermal conductivity in a magnetic field. Furthermore, the filamentation of a laser via the thermal mechanism is found to have an increased spatial growth rate in a magnetised plasma. We discuss the effect of these results on recent magnetised inertial fusion experiments where filamentation can be detrimental to laser propagation and uniform laser heating. We conclude that the application of external magnetic fields to laser-plasma experiments requires the inclusion of the extended electron transport terms in simulations of laser propagation.

The Comparison of the Efficacy and Safety of Q-Switched Potassium Titanyl Phosphate Laser and Long-Pulsed Neodymium-Doped Yttrium Aluminum Garnet Laser in the Treatment of Erythematotelangiectatic and Papulopustular Rosacea

The Comparison of the Efficacy and Safety of Q-Switched Potassium Titanyl Phosphate Laser and Long-Pulsed Neodymium-Doped Yttrium Aluminum Garnet Laser in the Treatment of Erythematotelangiectatic and Papulopustular Rosacea

Relaxation oscillation suppressed, narrow linewidth, high beam quality, 1319 nm long-pulsed duration laser.

We first report a 1319nm long-pulsed duration laser with relaxation oscillation suppressed by placing lithium triborate crystals into the laser cavity. Two more etalons were added into the laser cavity to further increase the difference in cavity loss between oscillating and non-oscillating modes. With very little reduction in average output laser power, the smooth temporal profile laser pulse was obtained with a pulse duration of 150μs. The average output power was 5.45W, and the beam qualities Mx2 and My2 were 1.12 and 1.20.

Fiber-optic laser-induced breakdown spectroscopy of zirconium metal in air: Special features of the plasma produced by a long-pulse laser

The decommissioning of the Tokyo Electric Power Company (TEPCO) Fukushima Daiichi Nuclear Power Plant is an essential issue in nuclear R&D. Fiber-optic laser-induced breakdown spectroscopy (Fiber-optic LIBS) could be used for in-situ elemental analysis of the inside of the damaged reactors. To improve the performances under difficult conditions, using a long-pulse laser can be an efficient alternative. In this work, the emission spectra of zirconium metal in air obtained for a normal-pulse laser (6ns) and a long-pulse laser (100 ns) (wavelength: 1064nm, pulse energy: 12.5mJ, spot diameter: 0.35mm) are compared to investigate the fundamental aspects of fiber-optic LIBS with the long-pulse laser. The spectral features are considerably different: when the long-pulse laser is used, the atomic and molecular emission is remarkably enhanced. The enhancement of the atomic emission at the near infrared (NIR) region would lead to the observation of emission lines with minimum overlapping. To understand the differences in the spectra induced respectively from the normal-pulse laser and the long-pulse laser, photodiode signals, time-resolved spectra, plasma parameters, emission from the ambient air, and emission regions are investigated, showing the particular characteristics of the plasma produced by the long-pulse laser.

Laser pulse shape design for laser-indirect-driven quasi-isentropic compression experiments

Laser pulse shape design is a key work in the design of indirect-laser-driven experiments, especially for long pulse laser driven quasi-isentropic compression experiments. A method for designing such a laser pulse shape is given here. What’s more, application experiments were performed, and the results of a typical shot are presented. At last of this article, the details of the application of the method are discussed, such as the equation parameter choice, radiation ablation pressure expression, and approximations in the method. The application shows that the method can provide reliable descriptions of the energy distribution in a hohlraum target; thus, it can be used in the design of long-pulse laser driven quasi-isentropic compression experiments and even other indirect-laser-driven experiments.

长脉冲激光辐照Si-APD温度演化过程的数值模拟与实验研究

长脉冲激光辐照Si-APD温度演化过程的数值模拟与实验研究

Theoretical simulation analysis of long-pulse laser induced damage in a BK7:SiO2/HfO2 optical anti-reflective films

The three dimensions (3-D) temperature field distribution (TFD) equation is established based on Newton’s law of cooling, which is focusing on optical anti-reflection films (OARFs) irradiated by flat-topped multi-Gaussian laser beam. The TFD of HfO2/SiO2 composite films coating on BK7 substrate(BK7:SiO2/HfO2) irradiated by single long-pulse laser is obtained by means of numerical simulation. The result shows that the thermal effect of OARFs is significant when irradiated by the flat-topped long-pulse laser. Moreover, the main damage of OARFs after long-pulse laser strikes is not films fusion but delamination. The delamination is caused by thermal conduction from the films to the BK7 substrate, then the fusing of BK7 substrate, following by the separation of films. The results provide a theoretical basis for progress analysis and mechanism study of long-pulse laser induced damage in OARFs.

Long-pulse quasi-CW laser cutting of metals

Long-pulse quasi-CW laser cutting of metals is well suited to small-scale manufacturing settings where process flexibility is of high value and investment capacity is limited. This process refers to cutting operations performed with millisecond laser pulses obtained through modulation of the pump source to achieve continuous-wave (CW) operation over limited time intervals. The ability to minimize heat conduction losses, comprising the vast majority of absorbed laser power at low velocity, allows processing of relatively thick sections compared to what would be possible at the same average power with a CW laser source. The present study quantifies the reduction in heat conduction losses with pulsed exposure by employing a simple power-balance representation of the heat flow problem. Laser-cutting experiments are performed with inert and active assist gases on 1- and 4-mm thick steel samples, varying peak power (0.3–3 k W), pulse energy (0.3–12 J), repetition rate (25–1000 H z), and velocity (1–40 m m/s). The lowest minimum laser cutting power and highest cutting efficiency are achieved with maximum peak power and lowest permissible pulse overlap for a continuous cut. Under these conditions, heat conduction losses are reduced by more than 60% with nitrogen assist gas compared to CW exposure and more than 50% with oxygen. The calculated average cutting front temperatures are 450–630 ∘C and 620–900 ∘C, respectively, well below the melting temperature of steel. Lowest dross adhesion and cut edge surface roughness are obtained with oxygen assist gas, leading to both the lowest minimum average cutting power and highest cut quality. These results demonstrate an efficient process that improves the feasibility of low velocity laser cutting and therefore the range of industrial applications in which laser technology can employed.

Laser-Induced Breakdown Spectroscopy and Plasma Characterization Generated by Long-Pulse Laser on Soil Samples

The plasma is generated by focusing a long-pulse (80 μs) Nd:YAG laser on chromium-doped soil samples. The calibration curves are drawn using the intensity ratio of the chromium spectral line at 425.435 nm with the iron spectral line (425.079 nm) as reference. The regression coefficient of the calibration curve is 0.993, and the limit of detection is 16 mg/kg, which is 19% less than that for the case of a Q-switched laser In the method of long-pulse laser-induced breakdown spectroscopy, the laser-induced plasma had a temperature of 15795.907 K and an electron density of 2.988 × 1017 cm–3, which exceeded the corresponding plasma parameters of the Q-switched laser-induced breakdown spectroscopy by 75% and 24% respectively.

Successful Treatment of Classic Kaposi Sarcoma With Long-Pulse Neodymium-Doped Yttrium Aluminum Garnet Laser: A Preliminary Study.

Kaposi sarcoma (KS) is a systemic disease that can present with cutaneous lesions with or without internal involvement, mostly caused by infection with human herpesvirus-8. The treatment options include surgical excision, cryotherapy, radiotherapy, intralesional chemotherapy, laser, and elastic stockings for the prevention of lymphedema. This article presents 7 cases with classic KS treated with the long-pulse neodymium:yttrium-aluminum-garnet (Nd:YAG) laser. Forty-nine lesions of 7 KS patients (5 stage 1, 2 stage 2A) were treated with Nd:YAG laser with a spot size of 4 to 6 mm and a fluence of 180 J/cm increased by 10 J/cm in the neighboring area to a maximum of 260 J/cm. The pulse sequencing was 1.5, and delay time was 5 milliseconds. Sessions were continued at 4-week intervals for 2 to 4 sessions. All patients exhibited clinical and histological improvement. One session was sufficient for small lesions, whereas coalescing and multicentric lesions required up to 4 sessions. All the lesions healed in 2 to 4 weeks, with the only complication being mild atrophic scars. With the advantage of penetrating into deeper sites than other lasers, long-pulse Nd:YAG is an efficient and safe local treatment alternative especially for papulonodular and deeper lesions located on bony structures.