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Evaluation of the Safety and Efficacy of a Picosecond Alexandrite Laser With DLA for Acne Scars in Chinese Patients
摘要： Background and Objectives: Recently, picosecond laser treatment has been used as an effective treatment for acne scars. To evaluate the efficacy and safety of a picosecond alexandrite laser with a diffractive lens array in the treatment of acne scars in Chinese patients. Study Design/Materials and Methods: Patients with facial acne scars were treated with a picosecond alexandrite laser in three sessions at 4‐ to 6‐week intervals and followed up for 2 months. Primary outcomes were measured by physicians’ blinded evaluation of the acne scar using the ECCA (échelle d’éva physicians’luation clinique des cicatrices d’acné) grading scale. The secondary outcomes included the investigator global assessment (IGA) on the improvement of post‐inflammatory erythema (PIE), patients’ assessment of improvement on a 4‐point scale and of satisfaction on a 5‐point scale. Pain scores and adverse effects were also evaluated. Result: Twenty patients with Fitzpatrick skin types III and IV were enrolled in the study and completed all treatment and follow‐up visits. The mean ECCA scores fell from 197.75 ± 35.26 to 142.00 ± 35.92 (a 28% improvement), and the change was significant (P = 0.000). The mean IGA score of PIE improvement was 3.03 ± 0.75 (0 = no improvement and 4 = 76–100% improvement). On the basis of the patients’ self‐assessment, the average improvement scores were 2.30 ± 0.98 (0 indicating 0–25% improvement and 3 indicating >75% improvement). In total, 50% and 30% of the patients were “satisfied” and “very satisfied,” respectively, with the treatment. The mean pain score was 3.20 ± 0.50 (0 = no pain, 10 = maximum pain) with topical anesthesia. The adverse effects included transient and mild erythema, edema, and scabbing. Conclusions: Treatment with a picosecond alexandrite laser with a diffractive lens array is effective and safe for acne scars in Chinese patients. Lasers Surg. Med. ? 2019 Wiley Periodicals, Inc.
关键词： picosecond laser,post‐inflammatory erythema,alexandrite laser,acne scars,fractional laser
更新于2025-09-12 10:27:22
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Comparison of a picosecond alexandrite laser versus a Q-switched alexandrite laser for the treatment of nevus of Ota: A randomized, split-lesion, controlled trial
摘要： Background: Novel picosecond lasers have been available for various pigmentary disorders. However, there are limited data directly comparing picosecond lasers and Q-switched lasers for treatment of nevus of Ota. Objective: To compare the efficacy and safety of a picosecond alexandrite laser (PSAL) compared with a Q-switched alexandrite laser (QSAL) for the treatment of nevus of Ota. Methods: Each lesion of the 56 participants enrolled was split into two parts and randomly assigned to either PASL or QSAL treatment arm. Each lesion was treated up to 6 sessions at a 12-week interval. The efficacy and safety were determined based on blinded visual evaluation and self-report at each follow-up visit. Results: PSAL arm achieved a significantly better clearance (4.53 vs 4.0) with fewer sessions (5.26 vs 5.87) and less severe pain (5.61 vs 6.40). Patients were more satisfied with PSAL than QSAL (4.5 vs 4.0). Occurrences of post inflammatory hyperpigmentation (26% vs 34%) and hypopigmentation (21% vs 47%) were also lower in PSAL than QSAL arm. Limitations: Lack of objective assessments and outcome measures. Conclusions: PSAL demonstrated better clinical results and fewer adverse events than QSAL for the treatment of nevus of Ota.
关键词： photomechanical effect,post-inflammatory hypopigmentation,Q-switched alexandrite laser,nevus of Ota,picosecond alexandrite laser,split-lesion
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) - Development of Figure-8 Variable Pulse Width Fiber Laser using Coherent Resonator Coupling Technology
摘要： A femtosecond pulsed laser has an extremely short pulse width and high peak power and is used for the field of microfabrication. On the other hand, laser cutting and drilling requires picosecond pulsed laser with high pulse energy. In general, a diffraction grating or a band pass filter is used to control pulse width. However, these components are not affordable and the optical system with them becomes complicated. Therefore, we have developed all fiber variable pulse width laser by applying a coherent resonator coupling technology that increases the output power by coupling the phases of longitudinal modes generated by sharing an output coupler in multiple laser resonators. In the coherent resonator coupling, resonator length difference decreases coupled longitudinal modes and narrows spectral width (?ν). Thus, pulse width (?t) is widened according to equation (1). ?t ? ?ν = const (1) We will describe the configuration of the resonator used in the experiment. A resonator coupling technology is applied to a figure-8 fiber laser. The figure-8 fiber laser is a ring resonator that contains a nonlinear optical loop mirror. It operates as a resonator only when a phase difference occurs between the clockwise light that travels through the loop of the mirror and the counter-clockwise one. The phenomenon functions as a saturable absorption effect and generates femtosecond pulses. Further, we use a variable delay line in one of the resonator to control resonator length difference. Figure 1 shows the configuration of the figure-8 variable pulse width fiber laser and Fig. 2 shows the configuration of a nonlinear optical loop mirror.
关键词： femtosecond pulsed laser,figure-8 fiber laser,picosecond pulsed laser,nonlinear optical loop mirror,coherent resonator coupling technology
更新于2025-09-12 10:27:22
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Dependence of the Two-Photon Absorption Coefficient of Steel on the Pulse Duration During Its Ablation by Femto- and Picosecond Laser Pulses
摘要： The dependences of the depth of single-pulse ablation of the steel surface on the energy density of ultrashort laser pulses (0.3–12 ps) with a wavelength of 515 nm have the form different from the usual logarithmic one for linear absorption of radiation. Since the density of states of free conduction electrons in the s band is low, and the d band of strongly bound electrons with a high density of states is located around the Fermi level, these dependences have been approximated within the two-photon absorption model. The two-photon absorption coefficient increases almost linearly with the duration of laser pulses, which indicates the saturation of absorption and allows estimating the corresponding parameters of the electronic subsystem.
关键词： picosecond,two-photon absorption,femtosecond,ultrashort laser pulses,steel ablation
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) - Picosecond Widely-Tunable Mid-IR Source for Gas Detection
摘要： Portable and remote sensing solutions to detect the nature of gases in the air are highly demanded. In particular for instance, for the measurement of fire smoke or uncontrolled discharge on risk sites or on an accident including a vehicle transporting hazardous substances [1]. Spectroscopic-based solutions would need a widely-tunable and powerful mid-infrared compact laser source that could be used on field and scan a large number of species. In a previous research from A Puiu et al. [2], the authors described an interesting system for acetone detection at 3.3 μm. The principle used was differential absorption (DIAL) based on a tunable mid-IR source from 3 to 3.45 μm. This source was based on an optical parametric oscillator (OPO) pumped by a Nd:YAG laser. This laser delivered 3.4 mJ at 20 Hz repetition rate and with 7 ns pulse duration. With a set-up based on a gas chamber and mid-IR detection unit for direct absorption measurements the authors demonstrated the capability of their system for detecting acetone concentrations in the range from 1 to 10 % which is the typical level of concentration expected at the vicinity of a bomb factory for instance. Such results are really impressive for a system that is potentially transportable. However, regarding this aspect, mainly because of the footprint and weight of the laser system, portability of the detection unit was a bit limited. Thus, in our case we explored a solution based on a fiber laser pumped OPO. The developed picosecond laser source exhibits short pulses and narrow linewidth (0.4 cm-1). This fiber laser is based on a mode-locked oscillator [3], a Fiber Bragg Grating (FBG) mounted on a piezo electric element for wavelength tuning and several fiber amplifiers. The OPO system was provided by the company LASERSPEC (Belgium) and permits to reach a spectrum ranging from 2700 to 3500 nm. A typical experimental set-up was prepared for characterizing this source for gas sensing [4]. The OPO laser beam was split in two. One beam was sent to a FTIR spectrometer and the other one to an 18-cm-long cell containing the gas under study (See Fig. 1). Acetone detection was demonstrated for various concentrations (Fig. 2). FTIR measurements are in good agreement. In conclusion, we present promising results on acetone with detection levels down to 1% at 3.3 μm (2970 cm-1) using an absorption spectroscopy system based on a widely-tunable compact fiber laser / OPO source.
关键词： mid-IR source,fiber laser,OPO,widely-tunable,picosecond,gas detection
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) - Towards a kW-Class Picosecond Laser at 1 kHz
摘要： Secondary sources development such as X-rays for medical applications demand diode-pumped high-energy, high-power and high repetition rate picosecond lasers leading to a race to the kW milestone. Year after year, the pulse energy increased to few hundreds of millijoules at 1 kHz [1], but all the kW systems are based on the Yb:YAG thin disk technology which until now, to the best of our knowledge, has come short to deliver the full kilowatt level at 1 kHz. On the other side, cryogenically cooled bulk Yb:YAG amplifiers has shown its capabilities to reach 1 J at 500 Hz with 3.8 ps pulses [2]. Since two years, CELIA has launched new technology developments for a new system (HORIZON) aiming to reach 1 J, 1 kHz, 1 ps. We selected Yb:YAG crystal as laser gain medium since its thermal properties and its low quantum defect are suitable for high power laser generation. However, its narrow spectral bandwidth and its high saturation fluence impose large constraints on both the amplifier and compressor architectures. Cutting-edge technologies such as hypercompressor [3], divided pulse amplification [4], thin-disk and liquid-cooled disks are explored to address these limitations.
关键词： thin disk technology,cryogenically cooled bulk Yb:YAG amplifiers,high repetition rate,high-power,divided pulse amplification,hypercompressor,picosecond lasers,Yb:YAG,high-energy
更新于2025-09-12 10:27:22
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Maskless, rapid manufacturing of glass microfluidic devices using a picosecond pulsed laser
摘要： Conventional manufacturing of glass microfluidic devices is a complex, multi-step process that involves a combination of different fabrication techniques, typically photolithography, chemical/dry etching and thermal/anodic bonding. As a result, the process is time-consuming and expensive, in particular when developing microfluidic prototypes or even manufacturing them in low quantity. This report describes a fabrication technique in which a picosecond pulsed laser system is the only tool required to manufacture a microfluidic device from transparent glass substrates. The laser system is used for the generation of microfluidic patterns directly on glass, the drilling of inlet/outlet ports in glass covers, and the bonding of two glass plates together in order to enclose the laser-generated patterns from the top. This method enables the manufacturing of a fully-functional microfluidic device in a few hours, without using any projection masks, dangerous chemicals, and additional expensive tools, e.g., a mask writer or bonding machine. The method allows the fabrication of various types of microfluidic devices, e.g., Hele-Shaw cells and microfluidics comprising complex patterns resembling up-scaled cross-sections of realistic rock samples, suitable for the investigation of CO2 storage, water remediation and hydrocarbon recovery processes. The method also provides a route for embedding small 3D objects inside these devices.
关键词： glass microfluidic devices,laser micromachining,picosecond pulsed laser,maskless manufacturing,laser microwelding,rapid prototyping
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) - Stable 1100–2400 nm Supercontinuum in YAG with Picosecond Pumping for Simplified OPCPA
摘要： The generation of a supercontinuum (SC) in a bulk material is an inexpensive and effective method for substantially expanding the spectrum of laser pulses. Accordingly, the broad spectrum of SC makes it ideal for seeding an Optical Parametric Chirped Pulse Amplifier (OPCPA). Stable SC in the wavelength range from ~ 500 nm to ~ 1000 nm in a YAG crystal pumped with picosecond pulses [1] simplifies TW-class laser architecture [2] due to the inherent signal and pump synchronization in OPCPA. Moreover, a stable SC in the range up to 2.5 μm would eliminate the idler generation and pave the way for the development a more reliable and compact OPCPA in the IR spectral range. We demonstrate a single-filament SC covering the wavelength range from ~ 1100 nm to more than 2400 nm, with pulse energy stability and beam pointing stability exceeding the Chirped Pulse Amplifier (CPA) - compressor [2] used as a pumping source. Such a highly stable source of broadband seed pulses together with an inexpensive CPA-compressor based on Yb:YAG rods [2] significantly simplifies the development of compact high-intensity OPCPA systems around the 2 μm spectral range.
关键词： laser pulses,picosecond pumping,OPCPA,YAG,supercontinuum
更新于2025-09-12 10:27:22
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Treatment of gingival pigmentation with a 755-nm alexandrite picosecond laser
摘要： Hyperpigmentation of the gums can be associated to several etiological factors. Although it is physiological in most cases it can cause esthetic concerns in some patients. The objective of our study was to evaluate the clinical efficacy and patient satisfaction with the treatment of gingival hyperpigmentation with picosecond alexandrite laser of 755 nm. We selected two patients with gingival hyperpigmentation on the anterior face of the upper and lower gums of years of evolution. Malignancy, drug ingestion, exposure to tobacco and underlying genetic and endocrine alterations were ruled out. Clinical photographs were taken before treatment and 2 weeks after the procedure. In both cases, anterior gingival areas were depigmented with satisfaction. The patients did not complain of severe pain or discomfort. Two weeks after the procedure the gingiva showed almost complete depigmentation. In conclusion, the 755-nm alexandrite picosecond laser seems to be safe and effective for the esthetic treatment of gingival hyperpigmentation.
关键词： Pigment laser,Alexandrite laser,Picosecond laser,Laser
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) - Shaping of Picosecond Pump Pulses by SHG Depletion for Wide-Bandwidth TW-Class NOPCPA
摘要： On a global scale, great efforts were made to create TW-class laser systems based on an Optical Parametric Chirped Pulse Amplifier (OPCPA). The generation of stable white light supercontinuum (WLC) in the wavelength range from ~ 500 nm to ~ 1000 nm with picosecond pump pulses simplifies the OPCPA architecture due to the inherent signal and pump synchronization. In the OPA process, the resulting gain depends on the temporal profile of the pump pulse. For strongly chirped signal pulses, the amplification process may possibly lead to a significant decrease in the spectral bandwidth. This problem can be avoided by controlling the temporal shape of the pump pulse. We demonstrate the compact TW-class VIS-IR wavelength range NOPCPA with an almost lossless spectral bandwidth achieved due to the formation of “M”-shaped ps pumping pulses after the SHG-conversion. Moreover, the reuse of depleted pump pulses after some SHG and NOPA stages provides an increase in the overall pump-to-signal energy conversion efficiency.
关键词： TW-class laser systems,white light supercontinuum,SHG-conversion,picosecond pump pulses,Optical Parametric Chirped Pulse Amplifier,NOPCPA
更新于2025-09-12 10:27:22