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Optics Express Jul 2023We report a high-energy, picosecond, mid-infrared (MIR) optical parametric oscillator (OPO), in which a length of hollow-core-fiber (HCF) is employed to enable operation...
We report a high-energy, picosecond, mid-infrared (MIR) optical parametric oscillator (OPO), in which a length of hollow-core-fiber (HCF) is employed to enable operation at 1-MHz repetition rate in a compact cavity format. The OPO is synchronously pumped by an ytterbium-doped-fiber (YDF) master-oscillator-power-amplifier (MOPA) system, seeded by a 1040-nm gain-switched laser diode (GSLD). Using periodically poled lithium niobate (PPLN) as the nonlinear crystal, the OPO generates signal and idler beams with tunable wavelengths in the range of 1329-1641 nm and 2841-4790 nm, respectively. The OPO provides 137-ps pulses with a maximum signal energy of 10.05 µJ at 1600 nm and a maximum idler energy of 5.13 µJ at 2967 nm. This, to the best of our knowledge, represents the highest energy MIR pulses, as well as the highest total converted pulse energy (15.18 µJ), ever achieved from a fiber laser pumped picosecond OPO.
PubMed: 37475426
DOI: 10.1364/OE.494037 -
Optics Express Nov 2022Ultrafast deep-UV laser sources have extensive applications across a wide number of fields, whether biomedicine, photolithography, industrial processing, or...
Ultrafast deep-UV laser sources have extensive applications across a wide number of fields, whether biomedicine, photolithography, industrial processing, or state-of-the-art scientific research. However, it has been challenging to obtain deep-UV laser sources with high conversion efficiency and output peak power. Here, we simultaneously demonstrated high-peak-power picosecond deep-UV laser sources at two typical wavebands of 263.2 and 210.5 nm via the efficient fourth- and fifth-harmonic generation. The highest peak power of 263.2 and 210.5 nm laser radiations were up to 2.13 GW (6.72 ps) and 1.38 GW (5.08 ps). The overall conversion efficiencies from the fundamental wave to the fourth and fifth harmonic were up to 42.9% and 28.8%, respectively. The demonstrated results represent the highest conversion efficiencies and output peak powers of picosecond deep-UV laser sources at present to our knowledge. Additionally, we also systematically characterized the deep-UV optical properties of typical birefringent and nonlinear borate crystals, including α-BaBO, β-BaBO, LiBO, and CsLiBO crystals. The experiments and obtained numerous new optical data in this work will contribute to the generation of ultrahigh-peak-power deep-UV and vacuum-UV laser sources and crucial applications in both science and industry, such as high-energy-density physics, material science, and laser machining.
PubMed: 36523035
DOI: 10.1364/OE.474513 -
Biochemistry Aug 2020Due to the recent advances in X-ray free electron laser techniques, bilin-containing cyanobacteriochrome photoreceptors have become prime targets for the ever-expanding...
Due to the recent advances in X-ray free electron laser techniques, bilin-containing cyanobacteriochrome photoreceptors have become prime targets for the ever-expanding field of time-resolved structural biology. However, to facilitate these challenging studies, it is essential that the time scales of any structural changes during the photocycles of cyanobacteriochromes be established. Here, we have used visible and infrared transient absorption spectroscopy to probe the photocycle of a model cyanobacteriochrome system, TePixJ. The kinetics span multiple orders of magnitude from picoseconds to seconds. Localized changes in the bilin binding pocket occur in picoseconds to nanoseconds, followed by more large-scale changes in protein structure, including formation and breakage of a second thioether linkage, in microseconds to milliseconds. The characterization of the entire photocycle will provide a vital frame of reference for future time-resolved structural studies of this model photoreceptor.
Topics: Bacterial Proteins; Cyanobacteria; Kinetics; Light; Models, Molecular; Protein Conformation
PubMed: 32786403
DOI: 10.1021/acs.biochem.0c00382 -
Biochimica Et Biophysica Acta.... Feb 2023Since the first membrane models in the 1970s, the concept of biological membranes has evolved considerably. The membrane is now seen as a very complex mixture whose... (Review)
Review
Since the first membrane models in the 1970s, the concept of biological membranes has evolved considerably. The membrane is now seen as a very complex mixture whose dynamic behavior is even more complex. Solid-state NMR is well suited for such studies as it can probe the movements of the membrane from picoseconds to seconds. Two NMR observables can be used: motionally averaged spectra and relaxation times. They bring information on order parameters, phase transitions, correlation times, activation energies and membrane elasticity. Spectra are used to determine the nature of the membrane phase. The order parameters can be measured directly from spectra that are dominated by quadrupolar, dipolar and chemical shielding magnetic interactions and allow describing the lipid membrane as being very rigid at the glycerol and chain level and very fluid at its center and surface. Correlation times and activation energies can be measured for intramolecular motions (pico to nanoseconds), molecular motions (nano to 100 ns) and collective modes of membrane deformation (microseconds). Sterols modulate membrane phases, order parameters, correlation times and membrane elasticity. In general terms, sterols tend to act to reduce the impact of environmental changes on molecular order and dynamics. They can be described as regulators of membrane dynamics by keeping them in a state of dynamics that changes very little when the temperature or other factors change. The presence of such large-scale membrane dynamics is proposed as a means of adapting to evolutionary constraints.
Topics: Magnetic Resonance Spectroscopy; Elasticity; Membranes; Motion; Sterols
PubMed: 36442647
DOI: 10.1016/j.bbamem.2022.184097 -
Clinical, Cosmetic and Investigational... 2021We aimed to investigate picosecond laser effects regarding rat tattoo removals. We systematically detected the metabolic pathways considering tattoo pigment particles in...
OBJECTIVE
We aimed to investigate picosecond laser effects regarding rat tattoo removals. We systematically detected the metabolic pathways considering tattoo pigment particles in rat models.
MATERIALS AND METHODS
We employed fluorescein to mark the tattoo dye and utilized a pattern needle to prepare tattoo on rat so as to establish the tattoo removal effects of picosecond laser methods employing animal models. We applied a picosecond laser to process the tattoo and observed the effects along with metabolic pathways for tattoo removal via pathology and imaging approaches.
RESULTS
Based on the results of characterization, pathology and fluorescence, we discovered that the picosecond laser could effectively remove the pigment particles on rat skin, part of which would be metabolized out of the body through the circulatory system. After picosecond laser treatment, the fluorescence intensity of the rat skin engraved part was gradually weakened. At 8 h after the treatment, the metabolic organs had weak fluorescence, and there was no fluorescence in the metabolic organs at 12 h and 24 h after the treatment.
CONCLUSION
The picosecond laser had perfect tattoo removal effects, which could be utilized as a reference for clinical tattoo removal.
PubMed: 34594124
DOI: 10.2147/CCID.S332265 -
Annual Review of Biochemistry 2014RNA dynamics play a fundamental role in many cellular functions. However, there is no general framework to describe these complex processes, which typically consist of... (Review)
Review
RNA dynamics play a fundamental role in many cellular functions. However, there is no general framework to describe these complex processes, which typically consist of many structural maneuvers that occur over timescales ranging from picoseconds to seconds. Here, we classify RNA dynamics into distinct modes representing transitions between basins on a hierarchical free-energy landscape. These transitions include large-scale secondary-structural transitions at >0.1-s timescales, base-pair/tertiary dynamics at microsecond-to-millisecond timescales, stacking dynamics at timescales ranging from nanoseconds to microseconds, and other "jittering" motions at timescales ranging from picoseconds to nanoseconds. We review various modes within these three different tiers, the different mechanisms by which they are used to regulate function, and how they can be coupled together to achieve greater functional complexity.
Topics: Base Pairing; Genetic Techniques; Hydrogen-Ion Concentration; Kinetics; Ligands; Magnetic Resonance Spectroscopy; Models, Molecular; Motion; Nucleic Acid Conformation; Protein Conformation; Proteins; RNA; Temperature; Thermodynamics
PubMed: 24606137
DOI: 10.1146/annurev-biochem-060713-035524 -
Journal of Cutaneous and Aesthetic... 2021Melasma is an acquired and treatment-resistant aging facial skin condition prevalent among the older Asian females. The Q-switched toning laser is the most widely used...
BACKGROUND
Melasma is an acquired and treatment-resistant aging facial skin condition prevalent among the older Asian females. The Q-switched toning laser is the most widely used for the treatment of moderate to severe melasma in Asia. Recently, the picosecond laser has been introduced for various pigmentary disorders such as melasma. We evaluated the efficacy and safety of dual toning combined with 1064 nm Nd:YAG picosecond and quasi-long-pulsed laser in the treatment of severe melasma.
SUBJECTS AND METHODS
Twenty Vietnamese females, mean age 41.9 ± 6.4 years, Fitzpatrick skin type IV, with clinical diagnosis of severe dermal and mixed-type melasma were treated by at least eight sessions picosecond Nd:YAG 1064 nm reducing Melasma Area and Severity Index (MASI) to less than 15%. Then they were treated with 3 sessions of dual toning combined picosecond Nd:YAG 1064 nm laser having an energy and spot size of 0.6-0.8 J/cm and 8 mm with micropulsed mode Nd:YAG 1064 nm laser (350 µs) having an energy and spot size of 2.6 J/cm and 15 mm with ICD off. Mild and even erythema was the endpoint (40-42°C using the infrared thermometer). Treatments were given every 4 weeks. Improvement was rated by MASI at the baseline (T1), after eight sessions of picotoning (T2), and three sessions of dual toning (T3).
RESULTS
The mean MASI score of 20 patients at baseline (T1) was 16.24 ± 4.88 (min 6.0; max 28.8); after at least eight picotoning sessions, the mean MASI was 15.12 ± 4.69, representing a 7.44 ± 4.41% reduction in MASI score. The MASI score of the dual toning laser continued to decrease after three dual toning sessions from 15.12 ± 4.6 to 9.77 ± 3.86 (MASI score reduced by a mean of 5.35 ± 2.64), achieving 35.15 ± 13.51% reduction from T2 and 40.17 ± 12.14% reduction from baseline MASI (T1). There were no unexpected side effects in any patients.
CONCLUSION
The dual toning method using the 1064 nm Nd:YAG picosecond and microsecond laser was safe and effective and well tolerated by all patients without downtime. However, larger number of studies should be conducted with more objective measurement techniques to confirm the results of this preliminary study.
PubMed: 34084016
DOI: 10.4103/JCAS.JCAS_30_20 -
Optics Express Oct 2021We present a free-running 80-MHz dual-comb polarization-multiplexed solid-state laser which delivers 1.8 W of average power with 110-fs pulse duration per comb. With a...
We present a free-running 80-MHz dual-comb polarization-multiplexed solid-state laser which delivers 1.8 W of average power with 110-fs pulse duration per comb. With a high-sensitivity pump-probe setup, we apply this free-running dual-comb laser to picosecond ultrasonic measurements. The ultrasonic signatures in a semiconductor multi-quantum-well structure originating from the quantum wells and superlattice regions are revealed and discussed. We further demonstrate ultrasonic measurements on a thin-film metalized sample and compare these measurements to ones obtained with a pair of locked femtosecond lasers. Our data show that a free-running dual-comb laser is well-suited for picosecond ultrasonic measurements and thus it offers a significant reduction in complexity and cost for this widely adopted non-destructive testing technique.
PubMed: 34809002
DOI: 10.1364/OE.440856 -
Frontiers in Medicine 2023Increasing numbers of studies demonstrated that picosecond lasers (Picos) were effective and safe for melasma. However, A limited number of randomized controlled trials...
Comparison of the efficacy and safety of picosecond Nd:YAG laser (1,064 nm), picosecond alexandrite laser (755 nm) and 2% hydroquinone cream in the treatment of melasma: A randomized, controlled, assessor-blinded trial.
BACKGROUND
Increasing numbers of studies demonstrated that picosecond lasers (Picos) were effective and safe for melasma. However, A limited number of randomized controlled trials (RCTs) regarding Picos contribute to a modest level of evidence. Topical hydroquinone (HQ) remains to be the first-line therapy.
OBJECTIVE
To compare the efficacy and safety of non-fractional picosecond Nd:YAG laser (PSNYL), non-fractional picosecond alexandrite laser (PSAL), and 2% HQ cream in the treatment of melasma.
METHOD
Sixty melasma patients with Fitzpatrick skin types (FST) III-IV were randomly assigned to the PSNY, PSAL, and HQ groups at a 1:1:1 ratio. Patients in PSNYL and PSAL groups received 3 laser sessions at 4-week intervals. The 2% HQ cream was applied twice daily for 12 weeks in patients of the HQ group. The primary outcome, the melasma area and severity index (MASI) score, was evaluated at weeks 0, 4, 8, 12, 16, 20, and 24. The patient assessment score by quartile rating scale was rated at weeks 12, 16, 20, and 24.
RESULTS
Fifty-nine (98.3%) subjects were included in the analysis. Each group showed significant change from baseline in MASI scores from week 4 to week 24. The MASI score in the PSNYL group showed the greatest reduction compared to the PSAL group ( = 0.016) and HQ group ( = 0.018). The PSAL group demonstrated comparable MASI improvement as the HQ group ( = 0.998). The PSNYL group had the highest patient assessment score, followed by the PSAL group and then the HQ group, although only the differences between PSNYL and HQ groups at weeks 12 and 16 were significant. Four patients (6.8%) experienced recurrence. Other unanticipated events were transient and subsided after 1 week to 6 months.
CONCLUSION
The efficacy of non-fractional PSNYL was superior to that of non-fractional PSAL, which was not inferior to 2% HQ, thus non-fractional Picos providing an alternative for melasma patients with FSTs III-IV. The safety profiles of PSNYL, PSAL, and 2% HQ cream were similar.
CLINICAL TRIAL REGISTRATION
https://www.chictr.org.cn/showprojen.aspx?proj=130994, ChiCTR2100050089.
PubMed: 37056729
DOI: 10.3389/fmed.2023.1132823 -
Micromachines Dec 2023This paper presents a study and comparison of surface effects induced by picosecond and nanosecond laser modification of a Ti6Al4V alloy surface under different ambient...
Microstructure Formations Resulting from Nanosecond and Picosecond Laser Irradiation of a Ti-Based Alloy under Controlled Atmospheric Conditions and Optimization of the Irradiation Process.
This paper presents a study and comparison of surface effects induced by picosecond and nanosecond laser modification of a Ti6Al4V alloy surface under different ambient conditions: air and argon- and nitrogen-rich atmospheres. Detailed surface characterization was performed for all experimental conditions. Damage threshold fluences for picosecond and nanosecond laser irradiation in all three ambient conditions were determined. The observed surface features were a resolidified pool of molten material, craters, hydrodynamic effects and parallel periodic surface structures. Laser-induced periodic surface structures are formed by multi-mode-beam nanosecond laser action and picosecond laser action. Crown-like structures at crater rims are specific features for picosecond Nd:YAG laser action in argon-rich ambient conditions. Elemental analysis of the surfaces indicated nitride compound formation only in the nitrogen-rich ambient conditions. The constituents of the formed plasma were also investigated. Exploring the impact of process control parameters on output responses has been undertaken within the context of laser modification under different environmental conditions. Parametric optimization of the nanosecond laser modification was carried out by implementing an advanced method based on Taguchi's parametric design and multivariate statistical techniques, and optimal settings are proposed for each atmosphere.
PubMed: 38276833
DOI: 10.3390/mi15010005