Sub-millisecond Pulse Research Articles

Nd:YAG Technology for Laser Hair Removal: What's New?

ABSTRACTBackgroundSince its inception, the Neodymium‐doped yttrium aluminum garnet (Nd:YAG) 1064‐nm laser has been widely used for the treatment of hair removal. Selective photothermolysis forms the basis of its function. Without harming the skin, the laser damages the hair follicle, offering safety and potentially positive outcomes. Many years after its debut, newly developed Nd:YAG laser technology and additional indicators have been found.MethodsThe quality of the evidence was evaluated using PubMed and Google Scholar searches. A selection of articles published between 2019 and 2024 underwent a retrospective review.ResultsUpdated technology, including the “in‐motion” technique, submillisecond pulse, and the combination of alexandrite and Nd:YAG lasers, achieves effective hair reduction with a higher safety profile. Other effects of the Nd:YAG laser on sweat glands, its bactericidal effects, and its long‐term effects on laser providers are discussed in this literature.ConclusionWith minimal short‐ and long‐term side effects, the latest technology and techniques of Nd:YAG laser treatment at a wavelength of 1064 nm have been shown to be beneficial and promising for hair removal.

Features of the formation and diagnostics of powerful metal ion beams with submillisecond duration

The article presents the results of experimental studies on the formation of repetitively-pulsed beams of titanium ions with submillisecond pulse duration from the continuous vacuum arc discharge plasma. The influence of ion-electron emission on the overestimation of the measured ion current with a power density of tens and hundreds of kilowatts per square centimeter was studied using various methods. It has been established that at an average energy of titanium ions of about 80 keV, due to ion-electron emission, the measured current is three times higher than the real ion beam current. Complicating the measurement of the current and energy parameters of the ion beam, the ion-electron emission ensures the neutralization of its space charge during the entire duration of the pulse. An increase in the ion current density due to ballistic focusing to more than 1 A/cm2 does not change the ion-electron emission coefficient. It is shown that, as a result of incomplete ion beam space charge neutralization, its crossover is shifted by 20 mm beyond the geometric focus of the system. The possibility of forming submillisecond high-intensity titanium ion beams with a current density exceeding 2.8 A/cm2, a power density exceeding 200 kW/cm2, and a pulse energy exceeding 100 J has been experimentally demonstrated. Data are obtained on the change in the current density over the ion beam cross-section depending on the accelerating voltage amplitude, the vacuum arc discharge current, and the distance from the focusing electrode.

Latitude and Amplitude Modulation of the Beam Current for Controlling its Power during a Submillisecond Pulse

Latitude and Amplitude Modulation of the Beam Current for Controlling its Power during a Submillisecond Pulse

Integration of Li4Ti5O12 Crystalline Films on Silicon Toward High-Rate Performance Lithionic Devices.

The growth of crystalline Li-based oxide thin films on silicon substrates is essential for the integration of next-generation solid-state lithionic and electronic devices including on-chip microbatteries, memristors, and sensors. However, growing crystalline oxides directly on silicon typically requires high temperatures and oxygen partial pressures, which leads to the formation of undesired chemical species at the interface compromising the crystal quality of the films. In this work, we employ a 2 nm gamma-alumina (γ-Al2O3) buffer layer on Si substrates in order to grow crystalline thin films of Li4Ti5O12 (LTO), a well-known active material for lithium-ion batteries. The ultrathin γ-Al2O3 layer enables the formation of a stable heterostructure with sharp interfaces and drastically improves the LTO crystallographic and electrochemical properties. Long-term galvanostatic cycling of 50 nm LTO films in liquid-based half-cells demonstrates a high capacity retention of 91% after 5000 cycles at 100 C. Rate capability tests showcase a specific charge of 56 mA h g-1 at an exceptional C-rate of 5000 C (15 mA cm-2). Moreover, with sub-millisecond current pulse tests, the reported thin-film heterostructure exhibits rapid Li-ion (de)intercalation, which could lead to fast switching timescales in resistive memory devices and electrochemical transistors.

Comparison of submillisecond pulse (FRAC3) and long-pulse 1064 nm Nd:YAG laser hair removal.

BackgroundLaser hair reduction gained popularity in the last decade and is presently the most frequently used long‐term hair removal method. It works on the principle of selective photothermolysis—the laser damages the hair follicle without damaging the skin. Shorter Nd:YAG pulses are also effective in hair reduction, while maintaining better comfort for the patient.AimsThe aim of this study was to compare the short and long pulsed methods of Nd:YAG for facial hair removal on darker Fitzpatrick skin types (IV–V).Patients/MethodsThis prospective split face, evaluator‐blinded comparison of short‐pulse Nd:YAG laser versus long‐pulse Nd:YAG laser study included 10 untanned healthy women. There were two outcome measers, two blinded dermatologists compared baseline photographs with those taken 3 months after last session and FotoFinder was used to compare the terminal hair count reduction at the baseline and 3 months after 6th session.ResultsBoth blinded assesors observed significant hair reduction with both lasers; excellent results were achieved in 20% with long pulse and in 55% with short pulse. Both treatment options showed reduction in number of terminal hair with statistical significance using FotoFinder. Comparison of the efficacy of the two pulse durations measured by percent reduction in the number of terminal hair 3 months after the last session showed no significant difference between the groups.ConclusionHair reduction using 1064 nm Nd:YAG is a safe and effective method of hair reduction especially in darker skin types. We have shown that short pulses are better or at least equally safe and effective as the “gold standard” long pulses.

Широтная и амплитудная модуляция тока пучка для управления его мощностью в течение импульса субмиллисекундной длительности

Methods for controlling the power electron beam in a source based on a low-pressure arc discharge with layer stabilization of the emission plasma boundary are described. The control is carried out by the method of amplitude and latitude modulation within the duration of the beam current pulse with a time resolution of 10 μs at a submillisecond pulse duration. Two ways to control the power of the electron beam are implemented: the first one is based on changing the concentration of the emission plasma by modulating the arc discharge current, the second method uses grid control (the mode of operation of the plasma triode) at the constant discharge current. Simplified diagrams of the power supply sources of the discharge and intergrid control voltage, typical oscillograms of the main currents of the discharge system, a graph of a quick-acting power change, and a control characteristic of a plasma triode are presented.

Spatio-temporal ablation dynamics and plasma chemistry of aluminum induced by temporally modulated ytterbium fiber laser

In this work, we studied single-pulse ablation dynamics of a temporally modulated continuous wave laser–material interaction with Al using in situ multimodal time-resolved diagnostics that describe in detail the associated physical and chemical processes. Time-resolved scattering, emission imaging, and optical emission spectroscopy unveiled a sequence of events spread out across three distinct phases: (i) early phase ablation process, associated with particle generation and liquid Al column formation (<20 μs), (ii) secondary detonation when sufficient ejected material is accumulated over the surface (20–50 μs), and (iii) molten liquid Al pool oscillation on the surface, followed by large droplet ejection from the liquid pool (100–500 μs). Atomic Al and AlO were observed with optical emission spectroscopy at different ratios during the entire lifetime of the event, verifying the formation of oxidized Al vapor upon its interaction with air. Morphological and compositional characterization confirmed surface oxidation and material re-solidification in the form of protrusions produced during the irradiation process. This work provides insights into the complex physical and chemical mechanisms of single-pulse ablation in the sub-millisecond laser pulse regime, which are critically important for parameter optimization in a variety of laser processing, microfabrication, and deposition applications.

Regulation of mRNA translation by a photoriboswitch.

Optogenetic tools have revolutionized the study of receptor-mediated processes, but such tools are lacking for RNA-controlled systems. In particular, light-activated regulatory RNAs are needed for spatiotemporal control of gene expression. To fill this gap, we used in vitro selection to isolate a novel riboswitch that selectively binds the trans isoform of a stiff-stilbene (amino-tSS)-a rapidly and reversibly photoisomerizing small molecule. Structural probing revealed that the RNA binds amino-tSS about 100-times stronger than the cis photoisoform (amino-cSS). In vitro and in vivo functional analysis showed that the riboswitch, termed Werewolf-1 (Were-1), inhibits translation of a downstream open reading frame when bound to amino-tSS. Photoisomerization of the ligand with a sub-millisecond pulse of light induced the protein expression. In contrast, amino-cSS supported protein expression, which was inhibited upon photoisomerization to amino-tSS. Reversible photoregulation of gene expression using a genetically encoded RNA will likely facilitate high-resolution spatiotemporal analysis of complex RNA processes.

Short-pulse excitation of microwave plasma for efficient diamond growth

To realize a variety of potential applications of diamonds, particularly in the area of power electronics, it is indispensable to improve their growth efficiency. Most conventional approaches have tried to achieve this simply by increasing the gas temperature; however, this makes it difficult to grow large diamond crystals. To improve the growth efficiency while lowering the gas temperature, we propose that using a pulse-modulated microwave plasma with a sub-millisecond pulse width can enhance the power efficiency of the growth rate of single-crystal diamonds. We found that using a sub-millisecond pulse-mode discharge could almost double the growth rate obtained using continuous mode discharge for a fixed average microwave power and gas pressure. A comparison between experimental observations of the optical emission spectra of the discharge and a numerical simulation of the gas temperature suggests that a decrease in the gas temperature was achieved, and highlights the importance of electron-dominated reactions for obtaining the enhancement of the growth rate. This result will have a large impact in the area of diamond growth because it enables diamond growth to be more power efficient at reduced temperatures.

Millisecond duration pulses for flow-through electro-induced protein extraction from E. coli and associated eradication

Pulsed electric fields are used to induce membrane permeabilization on cells. In the case of species with cell wall (yeasts, microalgae), it was previously shown that when the pulse duration was several ms long, this resulted in a cytoplasmic soluble protein slow leakage. In this work, we show that a similar consequence can be obtained with different strains of E. coli. Experimental evidences of a resulting wall alteration are described. Pre-industrial flow process pilots are used. As the membrane electropermeabilization can be irreversible by applying a proper choice of the pulse parameters, this approach is used for bacterial inactivation in flow process. It is observed that sub-millisecond pulse trains are more cost effective than longer ones.

Study of the dynamics of the absorption spectra of human tooth enamel and dentine under heating and ablation by submillisecond pulse radiation of an erbium laser with a generation wavelength of 2.79 μm

We studied the absorption spectrum of intact human tooth enamel and dentine in the range of 0.26–10 μm. We present the infrared absorption spectra of destruction products of human tooth enamel and dentine by submillisecond laser pulses on a crystal of yttrium-scandium-gallium garnet, activated by chrome and erbium ions with a wavelength of 2.79 μm. We discuss the effect of water spraying on the mechanism of laser ablation and the infrared absorption spectra. We report for the first time transformations observed in the absorption spectra of human tooth enamel in the wavelength range of 2.5–3.5 μm under its heating to +700°C.

Improvement of the atmospheric discharge laser-triggered ability using multiple pulses from a kilohertz KrF laser

The potential ability of lasers to control lightning can be improved by using a train of pulses with submillisecond separations. Laser-triggered experiments in a small-scale (10-mm gap) atmospheric discharge facility show that the triggering is dramatically enhanced when a five-pulse train of sub-Joule energy is used instead of a single pulse. This effect increases rapidly as the pulse interval is reduced. It appears that at a submillisecond pulse interval, sufficient positive and negative ions survive in subsequent pulses, thus enabling easy deionization. Hence, significant plasma buildup occurs from one pulse to the next. However, this persistence of ions would appear to imply that the rate of recombination (effectively a charge transfer between ions) is considerably lower than previously believed.

Dynamics of Al[sub 2]O[sub 3] Particles Accelerated in the Field of a Submillisecond Pulse from an YAG : Er Laser

The effect of the laser energy density on the velocity of sapphire particles accelerated in the field of a submillisecond pulse from an YAG: Er laser is reported for the first time. An original velocity-measuring system is described. It is shown that the acceleration of sapphire particles immersed in water (suspension) requires an energy that is nearly half as great as that needed to accelerate the particles containing the water adsorbed by the surface (powder). It is found that the particle velocity is nonuniformly distributed over the period of the laser pulse action.

Melanin granule model for laser-induced thermal damage in the retina

An analytical model for thermal damage of retinal tissue due to absorption of laser energy by finite-sized melanin granules is developed. Since melanin is the primary absorber of visible and near-IR light in the skin and in the retina, bulk heating of tissue can be determined by superposition of individual melanin granule effects. Granules are modeled as absorbing spheres surrounded by an infinite medium of water. Analytical solutions to the heat equation result in computations that are quick and accurate. Moreover, the model does not rely on symmetric beam profiles, and so arbitrary images can be studied. The important contribution of this model is to provide a more accurate biological description of sub-millisecond pulse exposures than previous retinal models, while achieving agreement for longer pulses. This model can also be naturally extended into the sub-microsecond domain by including vaporization as a damage mechanism. It therefore represents the beginning of a model which can be applied across the entire pulse duration domain.

Melanin granule model for laser-induced thermal damage in the retina

An analytical model for thermal damage of retinal tissue due to absorption of laser energy by finite-sized melanin granules is developed. Since melanin is the primary absorber of visible and near-IR light in the skin and in the retina, bulk heating of tissue can be determined by superposition of individual melanin granule effects. Granules are modeled as absorbing spheres surrounded by an infinite medium of water. Analytical solutions to the heat equation result in computations that are quick and accurate. Moreover, the model does not rely on symmetric beam profiles, and so arbitrary images can be studied. The important contribution of this model is to provide a more accurate biological description of submillisecond pulse exposures than previous retinal models, while achieving agreement for longer pulses. This model can also be naturally extended into the sub-microsecond domain by including vaporization as a damage mechanism. It therefore represents the beginning of a model which can be applied across the entire pulse duration domain.