YLF Laser Radiation Research Articles

Delivery of the diode pumped Er:YLF laser radiation by special hollow glass waveguides

Delivery of the diode pumped Er:YLF laser radiation by special hollow glass waveguides

Investigation of active laser delivery and antimycotic activity of zinc-containing nanomaterials and photodynamic drugs in the treatment of onychomicosis

One of the most common nail pathologies is onychomycosis, a fungal nail infection. The low efficiency of existing methods for the treatment of onychomycosis stimulates the search for new drugs and technologies for their delivery under the nail plate. The aim of the investigation was to study the possibility of using Er:YLF laser radiation for sequential laser microporation of the human nail plate and active laser delivery of modern photodynamic preparations and zinc-containing nanomaterials under the nail plate, as well as to determine their antimycotic activity against the Candida albicans fungus under photodynamic exposure with a wavelength of 656±10 nm. A 0.001 % aqueous solution of methylene blue, a chlorine-containing Revixan gel, as well as zinc-containing nanomaterials, which are aqueous solutions of polyvinylpyrrolidone gel with different concentrations of Zn(NO3)2 nanoparticles and acidity, were studied. It was established that the smallest number of laser pulses required for in vitro microporation of the nail plate and active laser delivery under the nail plate is required when using a 0.001 % aqueous solution of methylene blue, and the largest is required when using Revixan gel. For zinc-containing nanomaterials, an increase in the concentration of Zn(NO3)2 nanoparticles from 14 to 40 % leads to an increase in the number of laser pulses required for active drug delivery under the nail plate by 1.25 times, while a change in the acidity of the pH gel from 7.0 to 6.7 does not has a significant impact on it. It was found that all the studied drugs in combination with photodynamic action at a wavelength of 656±10 nm have an antimycotic effect on the Candida albicans fungus culture. The minimum growth rate of Candida albicans colonies was observed when using the Revixan gel, for which the antimycotic activity reached 73.8 %. The obtained results can be applied in the development of laser systems and technologies for the treatment of fungal diseases, including for photodynamic therapy of onychomycosis.

Theoretical and Experimental Study of the Water-Based Drug Delivery under the Nail Plate by Er-Laser Radiation

Double-stage active laser drug delivery (DSLADD) of an aqueous solution of methylene blue using Er:YLF laser radiation experimentally was investigated. Model for describe of the delivery of local drugs under a microporated nail plate taking into account the peculiarities of laser radiation exposure, capillary effects in microholes and diffusion in the nail plate was developed. The phenomenon of spreading of the drug consisting in the fact that after laser action drug is distributed in the nail bed not only in the area of the nail bed located directly under the microhole, but also along the border of the nail plate and the nail bed around the microhole was observed for the first time. Calculations performed within the framework of the developed model showed that, taking into account spreading phenomenon, the density of filling the nail area with microholes can be significantly reduced, which can proportionally increase the productivity of laser delivery in general.

Investigation of the Dual‐Stage Method of Active Er:YLF Laser Drug Delivery Through the Nail and Laser‐Induced Transformations of the Drug Extinction Spectrum

A novel dual-stage method for active laser drug delivery (DSLADD) in the treatment of nail diseases is being presented. This method includes sequentially performed microporation of the nail with submillisecond pulses of Er:YLF laser radiation through a layer of an aqueous solution of drug deposited on the nail surface (Stage 1) and exposure this layer to the same laser radiation to deliver drug under the nail plate (Stage 2). The delivery of methylene blue (MB) as one of the possible drugs in the treatment of nail diseases is investigated. The influence of the thickness of the MB layer, as well as the energy and number of applied laser pulses, on the rate of active laser delivery is discussed. To illustrate the possible effect of delivery on the drug delivered, special attention is paid to the deformation of the extinction spectrum of MB solution after laser irradiation. Diode-pumped Er:YLF laser was used for DSLADD. The process of DSLADD under the nail plate was investigated using digital video microscopy. For different values of the thickness of MB solution layer applied to the nail plate and the energy of laser pulses, the number of laser pulses required to create a single through a microchannel in the nail plate and the number of laser pulses required to deliver the solution to the ventral side of the nail plate after its microporation were registered. The mass and the dose of MB solution penetrated under the nail plate, and the rate of MB solution delivery through a single microchannel was determined. Investigation of the influence of Er:YLF laser radiation parameters on the extinction spectrum of the drug was performed using a fiber spectrometer. The extinction spectra of the 0.001% aqueous solution of MB were recorded before and after exposure to a different number of Er:YLF laser pulses with the energy of 1-4 mJ. It was found that the minimum number of laser pulses required for active Er:YLF laser drug delivery under the nail corresponds to the MB layer thickness of 100 μm and the laser pulse energy of 4 mJ. It is shown that in this case, the rate of active laser delivery of MB solution reaches 0.26 ± 0.03 mg/pulse. The radiation of the Er:YLF laser affects the shape of the extinction spectrum of the aqueous solution of MВ, which is associated with the transition of the dye from the monomeric to dimeric state. Depending on the laser pulse energy, the fraction of a certain conformational state in the aqueous MB solution can decrease or increase, stimulating a possible change in its photodynamic and antiseptic activity. For the first time, a novel DSLADD through the nail has been described and investigated in vitro. It was demonstrated that at Er:YLF laser pulse repetition rate of f = 30 Hz, microporation of the nail plate and drug delivery through a single microchannel will be about 1.5 s. Lasers Surg. Med. © 2021 Wiley Periodicals LLC.

Лазерная доставка и спектральное исследование хлоринсодержащего препарата для лечения онихомикоза при последовательном лазерном (λ=2819 nm) и фотодинамическом (λ=656± 10 nm) воздействии

For the first time, the possibility of a dual-stage active laser delivery of a modern chlorin-containing photodynamic preparation under the nail plate for photodynamic therapy of onychomycosis was investigated and demonstrated. The extinction spectra of the photodynamic preparation Revixan (Areal Ltd., Russia) were investigated at different temperatures, as well as before and after exposure to Er:YLF-laser radiation with a wavelength of 2810 nm and photodynamic LED radiation with a wavelength of 656 ± 10 nm. It is shown that after heating and laser exposure, the amount of monomers in the chlorin-containing photodynamic preparation increases, and after photodynamic exposure decreases, which can affect the effectiveness of photodynamic therapy of onychomycosis.

Nanosecond room-temperature Fe : ZnSe laser pumped inside the resonator of a transversely diode-pumped Er : YLF laser

Lasing at room temperature is obtained in a Fe : ZnSe crystal installed as a passive Q-switch in a diode-pumped Er : YLF laser resonator. A miniresonator of the Fe : ZnSe laser is formed by mirrors pressed against the optical surfaces of the crystal with high reflectivities at λ = 4 − 4.5 μm and a high transmittance for the Er : YLF laser generation lines. In the Er : YLF laser resonator, short pulses of ∼100 ns duration at λ = 2.65 μm are generated, stipulated by passive Q-switching of the resonator by the Fe : ZnSe crystal. The absorption of the Er : YLF laser radiation in the Fe : ZnSe crystal leads to the pumping of Fe : ZnSe laser, which generates pulses with a duration of less than 50 ns and an energy of ∼0.5 μJ at λ = 4.2 μm. The laser operates in the pulse-periodic pump regime with a repetition rate up to 200 Hz.

Microperforation of the human nail plate by radiation of erbium lasers

The nail plate forms a barrier that limits the effectiveness of drug delivery in the treatment of nail diseases and prevents the outflow of fluid in the case of subungual hematoma formation. Microperforation of the nail plate through laser radiation can increase the effectiveness of drug delivery and ensure the possibility of blood outflow. This study detected and identified the type and threshold of effects that arise from exposing the nail plate to Yb,Er: Glass (λ = 1.54 μm) and Er:YLF (λ = 2.81 μm) laser radiation. The rate and efficiency of nail plate ablation by the radiation of these lasers were studied. The effect of the storage time of a freshly extracted nail plate in open air on its ablation rate by Er:YLF (λ = 2.81 μm) laser radiation was also investigated. The impact of the Yb,Er:Glass and Er:YLF laser pulses on the nail plate caused bleaching, carbonization, ablation with microcrater formation, and microperforation. The laser energy densities WE (thresholds) required for these effects were determined. The maximum ablation rate for Yb,Er:Glass laser radiation was 8 μm/pulse at WE = 91±2 J/cm2, whereas that for Er:YLF laser radiation was 12 μm/pulse at WE= 10.5±0.5 J/cm2. The maximum ablation efficiency for Yb,Er:Glass laser radiation was 0.1 μm/mJ at WE = 10.5±0.5 J/cm2, whereas that for Er:YLF laser radiation was 4.6 μm/mJ at WE = 5.3±0.3 J/cm2. The laser ablation rate depends on the storage time and conditions of the freshly extracted nail plate. For example, when exposed to Er:YLF laser radiation, the laser ablation rate decreased by half from the initial maximum value in 96 h of air storage and returned to the initial value after 1 h of storage in distilled water.

Application of optoelectronic negative feedback to ordering of the temporal structure of the diode-pumped Nd:YLF laser radiation

The conditions of the generation of radiation with ordered temporal structure are determined for a solid-state laser with external negative feedback. Experiments are performed based on the Nd:YLF laser longitudinally pumped by a high-power diode array. Lasing was controlled using an intracavity electro-optic modulator based on a lithium tantalate crystal. Intensity smoothing and self-mode-locking regimes with generation of several short pulses in the axial interval are implemented by varying the delay in the feedback circuit. Under conditions of amplification above the stability boundary, the secondary electro-optic effect manifestation was detected in the lithium tantalate crystal.

Visualization of 2-μm radiation by BiF3:Ho3+ and BiF3:Ho3+/Yb3+ ceramics

A series of ceramic samples of the compositions BiF3:1%Ho3+, BiF3:4%Ho3+, BiF3:1%Ho3+ + 1%Yb3+, and BiF3:1%Ho3+ + 3%Yb3+ is synthesized and the conversion of Tm:YLF laser radiation (λ = 1908 nm) is studied. The luminescence spectra exhibit bands in the regions of 490, 545, and 650 nm. The kinetic measurements of the afterglow of the green and red bands show that the population of the 5S2 and 5F4 states in the BiF3:1%Ho3+ samples occurs due to successive absorption of excitation photons, while the 5F5 level of Ho3+ is populated due to the ion–ion interaction. Codoping with Yb3+ leads to a decrease in the visualization threshold power density to 2 W/cm2.

Diode-pumped tunable Tm : YLF laser for mid-infrared gas spectroscopy

The spectral characteristics of the longitudinally diode-pumped Tm : YLF laser radiation are experimentally studied. The laser wavelength was tuned within a spectral range of 1860 - 1940 nm with a linewidth not exceeding 1 nm. The effect of water vapour on the spectral characteristics is studied.

Efficient lasing at 2.1 μm in a Ho:YAG laserpumped by a Tm:YLF laser

A laser based on a Ho:YAG crystal operating at a wavelength of ∼2.1 μm under pumping by Tm:YLF laser radiation with a wavelength of 1.908 μm is studied. The laser operates in cw and repetitively pulsed regimes with a high beam quality (quality factor M2≤1.2). The cw radiation power reached 15 W with the total optical efficiency of ∼55 %. In the active Q-switched regime (achieved using an acousto-optic Q-switch), a highly stable repetitively pulsed lasing was obtained with a pulse repetition rate of 2.5–10 kHz, a pulse duration of 25–55 ns, and an average power up to 14.7 W. Using intracavity frequency selection, lasing was obtained at individual spectral lines in three wavelength regions, near 2.09, 2.097, and 2.123 μm.

Multiple-ion-beam time-of-flight mass spectrometer

An innovative approach to increase the throughput of mass spectrometric analyses using a multiple-ion-beam mass spectrometer is described. Two sample spots were applied onto a laser desorption/ionization target and each spot was simultaneously irradiated by a beam of quadrupled Nd:YLF laser radiation (261.75 nm) to produce ions by laser-desorption ionization. Acceleration of the ions in an electric field created parallel ion beams that were focused by two parallel einzel lens systems. After a flight path of 2.34 m, the ions were detected with a microchannel plate-phosphor screen assembly coupled with a charge coupled device camera that showed two resolved ion beams. Time-of-flight mass spectra were also obtained with this detector. Experiments were performed using both metal atom cations (Ti+ and Cr+) produced by laser desorption/ionization and the molecular ions of two different proteins (myoglobin and lysozyme), created by matrix assisted laser desorption/ionization using an excess of nicotinic acid as matrix.