CO2 Laser Light Research Articles

Effects of “blue” (λ = 450 nm) and pulsed periodic CO2 (λ = 10.6 μm) laser light at the skin of laboratory animals. A comparative experimental study

Effects of “blue” (λ = 450 nm) and pulsed periodic CO2 (λ = 10.6 μm) laser light at the skin of laboratory animals. A comparative experimental study

Transcutaneous selective laser photodestruction for the treatment of petechial arachnoid capillary angiodysplasia of the skin in children

Introduction. Petechial – arachnoid capillary angiodysplasia (PACA) of the skin is an acquired pathological benign vascular formation that is met in 66% of children aged 4–9. PACA looks like a spider with a vascular red spot in the center and thin vascular rays coming from it. PACA has a benign course; it is slowly and gradually growing over time, and in rare cases it can disappear spontaneously. There have been proposed some techniques for removing PACA: cryodestruction, electrocoagulation, laser coagulation – with CO2-laser light (wavelength 10.6 mkm), copper vapor laser (wavelength 511 and 578 nm), pulsed dye laser (wavelength 585–595 nm). The main disadvantage of cryodestruction, electrocoagulation and laser coagulation with CO2-laser is a high risk of scarring, hyperpigmentation and frequent relapses. While irradiation with copper vapor laser and pulsed dye laser requires repeated exposures to achieve optimal results.Purpose. To improve outcomes in managing children with PACA using a new modality of transcutaneous selective laser photodestruction.Material and methods. For the last two years, 61 children having PACA were treated with transcutaneous selective laser photodestruction in Clinical and Research Institute of Emergency Pediatric Surgery and Trauma (Moscow, Russian Federation ). The researchers used “green” laser light having the following parameters: wavelength 520±10.0 nm, peak power 2.0±0.5 W, pulse duration 1.9 ms, pulse frequency 50 Hz, exposure time 2.0±0.5 sec.Results and discussion. 59 patients had no any residual elements after the first session; the other two had repeated photodestruction because of residual elements. No scar deformity was seen in any of 61 cases after treatment.Conclusion. The present clinical trial has demonstrated that transcutaneous selective laser photodestruction, if to consider spatial localization of PACA structural elements in the skin, allows to precisely irradiate only the central vascular element and to achieve radically good clinical and esthetic outcomes after treatment.

Carbon dioxide laser in the treatment of benign skin neoplasms

Purpose: to assess the effectiveness of carbon dioxide laser light in the treatment of benign skin neoplasms.Material and methods. The researchers have analyzed outcomes in 1394 patients treated for benign skin neoplasms. In the main group (n = 1184), laser photocoagulation (vaporization) and laser photohydraulic preparation were applied. Laser surgical devices “Lancet-1” and “Lancet-2” in continuous and pulsed modes, power up to 20 W, focused beam up to 1 mm were used. In the control group (n = 210), traditional techniques (excision and electrocoagulation) were applied.Results. High effi ciency of CO2 laser light for the removal of benign skin neoplasms has been confi rmed. Such a technique has a minimal rate of complications and relapses and satisfactory aesthetic outcomes, compared to the conventional treatment.Conclusion. Carbon dioxide laser light is highly effective for treating benign skin neoplasms.

Detection of 9.5 μm CO2 laser pulses in indium doped PbTe p-n junction

A unique feature of the PbTe semiconductor is the growth of its forbidden energy gap with increasing temperature. This allows saving diode-typical characteristics at temperatures up to 180 K. PbTe p-n diodes were fabricated by means of indium donor diffusion into PbTe single crystals grown using the Czochralski technique. The dark saturation current density was ~10−5 A/cm2 at T = 100 K, whereas at T = 180 K it reached ~10−1 A/cm2. The photovoltage signals induced by a pulsed CO2 laser light across PbTe p-n junction were investigated over the 100–180 K temperature range. The two-photon absorption-caused photovoltaic effect is observed for the first time in In doped PbTe p-n junction for 9.5 μm wavelength at T = 100 K.

Combined CO2 laser and intense pulsed light therapy in the treatment of vascular lesions

Combined CO2 laser and intense pulsed light therapy in the treatment of vascular lesions

Molybdenum gratings as a high‐temperature refractory platform for plasmonic heat generators in the infrared

The aim of this work is to study the heating efficiency of refractory microstructures by excitation of surface plasmon polaritons in the far infrared that can be used for high-temperature applications. The work has designed metal grating couplers on molybdenum films to maximise the absorption of a 10.6 µm CO 2 laser light source. Molybdenum has been chosen since it is an industrial refractory metal combined with the fact that its optical properties in the far infrared are similar to gold but with stable high-temperature performance. Linear gratings have been used as plasmonic couplers on large area substrates produced by laser milling. Real-time absolute temperature measurements have been performed showing a 42% increase in the maximum achievable temperature from 702 to 985 K.

In situ tuning of whispering gallery modes of levitated silica microspheres

We demonstrated the tuning of whispering gallery modes (WGMs) of a silica microsphere during optical levitation through the annealing process. We determined the annealing temperature from the power balance between the CO2 laser light heating and several cooling processes. Cooling caused by heat conduction through the surrounding air molecules is the dominant process. We achieved a blue shift of the WGMs as large as 1 \%, which was observed in the white-light scattering spectrum from the levitated microsphere.

A Proliferation Assessment of Third Generation Laser Uranium Enrichment Technology

ABSTRACTLong-standing efforts to develop a commercially viable laser-based process for uranium enrichment, initially with atomic and later molecular isotope separation, have had limited success. This article discusses a model for a third generation of laser enrichment technology where CO2 laser light is Raman scattered to generate 16 μm photons that excite a vibrational mode in uranium-235 hexafluoride molecules within an adiabatically expanding free carrier gas jet, allowing for the partial separation of uranium isotopes by condensation repression. The SILEX (Separation of Isotopes by Laser Excitation) process being developed as part of the Global Laser Enrichment project may be one example of this separation technique. An ideal, asymmetric cascade for enriching uranium to weapon-grade levels is presented, and an analysis of the minimum laser performance requirements is included. Optimal running parameters, physical space constraints, and energy efficiency estimates are discussed. An assessment of the technical skills required is also provided. Finally, material available in an online supplement discusses possible lasers that may be utilized in such a process, and offers an introduction to dimer formation, a laser-based enrichment cascade, and a model for estimating the enrichment factor.

Fractional CO2 Laser Versus Intense Pulsed Light in Treating Striae Distensae.

Context:Striae distensae are linear atrophic dermal scars covered with flat atrophic epidermis. They may cause disfigurement, especially in females. Many factors may cause striae distensae such as steroids, obesity, and pregnancy. Although there is no standard treatment for striae; many topical applications, peeling, and light and laser systems have been tried.Aims:To evaluate and compare the efficacy of fractional CO2 laser with intense pulse light in treating striae distensae.Subjects and Methods:Forty patients with striae distensae were recruited. Twenty of them were treated by fractional CO2 laser and 20 were treated with intense pulse light. Length and width of the largest striae were measured pre- and post-treatment. Patient satisfaction was also evaluated and graded. Patients were photographed after each treatment session and photos were examined by a blinded physician who had no knowledge about the cases.Results:Both groups showed significant improvement after treatments (P < 0.05). Patients treated with fractional CO2 laser showed significant improvement after the fifth session compared with those treated with ten sessions of intense pulsed light (P < 0.05) in all parameters except in the length of striae (P > 0.05).Conclusions:The current study has provided supportive evidence to the effectiveness of both fractional CO2 laser and intense pulse light as treatments for striae distensae. Fractional CO2 laser was found to be more effective in the treatment of striae distensae compared with intense pulse light.

Biocomposite adhesion without added resin: understanding the chemistry of the direct conversion of wood into adhesives

Biomass is transformed with CO2 laser light into a heat setting adhesive achieving direct adhesion without added resins. 90% of the adhesive is composed of partially depolymerized cellulose and lignin.

Normal incidence infrared modulator based on single quantum well intersubband transitions

An infrared modulator of which the working principle is based on evanescent wave generation and intersubband transitions in a single AlGaAs/GaAs quantum well is presented here. CO2 laser light at normal incidence is coupled to an evanescent wave by means of a sub-wavelength diffraction grating. Modulation of the zeroth order reflective mode is achieved by applying an electric field across the quantum well. The model for deriving the complex refractive index of the quantum well region is presented and used for numerical diffraction efficiency simulations as a function of the groove height and period. Two specimens with different groove heights were fabricated. Experiments are conducted at a wavelength of 10.6 µm. At this wavelength a relatively strong absolute modulation depth of about 20% could be observed. The experimental results are in good agreement with our model and diffraction efficiency calculations.

Comparison of KTP, Thulium, and CO2 laser in stapedotomy using specialized visualization techniques: thermal effects

High-speed thermal imaging enables visualization of heating of the vestibule during laser-assisted stapedotomy, comparing KTP, CO2, and Thulium laser light. Perforation of the stapes footplate with laser bears the risk of heating of the inner ear fluids. The amount of heating depends on absorption of the laser light and subsequent tissue ablation. The ablation of the footplate is driven by strong water absorption for the CO2 and Thulium laser. For the KTP laser wavelength, ablation is driven by carbonization of the footplate and it might penetrate deep into the inner ear without absorption in water. The thermal effects were visualized in an inner ear model, using two new techniques: (1) high-speed Schlieren imaging shows relative dynamic changes of temperatures up to 2ms resolution in the perilymph. (2) Thermo imaging provides absolute temperature measurements around the footplate up to 40ms resolution. The high-speed Schlieren imaging showed minimal heating using the KTP laser. Both CO2 and Thulium laser showed heating below the footplate. Thulium laser wavelength generated heating up to 0.6mm depth. This was confirmed with thermal imaging, showing a rise of temperature of 4.7 (±3.5)°C for KTP and 9.4 (±6.9) for Thulium in the area of 2mm below the footplate. For stapedotomy, the Thulium and CO2 laser show more extended thermal effects compared to KTP. High-speed Schlieren imaging and thermal imaging are complimentary techniques to study lasers thermal effects in tissue.

In vivo study of necrosis on the liver tissue of Wistar rats: a combination of photodynamic therapy and carbon dioxide laser ablation

Photodynamic therapy (PDT) is known to be limited to applications in large volume tumors due to its limited penetration. Therefore, a combination of PDT and carbon dioxide (CO2) laser ablation may constitute a potential protocol to destroy bulk tumors because it involves an association of these two techniques allowing the removal of visible lesions with a high selectivity of destruction of remnant tumors. The main aim of this study is to investigate the most appropriate procedure to combine use of a CO2 laser and PDT on livers of healthy rats, and to analyze different techniques of this treatment using three types of photosensitizers (PSs). Forty eight animals were separated to form six groups: (1) only CO2 laser ablation, (2) drug and CO2 laser ablation, (3) only PDT, (4) drug and light (PDT) followed by CO2 laser ablation, (5) ablated with CO2 laser followed by PDT, and (6) drug followed by CO2 laser ablation and light. For each group, three types of photosensitization were used: topical 5-aminolevulinic acid (ALA), intravenous ALA and intravenous Photogem®. Thirty hours after the treatments, the animals were sacrificed and the livers removed. The depth of necrosis was analyzed and measured, considering microscopic and macroscopic aspects. The results show that the effects of the PDT were considerably enhanced when combined with CO2 laser ablation, especially when the PDT was performed before the CO2 laser ablation.

Changes in Gene Expression ofStreptococcus mutansin Planktonic Environment Following CO2Laser Irradiation

Abstract Objective: The aim of this work was to study the effect of CO2 laser light on gene expression of Streptococcus mutans in a planktonic environment irradiated by sublethal energies. The use of the CO2 laser for oral clinical applications has great benefits over the traditional procedures, including a reduced bacterial environment. In order to determine the sublethal irradiation dose, S. mutans in suspension was irradiated with a continuous wave CO2 laser (wavelength 10.6 μm) for duration times of 0.5-1.5 min at fluences ranging from 65 to 536 J/cm(2), following bacterial growth and viability measurements. The effect of CO2 laser irradiation at sublethal dose on gene expression was evaluated by DNA microarray. Temperature rise in the suspension caused by laser irradiation was measured using thermocouple electrodes. Bacterial growth and viability began to decrease after exposure to laser irradiation using 284 J/cm(2). Following irradiation with sublethal fluences of 134 and 268 J/cm(2), changes in gene expression were found with seven downregulated genes being common to both fluences. The temperature rise in the bacterial sample after irradiation with 268 J/cm(2) was from room temperature to only 35°C. CO2 laser irradiation inhibited viability and growth of S. mutans in suspension in a dose-dependent manner. Irradiation of planktonic bacterial suspensions with sublethal fluences resulted in changes mostly of downregulation in gene expression in a fashion similar to S. mutans in biofilm, except that different genes were involved.

Vibrational Spectrum of HMX at CO2 Laser Wavelengths: A Combined DRIFT and LPAS Study

The vibrational spectrum of solid standard HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) was investigated. Two spectroscopic techniques were adopted for their different sensitivity and resolution. A preliminary survey of the absorption bands of the compound was performed in the 8000–400 cm−1 spectral range by employing the diffuse reflectance infrared Fourier transform (DRIFT) technique at room temperature. The high-resolution line spectrum of HMX was obtained in the 9.2–10.8 μm spectral range by laser photoacoustic spectroscopy (LPAS) method, using a line tuneable 10 W stabilised cw CO2 laser light source. By comparing the data collected with the two techniques in the common frequency range, a very good agreement was observed.

Electronic spectral parameters and IR nonlinear optical features of novel Ag0.5Pb1.75GeS4 crystal

In this paper, we report on novel Ag0.5Pb1.75GeS4 single crystals grown by the Bridgman–Stockbarger method. For these crystals we have performed X-ray photoelectron spectroscopy (XPS) studies of the valence-band and core-level electron states. Second harmonic generation efficiency of Ag0.5Pb1.75GeS4 powder samples by using CO2 laser light depending on the power density up to 1100MW/cm2 has been obtained within the temperature range 77–520K. The obtained dependences indicate relatively strong enhancement of photoinduced SHG output efficiencies as temperature increases. Both the spectra taken at ambient and 520K temperatures have shown similar behavior—rapid growth to saturated values of SHG efficiency with an increase of fundamental beam power density up to 400MW/cm2, then slowly decreasing with power density reaching a value of 800MW/cm2 and finally these features show a second small maximum at a fundamental beam power density equal to 900MW/cm2. Beyond this power density both SHG values start to decrease.

Proefschriften 25 jaar na dato 29. CO2-laserchirurgie van leukoplakie van het mondslijmvlies

With a CO2 laser superficial lesions of the oral mucosa can be removed by evaporation. During CO2 laser evaporation there is minimal damage to the surrounding tissue, resulting in minimal scarring after healing. Therefore the CO2 laser seems to be a modality which is appropriate for the treatment of leukoplakia of the oral mucosa. In 1985, the effect of CO2 laser light on mucosa and the healing after CO2 laser evaporation was studied. In addition, clinical research was carried out concerning the effectiveness of CO2 laser evaporation in the treatment of 103 cases of leukoplakia of the oral mucosa The cure-rate was 91% and no malignant degenerations were seen in the treated area. The group was expanded (282) and evaluated again, with a cure-rate of 90%. In 1% of the cases, malignant degenerations were seen. CO2 laser evaporation seems the modality of choice for the treatment of leukoplakia of the oral mucosa.

Micromachining of Transparent Materials with Fresnel Diffraction of Infrared Radiation

A simple and productive micromachining method of a silica glass using a TEA (transversely excited atmospheric) CO2 laser (10.6 μm) was investigated. A copper grid mask with a thickness of 2 μm, square apertures of 20×20 μm was attached to the silica glass surface, and it was irradiated by the TEA CO2 laser light. As a result, circular holes were formed on the silica glass surface at the center of each aperture in a spatial resolution down to the sub-wavelength scale. The minimum diameter of the hole was less than 3 μm, which is less than one third of the wavelength of the TEA CO2 laser. A depth of the holes ranging from 100 nm to 600 nm could be micromachined on silica glass surface. The mechanism of the micromachining was discussed based on electric field distributions of the CO2 laser light by a 3D full-wave electromagnetic field simulation solver. The simulation results are in good agreement with the experimental results. It was found that the micromachining of the circular holes were caused by Fresnel diffraction of the CO2 laser light at the apertures.

Transition of flat flames to turbulent motion induced by external laser irradiation

Experiments with flames premixed C2H4/CO2-O2 (Le<1) in a tube have been conducted. The mixture was ignited at the top, open end of the tube, and a flame front propagated downward toward the closed end of tube. To investigate details of motion of flame tip fluctuations at the initial moment of irradiating the CO2 laser light, a completely flat flame front was considered a default flame, corresponding to the primary acoustic instability as reported by Searby [1]. The laser exposure to the mixture induced local flame front deformation, resulting in a strong turbulent flame transforming eventually via the secondary acoustic instability. To elucidate the effect of the flame curvature, the flame velocity and curvature prior to establishment of the secondary acoustic instability were analyzed using a high speed camera. The results showed a sudden acceleration of the flame tip front during the advancing period. This was followed by a time lag between the flame velocity and curvature, indicating an increase in the flame velocity even with the decreasing flame curvature. These behaviors can be explained by selective acceleration at the center of the flame by an acoustic field and diffusive-thermal effects at a critical curvature beyond which flame extinction occurs.

CW-CO2 Laser photoinitiated polymerization of Methyl Methacrylate

Photoinitiated polymerization of methyl methacrylate has been observed using cw-CO2 laser radiation of (10.6 µm). Both of DSC and TGA thermal analysis techniques were used for identification of the thermal characteristics (Tg, Tc, and Tm) as well as the thermal stability of the laser photoinitiated PMMA and they compared with that corresponding to classical, conventionally initiated PMMA. In cw-CO2 laser radiation, each of powers (10, 15, and 20W) was used. Although a definite increase in Tg value and thermal stability were observed while power are (10W,15W and 20W), the polymerization pattern remained basically the same in all these cases. Multi-Photon absorption reaction phenomenon was attributed to elucidate the mechanism of interaction between the CO2 laser light and MMA monomer molecule.