Efficient Distributed Feedback Dye Laser in Silk Fibroin Films

We observed longitudinal single-mode operation in a distributed feedback dye laser consisting of silk fibroin films doped with Rhodamine 6G dye and infiltrated with silica or silver nanoparticles.

One-dimensional analytical model for oxide thin film growth on Ti metal layers during laser heating in air

This paper presents the theoretical and experimental results for oxide thin film growth on titanium films previously deposited over glass substrate. Ti films of thickness 0.1 μm were heated by Nd:YAG laser pulses in air. The oxide tracks were created by moving the samples with a constant speed of 2 mm/s, under the laser action. The micro-topographic analysis of the tracks was performed by a microprofiler. The results taken along a straight line perpendicular to the track axis revealed a Gaussian profile that closely matches the laser's spatial mode profile, indicating the effectiveness of the surface temperature gradient on the film's growth process. The sample's micro-Raman spectra showed two strong bands at 447 and 612 cm -1 associated with the TiO 2 structure. This is a strong indication that thermo-oxidation reactions took place at the Ti film surface that reached an estimated temperature of 1160 K just due to the action of the first pulse. The results obtained from the numerical integration of the analytical equation which describes the oxidation rate (Wagner equation) are in agreement with the experimental data for film thickness in the high laser intensity region. This shows the partial accuracy of the one-dimensional model adopted for describing the film growth rate. © 2001 Elsevier Science B.V.

The effect of CO 2 laser irradiation on failed implant surfaces

The aim of this investigation was to evaluate the cleaning effect of CO 2 on surface topography and composition of failed dental implant surfaces. Ten failed dental implants were retrieved from nine patients (mean age, 46.33 ± 5.81 years) as a result of early or late failure. The implants were divided into two parts: one side of the implant was irradiated with a CO 2 laser (test side), while the other side did not receive irradiation (control side). The CO 2 laser was operated at 1.2 W in a continuous wave for 40 seconds (40 J energy). The handpiece of the CO 2 laser was kept at a distance of 30 mm from the implant surface, resulting in a spot area of 0.031415 cm 2 (38.20 W/cm 2; 1559 J/cm 2) in scanning mode (cervical-apical). One unused dental implant was used as a negative control for both groups. All implant surfaces were examined by scanning electron mi croscopy (SEM) and energy-dispersive spectrometer x-ray (EDS) for element analysis. SEM showed that the surface of the test sides consisted of different degrees of organic residues, appearing mainly as dark stains similar to those observed on the control sides. None of the test surfaces presented alterations such as crater-like alterations, lava-like layers, or melting compared with the nonirradiated surfaces. Foreign elements such as carbon, oxygen, sodium, calcium, and aluminum were detected on both sides. These results suggest that CO 2 laser irradiation does not modify the implant surface, although the cleaning effect was not satisfactory.

Treatment of developmental defect of upper lip with carbon dioxide laser radiation (CO2): First surgical time

With the exception of the cleft lip, developmental defects (DD) of the lip are rare. The upper lip originates from the ectomesenchyme and is formed by the merging of the nasal medial and lateral processes with the maxillary process. Disturbances during this formation period can cause DD with functional and/or esthetic repercussions. We present a case of DD of the upper lip in a patient with a history of progressive growth of the left lateral portion of the upper lip that occurred from the time of birth until the age of 22 years. Clinical examination revealed hypertrophy of the area from the left philtral columns to the left commissure of the lip, extending the portion of the surface mucosa creating a flaccid and asymptomatic tissue mass. All other buccal structures appeared to be within normal limits and without any evidence of defects or deformities. In the surgical planning we decided to carry out corrective surgery in two phases. The first phase accomplished a conservative excision of the total abnormal labial tissue mass with a CO2 laser radiation (5 W in continuous mode, bunch diameter φ = 0.6 mm with a power density of 768 W/cm2 and fluency of 0.231 J/cm2) being careful to preserve the vermilion portion of the lip. Postsurgical clinical evaluations were done every three days until the skin sutures were removed and then every seven days until two months post surgery. While the entire mass of excessive tissue could not be completely removed, the removal of the excessive mucosal tissue produced a very good outcome relative to lip function, with a good esthetic result without scarring, and good tissue mobility. The results showed that the CO2 laser is an extremely useful instrument that can provide excellent control of the surgical field and allow for healing that produces excellent functional and esthetic results. © 2005 Taylor & Francis.

Low-level laser therapy in pediatric bell's palsy: Case report in a three-year-old child

Objectives: The objective of this study was to apply low-level laser therapy (LLLT) to accelerate the recovery process of a child patient with Bell's palsy (BP). Design: This was a prospective study. Subject: The subject was a three-year-old boy with a sudden onset of facial asymmetry due to an unknown cause. Materials and methods: The low-level laser source used was a gallium aluminum arsenide semiconductor diode laser device (660 nm and 780 nm). No steroids or other medications were given to the child. The laser beam with a 0.04-cm2 spot area, and an aperture with approximately 1-mm diameter, was applied in a continuous emission mode in direct contact with the facial area. The duration of a laser session was between 15 and 30 minutes, depending on the chosen points and the area being treated. Light was applied 10 seconds per point on a maximum number of 80 points, when the entire affected (right) side of the face was irradiated, based on the small laser beam spot size. According to the acupuncture literature, this treatment could also be carried out using 10-20 Chinese acupuncture points, located unilaterally on the face. In this case study, more points were used because the entire affected side of the face (a large area) was irradiated instead of using acupuncture points. Outcome measures: The House-Brackmann grading system was used to monitor the evolution of facial nerve motor function. Photographs were taken after every session, always using the same camera and the same magnitude. The three-year-old boy recovered completely from BP after 11 sessions of LLLT. There were 4 sessions a week for the first 2 weeks, and the total treatment time was 3 weeks. Results: The result of this study was the improvement of facial movement and facial symmetry, with complete reestablishment to normality. Conclusions: LLLT may be an alternative to speed up facial normality in pediatric BP. © Copyright 2013, Mary Ann Liebert, Inc. 2013.

Resistência adesiva de reparos em resina composta: tratamento da superfície com ponta diamantada, jato de óxido de alumínio e laser de Er:YAG

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Avaliação morfológica ultra-estrutural e pirométrica de dentes humanos irradiados com laser de diodo 808nm

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Histeroscopia ambulatorial com laser diodo: uma nova modalidade para tratamento de pólipos endometriais

Pós-graduação em Ginecologia, Obstetrícia e Mastologia - FMB

Estudo clínico comparativo entre sutura convencional e vaporização a laser de dióxido de carbono (CO2) em pele de ratos

The proposal of this study was to compare a wound healing between conventional suture and vaporization with CO2 laser in rats skin. ln such case 24 rats were utilized, making two longitudinal incisions in dorsum by scalpel. ln the left side incision the wound was sutured with nylon thread. ln the right side incision the wound were close by approach and vaporized with C02 laser, defocusing, 8 watts in continuous mode. The wound healing was followed by clinical photographic taking at the times: immediately after the procedure, 24 hours, 3, 7, 14, and 21 days. The results showed an early delay of reparation in healing vaporized in comparison with the sutured one, however occurred 21 days both repair tissue showed the same clinical characteristic. This results suggested that the C02 laser can be used by eventual substitute of suture.

Application of pulsed Nd:YAG laser in thin foil microwelding

Experimental investigations were carried out using a Nd:YAG laser operating in pulsed mode for welding a lap joint between thin foil and thick sheet. The pulse energy was varied from 1.5 to 3.0 J at increments of 0.25 J with a 4 ms pulse duration. The base material used for this study was AISI 316L foils with 100 mu m thickness and sheet with 3.0 mm thickness. The welds were analysed by optical and electronic microscopy, tensile shear tests and micro hardness. The results indicate that pulse energy control is of considerable importance to join thin foil and thick sheet with good quality. The ultimate tensile strength of the welded joints increased at first and then decreased as the pulse energy increased. The process appeared to be very sensitive to the gap between couples. Large voids delimited by the molten zone boundary were observed in joints welded with high pulse energy.

Diffusive random laser modes under a spatiotemporal scope

At present the prediction and characterization of the emission output of a diffusive random laser remains a challenge, despite the variety of investigated materials and theoretical interpretations given up to now. Here, a new mode selection method, based on spatial filtering and ultrafast detection, which allows to separate individual lasing modes and follow their temporal evolution is presented. In particular, the work explores the random laser behavior of a ground powder of an organic-inorganic hybrid compound based on Rhodamine B incorporated into a di-ureasil host. The experimental approach gives direct access to the mode structure and dynamics, shows clear modal relaxation oscillations, and illustrates the lasing modes stochastic behavior of this diffusive scattering system. The effect of the excitation energy on its modal density is also investigated. Finally, imaging measurements reveal the dominant role of diffusion over amplification processes in this kind of unconventional lasers. (C) 2015 Optical Society of America

Laser Optical Plankton Counter and Zooscan intercomparison in tropical and subtropical marine ecosystems

Two recently developed instruments, the Laser Optical Plankton Counter (LOPC) and the Zooscan, have been applied to study zooplankton biomass size spectra in tropical and subtropical marine ecosystems off Brazil. Both technologies rely on optical measurements of particles and may potentially be used in zooplankton monitoring programs. Vertical profiles of the LOPC installed in a 200 mu m ring net have been obtained from diverse environmental settings ranging from turbid and nearshore waters to oligotrophic open ocean conditions. Net samples were analyzed on the Zooscan and counted under a microscope. Particle biovolume in the study area estimated with the LOPC correlated with plankton displacement volume from the net samples, but there was no significant relationship between total areal zooplankton biomass determined with LOPC and the Zooscan. Apparently, normalized biomass size spectra (NBSS) of LOPC and Zooscan overlapped for particles in the size range of 500 to 1500 mu m in equivalent spherical diameter (ESD), especially at open ocean stations. However, the distribution of particles into five size classes was statistically different between both instruments at 24 of 28 stations. The disparities arise from unequal flow estimates, from different sampling efficiencies of LOPC tunnel and net for large and small particles, and possibly from the interference of non-zooplankton material in the LOPC signal. Ecosystem properties and technical differences therefore limit the direct comparability of the NBSS slopes obtained with both instruments during this study, and their results should be regarded as complementary.

Laser locking to the Hg-199 S-1(0)-P-3(0) clock transition with 5.4x10(-15)/root tau fractional frequency instability

With Hg-199 atoms confined in an optical lattice trap in the Lamb-Dicke regime, we obtain a spectral line at 265.6 nm for which the FWHM is similar to 15 Hz. Here we lock an ultrastable laser to this ultranarrow S-1(0) - P-3(0) clock transition and achieve a fractional frequency instability of 5.4 x 10(-15) / root tau for tau <= 400 s. The highly stable laser light used for the atom probing is derived from a 1062.6 nm fiber laser locked to an ultrastable optical cavity that exhibits a mean drift rate of -6.0 x 10(-17) s-(1) (-16.9 mHzs(-1) at 282 THz) over a six month period. A comparison between two such lasers locked to independent optical cavities shows a flicker noise limited fractional frequency instability of 4 x 10(-16) per cavity. (c) 2012 Optical Society of America

Phase-Locked loops lock-in range in Frequency Modulated-Atomic Force Microscope nonlinear control system

Since the mid 1980s the Atomic Force Microscope is one the most powerful tools to perform surface investigation, and since 1995 Non-Contact AFM achieved true atomic resolution. The Frequency-Modulated Atomic Force Microscope (FM-AFM) operates in the dynamic mode, which means that the control system of the FM-AFM must force the micro-cantilever to oscillate with constant amplitude and frequency. However, tip-sample interaction forces cause modulations in the microcantilever motion. A Phase-Locked loop (PLL) is used to demodulate the tip-sample interaction forces from the microcantilever motion. The demodulated signal is used as the feedback signal to the control system, and to generate both topographic and dissipation images. As a consequence, a proper design of the PLL is vital to the FM-AFM performance. In this work, using bifurcation analysis, the lock-in range of the PLL is determined as a function of the frequency shift (Q) of the microcantilever and of the other design parameters, providing a technique to properly design the PLL in the FM-AFM system. (C) 2011 Elsevier B.V. All rights reserved.

Influence of prior 810-nm-diode intracanal laser irradiation on hydrophilic resin-based sealer obturation

Dentin wall structural changes caused by 810-nm-diode laser irradiation can influence the sealing ability of endodontic sealers. The objective of this study was to evaluate the apical leakage of AH Plus and RealSeal resin-based sealers with and without prior diode laser irradiation. Fifty-two single-rooted mandibular premolars were prepared and divided into 4 groups, according to the endodontic sealer used and the use or non-use of laser irradiation. The protocol for laser irradiation was 2.5W, continuous wave in scanning mode, with 4 exposures per tooth. After sample preparation, apical leakage of 50% ammoniacal silver nitrate impregnation was analyzed. When the teeth were not exposed to irradiation, the Real Seal sealer achieved the highest scores, showing the least leakage, with significant differences at the 5% level (Kruskal-Wallis test, p = 0.0004), compared with AH Plus. When the teeth were exposed to the 810-nm-diode laser irradiation, the sealing ability of AH Plus sealer was improved (p = 0282). In the Real Seal groups, the intracanal laser irradiation did not interfere with the leakage index, showing similar results in the GRS and GRSd groups (p = 0.1009).