Enhanced multiwavelength holographic profilometry by laser mode selection

A method for improving the accuracy of surface shape measurement by multiwavelength holography is presented. In our holographic setup, a Bi12TiO20 photorefractive crystal was the holographic recording medium, and a multimode diode laser emitting in the red region was the light source in a two-wave mixing scheme. on employing such lasers the resulting holographic image appears covered with interference fringes corresponding to the object relief, and the interferogram spatial frequency is proportional to the diode laser's free spectral range (FSR). Our method consists in increasing the effective free spectral range of the laser by positioning a Fabry-Perot etalon at the laser output for mode selection. As larger effective values of the laser FSR were achieved, higher-spatial-frequency interferograms were obtained and therefore more sensitive and accurate measurements were performed. The quantitative evaluation of the interferograms was made through the phase-stepping technique, and the phase map unwrapping was carried out through the cellular-automata method. For a given surface, shape measurements with different interferogram spatial frequencies were performed and compared with respect to measurement noise and visual inspection. (c) 2007 Society of Photo-Optical Instrumentation Engineers.

Enhanced multi-wavelength holographic profilometry by laser mode selection

The application of multi-wavelength holography for surface shape measurement is presented. In our holographic setup a Bi12TiO 20 (BTO) photorefractive crystal was the holographic recording medium and a multimode diode laser emitting in the red region was the light source in a two-wave mixing scheme. The holographic imaging with multimode lasers results in multiple holograms in the BTO. By employing such lasers the resulting holographic image appears covered of interference fringes corresponding to the object relief and the interferogram spatial frequency is proportional to the diode laser free spectral range (FSR). We used a Fabry-Perot étalon at the laser output for laser mode selection. Thus, larger effective values of the laser FSR were achieved, leading to higher-spatial frequency interferograms and therefore to more sensitive and accurate measurements. The quantitative evaluation of the interferograms was performed through the phase stepping technique (PST) and the phase map unwrapping was carried out through the Cellular-Automata method. For a given surface, shape measurements with different interferogram spatial frequencies were performed and compared, concerning measurement noise and visual inspection.

Therapeutic Effects of Low-Level Laser Therapy After Premolar Extraction in Adolescents: A Randomized Double-Blind Clinical Trial

Objective: The purpose of this study was to evaluate the effect of low-level laser therapy (LLLT) on wound healing process and pain levels after premolar extraction in adolescents. Background data: The advantage of using LLLT in oral surgeries is the reduction of inflammation and postoperative discomfort; however, the optimal dosing parameters and treatment effects in surgical procedures are inconclusive. Methods: A double-blind, randomized, controlled clinical trial was conducted with 14 patients who were to undergo surgical removal of premolars. Patients were randomly allocated to the LLLT (test) group and placebo (control) group. Patients in the test group received 5.1 J (60 J/cm(2)) of energy density of a gallium-aluminum-arsenide (GaAlAs) diode laser (wavelength, 830 nm; output power, 0.1 W) at three different points intraorally, 1 cm from the target tissue immediately and at 48 and 72 h after the surgical procedure. For patients in the placebo group, the laser device was applied to the same points without activating the hand piece. The wound healing process was evaluated by an independent examiner by visual inspection with the support of digital photographs at baseline and 2, 7, and 15 days postoperatively. Patients recorded the degree of pain using the visual analogue scale (VAS). Results: Compared with the placebo group, the test group showed a lower intensity of pain, but this difference was not statistically significant at any time point. The wound healing process was similar in both groups. Conclusions: Within the limitations of this study, the LLLT parameters used neither increased the wound healing process nor significantly decreased pain intensity after premolar extraction in adolescents.

Er : YAG laser: Antimicrobial effects in the root canals of dogs' teeth with pulp necrosis and chronic periapical lesions

Objective: Our goal in this study was to evaluate the antimicrobial effect of Er:YAG laser applied after biomechanical preparation of the root canals of dog's teeth with apical periodontitis. Background Data: Various in vitro studies have reported effective bacterial reduction in infected root canals using Er:YAG laser. However, there is no in vivo research to support these results. Methods: Forty root canals of dogs' premolar teeth with pulp necrosis and chronic periapical lesions were used. An initial microbiological sample was taken, and after biomechanical preparation was carried out, a second microbiological sample was taken. The teeth were divided into two groups: Group I-biomechanical preparation was taken of root canals without Er:YAG laser application; Group II-biomechanical preparation was taken of root canals with Er:YAG laser application using 140-mj input, 63-mJ output/15 Hz. After coronal sealing, the root canals were left empty for 7 days at which time a third microbiological sample was taken. The collected material was removed from the root canal with a #40 K file and placed in transport media. It was serially diluted and seeded on culture dishes selective for anaerobes, aerobes, and total streptococci. Colony-forming units per milliliter (CFU/mL) were counted. Results: Groups I and II showed an increase of CFU/mL for all microorganisms 7 days after treatment, being statistically significant for anaerobes in Group I and for anaerobes and total streptococci in Group II. When comparing CFU/mL of Groups I and II, there was a statistically significant increase after 7 d for total streptococci in Group II. Conclusion: Er:YAG laser applied after biomechanical preparation did not reduce microorganisms in the root canal system.

Low-level laser on femoral growth plate in rats

OBJETIVO: Determinar a influência do Laser Terapêutico de Baixa Potência sobre a placa de crescimento de ratos. MÉTODOS: Trinta ratos Wistar machos com 40 dias de idade foram divididos em dois grupos, G1 e G2. O grupo G1 foi submetido à irradiação com laser GaAlAs 830 nm, potência de saída de 40 mW, e densidade de energia de 10 J/cm2. A irradiação foi aplicada diariamente por um período máximo de 21 dias. O mesmo procedimento foi realizado no grupo G2, com a probe desativada. Cinco animais em cada grupo foram sacrificados nos dias 7, 14 e 21 e submetidas à análise histomorfométrica. RESULTADOS: em ambos os grupos, o disco fisário esteve radiograficamente visível em todos os momentos nas incidências craniocaudal e médio-lateral. No 21º dia a porcentagem de comprimento longitudinal do fêmur foi maior em G1 que em G2 em relação ao valor basal, e o número de condrócitos da zona hipertrófica foi maior em G1 que em G2. A zona de cartilagem calcificada estava maior em G1 em relação a G2 em todos os momentos de avaliação. A angiogênese foi maior em G1 que em G2 nos 14º e 21º dias. CONCLUSÃO: A terapia com laser terapêutico de baixa potência influenciou negativamente o disco fisário distal do fêmur de ratos.

Study of the morphological alterations to enamel and dentin in human and bovine teeth after irradiation with Er : YAG laser

Objective: the purpose of this study is to make use of scanning electron microscopy in order to comparatively analyze the morphological alterations to human and bovine enamel and dentin. Earlier data: Many a morphological study involving Er:YAG laser can be found in the literature. Still, not a single study comparing the effects of this infrared laser in human and bovine teeth has been reported. Materials and Methods: Thirty-two slices of human and bovine enamel and dentin were evenly divided into four groups. With the exception of the control group, the samples were irradiated with Er:YAG laser, focused at a distance of 12 mm and a 10-Hz frequency, with 150, 250, and 350 mJ of output energy per pulse for 10 seconds. After irradiation all specimens were observed under a scanning electron microscope. Results: There was practically no morphological difference for those samples that underwent 150 mJ/pulse irradiation. The dentin exposed to 250 mJ had a few open dentinal tubules. These were seen in enamel after a 350 mJ irradiation, in which the energy was able to reach the dentin. Conclusions: the breadth of this study allows us to state that the pattern between the species grew more heterogenous as the energy density was increased and that irradiation with 150 mJ/pulse resulted in greater likeness in human and bovine enamel and dentin.

Measurement of low-derivative surface lenses by two-laser holography with Bi12TiO20 crystals

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Biomechanical effect of one session of low-level laser on the bone-titanium implant interface

Low-level laser (LLL) has been used on peri-implant tissues for accelerating bone formation. However, the effect of one session of LLL in the strength of bone-implant interface during early healing process remains unclear. The present study aims to evaluate the removal torque of titanium implants irradiated with LLL during surgical preparation of implant bed, in comparison to non-irradiation. Sixty-four Wistar rats were used. Half of the animals were included in LLL group, while the other half remained as control. All animals had the tibia prepared with a 2 mm drill, and a titanium implant (2.2 × 4 mm) was inserted. Animals from LLL group were irradiated with laser (gallium aluminum arsenide), with a wavelength of 808 nm, a measured power output of 50 mW, to emit radiation in collimated beams (0.4 cm2), for 1 min and 23 s, and an energy density of 11 J/cm2. Two applications (22 J/cm 2) were performed immediately after bed preparation for implant installation. Flaps were sutured, and animals from both groups were sacrificed 7, 15, 30, and 45 days after implant installation, when load necessary for removing implant from bone was evaluated by using a torquimeter. In both groups, torque values tended to increase overtime; and at 30 and 45 days periods, values were statistically higher for LLL group in comparison to control (ANOVA test, p < 0.0001). Thus, it could be suggested that a single session of irradiation with LLL was beneficial to improve bone-implant interface strength, contributing to the osseointegration process. © 2012 Springer-Verlag London Ltd.

Ablação de esmalte e dentina bovinos e humanos com laser de Ti:safira no regime de femtossegundos: análises morfológicas e fisico-químicas comparativas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Effects of Low-Level Laser Therapy on Biceps Braquialis Muscle Fatigue in Young Women

Objective: This study aims to investigate the effects of low-level laser therapy (LLLT) on biceps brachi muscular fatigue in 20 young females. Background data: Exhausting physical activity leads to muscular fatigue, which could decrease muscular strength, and may cause impairment in motor control and muscle pain. Several biochemical and biophysical resources have been studied in an attempt to accelerate the recovery of muscle fatigue. Among these, LLLT is emphasized. Methods: Twenty subjects were randomized in one laser group and one placebo group in two sessions of a crossover design experimental procedure; the second session taking place within 7 days of the first. In the first session, subjects underwent a collection of surface electromyographic (SEMG) data of the biceps brachii muscle, followed by active or placebo LLLT at the same muscle, followed then by another EMG sample of biceps brachii. Blood samples were collected five times during the experimental procedure. Second session procedures were identical to the first, with exception of LLLT, which was the opposite of the first session. The fatigue protocol consisted of 60sec of elbow flexion-extension movement performed with 75% of one maximum repetition. Blood lactate, EMG fatigue, and the number of elbow flexion-extension repetitions during the fatigue protocol were used to evaluate the effects of laser therapy (808nm wavelength, 100mW output power, power density of 35.7 W/cm(2), 70sec each point and 7J/point on eight points). Results: No statistical differences were found for eletromyographic fatigue and blood lactate values between groups. Mean numbers of elbow flexion-extension repetitions were 22.6 +/- 7.58 after placebo, and 25.1 +/- 9.89 after active LLLT group, but these differences were not statistically significant (p=0.342). Conclusions: LLLT had limited effects on delaying muscle fatigue in a young female sample, although a tendency was observed in the active laser group toward showing lower electromyography fatigue of biceps brachii muscle. No intergroup differences were found in the number of muscle contractions and lactate concentration.

Laser emission of a Nd-doped mixed tellurite and zinc oxide glass

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Laser stimulated piezoelectricity in Er3+ doped GeO2-Bi2O3 glasses containing silicon nanocrystals

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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

Effect of low-level laser therapy in an experimental model of osteoarthritis in rats evaluated through raman spectroscopy

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Lensometry by two-laser holography with photorefractive Bi12TiO20

Refractive and profilometric measurements of lenses were performed through holography with a photorefractive Bi12TiO20 crystal as the recording medium. Two properly aligned diode lasers emitting in the red region were employed as light sources. Both lasers were tuned in order to provide millimetric and sub-millimetric synthetic wavelengths. The surfaces of the test lens were covered by a 25-μm opaque plastic tape in order to allow the lens profilometry upon illuminating them with a collimated beam. The resulting holographic images appear covered by interference fringes corresponding to the wavefront geometry of the wave scattered by the lens. For refractive index measurement a diffusely scattering flat surface was positioned behind the uncovered lens which was also illuminated by a plane wave. The resulting contour interferogram describes the form of the wavefront after the beam traveled back and forth through the lens. The fringe quantitative evaluation was carried out through the four-stepping technique and the resulting phase map and the Branch-cut method was employed for phase unwrapping. The only non-optical procedure for lens characterization was the thickness measurement, made by a dial caliper. Exact ray tracing calculation was performed in order to establish a relation between the output wavefront geometry and the lens parameters like radii of curvature, thickness and refractive index. By quantitatively comparing the theoretical wavefront geometry with the experimental results relative uncertainties bellow 3% for refractive index and 1 % for focal length were obtained. © 2008 American Institute of Physics.