Continuous Diode Laser Research Articles

Surface reconstruction of porous substrates in sintered bronze by cw-high power diode laser

The present investigation deals with the application of a continuous wave-high power diode laser to modify the surface of porous substrates made from spherical particles in sintered bronze. In particular, the influence of laser power and interaction time on the capability of the laser processing to restructure the substrate morphology was investigated. Scanning Electron Microscope (SEM) and contact-gage surface profiler were used to analyze the evolution of the substrate morphology after laser treatments, whilst their mechanical properties were evaluated by micro-hardness and scratch tests.The experimental findings showed a decrease in the surface roughness of the porous substrates after laser treatments of ∼70%. In addition, an improvement in micro-hardness, scratch and wear resistance could also be achieved. Indeed, large laser power combined with high scan speed took to the most attractive results, thus favoring the onset of a promising morphological structure and the establishment of improved hardness and scratch resistance.

Laser surface modification (LSM) of thermally-sprayed Diamalloy 2002 coating

Thermally-sprayed Diamalloy 2002 is widely used as overlay coating in several applications for their good wear and corrosion protection. Although, in the past, any effort has been produced to deposit Diamalloy 2002 with a low degree of defectiveness, some residual porosity and cracks can often affect the final property of the resulting coatings. Different techniques are commonly used to improve the performance of Diamalloy 2002. Recently, laser post-treatment seems to be one of the most promising, being an effective, non-contact, mini-invasive technology.In this respect, the present investigation deals with the application of a continuous wave high power diode laser to post-treat Diamalloy 2002 deposited by HVOF on AA 6082 T6 aluminum alloy. Different laser power and scan speed were investigated in order to identify the process window most favorable to improve the overall mechanical property of Diamalloy 2002 coatings. The changes in morphology, micro-structure and chemical composition of the coatings after laser post-treatments were investigated by inductive gage profilometry and combined SEM-EDXS. Further, the changes in the mechanical properties of the coatings were investigated in terms of hardness, elastic modulus, scratch and wear resistance. Consistent improvements in mechanical property can be achieved by Diamalloy 2002 when laser processing is performed at higher power and reduced scan speed. Yet, too much increase in power density should be always avoided as it can be detrimental to the final property of the coatings and cause high defectiveness and their failure.

Development and characterization of a single particle laser ablation mass spectrometer (SPLAM) for organic aerosol studies

Abstract. A single particle instrument was developed for real-time analysis of organic aerosol. This instrument, named Single Particle Laser Ablation Mass Spectrometry (SPLAM), samples particles using an aerodynamic lens system for which the theoretical performances were calculated. At the outlet of this system, particle detection and sizing are realized by using two continuous diode lasers operating at λ = 403 nm. Polystyrene Latex (PSL), sodium chloride (NaCl) and dioctylphtalate (DOP) particles were used to characterize and calibrate optical detection of SPLAM. The optical detection limit (DL) and detection efficiency (DE) were determined using size-selected DOP particles. The DE ranges from 0.1 to 90% for 100 and 350 nm DOP particles respectively and the SPLAM instrument is able to detect and size-resolve particles as small as 110–120 nm. During optical detection, particle scattered light from the two diode lasers, is detected by two photomultipliers and the detected signals are used to trigger UV excimer laser (λ = 248 nm) used for one-step laser desorption ionization (LDI) of individual aerosol particles. The formed ions are analyzed by a 1 m linear time-of-flight mass spectrometer in order to access to the chemical composition of individual particles. The TOF-MS detection limit for gaseous aromatic compounds was determined to be 0.85 × 10−15 kg (∼4 × 103 molecules). DOP particles were also used to test the overall operation of the instrument. The analysis of a secondary organic aerosol, formed in a smog chamber by the ozonolysis of indene, is presented as a first application of the instrument. Single particle mass spectra were obtained with an effective hit rate of 8%. Some of these mass spectra were found to be very different from one particle to another possibly reflecting chemical differences within the investigated indene SOA particles. Our study shows that an exhaustive statistical analysis, over hundreds of particles, and adapted reference mass spectra are further needed to understand the chemical meaning of single particle mass spectra of chemically complex submicrometer-sized organic aerosols.

Chemical Vapor Deposition of Highly Adherent Diamond Coatings onto Co-Cemented Tungsten Carbides Irradiated by High Power Diode Laser

The present investigation deals with the definition of a new eco-friendly alternative to pretreat Co-cemented tungsten carbide (WC-Co) substrates before diamond deposition by hot filament chemical vapor deposition (HFCVD). In particular, WC-5.8 wt %Co substrates were submitted to a thermal treatment by a continuous wave-high power diode laser to reduce surface Co concentration and promote the reconstruction of the WC grains. Laser pretreatments were performed both in N(2) and Ar atmosphere to prevent substrate oxidation. Diamond coatings were deposited onto the laser pretreated substrates by HFCVD. For comparative purpose, diamond coatings were also deposited on WC-5.8 wt %Co substrates chemically etched by the well-known two-step pretreatment employing Murakami's reagent and Caro's acid. Surface morphology, microstructure, and chemical composition of the WC-5.8 wt %Co substrates after the different pretreatments and the deposition of diamond coatings were assessed by surface profiler, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction analyses. Wear performance of the diamond coatings was checked by dry sliding linear reciprocating tribological tests. The worn volume of the diamond coatings deposited on the laser pretreated substrates was always found lower than the one measured on the chemically etched substrates, with the N(2) atmosphere being particularly promising.

Effect of Laser Treatment on Olfactory Dysfunction

Olfactory disorders are not rare and affect quality of life in patients. The purpose of our study was to evaluate the outcomes of an outpatient-based diode laser inferior turbinate reduction (ITR) in otherwise therapy-refractory olfactory disorder. In a prospective clinical investigation, 20 patients (7 male, 13 female, mean age 53.2±15.34) with olfactory disorder and 10 patients (8 male, 2 female, mean age 52.5±17.55) without olfactory disorder underwent ITR under videoendoscopic control with a continuous diode laser in "contact" mode after topical anesthetic preparation. Treatment efficiency was assessed before and 2months after surgery. Subjective nasal airflow (NA) and the olfactory function were rated by means of visual analogue scales (VAS). Olfactory function was assessed using the "Sniffin' Sticks" test battery. VAS showed very low median values for intraoperative pain (0) [0-1.20] and high postoperative patient satisfaction (8) [5-9]. After 2months there was no significant improvement of objective olfactory function as measured by the TDI score (threshold, discrimination and identification). The VAS displayed a slight significant improvement in the group of patients with olfactory disorder from 2.95 to 3.65 (P=0.04). After 2months, NA data revealed a statistically significant improvement of subjective VAS from 5.05 to 6.25 (P<0.0005) and of objective NA from 353.77 to 443.50 (P=0.007) as measured by rhinomanometry in both groups. Outpatient diode laser ITR represents an effective option providing recovery by NA improvement but not a significant improvement of the olfactory function.

Effects of Superposed Continuous Diode Laser on Welding Characteristics for Aluminum Alloy in Pulsed Nd:YAG Laser Welding

Effects of Superposed Continuous Diode Laser on Welding Characteristics for Aluminum Alloy in Pulsed Nd:YAG Laser Welding

Association of laser phototherapy with PRP improves healing of bisphosphonate-related osteonecrosis of the jaws in cancer patients: A preliminary study

The aim of this study was to compare retrospectively the effect of three different treatments on the healing outcome of bisphosphonate-related osteonecrosis of the jaws (BRONJ) in cancer patients. Twenty-two cancer patients were treated for BRONJ with one of the following protocols: clinical (pharmacological therapy), surgical (pharmacological plus surgical therapy), or PRP plus LPT (pharmacological plus surgical plus platelet rich plasma (PRP) plus laser phototherapy (LPT). The laser treatment was applied with a continuous diode laser (InGaAlP, 660 nm) using punctual and contact mode, 40 mW, spot size 0.042 cm(2), 6 J/cm(2) (6 s) and total energy of 0.24 J per point. The irradiations were performed on the exposed bone and surrounding soft tissue. The analysis of demographic data and risk factors was performed by gathering the following information: age, gender, primary tumor, bisphosphonate (BP) used, duration of BP intake, history of chemotherapy, use of steroids, and medical history of diabetes. The association between the current state of BRONJ (with or without bone exposure) and other qualitative variables was determined using the chi-square or Fisher's exact test. In all tests, the significance level adopted was 5%. Most BRONJ lesions occurred in the mandible (77%) after tooth extraction (55%) and in women (72%). A significantly higher percentage of patients reached the current state of BRONJ without bone exposure (86%) in the PPR plus LPT group than in the pharmacological (0%) and surgical (40%) groups after 1-month follow-up assessment. These results suggest that the association of pharmacological therapy and surgical therapy with PRP plus LPT significantly improves BRONJ healing in oncologic patients. Although prospective studies with larger sample sizes are still needed, this preliminary study may be used to inform a better-designed future study.

Adhesion and wear resistance of CVD diamond coatings on laser treated WC–Co substrates

Abstract A novel method using a high power diode laser to selectively remove cobalt binder from the outermost layer of Co-cemented tungsten carbide (WC–Co 5.8 wt.%) is hereby discussed. A continuous 940-nm wavelength diode laser source at power of 600–1500 W and scanning speed of 1 mm/s was used to perform the thermal treatments. Hot Filament-Chemical Vapour Deposition (HF-CVD) was then used to deposit PolyCrystalline Diamond (PCD) coatings. Increasing the laser fluence, Co-binder was progressively and selectively evaporated from the WC–Co substrate. The selective removal of the Co-binder from the outermost layer of WC–Co induces a significant corrugation of the substrate, very promising to deposit on it high quality diamond with improved adhesion. Indeed, too much high laser fluence must be avoided, as it would tend to induce the resintering or the local melting of the tungsten carbide grains.

Irradiation at 636 nm Positively Affects Diabetic Wounded and Hypoxic Cellsin Vitro

This study investigated the effect of low-intensity laser irradiation (LILI) on pro-inflammatory cytokines involved in wound healing processes in diabetes and hypoxia. Diabetes is associated with impaired wound healing and a prolonged inflammatory phase. Pro-inflammatory cytokines such as interleukin (IL)-1β, tumor necrosis factor (TNF)-α and IL-6 are elevated in diabetes. LILI has been reported to accelerate wound healing and decrease inflammatory cytokines. A human skin fibroblast cell line (WS1) was used in vitro. Cells were exposed to various insults, namely, wounding, and a diabetic or hypoxic environment. Experimental cells were exposed to an energy density of 5 J/cm(2) using a continuous wave 636-nm diode laser at an average power of 95 mW, an illuminated area of 9.05 cm(2), and an irradiance of 11 mW/cm(2) (irradiation time, 476 sec). The effect of laser irradiation on cytokine expression was examined at 1 or 24 h post-irradiation. Cellular morphology, viability, proliferation, and cytokine expression (IL-1β, IL-6, and TNF-α) were investigated. Translocation of nuclear factor-kappa B (NF-κB) was also determined. There was a higher rate of migration in irradiated wounded cultures, and irradiated hypoxic cells showed an improvement in cellular morphology. All cell models showed an increase in proliferation. Normal wounded cells showed a decrease in apoptosis, TNF-α, and IL-1β. Diabetic wounded cells showed an increase in viability and a decrease in apoptosis and IL-1β, whereas hypoxic cells showed an increase in viability and IL-6, and a decrease in apoptosis and TNF-α. NF-κB was translocated into the nucleus post-irradiation. Phototherapy resulted in hastened wound closure, increased proliferation, and normalization of cellular function. The decrease in the different pro-inflammatory cytokines and NF-κB translocation was model and time dependent. Overall, laser irradiation resulted in a reduction in inflammatory cytokines and directed cells into the cell survival pathway.

Laser Micro Welding System and its Application to Seam Welding of Rechargeable Battery

The welding of aluminum alloys has been increasing in demand for lightening electronic products and automobiles. The authorshave developed hybrid laser system which is consisted of a pulsed Nd:YAG laser and a continuous diode laser (hereafter LD) inorder to perform the high efficiency and high quality welding of aluminum alloys. A pulsed Nd:YAG laser of 1064nm inwavelength and a continuous LD of 808nm in wavelength are superposed on the same beam axis, and the superposed laser beamsof two wavelengths are delivered to the processing head through an optical fiber. The bead width and depth increases with thepower of continuous LD, which leads to overlapping welding even under a high speed condition.

3245 Effect of Continuous Diode Laser on Crack Generation in Pulsed Nd:YAG Laser Welding of Aluminum Alloy

3245 Effect of Continuous Diode Laser on Crack Generation in Pulsed Nd:YAG Laser Welding of Aluminum Alloy

Co removal and phase transformations during high power diode laser irradiation of cemented carbide

The use of a continuous wave-high power diode laser for removing surface Co-binder from Co-cemented tungsten carbide (WC–Co (5.8wt%.)) hardmetal slabs was investigated. Combined scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction analyses were performed in order to study the phase transformations and micro-structural modifications of the WC–Co substrates occurring during and after laser irradiation. The micro-structure of the WC–Co progressively transforms as energy density increased, exhibiting stronger removal of Co and WC grain growth. At very high energy density, local melting of the WC grains with the formation of big agglomerates of interlaced grains is observed, and the crystalline structure of the irradiated substrate shows the presence of a brittle ternary eutectic phase of W, Co and C (often referred to as the η-phase). The latter can be detrimental to the mechanical properties of WC–Co. Therefore, the proper adjustment of the laser processing parameters plays a crucial role in surface treatments of WC–Co substrates prior to post-processing like diamond deposition.

Prognostic Value of Anterior Rhinomanometry in Diode Laser Turbinoplasty

To identify objective criteria predicting the success of diode laser-assisted turbinoplasty. Prospective before-and-after trial with follow-up of 8 weeks. Outpatient department of a tertiary referral center. Forty-one patients with nasal obstruction caused by hyperplastic inferior nasal turbinates. Active anterior rhinomanometry with and without decongestion was used to assess the patients both before and after diode laser-assisted turbinate surgery. Surgery was performed under local anesthesia in "contact mode" using a continuous diode laser. In addition, a questionnaire assessed the subjective postoperative benefit. Presurgical effect of topical decongestion was correlated with postoperative improvement of nasal airflow and patients' subjective satisfaction. Turbinoplasty significantly improved the mean (SD) nasal airflow by 37.1% (52.4%) (95% confidence interval [CI], 20.6%-53.7%), from 509.8 (189.2) cm³/s (95% CI, 450.1-569.5) to 660.9 (285.4) cm³/s (95% CI, 570.8-751.0) (P < .001). There was no significant correlation between patients' subjective satisfaction and improvement of nasal airflow postoperatively (r(s) = -0.01; P = .93). There was a strong correlation between the presurgical effect of topical decongestion and the improvement of nasal airflow by surgery (r(s) = 0.42; P = .01). The correlation was even stronger when the absolute values were adjusted by the preoperative nasal airflow baseline (r(s) = 0.55; P = .01). Rhinomanometry with topical decongestion has a high predictive value for the objective outcome of diode laser-assisted turbinoplasty. Thus, performing a rhinomanometry with topical decongestion and calculating the relative spread of decongestion can help to estimate the patients' benefit from diode laser-assisted turbinate surgery.

Investigation on Welding Phenomenon for Aluminum Alloy by Superposition of Pulsed YAG Laser and Diode Laser

A pulsed Nd:YAG laser and a continuous diode laser were spatially superposed for higher absorption of laser beam to aluminum alloy. 12-20% increase in the bead width and 15-30% increase in the weld depth could be obtained by the superposition of continuous diode laser and pulsed Nd:YAG laser. Moreover, the unsteady thermal analysis with a key-hole effect indicated that the temperature of specimen surface with a continuous diode laser could be kept approximately 300K higher than that without a continuous diode laser. Therefore, it was clarified that the bead width and depth would increase greatly due to higher absorption of Nd:YAG laser to aluminum alloy by the superposition of a continuous diode laser.

The effect of continuous and pulsed beam modes on cut path deviation in diode laser cutting of glass

During laser cleaving of brittle materials, with the controlled fracture technique, thermal stresses are generated which induce the crack and extend it along the cutting path, subsequently causing material separation. One of the problems in laser cutting of glass with this technique is the cut path deviation at the leading and the trailing edges of the glass sheet. Previous work with a continuous beam diode laser has shown the deviation to be partly due the high magnitudes of thermal stresses generated near the edges of the sheet. This paper reports on the effects of using a pulsed diode laser to cut soda lime glass. The effect of pulse parameters and cutting speed on the quality output variables such as cut deviation angle and surface finish are studied. Finite element modelling is also used to simulate the effects of the moving beam on stress generations to facilitate the understanding of the process mechanisms, and the results are compared with the experimental data. This work shows how to minimise the cut path deviation at the edges by reducing thermal stresses using optimum pulsed diode laser parameters and providing additional flexibility to the process.

Effect of phototherapy with low intensity laser on local and systemic immunomodulation following focal brain damage in rat

Brain injury is responsible for significant morbidity and mortality in trauma patients, but controversy still exists over therapeutic management for these patients. The objective of this study was to analyze the effect of phototherapy with low intensity lasers on local and systemic immunomodulation following cryogenic brain injury. Laser phototherapy was applied (or not-controls) immediately after cryogenic brain injury performed in 51 adult male Wistar rats. The animals were irradiated twice (3 h interval), with continuous diode laser (gallium–aluminum–arsenide (GaAlAs), 780 nm, or indium–gallium–aluminum–phosphide (InGaAlP), 660 nm) in two points and contact mode, 40 mW, spot size 0.042 cm 2, 3 J/cm 2 and 5 J/cm 2 (3 s and 5 s, respectively). The experimental groups were: Control (non-irradiated), RL3 (visible red laser/ 3 J/cm 2), RL5 (visible red laser/5 J/cm 2), IRL3 (infrared laser/3 J/cm 2), IRL5 (infrared laser/5 J/cm 2). The production of interleukin-1IL-1β (IL-1β), interleukin6 (IL-6), interleukin-10 (IL-10), and tumor necrosis factor-α (TNF-α) was analyzed by enzyme immunoassay technique (ELISA) test in brain and blood samples. The IL-1β concentration in brain of the control group was significantly reduced in 24 h ( p < 0.01). This reduction was also observed in the RL5 and IRL3 groups. The TNF-α and IL-6 concentrations increased significantly ( p < 0.01 and p < 0.05, respectively) in the blood of all groups, except by the IRL3 group. The IL-6 levels in RL3 group were significantly smaller than in control group in both experimental times. IL-10 concentration was maintained stable in all groups in brain and blood. Under the conditions of this study, it is possible to conclude that the laser phototherapy can affect TNF-α, IL-1β and IL-6 levels in the brain and in circulation in the first 24 h following cryogenic brain injury.

Improvement in Quality of Life of An Oncological Patient by Laser Phototherapy

Common side effects of radiotherapy (RT) to the head and neck include oral mucositis, xerostomia, and severe pain. The aim of this study is to report improvement in the quality of life of an oncological patient by laser phototherapy (LPT). The patient, a 15-year-old girl diagnosed with mucoepidermoid carcinoma, underwent surgical excision of a tumor of the left palatomaxilla. After that, she was subjected to 35 sessions of RT (2 Gy/d). Clinical examination revealed the spread of severe ulcerations to the jugal mucosa, gums, lips, hard palate, and tongue (WHO mucositis score 3). She had difficulty in moving her tongue and she was unable to eat any solid food. Oral hygiene orientation and LPT were performed throughout all RT sessions. A continuous diode laser, 660 nm, 40 mW, 6 J/cm(2), 0.24 J per point in contact mode, with spot size of 0.04 cm(2) was used in the entire oral cavity. A high-power diode laser at 1 W, 10 sec per cm of mucositis, approximately 10 J/cm(2), was used in defocused mode only on ulcerative lesions. After the first laser irradiation session, decreases in pain and xerostomia were reported; however, a more significant improvement was seen after five sessions. At that point although the mucositis score was still 2, the patient reported that she was free of pain, and consequently a palatine plate could be made to rehabilitate the entire surgical area. Seventeen laser irradiation sessions were necessary to eliminate all oral mucositis lesions. Normal oral function and consequent improvements in the quality of life of this oncologic patient were observed with LPT.

High Efficiency and High Quality Welding of Aluminum Alloy by Hybrid System Combined Nd:YAG Laser and Diode Laser

Recently the welding of aluminum alloy has been strongly required for the lightening the electronic products, the automobiles and so on. Then the hybrid laser system was newly developed in order to perform the high efficiency and high quality welding of aluminum alloy. The high electric-optical conversion efficiency was achieved by the new diode pumped pulsed Nd:YAG laser. The hybrid system is consisted of a newly developed pulsed Nd:YAG laser and a continuous diode laser, and it can deliver two lasers by one fiber. Higher absorption of laser energy into the aluminum alloy can be expected under the continuous irradiation of diode laser (λ= 808 nm), since the absorption into aluminum alloy shows the maximum at λ= 850 nm. The suitable bead width and depth could be obtained with better surface integrity when the pulse waveform took the highest peak at the first period. The bead width and depth increased with increasing the power of continuous diode laser, which leads to overlapping welding even under high speed condition. Moreover, the high efficiency and high quality welding of aluminum battery case could be accomplished by the newly developed hybrid system, in which the suitable pulse energy and the peak power could be given even under the high pulse repetition rate.

The nonlinear optical properties and photoinduced anisotropy of a novel stilbene-containing fluorinated polyimide

The nonlinear optical properties and photoinduced anisotropy of a novel stilbene-containing fluorinated polyimide were investigated. Large macroscopic second-order optical nonlinearity ( d 33 = 35.4 pm/V) was obtained in a poled thin film using the Maker fringe method. A nonlinear absorption coefficient ( β) of 0.65 × 10 −5 cm/W and third-order nonlinear refractive index ( n 2) of −1.13 × 10 −10 cm 2/W were determined by Z-scan measurements. Photoinduced birefringence (Δ n) of 1.02 × 10 −2 was observed using a continuous Nd:YAG laser at 532 nm as pump light and a continuous diode laser at 650 nm as probe light.

Effect of diode laser on motility, plasma and acrosomal membrane integrity, and mitochondrial membrane potential of cryopreserved stallion spermatozoa

ao). Sperm motility depends on energy consumption. In some species sperm mitochondria play an important role in the production of energy for tail activity. Low-level laser irradiation increases this production as a modulation tool. The objective of this study was to analyze the effect of a continuous 650-nm wave length diode laser irradiation with 6 J/cm 2 for 120 s, in the motility, plasma and acrosomal membrane integrity and mitochondrial membrane potential in fresh and frozen equine spermatozoa. Five ejaculates were obtained from each of five stallions (n = 25). Semen was packaged into 0.5-mL straws with 200 × 10 6 cells/mL in a Botu-Crio TM (Biotech- Botucatu-Ltda/ME, Botucatu, Brazil) and frozen by automated technique using a programmed machine (TK3000 ® , TK Tecnologia em Congelac ¸ ˜ ao-Ltda, Uberaba, Brazil). Fresh samples were divided in two groups: spermatozoa treated with laser and Control 1—non-treated spermatozoa. Frozen samples were divided in three groups: spermatozoa treated with laser before freezing; spermatozoa treated with laser after thawing and Control 2—cryopreserved spermatozoa. Cryop- reserved samples were analyzed immediately after thawing (time 0) and 2 h after thawing (time 2). Motility was evaluated by computer assisted sperm analyzer (CASA, Ivos-Ultimate of Hamilton Thorne Biosciences), plasma and acrosomal membrane integrity and mitochondrial membrane potential were evaluated by flow cytometry (FACSaria-Beckton-Dickeson, San Jose, USA). The data were analyzed by the SAS program, at 5% level of significance. Beat cross frequency (BCF) test was higher (p 0.05) from the other groups at time 2, but at time 0 the percentage of progressive motility was lower (2.0 ± 0.3%) and different (P < 0.05) from the other groups (6.5 ± 1.3% in spermatozoa treated with laser before freezing; 5.5 ± 1.1% in Control 2). These results indicated that the irradiation with 650-nm wave length diode laser improves beat cross frequency in fresh semen and provides a long-term (2 h) protection for plasma and acrosomal membranes of equine spermatozoa. New studies with different diode laser wave length should be driven in order to improve stallion semen cryopreservation.