Blue diode laser and its applications in manufacturing: A brief review

In this study, the efficacy of using Sauropus androgynus (L) Merr, a katuk leaf chlorophyll photosensitizer, to reduce Aggregatibacter actinomycetemcomitans and Enterococcus faecalis biofilm was investigated. A red and blue diode laser is used as the light source. The sample was split into four groups: a negative control group, a positive control group, a blue laser treatment group (B), and a red laser treatment group (R), both with and without the addition of katuk leaf chlorophyll 1.6 mg/ml, and with varying densities of laser energy exposure of 2.5 J/cm2, 5 J/cm2, 7.5 J/cm2, and 10 J/cm2. Laser exposure and chlorophyll photosensitizer were tested using ELISA and ANOVA. At an energy density of 10 J/cm2, the optimal bacterial mortality rate was obtained in each treatment group. Namely, in the Aggregatibacter actinomycetemcomitans biofilm, the negative group, the number of deaths was 73.30% using a blue diode laser and 63.25% using a red diode laser. In the positive group, the number of deaths was 86.12% using a blue diode laser and 83.29% using a red diode laser. In the Enterococcus faecalis biofilm, in the negative group, the number of deaths was 67.78% using the blue diode laser and 75.33% using the red diode laser, and in the positive group, the number of deaths was 71.71% using the blue diode laser and 86.41 using a red diode laser. Exposure to blue and red diode lasers activates chlorophyll in katuk leaves, killing bacteria and reducing biofilms.

The aim of this in vitro study was to evaluate the effect of radiant heat on surface hardness of three conventional glass ionomer cements (GICs) by using a blue diode laser system (445nm) and a light-emitting diode (LED) unit. Additionally, the safety of the laser treatment was evaluated. Thirty disk-shaped specimens were prepared of each tested GIC (Equia Fil, Ketac Universal Aplicap and Riva Self Cure). The experimental groups (n = 10) of the study were as follows: group 1 was the control group of the study; in group 2, the specimens were irradiated for 60s at the top surface using a LED light-curing unit; and in group 3, the specimens were irradiated for 60s at the top surface using a blue light diode laser system (445nm). Statistical analysis was performed using one-way ANOVA and Tukey post-hoc tests at a level of significance of a = 0.05. Radiant heat treatments, with both laser and LED devices, increased surface hardness (p < 0.05) but in different extent. Blue diode laser treatment was seemed to be more effective compared to LED treatment. There were no alterations in surface morphology or chemical composition after laser treatment. The tested radiant heat treatment with a blue diode laser may be advantageous for the longevity of GIC restorations. The safety of the use of blue diode laser for this application was confirmed.

A hybrid laser system which combines preheating with a blue diode laser with welding with a single mode fiber laser was developed to realize a highly efficient laser welding of copper. With the hybrid laser system, the blue diode laser and the single mode fiber laser were combined coaxially and a stair shape beam profile was formed at the processing point. Each laser was irradiated to a copper sample and the output power of the blue diode laser was varied to investigate an effect of preheating with it on the welding with the single mode fiber laser. The melting and solidification dynamics of copper was evaluated with a high speed video camera and a thermo camera. As the results, it was found that the melting volume of copper and the temperature at the processing point increased by preheating with the blue diode laser. The copper wire with 2.0×3.5×50 mm was weld in 0.3sec by using hybrid laser with 1kW single mode fiber laser and 200W blue diode laser. Thus, it was concluded that a highly efficient welding of copper was achieved with the preheating with the blue diode laser.

Three lasers were directly compared, including the Ho:YAG laser (λ = 2100 nm), Tm fiber laser (λ = 1940 nm) operating in 3 different modes (CW, regular pulse, and super pulse), and blue diode laser (λ = 442 nm) for vaporization and coagulation efficiency for treating blood-rich soft tissues, ex vivo, in a porcine kidney model at quasi-contact cutting in water. In addition, experimental results were compared with published data on performance of KTP laser (λ = 532 nm) at similar experimental settings (Power = 60 W and cutting speed = 2 mm/s). Tm fiber laser in pulsed mode and blue laser produced highest vaporization rates of 3.7 and 3.4 mm3/s, respectively. Tm fiber laser (in both CW and pulsed modes) also produced the largest coagulation zone among the laser sources tested. A carbonization zone was observed for Tm fiber laser in CW and pulsed modes, as well as for the blue diode laser. Tm fiber laser in super-pulse mode and Ho:YAG laser both resulted in irregular coagulation zones without carbonization. Comparison with known data for KTP laser revealed that tissue effects of the blue laser are similar to that of the KTP laser. These results suggest that the combination of the two lasers (Tm fiber and blue diode) in one system may achieve high cutting efficiency and optimal coagulation for hemostasis during surgical treatment. Ex vivo testing of the combined system revealed feasibility of this approach. The combination of the CW Tm fiber laser (120W) and the blue diode laser (60W) emitting through a combination tip were compared with CW 120 W Tm fiber laser alone and 120 W Ho:YAG laser. Vaporization rates measured 34, 28, and 6 mm3/s, and coagulation zones measured 0.6, 1.3, and 1.7 mm, respectively. A carbonization zone was only observed with CW Tm fiber laser. The vaporization rate of combined CW Tm fiber laser / blue diode laser was comparable to published data for KTP laser for equivalent total power. Thus, high-power blue diode laser, Tm fiber laser, and their combination may provide an alternative to conventional Ho:YAG and KTP lasers for applications in urology and other surgical fields.

Effects of blue diode laser (445 nm) and LED (430–480 nm) radiant heat treatments on dental glass ionomer restoratives

Laser metal deposition of pure copper on stainless steel with blue and IR diode lasers

Laser cladding technique is widely used for industrial application such as oil, energy industry, and aircraft and so on because it is able to repair and to form a near net shape. This process have been employed infrared lasers with wavelength of 0.8-10.6μm since output power of these lasers have over 1000W. Metal processing efficiency was, however, low in these wavelength, because the absorption was low. Thus, we developed the laser cladding system with blue direct diode laser at the wavelength of 445nm. 6 blue diode lasers was combined on the focusing spot to reach the output power of 100W by a lens, which one blue diode laser module was maximum output power of 20W. By using this laser cladding system, a pure copper film coating on a SUS304 stainless steel plate was demonstrated from a copper powder. As the result, the copper layer was formed on SUS304 stainless steel plate at the width of 322μm and thickness of 534μm was formed on the substrate.

Mobile laser projection is of great commercial interest. Today, a key parameter in embedded mobile applications is the optical output power and the wall plug efficiency of blue and green lasers. We report on improvements of the performance of true blue riedge waveguide InGaN lasers at 452nm with cw-output power up to 800mW in overstress and mono mode operation up to 500mW in a temperatures range of 20°C to 80°C. We succeeded in high and almost temperature independent wall plug efficiencies >20% at stable output power levels from 200 to 500mW in cw-operation. Due to several improvements of our blue laser diodes we now estimate life times is in the order of 40khrs for 80mW output power in cw-operation at 40°C. Additional overstress degradation tests at power levels up to 200mW show a strong dependency of lifetime with output power. Furthermore, we present pioneering results on true green InGaN laser diodes on c-plane GaN-substrates. The technological challenge is to achieve In-rich InGaN-quantum wells with sufficiently high material quality for lasing. We investigated the competing recombination processes below laser threshold like nonradiative defect recombination by electro-optical measurements, such confirming that low defect densities are essential for stimulated emission. A model for alloy fluctuations in In-rich InGaN-MQWs based on spectral and time resolved photoluminescence measurements yields potential fluctuations in the order of E0=57meV for our blue laser diodes. To get a closer insight into the physics of direct green InGaN-Laser we investigated the inhomogeneous broadening of experimentally measured gain curves via Hakki-Paoli-measurements in comparison to calculated gain spectra based on microscopic theory showing the importance of strong LO-phonon coupling in this material system. Investigations of current dependent gain measurements and calculations yield a factor of 2 higher inhomogeneous broadening for our green lasers than for our blue laser diodes on c-plane GaN. Based on the improvements of the material quality and design we demonstrate true green InGaN-Laser in cw-operation at 522nm with more than 80mW output power on c-plane GaN. The combination of low laser threshold ~60-80mA, high slope efficiency ~0.65W/A and low operating voltage 6.9-6.4V of our green monomode RWG-Laser results in a high wall plug efficiency of 5-6% in a temperature range of 20-60°C.

In order to clarify the mechanism of copper layer formation, real-time temperature measurement in the film formation process when forming a copper layer using a blue direct diode laser was performed using a thermal imaging camera. Pure copper is widely used for heat sink, electro-circuit and so on because of highly thermal conductivity and electro-conductivity. Although a thermal spray method and an electro less plating method are industrial applied for copper layer formation, these methods have some issues, such as low adhesive strength and poor layer. Therefore, we tried laser cladding method using a blue direct diode laser. We developed a laser cladding system using a 100 W class blue direct diode laser which converges the laser emitted from the six blue direct diode laser modules into one point by the multiple laser processing head. We have clarified that the cladding velocity depends on the scanning speed of the stage by forming a copper layer on a stainless steel substrate using the equipment we developed and observing the cross section of the copper layer. In this study, the mechanism of layer formation at the time of forming the copper layer was clarified by measuring the change in the temperature distribution at the time of forming the copper film using the thermal imaging camera in real time.In order to clarify the mechanism of copper layer formation, real-time temperature measurement in the film formation process when forming a copper layer using a blue direct diode laser was performed using a thermal imaging camera. Pure copper is widely used for heat sink, electro-circuit and so on because of highly thermal conductivity and electro-conductivity. Although a thermal spray method and an electro less plating method are industrial applied for copper layer formation, these methods have some issues, such as low adhesive strength and poor layer. Therefore, we tried laser cladding method using a blue direct diode laser. We developed a laser cladding system using a 100 W class blue direct diode laser which converges the laser emitted from the six blue direct diode laser modules into one point by the multiple laser processing head. We have clarified that the cladding velocity depends on the scanning speed of the stage by forming a copper layer on a stainless steel substrate using the equipment we dev...

Due to high metal absorptivity, the 450nm blue diode laser revolutionizes the processing of high reflection metal (Cu, Au, SS), with its sputtering free, stable melt pool, and good surface quality. Therefore, high power blue diode laser can be used in the 3C field, electrical vehicle, and additive manufacturing fields. Moreover, low power blue diode laser can also be used for wood carving, laser display, and medical use. BWT Ltd was founded in 2003 in Beijing, China. For over 18 years, BWT has specialized in developing and manufacturing high-performance diode lasers for customers all over the world. BWT blue diode laser team has successfully launched the 1000Watt 330um 0.22NA high brightness 450nm blue diode laser in January of 2021. BWT blue diode laser products can be listed into three categories, according to their power range and applications. High power- metal processing 1KW 330um 0.22NA 500W 220um 0.22NA Middle power-3C field, laser display. 300W 200um 0.22NA 150W 105um 0.22NA Low power-wood craving, medical use. 50W 200um 0.22NA 30W 105un 0.22NA 3W 105um 0.22NA The advantages of BWT blue diode laser are high cost performance, a wide range of output powers, professional RD group, customer-oriented service, high stability and reliability, compact size, etc. Besides blue diode laser, BWT also provides other competitive products, such as: Medical multi-wavelength diode laser Wavelength locked pumping diode laser Vertical stack and fiber-coupled bar products Fiber laser and ultrafast laser. Please feel free to contact BWT through the channels below: Website: https://www.bwt-bj.com/en Email: sales@bwt-bj.com Telephone: +86-10-83681052/3/4

Researchers at the University of California, Santa Barbara, have achieved the highest ever power output and efficiency for a blue laser diode on a semipolar GaN substrate. Semipolar substrates are cut at a different angle from the standard c-plane of the crystal, and are predicted to result in more effective laser operation. Despite the advantages, such as higher gain and efficiency, several technological challenges have limited the efficacy of these semipolar substrates in most applications. Blue laser diodes can excite other phosphors to emit different wavelengths, resulting in white light The Santa Barbara team, however, have overcome these challenges through a polishing process, and the resulting laser demonstrates stable, continuous wave operation with high optical power densities. This could lead to greatly improved solid-state systems in all lighting, imaging, and display systems. Solid-state lighting systems are lighting systems based on semiconductor devices, typically diodes, and use considerably less power than traditional light sources, as explained by Robert Farrell, one of the authors and a researcher at UC Santa Barbara: “they are used primarily because they are more efficient than traditional white light sources such as incandescent or fluorescent lighting.” Quantifying this difference in efficiency makes the advantages of solid-state systems very clear, said Farrell, telling us that “incandescent bulbs and linear florescent bulbs use ∼15 lm/W and ∼100 lm/W, respectively, while state-of-the-art solid-state lighting systems operate at ∼150 lm/W and this is expected to surpass 200 lm/W as further developments in the technology are made.” The current generation of commercially available systems use LEDs for excitation. For lighting purposes, “the semiconductor device emits photons in the violet or blue range of the spectrum,” said Farrell, “and these excite one or more phosphors that emit in other regions of the visible spectrum. The combined emission of light from the semiconductor devices and the phosphors is used to produce high quality white light.” While LED lighting technology is relatively mature and developed, laser diode approaches show even more promise in terms of power and efficiency. Efficiency is not the only advantage, however, as the laser diodes have both the potential to decrease the cost of solid-state lighting systems, as well as to improve the directional control of light emission as lasers are a natural point source. Laser diodes naturally require a substrate cavity for operation. This cavity can be oriented at various angles to the substrate's crystal structure. Standard (polar or c-plane substrate) lasers use mirror facets formed by cleaving the semiconductor wafer along a crystallographic plane. This is not, however, the best solution. Non-polar substrates show greater promise than their polar counterparts, but for laser cavity orientations on semipolar crystal planes “there is not an orthogonal crystallographic plane that can be used for cleaving mirror facets,” explained Farrell. The consequences of this are fairly drastic as other techniques, such as dry etching or polishing, are therefore necessary. Unfortunately, it has not been clear if these techniques are stable under high optical power densities. The achievement of the UC Santa Barbara team has been, according to Farrell, “to show that polishing can be used to create mirror facets for semipolar blue laser diodes that are smooth, perpendicular to the laser cavity, and stable under CW operation with high optical power densities (greater than 30 MW/cm2).” Showing that blue semipolar laser diodes with polished mirror facets are stable during CW operation with high optical power densities firmly establishes them as a viable alternative to c-plane laser diodes. Is the story then complete? The team's results certainly represent an important step in the development of semipolar laser diodes for laser-based solid-state lighting. However, laser diode lighting is still at an early stage - shortcomings in the technology are still apparent. “In particular,” said Farrell, “the wall plug efficiency (currently around 40%) needs to be improved, and new phosphor geometries need to be developed for integration with laser diodes.” The mechanically polished facet Once these issues have been addressed, Farrell told us that the team expect, as the efficiency of laser diodes improves over time, “it will be possible for laser-based solid-state lighting systems to find applications in all areas of general lighting.”

The objective of this study was to examine a new blue light diode laser system (445nm) for dental soft tissue surgery on cellular level. An in vitro cell culture model was established to evaluate the effects of the 445-nm diode laser in comparison to an established infrared diode laser (IR). Monolayer cell cultures were irradiated and wound healing was morphometrically measured. Fluorescence staining was used for proof of potential DNA double-strand breaks as well as cytoskeleton alterations. Cellular live/dead discrimination was performed and temperature development during laser irradiation was measured with a thermographic infrared camera. A characteristic zone formation was detected after irradiation with both wavelengths. Despite a larger wound area after irradiation with 445nm, due to its higher temperature development, this laser system showed a faster wound healing in comparison to the IR laser. No increase of devitalized cells was documented with higher distances between laser tip and cell layer and thus without thermal interaction. Neither cytoskeleton alteration nor DNA double-strand breaks could be recorded after irradiation in non-contact mode. The blue diode laser system demonstrated an excellent direct thermal coupling to cells and tissues without side effects even by reduced power settings. The blue diode laser seems to be a promising technology for clinical application due to high absorption of blue light without major side effects in adjacent tissues even by reduced power settings.

This paper reports the latest device performance of high-power blue and green edge-emitting Laser Diodes (LDs). The epitaxial layers of LDs were grown by Metal Organic Chemical Vapor Deposition (MOCVD) on C-plane free-standing GaN substrates. And a ridge type structure was formed at the top of p-type layers. Fabricated every LD chip was mounted on a heat sink using a junction down method in a TO-Φ9 mm package. We optimized the epitaxial and the device structures for high efficiency and high optical output power. A new developed 455 nm blue LD showed the optical output power and the voltage of 5.90 W and 3.81 V at the forward current of 3 A under Continuous Wave (CW) operation. The wall-plug efficiency (WPE) of the 455 nm blue LD was 51.6 % at 3 A. This is the highest WPE reported so far. The peak WPE of the 455 nm LD was 52.4 % at the forward current of 2.2 A. And a new developed 525 nm green LD showed the optical output power and the voltage of 1.86 W and 4.12 V at the forward current of 1.9 A under CW operation. The wall-plug efficiency (WPE) of the 525 nm green LD was 23.8 % at 1.9 A. This is the highest WPE reported so far. The peak WPE of the 525 nm LD was 25.9 % at the forward current of 1.1 A.

Laser metal deposition (LMD), which is one of the additive manufacturing technologies, is suitable for making 3D objects with complex shapes. In this method, a blue diode laser is used to explore the formation of pure copper parts because of the high light absorption of pure copper in blue light. Inspired by this method, in this study, we developed a high-power blue diode laser with a wavelength of 450 nm. This laser had an output power of 100 W and a fiber core diameter of 100 μm. We also developed a multibeam LMD system with the blue diode laser in which metal powder was supplied perpendicularly to the processing point and multiple lasers were irradiated from the surroundings for additively manufactured pure copper. We investigated the differences in copper layer formation that are dependent on the properties of substrates. Upon using the multibeam LMD system, a pure copper layer formed on pure aluminum and stainless-steel substrates. The interaction of pure copper powder and the substrates was observed using a high-speed video camera. After laser irradiation, copper cladding samples were observed with an optical microscope and scanning electron microscope and energy dispersive x-ray spectroscopy to evaluate the cross-sectional area of the pure copper layer and the dilution zone. As a result, a pure copper layer formed on the aluminum surface under the laser irradiation condition under which the aluminum substrate was not subjected to melting by heating with the blue laser. It was suggested that the pure copper powder heated by the laser melted the aluminum and formed a copper layer on the aluminum substrate.

Due to the precise vaporization of the novel 450 nm blue diode laser in soft tissues (i.e., bladder and colon) in our previous studies, porcine stomach tissues were applied here to certify its efficacy in endoscopic mucosal resection (ESR)/endoscopic submucosal dissection (ESD) for hypothetical lesions ex vivo and in vivo. In an ex vivo study of ESR, 20 pieces of tissues (8 cm × 6 cm) from 7 fresh stomachsafter spraying saline were vaporized with a three-dimensional scanning system using the blue diode laser at a maximum of 30 W, a different treatment speed and working distance (WD). In ex vivo ESD, 18 pieces of tissues from 6 fresh stomachs were used and the same laser parameters were used to perform the procedure. The depth, width, and coagulation of the laser vaporization were measured. Furthermore, the large scales (2.0 cm × 1.5 cm) for 18 hypothetical lesions of the gastric mucosa and submucosa of the 6 fresh stomachs were also resected with a modified flexible endoscope. In vivo, six hypothetical lesions of six porcine were vaporized by the novel blue laser, and the resultant lesions at the acute and chronic stages were assessed by the naked eye and hematoxylin and eosin staining. In the contact mode, more tissue was vaporized, and the thickness of the coagulation was stable when the WD was 0-2 mm, whosevalue varied from 0.33 to 1.73 mm. In the gastroscopy model, the mean thickness of coagulation from the mucosa was 0.67 mm, and a significant carbonization zone was not observed. In vivo, the laser beam could accurately act on the hypothetical target. No bleeding and clear vision were present in the procedure. After 3 weeks, tissue healing was well recovered after laser coagulation, resection, and submucosal dissection. In the present study, the novel 450 nm blue diode laser exhibited ideal vaporization and thinner coagulation thickness in the porcine stomach, which indicated that it could be alternately used as a new device for stomach lesions.