This report shows the latest developments of Gallium nitride (GaN)-based blue (455nm) and green (525nm) edge-emitting laser diodes (LDs). The epitaxial layers were grown on c-plane free-standing GaN substrates by metal-organic chemical vapor deposition (MOCVD), and a ridge-type structure for refractive-index waveguide was fabricated. Each LD chip was mounted on a heat sink in a TO-Φ9 mm CAN package by a junction down method for improving thermal dissipation. Optimization of epitaxial layers and device structures has led to improve the wall-plug efficiency (WPE) of LDs. The WPE and the optical output power of the blue LD have reached to 52.4% and 5.99 W at the current of 3.0 A under continuous wave (CW) operation, respectively. We also confirmed that the WPE and the optical output power of the green LD were 24.2 % and 1.90 W at the CW current of 1.9 A, respectively. Each WPE is the highest value ever reported of blue and green LDs. On top of this, the lifetime tests of both LDs over 1000 hours indicate the long lifetime more than 30,000 hours defined by the time when an optical output power is expected to be lower than the half of initial value.
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.
This paper reports the latest device performance of high-power blue laser diodes (LDs). The epitaxial structures 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. The ridge width of the LD was 45 μm. Electrodes of the n-type and p-type were formed at the substrate and the ridge respectively. And the front and rear sides were obtained by cleavage at the m-plane surface. These faces were covered by dielectric mirrors. Every LD chip was mounted on a heat sink using a junction down method in a TO-Φ9 mm package for suppressing thermal resistance. 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 5.73 W and 3.82 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 50.0 % at 3 A. This is the highest WPE reported so far. The peak WPE of the 455 nm LD was 51.2 % at the forward current of 2 A.
Copper is widely used in many industries due to its high electrical conductivity, and copper welding is significant technology. High power near-infrared fiber lasers have been used in laser material processing in many fields since they provide high electric-optic conversion efficiency and excellent laser beam quality. However, copper welding with nearinfrared fiber lasers is challenging. Absorption of copper is low for near-infrared radiation, and copper diffuses heat rapidly at welding spots due to its high thermal conductivity. Previously we reported a hybrid laser system with a 150-W blue laser and a 1-kW near-infrared fiber laser for copper welding. Blue laser irradiation generates stable molten pool at welding spots due to high absorption of copper at the wavelength, and it assists near-infrared fiber laser to generate stable and spatter-less welding during the process. In this paper, we present a hybrid laser system with a 1-kW blue laser and a 3-kW near-infrared laser. The blue laser consists of blue laser diode modules with 250-W optical output power from optical fiber with 110-m core diameter. The laser diode modules contain blue laser diode chips in side lead packages, and the optical output power from the package is 13.2 W at 8.5-A rated current. We have also demonstrated laser processing to pure copper with the hybrid laser system. Uniform beads and approximately 2 mm penetration depth has been generated.
There has been a growing demand of laser welding for copper materials to manufacture industrial products with high electrical and thermal conductivities. The high thermal conductivity characteristic generates rapid thermal diffusion at a welding spot and hence reduces the power efficiency of laser welding. To overcome this issue, we propose to combine a blue laser beam performing a high absorptivity for copper materials, with a 1070-nm high power laser beam, launched from a single mode fiber laser. The blue laser beam can be focused at the welding spot with a sufficiently narrow beam waist, and the absorption of the blue light for copper materials is much higher than that of infrared light. Therefore, the focused blue laser beam causes rapid and highly efficient heat generation at the welding spot, and this localized heat is expected to improve the quality of laser welding. To generate the high-power blue laser beam efficiently, we fabricated a high power blue LD-integrated SLP which achieves an optical output power of 11.7 W at 10.5 A. We also fabricated a blue-DDL module using multiple SLPs and a stepped structure package adopted with a water-cooling system. The blue- DDL module can output a high fiber-coupled optical power exceeding 150 W. Next, we built a blue-NIR hybrid laser equipment which exhibits the excellent quality of laser welding by accurately controlled optical output power and beam spot diameters of both blue and NIR laser beams. In this paper, we describe the design and performance of blue LDintegrated SLP and blue-DDL module. We also report how the blue-NIR hybrid laser equipment contributes to improve the quality of the laser welding.
This paper reports the latest device performance of high-power blue and green Laser Diodes (LDs). The epitaxial structures of LDs including n-type, active and p-type layers were grown by metal organic chemical vapor deposition (MOCVD) on C-plane free-standing GaN substrates. And a ridge type structure and Electrodes of the n-type and p-type were formed. Front and rear mirror facets were obtained by cleavage at the m-plane surface. We optimized the epitaxial and the device structures for high efficiency, high optical output power and reliability. Every LD chip was mounted on a heat sink using a junction down method in a TO-Φ9 mm package for suppressing thermal resistance. A New developed 455 nm blue LD showed the optical output power and the voltage of 5.67 W and 3.93 V at the forward current of 3 A under Continuous Wave (CW) operation. The wall plug efficiency of the 455 nm blue LD was 48.1% at 3A. The wall plug efficiency of the high-power blue LD we developed is the highest reported so far. A new developed green LD at 525 nm showed the optical output power of 1.75 W and the wall plug efficiency of 21.2 % at the forward current of 1.9A. The optical output power, the voltage and the wall plug efficiency of a new 532 nm LD showed 1.53 W and 4.35 V, 18.5 % at the forward current of 1.9 A under CW operation. The peak wall plug efficiency of the 532 nm LD was 20 % at the optical output power of 1W.
KEYWORDS: Light sources, Semiconductor lasers, Laser based displays, Gallium nitride, High power lasers, Metalorganic chemical vapor deposition, Indium gallium nitride
We present latest development results of GaN based high power blue and green Laser Diodes (LDs). The epitaxial structures of LDs including n-type, active and p-type layers were grown by metal organic chemical vapor deposition (MOCVD) on C-plane free-standing GaN substrates. And a ridge type structure and Electrodes of the n-type and p-type were formed. Front and rear mirror facets were obtained by cleavage at the m-plane surface. We optimized the epitaxial and the device structures for high efficiency, high optical output power and reliability. Every LD chip was mounted on a heat sink using a junction down method in a TO-Φ9 mm package for suppressing thermal resistance. A New developed blue LD showed the optical output power and the voltage of 5.25 W and 4.03 V at the forward current of 3 A under Continuous Wave (CW) operation. The wall plug efficiency of the blue LD was 43.4% at 3A. And pure green LDs at 532 nm showed the optical output power of 1.19 W and the wall plug efficiency of 17.1 % at the forward current of 1.6A. Furthermore, 543 nm green LDs were fabricated on C-plane GaN substrates.
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