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Abstract
We succeeded fabricating high power blue (445nm) laser diodes (LDs) with an output power of 500mW. The operating current, voltage and wall-plug efficiency of these LDs were 480mA, 4.8V, and 21.7%, respectively. Estimated Lifetime of these LDs was over 10,000h under continuous-wave operation at 25.

1.Introduction
Since the first demonstration of Gann-based laser diode (LD) in1995 [1], we have been developing higher power and longer lifetime laser diodes (LDs). In 2000, we commercialized high-power violet (400-410nm) LDs with an output power of 30mW busing free-standing Gann substrates with epitaxial laterally overgrowth Gann (ELOG) [2, 3, 4]. Also, we have focused on expanding lasing wavelength range based on Aligning materials. By improving epitaxial growth technology, we succeeded developing wide range LDs from ultra-violet (365nm) to blue green(482nm) region under continuous-wave (CW) current operation [5,6]. And these frontier wavelength band LDs have been extending the possibility to new applications, for example, sensing device, biotechnology, photolithography, and printing.
And now, full color display systems using laser light sources are attracting the attention by extremely wide color expression. In three prime colors, red and green high power laser light sources are realized by using Aligned LDs and second harmonic generation (SHG) laser, respectively. On the other hand, in blue region, we have proposed Gann-based blue LDs with an emission wavelength of 445nm and output power of 200mW [7]. 􀀂However, further higher power blue LDs are required. When these LDs are operated at higher power than 200mW, some electrical damages to epic-layer, or to electrodes are enhanced duet excessive current. Moreover, rise of the optical density at facet may cause optical damage. These failures seriously affect the reliability of LDs and prohibit higher power operating. In this study, in order to fabricate higher power than 200mW and long lifetime blue LDs, we optimized the device structure and facet coating of LDs. And we reported the characteristics of high power blue LDs.

4. Reference
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