KEYWORDS: Semiconductor lasers, Reliability, Continuous wave operation, Crystals, Quantum wells, Light sources, High power lasers, Laser applications, Laser based medical tools, Laser PDT, Sensing systems
Laser light sources have being used in sensing and medical applications, and it is required for higher power, high efficiency, good beam quality and high reliability. We demonstrated single-mode CW 200mW red laser diodes with wavelength of 660nm, 675nm, and 690nm. These were fabricated from AlGaInP-based material with narrow stripe. These showed good temperature characteristics that the highest power reached 250mW upto 70°C and 200mW at 90°C for 660nm laser, exceeded 250mW upto 90°C for 675nm and 690nm lasers. Each characteristic temperature T0 was 112K, 169K, and 201K, respectively. The wall plug efficiency exceeded 32% at 25°C. The far field pattern showed Gaussian-like single transverse mode. Stable operation at high temperature was demonstrated in 1,500hours at 60°C, CW 200mW for 660nm laser and in 1,000hours at 100°C, CW 200mW for 675nm and 690nm lasers. CW 200mW operation is the world’s first in single-mode 660nm to 690nm laser diodes to the best of our knowledge. In the case of AlGaInPbased material, although longer wavelength is concerned degrading crystal quality in the active layer due to increasing lattice mismatch, no degradation observed the characteristics and the reliability. These red laser diodes will contribute to progress for sensing and medical applications.
Laser light source projector becomes popular due to the features of high brightness, wide color gamut and long lifetime of laser light source. One of the key performances that the market continues to request is the higher output power from the single laser diode. To meet the market demand and accelerate the laser projector installation, we developed AlGaInP based 638nm 3.5W pulse / 2.4W CW red laser diode for projector light source. We designed new chip with dual emitters in one chip with each emitter width of 75μm. The chip was then assembled into diameter 9mm TO-CAN package. The highest power at high temperature achieved 45°C 3.9W, 55°C 3.1W under pulsed operation with frequency 120Hz duty 30%, in case of CW operation 45°C 3.0W, 55°C 2.1W. The wall plug efficiency (WPE) at 25°C was reached each 43% under pulsed operation and 42% under CW operation. As a result of life test at 20°C 3.5W 5,500hours under CW operation and 45°C 3.5W 1,500hours under pulsed operation with frequency 120Hz duty 35%, the estimated life was exceeded MTTF 20,000 hours under 45°C 3.5W pulsed operation. The 3.5W pulsed operation and WPE of 43% are the world’s highest in 638nm LD to the best of our knowledge. This newly developed LD is suitable for red light source for projector.
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