In this research, watt-class green and blue laser diodes, which are fabricated on free-standing semipolar 20 21g f GaN and conventional c-plane GaN substrates, respectively are developed. Although several research groups have recently developed green laser diodes on semipolar GaN substrates, which have weaker piezoelectric fields and higher indium homogeneity in InGaN active regions compared to c-plane GaN, watt-level output power has yet to be achieved. By utilizing the 20 21g f plane, the first watt-class green lasers at 530 nm is successfully fabricated, and achieve maximum output powers in excess of 2 W, which to the best of our knowledge is the highest value reported for any GaN-based green laser diode. A wall-plug efficiency of 17.5% is realized at a current of 1.2 A under continuous-wave operation, which corresponds to an optical output of approximately 1 W and is the highest value reported to date. In addition, high-power and high-efficiency blue laser diodes at 465 nm are successfully fabricated on conventional c-plane GaN substrates. The output power and wall-plug efficiency are 5.2 W and 37.0%, respectively, at a current of 3.0 A under continuous-wave operation. These laser diodes are promising light sources meeting the ITU-R Recommendation BT.2020 for future laser display applications.

AlGaInN‐based blue–violet laser diodes with a single broad‐area stripe emitter were successfully fabricated on GaN substrates. Three stripe widths were examined; 10, 50, and 100 μm, and the maximum light output power of 0.94 W under cw operation at 20 °C was achieved for the sample with a stripe width of 10 μm. A super high‐power laser diode array was fabricated using 11 of these high‐performance laser chips, with a resultant output power of 6.1 W under cw operation at 20 °C. This result represents the highest reported output power for blue–violet laser diodes. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

We demonstrate a room-temperature continuous-wave operation of green vertical-cavity surface-emitting laser (VCSEL) with a 20 μm long cavity possessing a dielectric curved mirror formed over a {20−21} semi-polar gallium nitride substrate. The emission wavelength and the threshold current were 515 nm and 1.8 mA, respectively. We also confirmed that white light is generated by overlaying three prime colors of light, i.e. red, blue and green, emitted only from VCSEL.

We successfully developed high‐power and long‐lived pure blue laser diodes (LDs) having an emission wavelength of 440–450 nm. The pure‐blue LDs were grown by metalorganic chemical vapor deposition (MOCVD) on GaN substrates. The dislocation density was successfully reduced to ∼106 cm–2 by optimizing the MOCVD growth conditions and the active layer structure. The vertical layer structure was designed to have an absorption loss of 4.9 cm–1 and an internal quantum efficiency of 91%. We also reduced the operating current density to 6 kA/cm2 under 750 mW continuous‐wave operation at 35 °C by optimizing the stripe width to 12 µm and the cavity length to 2000 µm. The half lifetimes in constant current mode are estimated to be longer than 10000 h. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

We developed high-power and long-lived AlGaInN-based pure-blue semiconductor lasers emitting in the 440-450 nm wavelength range. The half lifetime (the time for the output power to degrade to half its initial value in constant current mode) was estimated to be more than 10000 hours at a power of 0.75 W under continuous-wave operation at 35°C.Reducing the density of structural defects newly originating from the multiple quantum well active layer and reducing the operating current density were shown to be important for producing high-performance pure-blue lasers.