Blue Diode Lasers
The recent achievement of compact blue‐emitting gallium nitride semiconductor lasers is likely to have far‐reaching technological and commercial effects. The lasers' short wavelengths—around 400 nm, half that of gallium arsenide‐based lasers—permit higher spatial resolution in applications such as optical storage and printing. And the high photon energy will open up new applications for these inexpensive, compact light sources. An aesthetic satisfaction with these devices stems from finally extending the existing and mature semiconductor laser technology for the near‐infrared and red to encompass the “new frontier” blue and near‐ultraviolet regions, thereby bridging the entire visible spectrum. At the same time, there are significant research opportunities arising from a plethora of poorly understood microscopic issues in the underlying material system, which include such fundamental properties as charge control, transport, and formation of optical gain for stimulated emission.