Semiconductor Lasers

Abstract

Semiconductor lasers cover the respectable wavelength range of about 0.4 to 11μn and are very pivotal in many aspects of human life. As Strite put it, the Holy Grail of GaN research is the realization of an injection laser which would represent the shortest-wavelength semiconductor laser ever demonstrated [12.1]. Although semiconductor lasers have many applications, for example, in communication as pumping sources, and mundane applications such as pointers, the most salient and imminent application of GaN-based lasers is in Digital Versatile Disks (DVD for short). This is a future version of the compact disk where the spot size and therefore the storage density is diffraction limited [12.2]. The present CD players utilize GaAs infrared lasers produced by Molecular Beam Epitaxy (MBE). The interim approach adopted by the industry relies on red lasers with which pit dimensions of about 0.4 μm can be read. Using a two-layer scheme in a DVD, the density can be increased from today’s 1 Gb to about 17 Gb per compact disk [12.3]. The cycle time in the consumer-electronics market is rather short in that even if red-laser-based DVDs are implemented, the blue laser can be introduced some two years after the red lasers. For consumer applications, CW-operation lifetimes on the order of 10,000 hours at 60°C are required. The nitride-based lasers with their inherently short wavelengths, when adopted, offer much increased data storage-capacity possibly in excess of 40 Gb per compact disk. Figure 12.1 presents a photograph of a Nichia InGaN laser emitting near 400 nm, which is intended for such an application.