Semiconductor lasers emitting at 1.3 micron and 1.55 micron wavelength are extremely important devices for fiber-optic communications and optical access networks. Most of the installed fiber base in the US is designed for 1.3 micron and there is therefore much interest in developing low cost semiconductor diode lasers to enable future applications such as "fiber to the home". Ideally, devices for these applications should operate at a single wavelength, be robust to environmental variations such as temperature and should be inexpensive. Traditional approaches rely on the use of edge emitting lasers which employ special distributed feedback structures to control the spectral quality of laser output. However, these devices have a low yield. Furthermore, since these devices are grown on Indium Phosphide they are highly temperature sensitive and require strict temperature control. An alternative device is the vertical-cavity surface-emitting laser (VCSEL). This is highly attractive since it offers intrinsically single wavelength emission, a high quality circular output beam for ease of coupling to optical fiber, low power consumption and is also potentially inexpensive to manufacture. These devices are well suited to a wide variety of applications, including optical fiber telecommunications and data communications, printing and storage.However, when grown using the Indium Phosphide/Indium Gallium Arsenide Phosphide (InP/InGaAsP) material system, these devices have poor performance due to high thermal sensitivity and refractive index properties. The most advanced approach so far is to use certain wafer fusion techniques to form a VCSEL. However, there are reliability issues due to complex processing and high fabrication costs. In a more recent approach, edge-emitting lasers, grown on GaAs containing nitrogen in the active region have been demonstrated. However, incorporating nitrogen into the semiconductor material is not a trivial issue.To overcome these limitations, researchers at Arizona State University have developed and successfully tested a novel quantum well structure, which does not contain nitrogen and is grown on GaAs for long wavelength (1.3 micron and 1.55 micron) operation. Moreover, this wholly new material system and structure, which absorbs at wavelengths greater than 1150nm takes advantage of the well-established aluminum gallium arsenide technology for VCSEL fabrication which overcomes the refractive index and thermal problems associated with other materials.
|Original language||English (US)|
|State||Published - Aug 21 1998|