Slow and Fast Light in Semiconductor Quantum-Well and Quantum-Dot Devices

The ability to manipulate the speed of light has recently become one of the most exciting emergent topics in optics. There are several experimental demonstrations showing the capability to slow down light more than six orders of magnitude in a variety of media, ranging from atomic vapor, solid state crystal, to semiconductors. These results have led to intensive research into new materials, devices, and system studies that examine their impact to new applications. It is believed that we are on the verge of a dramatic change in the way we envision and construct communication, processing and control systems. One direct application of slow and fast light devices is in the area of communications. One grand challenge remaining in information technology today is to store and buffer optical signals directly in optical format. As such, optical signals must be converted to electronic signals to route, switch, or be processed. This resulted in significant latencies and traffic congestions in current networks. In addition, keeping the data in optical domain during the routing process can greatly reduce the power, complexity and size of the routers. To this end, a controllable optical delay line can effectively function as an optical buffer, and the storage is proportional to the variability of the group velocity. In addition to optical buffers, slow and fast light devices can be used as tunable true-time delay elements in microwave photonics, which are important for remotely controlling phased array antenna. Other novel applications include nonlinear optics, optical signal processing, and quantum information processing. There are various approaches that can be used to vary the optical group velocity. Ultraslow or fast group velocity may result from a large material dispersion, waveguide dispersion, or both. In this paper, the authors provide a review of recent progress of slow and fast light using semiconductor devices. Specifically, they will discuss results obtained using se- miconductor quantum-well/quantum-dot absorber and optical amplifiers. Slow and fast light are controllable electrically by changing the bias current or voltage as well as optically by changing the pump laser intensity and wavelength. Delay-bandwidth tradeoff and other figures of merits are analyzed