Optical Bistability and Nonlinear Switching in Quantum Well Amplifiers
There is growing interest worldwide in the potential applications of diode laser amplifiers for all-optical logic, switching, wavelength conversion, pulse-shaping, and other aspects of signal processing. Two types of device are currently under study, corresponding to two different physical mechanisms of operation. In the first type the dispersive nonlinearity at wavelengths close to the band-gap is utilized to produce switching and bistability between two different states of transmission. In the second type the device consists of two or more sections, each with its own electrical contact, and the switching arises as a consequence of the absorptive nonlinearity when some sections are driven close to lasing threshold and the others receive little or no current. The advantages of the former device type are its ready availability and low switching energy (of order femtojoules), although it suffers from a marked sensitivity to the wavelength of the optical input. By comparison, the two-section device is claimed to show good tolerance to input wavelength and can give significantly higher contrast ratios between the “off” and “on” states.
KeywordsMultiple Quantum Well Saturation Intensity Absorptive Nonlinearity Optical Input Double Heterostructure
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