Gain Characteristics of Optical-Gate Switches Using InGaAs/GaAs Strained-Layer Quantum Wells

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Abstract
Gain characteristics in single, double and triple InGaAs/GaAs strained-layer quantum-well structures have been measured in a wide wavelength range, and an optical-gate switch with the 0.9 µ m wavelength band has been examined for use in an integrated device with low driving current operation. Gate switches are classified into two types: small-gain switches and large-gain switches. A switch with 0 dB gain is produced by reducing the active layer volume through the use of a single quantum-well structure with 1.8 mA driving current. A large-gain switch with 15 dB gain under a no-gain-saturation condition is achieved using a large optical confinement structure: a triple quantum-well structure with 10 mA driving current. The driving current dependence of the gain spectrum for the single, double, and triple quantum-well gate switches shows that carrier injection to the second quantized state plays an important role in the saturation of the increase in gain when the driving current is increased.