Approaches of optimization of coupled quantum wells with pronounced quantum-confined Stark effect in order to reach a high refractive index change are described. A numerical simulation was used to determine the optimal design parameters (quantum well width, barrier thickness and composition) based on GaAs/AlGaAs materials with two symmetric quantum wells, which provides the maximum modulation of the refractive index at a small absorption coefficient. It is demonstrated that, with the electric field strength varied within the range 0-20 kV cm −1 at an optical loss for interband absorption not exceeding 10 cm −1 , the refractive index can be changed by up to 0.0362.

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Semiconductor lasers based on MOVPE-grown asymmetric separate-confinement heterostructures with a broadened waveguide and emitting in the wavelength range 1.0 -1.1 mm are studied. It is found that the intensity of spontaneous emission from the active region increases with increasing pump current above the lasing threshold and that this is caused by a growth in the concentration of charge carriers in the active region due to the modal gain enhancement needed to compensate for the growing internal optical loss at high pulsed pump currents. It is shown that the increase in the internal optical loss with increasing pulsed pump current is one of the main reasons for saturation of the light -current characteristics of high-power semiconductor lasers.

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