No abstract

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.

The effect of a local current turn-on in the heterostructure plane has been observed for low-voltage lasers-thyristors. It was shown that the spatial dynamics of the current-turn-on region is determined by the blocking voltage and the control current amplitude. For the first mode (blocking voltages up to 15 V), the current nonuniformity in the heterostructure plane is determined by the flux distribution of the spontaneous emission from the active region in the laser part to the side of the p-base of the phototransistor part of the heterostructure. The transition to the second mode (blocking voltages exceeding 15 V) is due to the sharp rise in the generation rate of excess carriers in the p-base of the phototransistor part of the heterostructure. In this case, the size of the region in which the original current turn-on occurs decreases to 70 μm. It was found that the rate at which the current-turn-on region expands depends on the working conditions of the laser part of the laser-thyristor and is 50 and 20 μm/ns for the spontaneous generation and lasing modes, respectively. It was also found that the spatial dynamics of the current determines the spatial dynamics of the laser light turn-on in the lateral waveguide and the emission efficiency in generation of short (<10 ns) laser pulses. It was demonstrated that, at low control currents, the main contribution to the decrease in the emission efficiency is made by the residual optical loss in the turned-off part of the laser-thyristor. At higher amplitudes of the control current, the emission efficiency grows due to the decrease in the residual loss in the turned-off part of the laser-thyristor, which made it possible to raise the peak power to 47 W for 100-ns laser pulses.

No abstract

An experimental study of factors determining the optical feedback efficiency in the structure of a laser-thyristor emitting at a wavelength of 905 nm has been carried out. It is shown that the spontaneous emission spectrum undergoes a significant change in the working range of currents due to the presence of GaAs-spacers in the structure of the active region of the laser part and to the absence of saturation of the spontaneous emission flux beyond the lasing threshold. It is demonstrated that the influence exerted by the reverse voltage across the collector p-n junction of the transistor part comes down to the following two effects: deformation of the edge of the absorption spectrum and turn-on of the impact ionization. Experimental dependences of the photogeneration rate on both current and voltage were obtained for the p-base of the transistor part. These dependences are an important tool to be used in subsequent studies aimed to simulate and examine the injection and generation processes in power laser-thyristors.