Studies on Charge Carrier Transport in an Injection Laser with Frequency Modulation of the Optical Radiation

Аннотация

One of the promising approaches to solve the problem of increasing the efficiency for interelement connections consists in the use of integrated optical switching systems, whose main elements represent injection lasers with functionally integrated optical radiation modulators. Injection lasers make it possible to modulate the laser radiation by subpicosecond controlling pulses at a constant pumping current, as well as making it possible to implement the sources and modulators of optical radiation in a united A^IIIB^V nanoheterostructure with second-type heterojunctions. This work is devoted to the studies concerning the transport of charge carriers within a functionally integrated modulator laser with internal frequency modulation of the generated optical radiation using a proposed two-dimensional diffusion-drift model and a numerical simulation technique. The results of the numerical simulation of charge carrier transport in a modulator laser when the pumping current is switched on, as well as under pulsed variation of the controlling voltage, take the structural features, the transport effects, the mechanisms of stimulated and spontaneous radiative recombination, and the photon lifetime into account. It is shown that the maximum modulation frequency of laser radiation is determined by the subpicosecond time of the controlled spatial relocation of the charge-carrier density maxima in the quantum zones of the modulator laser, as well as by the photon lifetime in the laser resonator, and corresponds to the terahertz range. To increase the maximum modulation frequency, it is necessary to reduce the photon lifetime in the active zone of the modulator laser to values lower than 3 ps by changing the resonator’s parameters in a corresponding manner. The proposed model and the method of numerical simulation make it possible to optimize the parameters of a functionally integrated modulator laser, and to provide the required relationships between the maximum modulation frequency of the optical radiation, the modulation coefficient, and the density of the threshold pumping current.