Improvement of Performance of Modulation Response and Bandwidth of InAs/GaAs Quantum-Dot Laser Diode

Abstract

This paper proposes a design model of InAs QD laser diode structure, the dimensions of the proposed model have an active region of length 800 µm, width 12 µm, and a height of 375 nm. The proposed model of QD is disk shaped, its height is 2nm and diameter is 14nm. The QDs surface density per layer is 7×10 12 cm -2 , number of QDs layers are 5 layers, wetting layer thickness is 1nm and barrier thickness is 90nm.The evaluation of the proposed model is based on rate equations model. The InAs/GaAs QD lasers are capable of working at a very low threshold current, which is very important for the development of optical fiber communication systems. Modulation characteristics of InAs/GaAs quantum dot (QD) lasers of 1.3µm wavelength have been carefully studied at various bias currents and K-factor, the (-3 dB) bandwidth is improved at first as increasing the injected current, in addition, at large injected current, maximum value of the bandwidth is limited by K-factor, and the K-factor is mainly determined by the photon lifetime and the effective capture time, the K-factor can be minimized by choosing an optimum photon lifetime. The results show that the QD laser diode has a lower threshold current (2 mA), the threshold current density (20 A/cm 2 ), bias voltage 0.92 V, while output optical power has the range of (0-25 mW), the slope efficiency is 0.25W/A. The highest relaxation oscillation frequency at room temperature is 10.18 GHz, corresponding to a modulation bandwidth of 3 GHz due to the small damping factor. Using these parameters, the maximum modulation bandwidth (f -3dB max) is estimated as 15.56 GHz.