Abstract
This paper focuses on the effect of threshold current density on different characteristics of quantum dot based laser. To investigate the effect, different characteristics have been analyzed using quantum dot as the active layer material of the laser structure. Performance improvement of quantum dot laser using InN has been achieved in terms of minimization of the threshold current dependence such as mirror loss, modal gain, turn-on delay and so forth. Numerical results have been analyzed considering the values of threshold current densities of GaN, AlN and InN based quantum dot lasers. Analytical results show that internal loss increases linearly with the increase of the threshold current density. However, other characteristics like mirror loss, modal gain, turn-on delay have nonlinear dependence on the threshold current density for any material used in the active layer. The threshold current density of InN quantum dot based laser is lower than that of other existing quantum dot based lasers. Analytical results ascertained that mirror loss has been increased a little bit. Conversely, internal loss and modal gain have been minimized considerably using InN based quantum dot in the active layer of the laser structure. In addition, turn-on delay time has been also minimized significantly.
Highlights
Semiconductor laser has been considered as one of the most vital devices in the field of optoelectronic semiconductor technology over the decades [1]
In this paper we have analyzed the effect of threshold current density on major loss and gain phenomena along with the modulation characteristics of quantum dot based laser
From the results it is revealed that the internal loss has been minimized by 0.39% and 0.65% using InN based quantum dot in the active layer of the laser structure with respect to that of using GaN and AlN respsctively
Summary
Semiconductor laser has been considered as one of the most vital devices in the field of optoelectronic semiconductor technology over the decades [1]. In early days homostructured semiconductor lasers were fabricated using bulk semiconductor materials. These homostructured devices suffered from high threshold current density to create lasing action. As a result of the uncoltrolled emission of photons optical noise is generated. Another major problem of large active region was a large linewidth enhancement factor (LEF). Due to the increase in threshold current and modal and material gains, the index of refraction fluctuated as well. All these variations affected the uniformity of the wavelength of the standing waves inside the laser cavity [2]. Reduction of threshold current is one of the major issues nowadays
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