Quantum Dot Semiconductor Lasers
Development of advanced active regions for semiconductor diode lasers was the main direction which gave the largest contribution to enormous progress of diode lasers in various applications. With each new approach in device design, and fabrication technology, the properties of lasers greatly improved and, in turn, gave a strong push to the development of new systems and, sometimes, new directions and branches of industry. The first step was the proposal of current-injection lasers and their realization. The decisive step for the beginning of the use of diode lasers in real industrial applications was the concept of double heterostructures which offered a possibility to fabricate devices, with low threshold, current density allowing continuous wave operation at room temperature. Further progress was associated with the use of effects of size quantization in semiconductor heterostructures. Fig.1 illustrates the progress of semiconductor diode lasers with reducing the dimensionality of the active region when the threshold current density is taken as the Figure of merit . By threshold current density we mean the minimum current density of a semiconductor diode laser necessary to reach the population inversion and to overcome internal and external losses and to achieve modal gain.
KeywordsQuantum Well Threshold Current Density Internal Loss Semiconductor Diode Laser Differential Efficiency
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