The Optimization Of Novel Cascaded Coupled Multi-Active Regions Large Optical Cavity Semiconductor Lasers

Due to many advantages such as small volume, high power conversion efficiency, low dissipation of energy, direct current modulation, high rate of data transmission, high reliability, long lifetime and wide lasing spectrum and others, semiconductor laser diodes have been heavily used in many fields. Particularly, the high power laser diodes are the hotspot and focus of current research and industrialization.In this dissertation, we first analyaed the main problems and limits of high power semiconductor lasers with ordinary structure, then introduced the theory of the novel high efficiency high power tunneling cascaded regenerated coupling strained QW lasers proposed by professor Shen Guandi. Though analyzed the characteristics such as: inner quantum efficiency, slope efficiency, power conversion efficiency and threshold current, we summarize the main advantages of the novel type lasers. They are high quantum efficiency, achieving high output power at relative low current, overcome the catastrophic optical damage(COD) and improve the light beam quality.Using the new theory, we designed and fabricated InGaAs/GaAs/AIGaAs tunnel regenerated QW lasers (X=980nm). We verify the new physical theory proposed by Prof. Shen by testing and analyzing the new type diode we have made. We obtained the devices with inner quantum efficiency larger than 1. Also we found two problems hindering the advantages of novel type diodes: the heavy absorption loss of the GaAs tunnel junction and strong current expanding. The first problem restrains the TEO mode emitting. The second one increases the threshold current and decreases the slope efficiency.According to the results of the experiments, we analyzed the absorption mechanisms in the tunnel junction and qualitatively find two main mechanisms that are likely to result in the heavy absorption loss of the 980nm light:a)The absorption loss of inner energy band transition caused by the high free carrier density in the non-depletion layers.b)The absorption loss of inter energy band transition caimsed by the strong electric field and the energy gap shrinkage from the band tails at the interface of tunnel junction of the depletion layers.In order to diminish the tunnel junction absorption loss, we designed thinAl,,Ga0,As tunnel junction with larger energy gap. Using this Al,,Ga0.,As tunneljunction we fabricated a new large cavity structure with three active region andobtained the TE0 mode laser. It's equivalent facula widtl1 is 0.7lUm and the verticalbeam divergence is just l7o.There are innovations in post technology too. We fist adopted double facetstrip electrode structure to restrain current expanding. This devices' olltput powerhave more 25% than ordinary structure ones at 2A injection current. When thenumber of active regions is fout, the output power, the external quantum efficiencyand the slope efficiency can reach 5\\\ 2.9 and 3W/A respectively. The thresholdcurrent decreased and slope efficienc}' increased through adopting double facet stripelectrode structure and the novel devices' ad\'antages are till behaved.