Control of Spontaneous Emission from Selectively Grown Semiconductor Photonic Dots

垂直腔面发射激光器（VCSEL）有望在光并行信息处理中发挥重要作用，人们对VCSEL的集成化进行了研究。由于集成需要很高的激光阈值均匀性，因此很难实现大规模集成。在这方面，如果我们能在不久的将来实现无阈值激光器将是理想的。本课题首先制备了基于金字塔结构的三维光子限制结构，研究了激子-光子相互作用对自发辐射过程的控制，为实现这种无阈值激光操作奠定了基础，然后在GaAs衬底上选择性生长ZnS金字塔结构，制备了三维光学微腔。在λ 400 nm的波长范围内观察到高达λ 5000的谐振Q值。由于GaAs在该波长范围内是有损耗材料，因此具有如此高的谐振Q值是令人惊讶的。这是由于l ...更多信息 在X和L间接带跃迁的贡献下，折射率有足够大的差异，在这个波长范围内具有非常大的态密度。通过将这一发现扩展到更任意的波长，由ZnS金字塔制成的三维光学微腔生长在基于ZnSe的分布式布拉格反射器（DBR）上，其中DBR预期用作金字塔的基面的有效反射器。在DBR上生长的ZnS金字塔嵌入CdS量子点，以研究激子-光子相互作用。金字塔显示共振Q值超过1000，CdS量子点的自发辐射通过与共振模式的耦合而得到很好的增强。增强的PL峰以及半宽度表现出高度的温度稳定性。这表明，增强的峰值是由腔的性质，而不是由半导体光发射器很好地控制。这表明了自发辐射的温度依赖性非常低的良好特性，这是波长复用光通信的重要问题之一。少

Vertical cavity surface emitting lasers (VCSELs) are expected to play an important role for optical parallel information processing, and the integration of VCSELs has been studied. Since the integration needs very high uniformity of the lasing threshold, it is very difficult to realize large-scale integration. In this respect, it will be ideal if we could realize thresholdless lasers in near future. In this project, three-dimensional photonic confinement structure based on a pyramid was fabricated and exciton-photon interactions were studied to control the spontaneous emission processes, which will lead to realize such a thresholdless laser operations.Three-dimensional optical microcavities were prepared with ZnS pyramids selectively grown on GaAs substrates. The resonance Q values as large as 〜5000 was observed in the wavelength region of 〜400 nm. Since GaAs is lossy material in this wavelength range, it is a surprise to have such a high resonance Q value. This was attributed to the l … More arge enough difference of the refractive indices with the contribution from the X and L indirect band transitions, which have the very large density of states in this wavelength range. By extending this finding to more arbitrary wavelength, three-dimensional optical microcavities made of ZnS pyramids were grown on ZnSe -based distributed Bragg reflectors (DBRs), where DBR is expected to function as an efficient reflector from the base plane of the pyramids. Such ZnS pyramids grown on the DBRs were embedded with CdS quantum dots to study the exciton-photon interactions. The pyramids showed the resonance Q values over 1000 and spontaneous emission from the CdS quantum dots was well enhanced by the coupling to the resonance modes. The enhanced PL peak as well as the half width exhibited highly temperature-stabilized properties. This demonstrated that the enhanced peak is well controlled by the cavity properties, not by the semiconductor light emitter. This demonstrated the nice features of the very low temperature dependence of the spontaneous emission, which is one of the important issue for optical communications with wavelength multiplexing. Less