Xiang Wenbin, Bai Chunzheng, Zhang Zhen, Gu Bing, Wang Xiaoyong, Zhang Jiayu
Advanced Photonics Center, School of Electronic Science and Engineering, Southeast University, Nanjing 210096, China.
National Laboratory of Solid State Microstructures, College of Engineering and Applied Sciences, and School of Physics, Nanjing University, Nanjing 210093, China.
Nanomaterials (Basel). 2024 Sep 27;14(19):1568. doi: 10.3390/nano14191568.
Spherical quantum wells (SQWs) have proven to be excellent materials for suppressing Auger recombination due to their expanded confinement volume. However, research on the factors and mechanisms of their high-intensity optical properties, such as multiexciton properties and third-order optical nonlinearities, remains incomplete, limiting further optimization of these properties. Here, a series of CdS/CdSe (xML)/CdS SQWs with varying CdSe layer thicknesses were prepared. The modulation effects of CdSe shell variations on the PL properties, defect distribution, biexciton binding energy, and third-order optical nonlinearities of the SQWs were investigated, and their impact on the material's multiexciton properties was further analyzed. Results showed that the typical CdS/CdSe(3ML)/CdS sample exhibited a large volume-normalized two-photon absorption cross-section (18.17 × 10 GM/nm) and favorable biexciton characteristics. Optical amplification was observed at 12.4 μJ/cm and 1.02 mJ/cm under one-photon (400 nm) and two-photon (800 nm) excitation, respectively. Furthermore, different amplified spontaneous emission spectra were observed for the first time under one/two-photon excitation. This phenomenon was attributed to thermal effects overcoming the biexciton binding energy. This study provides valuable insights for further optimizing multiexciton gain characteristics in SQWs and developing optical gain applications.
球形量子阱（SQW）因其受限体积的扩大，已被证明是抑制俄歇复合的优异材料。然而，关于其高强度光学性质的因素和机制，如多激子性质和三阶光学非线性的研究仍不完整，限制了这些性质的进一步优化。在此，制备了一系列具有不同CdSe层厚度的CdS/CdSe（xML）/CdS球形量子阱。研究了CdSe壳层变化对球形量子阱的光致发光性质、缺陷分布、双激子结合能和三阶光学非线性的调制效应，并进一步分析了其对材料多激子性质的影响。结果表明，典型的CdS/CdSe(3ML)/CdS样品表现出较大的体积归一化双光子吸收截面（18.17×10 GM/nm）和良好的双激子特性。在单光子（400 nm）和双光子（800 nm）激发下，分别在12.4 μJ/cm²和1.02 mJ/cm²处观察到光放大。此外，首次在单/双光子激发下观察到不同的放大自发发射光谱。这种现象归因于热效应克服了双激子结合能。本研究为进一步优化球形量子阱中的多激子增益特性和开发光增益应用提供了有价值的见解。
