Circularly polarized photoluminescence (PL) spectroscopy measured at 19 K on GaAs/AlGaAs symmetric and asymmetric double quantum wells (DQW) is reported. The PL is obtained by exciting the sample with a circularly polarized (left or right) laser in order to create an initial unbalanced distribution of electron spins in the conduction band and, in this way, obtain the electron spin lifetime $τ_s$. The effects of the excitation laser wavelength were estimated by exciting with laser wavelengths of 701.0 nm, 787.0 nm, 801.5 nm and 806.5 nm. The increase of $τ_s$ with the excitation wavelength is attributed to the lower initial quasi-momentum $\bf{k}$ of the excited carriers, which also reduces spin-orbit relaxation processes. $τ_s$ was found to be higher in asymmetric DQWs: this is attributed to the wider QWs in these samples, which reduces spin relaxation due to the Dresselhaus mechanism. In addition, we also detected a smaller contribution from the Rashba mechanism by comparing samples with built-in electric fields of different orientations defined by doped barrier layers.
Effect of photonic crystal stop-band on photoluminescence of $a$-Si$_{1-x}$C$_x$:H
分析了由\textit{a} C $_x$：H和\textit{a}非晶层交替构成的一维（1D）光子晶体的周期结构中光子态局域密度变化的影响.使用\textit{a} -Si $_{1-x}$ C $_x$：H作为发射材料使得可以检查光致发光光谱轮廓的变换，其在宽度上与光子阻带相当。实验表明，在阻带附近，发光被增强和抑制。在阻带不同边缘的发光峰的相对强度随单个\textit{a} -Si $_{1-x}$ C $_x$：H薄膜的阻带位置和光致发光峰的失谐而变化。在所考虑的系统中的Purcell效应的理论描述的方法，其中的局域光子态密度的计算方面的一维模型。%实验测量和计算光谱之间获得了良好的一致性。结果表明，局域态密度的特定部分在1D光子晶体的阻带的长波长（低频）边缘处显著增加，这是由于光波的电场在\textit{a} -Si $_{1-x}$ C $_x$：H的空间区域中的主要局域化，该空间区域与\textit{a} -SiO $_2$相比具有更高的相对介电常数。
Telecommunication wavelength confined Tamm plasmon structures containing InAs/GaAs quantum dot emitters at room temperature
Quantum Engineering Technology Laboratories, H. H. Wills Physics Laboratory and Department of Electrical and Electronic Engineering, University of Bristol（布里斯托大学量子工程技术实验室、H.H.威尔斯物理实验室和电气电子工程系）；EPSRC National Epitaxy Facility, Centre for Nanoscience and Technology, University of Sheffield（谢菲尔德大学纳米科技中心EPSRC国家外延设施）
TMDCs have attracted a lot of attention in recent years due to their unique indirect to direct band gap transition from bulk to monolayer thickness. Strong confinement in the out-of-plane direction enhances the Coulomb potential between the charged particles (e-h pairs) and thus increases the exciton binding energy dramatically. The lattice inversion asymmetry in a monolayer creates two non-equivalent (but degenerate in energy) band edges protected by time reversal polarisation via pseudo-spin. However, the presence of strong spin-orbit coupling in the valence band and weak spin-splitting in t…
