Lüttgens Jan M, Berger Felix J, Zaumseil Jana
Institute for Physical Chemistry and Centre for Advanced Materials, Universität Heidelberg, D-69120 Heidelberg, Germany.
ACS Photonics. 2021 Jan 20;8(1):182-193. doi: 10.1021/acsphotonics.0c01129. Epub 2020 Dec 9.
Semiconducting single-walled carbon nanotubes (SWCNTs) are an interesting material for strong-light matter coupling due to their stable excitons, narrow emission in the near-infrared region, and high charge carrier mobilities. Furthermore, they have emerged as quantum light sources as a result of the controlled introduction of luminescent quantum defects (sp defects) with red-shifted transitions that enable single-photon emission. The complex photophysics of SWCNTs and the overall goal of polariton condensation pose the question of how exciton-polaritons are populated and how the process might be optimized. The contributions of possible relaxation processes, i.e., scattering with acoustic phonons, vibrationally assisted scattering, and radiative pumping, are investigated using angle-resolved reflectivity and time-resolved photoluminescence measurements on microcavities with a wide range of detunings. We show that the predominant population mechanism for SWCNT exciton-polaritons in planar microcavities is radiative pumping. Consequently, the limitation of polariton population due to the low photoluminescence quantum yield of nanotubes can be overcome by luminescent sp defects. Without changing the polariton branch structure, radiative pumping through these emissive defects leads to an up to 10-fold increase of the polariton population for detunings with a large photon fraction. Thus, the controlled and tunable functionalization of SWCNTs with sp defects presents a viable route toward bright and efficient polariton devices.
半导体单壁碳纳米管(SWCNTs)由于其稳定的激子、近红外区域的窄发射以及高电荷载流子迁移率,是一种用于强光物质耦合的有趣材料。此外,由于通过具有红移跃迁的发光量子缺陷(sp缺陷)的可控引入,使得单光子发射成为可能,它们已成为量子光源。SWCNTs复杂的光物理性质以及极化激元凝聚的总体目标提出了一个问题,即激子极化激元是如何被激发的,以及这个过程如何优化。利用角度分辨反射率和时间分辨光致发光测量,研究了具有广泛失谐的微腔中可能的弛豫过程,即与声子的散射、振动辅助散射和辐射泵浦的贡献。我们表明,平面微腔中SWCNT激子极化激元的主要激发机制是辐射泵浦。因此,纳米管低光致发光量子产率对极化激元激发的限制可以通过发光sp缺陷来克服。在不改变极化激元分支结构的情况下,通过这些发射缺陷的辐射泵浦导致在具有大光子分数的失谐情况下,极化激元激发增加高达10倍。因此,用sp缺陷对SWCNTs进行可控和可调谐功能化,为实现明亮且高效的极化激元器件提供了一条可行途径。