Optical Gain Spectrum and Confinement Factor of a Monolayer Semiconductor in an Ultrahigh-Quality Cavity,Nano Letters

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Optical Gain Spectrum and Confinement Factor of a Monolayer Semiconductor in an Ultrahigh-Quality Cavity
Nano Letters ( IF 9.6 ) Pub Date : 2023-12-08 , DOI: 10.1021/acs.nanolett.3c03357
Tianhua Ren _{1,

2} , Junyong Wang _{3,

4} , Kaizhen Han _{1,

2} , Yuye Kang _{1,

2} , Annie Kumar ₁ , Gong Zhang ₁ , Zhe Wang _{1,

2,

5} , Rupert F Oulton ₆ , Goki Eda _{2,

3,

5} , Xiao Gong _{1,

2}

Affiliation

Two-dimensional (2D) semiconductors have attracted great attention as a novel class of gain materials for low-threshold, on-chip coherent light sources. Despite several experimental reports on lasing, the underlying gain mechanism of 2D materials remains elusive due to a lack of key information, including modal gain and the confinement factor. Here, we demonstrate a novel approach to directly determine the absorption coefficient of monolayer WS₂ by characterizing the whispering gallery modes in a van der Waals microdisk cavity. By exploiting the cavity’s high intrinsic quality factor of 2.5 × 10⁴, the absorption coefficient spectrum and confinement factor are experimentally resolved with unprecedented accuracy. The excitonic gain reduces the WS₂ absorption coefficient by 2 × 10⁴ cm^–1 at room temperature, and the experimental confinement factor is found to agree with the theoretical prediction. These results are essential for unveiling the gain mechanism in emergent, low-threshold 2D-semiconductor-based laser devices.

中文翻译：

超高品质腔中单层半导体的光增益谱和限制因子

二维 (2D) 半导体作为低阈值片上相干光源的新型增益材料引起了极大的关注。尽管有一些关于激光的实验报告，但由于缺乏包括模态增益和限制因子在内的关键信息，二维材料的潜在增益机制仍然难以捉摸。在这里，我们展示了一种通过表征范德华微盘腔中的回音壁模式来直接确定单层 WS ₂吸收系数的新颖方法。通过利用腔体 2.5 × 10 ⁴的高内在品质因数，吸收系数谱和限制因子以前所未有的精度通过实验解析。室温下激子增益使WS ₂吸收系数降低了2 × 10 ⁴ cm ^–1 ，实验限制因子与理论预测一致。这些结果对于揭示新兴的低阈值二维半导体激光器件的增益机制至关重要。

更新日期：2023-12-08

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