Laboratory of Atomic and Solid State Physics and School of Applied and Engineering Physics , Cornell University , Ithaca , New York 14853 , United States.
Department of Physics , Penn State University , University Park , Pennsylvania 16802 , United States.
Nano Lett. 2018 May 9;18(5):3213-3220. doi: 10.1021/acs.nanolett.8b00987. Epub 2018 Apr 18.
We demonstrate robust optical bistability, the phenomenon of two well-discriminated stable states depending upon the history of the optical input, in fully suspended monolayers of WSe at low temperatures near the exciton resonance. Optical bistability has been achieved under continuous-wave optical excitation that is red-detuned from the exciton resonance at an intensity level of 10 W/cm. The observed bistability is originated from a photothermal mechanism, which provides both optical nonlinearity and passive feedback, two essential elements for optical bistability. The low thermal conductance of suspended samples is primarily responsible for the low excitation intensities required for optical bistability. Under a finite out-of-plane magnetic field, the exciton bistability becomes helicity dependent due to the exciton valley Zeeman effect, which enables repeatable switching of the sample reflectance by light polarization. Our study has opened up exciting opportunities in controlling light with light, including its wavelength, power, and polarization, using monolayer semiconductors.
我们在低温下展示了完全悬浮的 WSe 单层中，依赖于光学输入历史的稳健光学双稳性，这是一种现象，两个状态有很好的区分度。在连续波光学激发下实现了光学双稳性，该激发光相对于激子共振红移，强度为 10 W/cm。观察到的双稳性源自光热机制，该机制提供了光学非线性和无源反馈，这是光学双稳性的两个基本要素。悬浮样品的低热导性主要负责实现光学双稳性所需的低激发强度。在有限的面外磁场下，由于激子谷塞曼效应，激子双稳性变得依赖于螺旋度，这使得通过光偏振可重复地切换样品反射率。我们的研究为使用单层半导体用光来控制光（包括其波长、功率和偏振）开辟了令人兴奋的机会。
