Self-modulated photoluminescence of CrBr3 flake

The layered van der Waals magnetic insulator chromium bromine (CrBr3) has excellent optical properties and it provides an interesting platform for investigating light matter interactions. Here, we focused on its self-modulated photoluminescence (PL) spectrum. We find that there are interference fringes superposed on the PL curves due to the Fabry Perot resonance between the front and rear interfaces of CrBr3 flakes. Moreover, there is a huge Stokes shift between the PL spectrum and lowest absorption band, which can prevent reabsorption of PL and is a benefit for enhancing the resonant intensity of the PL spectrum. In addition, we investigate the PL spectrum variation under suppressing thermal vibration with decreasing temperature from 300 to 80 K, which shows the significant increase of PL intensity and blue shift of PL maximum peak. This work gives details of CrBr3 self-modulated PL properties and creates opportunities for using CrBr3 in optical devices and lasing components in future applications.