The study of external perturbation to the Raman modes is very novel and well understood. For example, pressure and temperature effects on solid are given below.
Pressure effects:
1. The applied pressure reduces the lattice parameters and consequently increases the bond strength. So frequency of Raman mode increases and its FWHM increases (due to quantum mechanical uncertainty principle).
Temperature Effects:
1. The temperature (high) increases the lattice parameter and consequently decreases the bond strength. So Raman mode frequency decreases and FWHM increases.
Similarly, I like to understand the effect on electric field in Raman mode frequency and its FWHM.
What will be the effect of electric field on phonon frequency and its lifetime (Full Width at Half Maximum)?