Converse piezoelectric effect and photoelastic effect in InGaN/GaN multiple quantum wells

We present microphotoluminescence and microRaman measurements with different optical excitation intensities in InGaN/GaN multiple quantum wells (MQWs). When the optical excitation density was increased, the InGaN $A1(LO)$ phonon was found to show a redshift in frequency and a blueshift in photoluminescence spectra has been observed. The change in the refractive index of MQWs was found to be strongly related to the blueshift of photoluminescence spectra and the redshift of the InGaN $A1(LO)$ phonon. Our results firmly establish that a converse piezoelectric effect responsible for a considerable photoelastic effect (change in refractive index produced by a strain) arising from the optical modulation does exist in InGaN/GaN MQWs.