Abstract
By optimizing existed distributed feedback reflector (DBR) microcavities (MCs) or designing new guided mode resonance (GMR) microcavities, we can make the coupling strength between photon and exciton larger than the exciton binding energy in GaAs based system. We call this very strong coupling region in which both upper and lower polariton energy are lower than that in the strong coupling case. Also we show that both the dissociation and saturation boundaries of lower polariton (LP) are much extended, which means condensation of exciton-polaritons is possible at room temperature. It opens the gate for new devices that use the BEC effect such as quantum simulation[1] and polariton laser[2].