Figure 1: Energy diagram of the exciton energy shift due to OSE.
From: Large polarization-dependent exciton optical Stark effect in lead iodide perovskites
The diagram shows energy levels for the ground state, 
, and the two bright exciton states, 
, labelled by the azimuthal quantum number of the total angular momentum, mj. The exciton transition energy is E0. When a photon with energy E0−Δ and with spin momentum σ+ interacts with the mj=1 exciton, then an entangled state with energy E0+δE forms (shaded box). The new state can be detected by a probe photon with the same spin, while the mj=−1 exciton is left unperturbed.
