We examine the selection rules for electronphoton interaction in a two-dimensional electron gas (2DEG) in the presence of the
Rashba spinorbit interaction (RSOI) and quantizing magnetic fields. In such a case, new channels open up for electronic transition
accompanied by the absorption of photons. As a result, two absorption peaks and a broadband absorption spectrum can be observed for
high-mobility samples at relatively high magnetic fields. We find that electronic transitions between the neighboring Landau levels within
the same spin orientation are the main channels for optical absorption in a spinsplit 2DEG.