The in-plane magnetic field (B-parallel to) dependence of cyclotron resonan
ce is investigated in both single and double layer two-dimensional electron
systems by Fourier spectrometry in tilted magnetic fields. The observed B-
parallel to dependence of the cyclotron mass (m(C)) is complicated and vari
es with perpendicular magnetic field in the double layer system. The splitt
ing of m(C) by B-parallel to around filling factor 2 is observed in the sin
gle layer system. (C) 2001 Elsevier Science B.V. All rights reserved.