PARAMETRIC DECAY OF A HELICON IN N-INSB

The parametric decay of a high power helicon into another helicon and an acoustic mode in a piezoelectric semiconductor is analysed using coupled mode theory. The acoustic mode is assumed to propagate across the applied magnetic field. The threshold electric field of the pump and the growth rates of the unstable modes well above threshold are obtained analytically. The analysis is applied to n‐InSb at 77 K. The threshold electric field is found to be of the order of 1.75 × 102 V m−1 and the growth rate at an electric field 1.75 × 103 Vm−1 is found to be of the order of 7.56 × 108 S−1. This order of wave amplitude is feasible presently. Copyright © 1979 WILEY‐VCH Verlag GmbH & Co. KGaA