We numerically investigate the solution of the Schrodinger equation in a on
e-dimensional system with gain. The gain is introduced by adding a positive
imaginary potential in the system. We find that the time-independent solut
ion gives that the amplification suppresses wave transmission at large gain
. Solutions from the time-dependent equation clearly demonstrate that when
gain is above a threshold value, the amplitude of the transmitted wave incr
eases exponentially with time. (C) 2001 Elsevier Science B.V. All rights re
served.