Inferences from the transfer function of maser media

The transfer function for transmission through a maser medium is derived. It is valid within the dynamic range of linear maser response and under the assumption of weak dispersion. All signal distortions due to propagation in a maser medium may be canceled by subsequent propagation in a complementary absorbing medium. The signal leaves the cascaded media undistorted with a delay corresponding to propagation at the vacuum velocity of light. This possibility of recovering the speed of light makes it difficult to talk of the propagation of information in a dispersive medium as taking place at a signal velocity below that of light. A potentially useful scheme is shown in which a severely distorting low-noise maser amplifier is used. After further amplification the signal distortions are eliminated by transmission through a complementary absorbing medium. The mathematical form of the transfer functions also leads to a new integral formula involving Bessel functions. © 1971 The American Institute of Physics.