  A conceptual mechanism of amplification of phonons by phonons on the basis of
nonlinear band-gap transmission (supratransmission) phenomenon is presented. As
an example a system of weakly coupled chains of anharmonic oscillators is
considered. One (source) chain is driven harmonically by boundary with a
frequency located in the upper band close to the band edge of the ladder
system. Amplification happens when a second (gate) chain is driven by a small
signal in the counter phase and with the same frequency as first chain. If the
total driving of both chains overcomes the band-gap transmission threshold the
large amplitude band-gap soliton emerges and amplification scenario is
realized. The mechanism is interpreted as nonlinear superposition of evanescent
and propagating nonlinear modes manifesting in a single or double soliton
generation working in band-gap or band-pass regimes, respectively. The results
could be straightforwardly generalized for all-optical or all-magnonic contexts
and has all the promises for logic gate operations.
