  We propose a single-photon frequency converter via a one-dimensional
waveguide coupled to a $V$-type atom. The on-demand classical field allows the
atom to absorb a photon with a given frequency, then emit a photon with a
carried frequency different from the absorbed one. The absorption and
re-emission process is formulated as a two-channel scattering process. We study
the single-photon frequency conversion mechanism in two kinds of realistic
physical system: coupled resonator waveguide with cosine dispersion relation
and an optical waveguide with linear dispersion relation respectively. We find
that the driving field prefers weak in coupled resonator waveguide but
arbitrarily strong in optical waveguide to achieve an optical transfer
efficiency.
