  We demonstrate a two-photon transition of rubidium (Rb) atoms from the ground
state (5$S_{1/2}$) to the excited state (4$D_{5/2}$), using a home-built
ytterbium (Yb)-doped fiber amplifier at 1033 nm. This is the first
demonstration of an atomic frequency reference at 1033 nm as well as of a
one-colour two-photon transition for the above energy levels. A simple optical
setup is presented for the two-photon transition fluorescence spectroscopy,
which is useful for frequency stabilization for a broad class of lasers. This
spectroscopy has potential applications in the fiber laser industry as a
frequency reference, particularly for the Yb-doped fiber lasers. This
two-photon transition also has applications in atomic physics as a background-
free high- resolution atom detection and for quantum communication, which is
outlined in this article.
