  In this letter, the characteristics of noise and long-term stability of near-
and mid-infrared (near-IR and mid-IR) gas-filled fiber Raman lasers have been
investigated for the first time. The results reveal that an increase in Raman
pulse energy is associated with a decrease in noise, and that the relative
pulse peak intensity noise (RIN) is always lower than the relative pulse energy
noise (REN). We also demonstrate that long-term drift of the pulse energy and
peak power are directly linked with the high amount of heat release during the
Raman Stokes generation. The demonstrated noise and long-term stability
performance provide necessary references for potential spectroscopic
applications as well as further improvements of the emerging mid-IR gas-filled
hollow-core fiber (HCF) Raman laser technology.
