Frequency stability measurements of 1.5 mu m erbium lasers locked to acetylene absorption lines

We report on the absolute frequency stabilization of Yb-Er: glass lasers ag ainst different acetylene absorption lines in the 1.5 mu m spectral region. An external frequency modulation technique was adopted to independently st abilize two diode-pumped erbium microlasers against the P(15) rovibrational line at 1534.099 nm. A long-term frequency stability below 10(-9) (200 kHz ) was measured on both the closed-loop error signal and on the beat note fr equency. From the beat signal analysis, a 1 ms laser linewidth of 50 kHz wa s observed. The Allan standard deviation of the beat frequency was below 10 (-10) for integration times between 10 ms and 1 s and as low as 4 x 10(-11) around 0.1 s.