A highly stabilized frequency-offset-locked He-Xe laser system is constructed for the high resolution laser spectroscopy of H
2CO (5
1.2 (ν=0)) →6
0.6 (ν5=1)) at3.51μm. It is composed of two He-Xe lasers. The first laser is the H
2CO-stabilizedHe-Xe laser which is used as a frequency reference. The second laser is frequency-offset-locked to the first laser by using the beat frequency between these lasers. Thefrequency stability of the frist laser is 1.0×10
-14 at τ=100
s, where τ representsthe integration time. The frequency traceability of the second laser to the first laseris expressed as 8.0×10
-13·τ
-1 for 10ms<τ<100
s. It is found that this value of thetraceability was independent of the frequency modulation of the first and second lasers.The variable range of the frequency of the second laser is 18MHz. In this range, thefrequency traceability of the second laser to the first laser is independent of the beatfrequency.
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