The accepted method of measuring long-term
frequency stability is to heterodyne the laser to
be tested with another laser of equal or greater
stability. By observing the variation of the
resulting beat frequencies, the combined drift of
the two lasers can be measured. The results will
be no better than the sum of the two instabilities
and will, therefore, provide a conservative
measure of frequency drift.
In the charts below, a Melles Griot frequency-stabilized HeNe was hetrodyned with the output from a Zeeman-stabilized laser. The charts show the performance over one minute and over an eight-hour typical workday. The laser can be cycled over a 20°C temperature range without mode hopping.
In the charts below, a Melles Griot frequency-stabilized HeNe was hetrodyned with the output from a Zeeman-stabilized laser. The charts show the performance over one minute and over an eight-hour typical workday. The laser can be cycled over a 20°C temperature range without mode hopping.
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