Calibration of laser frequency scan with an electro-optic modulator

An electro-optically modulated laser beam was used to excite the Yb1S0 (6s ) 2?3P1 (6 s 6 p ) transition. Fluorescence was recorded as the laser frequency was scanned across the transition. Each isotope generated multiple peaks in the spectrum separated by the modulation frequency that permitted the frequency scan to be calibrated. The resulting isotope shifts agree well with existing data obtained with an interferometer to monitor the change in laser frequency. Electro-optic modulators have the advantages of being relatively inexpensive and simpler to operate than interferometers whose length must typically be stabilized with a laser whose wavelength is locked to an atomic transition.