We demonstrate a new technique for saturated-absorption spectroscopy by use of copropagating beams that does not have the problem of crossover resonances. The pump beam is locked to a transition, and its absorption signal is monitored while the probe beam is scanned. As the probe comes into resonance with another transition, the pump absorption is reduced and the signal shows a Doppler-free dip. We use this technique to measure hyperfine intervals in the <i>D</i><sub>2</sub> line of <sup>85</sup>Rb with a precision of 70 kHz and to resolve hyperfine levels in the <i>D</i><sub>2</sub> line of <sup>39</sup>K that are less than 10 MHz apart.
© 2003 Optical Society of America
Ayan Banerjee and Vasant Natarajan, "Saturated-absorption spectroscopy: eliminating crossover resonances by use of copropagating beams," Opt. Lett. 28, 1912-1914 (2003)