Abstract

The Yb⁴ ion is known to have (i) a ground–state hyperfine resonance (¹⁷¹Yb⁺²S_1/2, F= 0 →1) that is precisely detectable by microwave-optical double resonance (Fig. 1), and (ii) at least two dipole-forbidden lines (E2 ²S_1/2→²D_5/2 – 1/2 • 822nm, and E3 ²S_1/2—2F_7/2 — 467nm) suitable for the control of a diode-laser-based optical frequency standard [1,2]. We have prepared a single ¹⁷¹Yb⁺ ion in a Paul trap, cooled it down to the Lamb-Dicke regime by irradiation with 369-nm frequency-doubled light of a cw dye laser, and detected its resonance scattering. Optical pumping into the ²D_3/2 level was undone by simultaneous excitation with 609-nm dye-laser light. Microwave π/2 pulse pairs (12.6 GHz, separation τ), sandwiched between the pulses of the resonance light and their frequency being stepped across the hyperfine resonance m_F = 0 → 0, generated Ramsey fringes. The observed minimum width of a fringe is 12Hz (τ = 40ms), Fig. 2.

© 1996 IEEE