Hyperfine quantum-beat spectroscopy has been utilized in a pump-probe configuration to measure magnetic dipole (A) and electric quadrupole (B) coupling constants in the 3d 2 D 3/2 and 3d 2 D 5/2 levels of three isotopes of potassium. For many of these levels, the largest hyperfine splitting is smaller than the natural width, and so a subnatural linewidth technique is required. In the experiments, the 3d levels are excited on the 4d 2 S 1/2 →3d 2 D j quadrupole transition with linearly polarized light. Time evolution of the alignment components in the d levels is probed by time-delayed resonant radiation on the 3d 2 D j →9 p 2 P j transitions. Comparison of the excitation rate for two orthogonal relative polarization directions of the pump and probe laser at each delay time permits derivation of a linear polarization degree. This quantity contains beats at the various hyperfine frequencies in the d levels. Fitting the experimentally obtained time dependence to theoretical expressions allows extraction of the hyperfine coupling constants. For the 3d 2 D 3/2 level of 40 K we obtain Aϭ0.96(4) MHz and Bϭ0.37(8) MHz, indicating a typical precision also obtained for the other levels and isotopes. ͓S1050-2947͑97͒04905-6͔
Second harmonic generation (SHG) obtained using a potassium dihydrogen phosphate (KDP) nonlinear crystal from a CW He-Ne laser as a pump source, which emits at 632.8 nm, is reported. The SHG efficiency at the power of the He-Ne laser utilized (18 mW) and the fundamental beam waist available (0.1 mm), was evaluated theoretically; the same efficiency was measured experimentally obtaining a value of (3.7-0.1)×10 −7 , in good agreement with theoretical predictions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.