OBSERVATION OF DOPPLER SIDE-BAND OF A LASER-COOLED CA-TEMPERATURE-OPERATED LASER-DIODE( ION BY USING A LOW)

The 729-nm radiation obtained from a commercially available laser diod e operated at a low temperature was used to observe the S-1/2 - D-5/2 electric-quadrupole-allowed transitions of a laser-cooled Caf ion in a small rf trap. The electron shelving method was used to measure the a bsorption spectrum of the electric-quadrupole-allowed transitions, and the motional sidebands due to the secular motion of the ion in the ha rmonic potential well of the rf trap were completely resolved. The eff ective temperature of the ion, estimated by comparing the observed sid eband intensities with the theoretical ones, was less than 4.4 mK. Thi s result is in good agreement with that obtained from the analysis of the linewidth measurement.