Physikalisch-Technische Bundesanstalt

Presently employed ion trap. A Paul trap consisting of a ring electrode (diameter 1.3 mm) and two endcaps is mounted in a quartz glass UHV chamber. Ions are generated at trap center by heating an Yb reservoir and an electron-emitting filament. After ion loading, reservoir and filament serve as contact potential compensation electrodes. 

Fluorescence emission of five laser-cooled ¹⁷²Yb ions. For contrast enhancement, the brightness information of the camera image was converted to colours (red: low brightness; blue: high brightness). The relatively larger residual motion of the ions outside the trap center makes them appear less bright and more diffuse. 

The components of an optical ion trap frequency standard. Cooling laser and interrogation laser light are applied alternately. In successive measurement cycles, the interrogation frequency is increased or decreased by a fixed amount so that the atomic resonance is excited in its wings. In this way, the fluorescence signal observed during the subsequent cooling phases contains information about the deviation of the frequency of the interrogation laser from the line centre of the reference transition. A control loop is used to stabilize the laser frequency to the line centre. 

Experimentally observed resonance signal due to excitation of a single trapped ¹⁷¹Yb⁺ ion to the ²D_3/2 (F=2, m_F=0) level. Each data point corresponds to an average over 20 measurement cycles .