Laser cooling of trapped ytterbium ions with an ultraviolet diode laser

Abstract

We demonstrate an ultraviolet diode laser system for cooling of trapped ytterbium ions. The laser power and linewidth are comparable to previous systems based on resonant frequency doubling, but the system is simpler, more robust, and less expensive. We use the laser system to cool small numbers of ytterbium ions confined in a linear Paul trap. From the observed spectra, we deduce final temperatures < 270 mK.Laser-cooled trapped ions are the basis for many emerging technologies in atomic physics, especially large-scale ion-trap quantum computing [1,2] and optical frequency metrology [3,4]. In particular, laser-cooled Yb + has been extensively investigated for optical clocks, owing to the narrow linewidths associated with transitions from the ground state to a number of metastable states [5,6]. However, laser cooling of ions is often impeded by the expense and fragility of the required single-frequency ultraviolet (UV) laser source, which generally consists of a single-frequency infrared laser whose output is then frequency-doubled in an external optical resonator. This approach is currently adopted for laser cooling of Yb + [5,6,7,8,9].Here we describe a simpler, more robust, and less expensive laser system for cooling Yb + based on a UV laser diode. The laser diode is tuned to the Yb + resonance wavelength at 369.5 nm using a combination of temperature tuning and optical feedback from a diffraction grating. Using this system, we have achieved Doppler cooling of small numbers

Individual Addressing of Trapped Ions and Coupling of Motional and Spin States Using rf Radiation

“…It is due to the delay time of 50 ms between cooling the ion and performing the measurements, and the low cooling efficiency during the measurement itself (for 100 ms). Other researchers have observed similar temperatures with 172 Yb + [16,20]. For this first demonstration of the coupling between spin and motional states of trapped ions in a magnetic field gradient [21], a higher temperature is in fact advantageous, since it increases the relative height of the motional sideband.…”

Versatile ytterbium ion trap experiment for operation of scalable ion-trap chips with motional heating and transition-frequency measurements

“…We measure the motional heating rate within our ion trap using a technique where the laser cooling beam is turned off for a certain time and ion fluorescence is monitored when the laser is turned on again [51,52]. There are currently several ions being investigated for quantum technology including Ba + [53], Be + [54], Ca + [55][56][57][58][59], Cd + [60], Mg + [61], Sr + [32,62], and Yb + [63][64][65][66]. Yb + is an attractive choice for quantum information processing and for frequency standards [67][68][69][70].…”

Laser Cooling With Ultrafast Pulse Trains

“…Later we developed a novel ultraviolet diode laser operating at a fundamental wavelength of 369.5 nm and used the laser for cooling on this transition (Sec. V, [3]). …”

“…We used a novel ultraviolet diode laser at 369.5 um to perform laser cooling on the S 1 / 2 -P 1 / 2 single-photon transition, achieving temperatures below 270 mK [3]. To the best of our knowledge, no shorter-wavelength laser has ever been used for laser cooling.…”

“…We searched for the two-photon transition, but have not yet observed it; our theoretical predictions indicate that modest improvements to the experiment would bring mode-locked laser cooling within reach. In the course of our search, we demonstrated a new diode laser system for laser-cooling Yb+ in the traditional manner [3]. We believe this is the shortest-wavelength laser ever directly used for laser cooling.…”