Utako Tanaka

Frequency Stabilization of Diode Laser Using External Cavity and Doppler-Free Atomic Spectra

We report on the frequency stabilization of a diode laser, in which the long- and short-term stabilities are simultaneously improved. We use an external cavity whose resonance frequency is locked to the center of a Doppler-free spectrum of the 85 Rb-D 2 line without direct laser frequency modulation. The obtained linewidth of the diode laser is less than 100 kHz and the long-term stability (trackability) estimated from the variation of the error signal is between 2×10 -12 and 2×10 -14 at the averaging time τ between 100 ms and 100 s. We also propose a conventional method of stabilization of the magnetic field at the Rb cell used for the frequency stabilization

Velocity control of an Yb beam by a frequency-doubled mode-locked laser

An ytterbium atomic beam has been decelerated with the use of a multimode light beam based on a frequency-doubled mode-locked Ti:sapphire laser. Compression of the atomic velocity distribution was achieved by the addition of a copropagating single-mode light beam. The contribution of each isotope to the observed compressed peaks of the velocity distribution is explained.

Design and Characteristic Measurement of Miniature Three-Segment Linear Paul Trap

We have fabricated a miniature three-segment linear Paul trap with r0=0.6 mm and 2Z0=4 mm. In order to perform quantum-state manipulation of trapped 40 Ca+ ions, we discuss the required harmonic oscillation frequencies which allow us to perform effective sideband cooling and have measured those that depend on the dimensions of the trap. A laser beam that has a component in the radial direction of the linear trap as well as that propagating along the trap axis has been used to detect the fluorescence spectra of the 42S1/2–42P1/2 transition. We have observed that the profile of the fluorescence spectrum obtained with the side laser beam is markedly different from that obtained with the axial laser beam due to micromotion. By applying additional DC voltages, the micromotion has been compensated, its amplitude has been estimated, and crystallization has been observed for two 40 Ca+ and four 40 Ca+ ions.

Laser cooling and isotope separation of Cd + ions confined in a linear Paul trap

Cadmium ions in a natural isotope mixture have been trapped in a linear Paul trap and laser cooled. The fluorescence spectra from all even isotopes, including the (108)Cd(+) isotopes with a natural abundance of 0.89%, were observed. Additionally, we eliminated the heavier isotopes from the trapping region by adjusting the tuning of the laser frequency and by changing the dc voltage applied to the end electrodes.

Design and characterization of a planar trap

We demonstrate laser cooling of 40Ca+ ions in a linear-type planar trap where all electrodes are located in a plane. We numerically calculate the potential of a 500 µm scale trap and then characterize the trap by measuring the secular frequencies. Linear crystals of 40Ca+ ions are formed after coarse micromotion compensation. Development of such traps is important for the construction of a many-zone ion-trap array for large-scale quantum information processing using ions. We also present other trap designs and results from numerical analysis.

Frequency Stabilization of Diode Laser Using Dichroic-Atomic-Vapor Laser Lock Signals and Thin Rb Vapor Cell

We report the frequency stabilization of a diode laser by applying the dichroic-atomic-vapor laser lock (DAVLL) method to a thin Rb vapor cell. A 1-mm-long Rb vapor cell is used to obtain a sub-Doppler spectrum that is required for frequency locking, which is easier than in the case of using a saturated absorption spectrometer. A 794-nm diode laser is tuned to the Rb D1 line, and sub-Doppler signals are observed by introducing a pumping beam and a probe beam in a perpendicular direction. We obtain error signals by subtracting the signals of σ+ polarized beams from that of σ- polarized beams in the presence of a magnetic field and stabilized the 794 nm diode laser frequency without modulating laser parameters. The stability of the 794-nm diode laser is evaluated using other independently stabilized diode laser.

Design of a surface electrode trap for parallel ion strings

We report a linear surface-electrode trap that can be used to form parallel ion strings. By adjusting the balance of the radio-frequency (RF) voltages applied to central and RF electrodes, the RF pseudopotential can be varied from single-well to double-well in the radial direction. Ions located on two parallel lines of the RF potential null are in principle free from excess micromotion if appropriate static voltages are applied. Calcium ions were trapped for the evaluation of the designed electrode. An ion string in the single-well potential and two ion strings in the double-well potential were observed by changing the RF voltages. Such traps could be used for quantum simulation of coupled spin systems.

Study for a 43Ca+ Optical Frequency Standard

The authors proceed with a research and development of an optical frequency standard based on the ²S_1/2 - ²D_5/2 transition of ⁴³Ca⁺ in a RF trap. For this purpose, motional sidebands of a single ⁴⁰Ca ⁺ ion were observed and a stable laser-diode system for spectroscopy of ⁴³Ca⁺ are being developed

Surface-electrode trap with an integrated permanent magnet for generating a magnetic-field gradient at trapped ions

We report on a surface-electrode trap with SmCo magnets arranged in a quadrupole configuration underneath the trap electrode. Because the distance between the magnets and the trapped ions can be as little as several hundred micrometers, a large magnetic field is produced without any heat management. The magnetic-field gradient was measured using the Zeeman splitting of a single trapped

Thin-cell sub-Doppler spectroscopy by spatially separated beam method and pump-probe method

^{40}