Ryuzo Ohmukai

High-power second-harmonic generation with picosecond and hundreds-of-picosecond pulses of a cw mode-locked Ti:sapphire laser.

A cw mode-locked Ti:sapphire laser was efficiently frequency doubled with a lithium triborate crystal in an external enhancement cavity. Second-harmonic output powers of 1.28 W and 860 mW have been generated at 399 nm with fundamental pulse widths of 1.5 and 320 ps, respectively. At the 1.5-ps pulse width the conversion efficiency was 75%. The spectral width of the 320-ps pulses, produced by modification of a laser cavity, is as narrow as the bandwidth of a normal cw, multimode, narrow-bandwidth Ti:sapphire laser. The frequency-doubled output can be thus used as a high-power, narrow-bandwidth light source in the UV region.

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.

Sum-Frequency Generation near 194 nm with an External Cavity by Simultaneous Enhancement of Frequency-Stabilized Fundamental Lasers

Continuous-wave coherent radiation near 194 nm has been generated by sum-frequency mixing with simultaneous enhancement of both fundamental lasers. An output power of 31 µ W was obtained at 194 nm. The frequency of a Ti: sapphire laser, which was used as one of the fundamental lasers, was stabilized with a frequency fluctuation of 80 kHz rms by using a mode-interference method.

Tunable 397-nm light source for spectroscopy obtained by frequency doubling of a diode laser.

Continuous-wave radiation of 1.8 mW at 397 nm was generated by frequency doubling a 100-mW GaAlAs diode laser in a lithium iodate crystal placed in an external enhancement cavity. The radiation had a narrow linewidth and a continuous frequency-scanning range of 6 GHz. The UV radiation obtained was applied to laser cooling of calcium ions stored in a rf trap.

Tunable 397 nm Light Source for Laser Cooling of Ca Ions Based on Frequency Doubling of Diode Laser

We have fabricated an rf ion trap and laser-cooling light sources to observe shelving transition in a single calcium ion. All the radiation required for laser cooling and observation of the transition can be prepared with diode lasers in this system. Continuous-wave radiation at 397 nm for laser cooling was generated by frequency doubling of a GaAlAs laser in an external enhancement cavity. As a preliminary experiment for observing the shelving transition, laser cooling of one hundred calcium ions was demonstrated using this radiation and another diode laser.

Laser Cooling of Ca^+ Ions and Observation of Collision Effects

This paper describes our recent experimental results on trapping and laser cooling of Ca + ions. The measurement of the characteristics of laser-cooled Ca + ions in an rf quadrupole ion trap, such as the fluorescence line shape and phase transition, is described. Observation of two types of collision-induced «quantum jumps» of a Ca + ion in a background gas of H 2 or air is also described. Since the rate of the collision-induced jumps is very high for Ca + , it is necessary to achieve an extremely high vacuum condition for frequency standard applications

Doppler-Free Optogalvanic Spectroscopy of Ca^+ and Ca

The high-resolution Doppler-free optogalvanic spectra of Ca+ and Ca were observed using a commercial hollow-cathode lamp and a single-mode cw ring Ti:sapphire laser or a dye laser. The measured full width at half-intensity-maximum (FWHM) of the Ca+ Doppler-free component was 167 MHz, which is sufficient for calibrating the wavelength for the laser cooling of Ca+ ions. The amount of collision broadening in the Ca+ spectrum was much greater than that in the Ca spectrum.

Atomic nanofabrication using an ytterbium atomic beam

Abstract Highly parallel and periodically narrow lines of ytterbium (Yb) atoms were successfully produced on a substrate using a near resonant laser light and direct-write atomic nanofabrication. Yb atoms are a promising material for nanofabrication using atom optics particularly due to their electric conductivity, the laser wavelength required for their manipulation, and the vapor pressure required for their fabrication. Collimated 174Yb atoms were channeled into the nodes of an optical standing wave with dipole force and then deposited onto a substrate. We clearly observed a grating pattern of Yb atoms fabricated on a substrate with a line separation of approximately 200 nm after examining the surface of the substrate with an atomic force microscope. This is the first demonstration of nanofabrication using the atom-optical approach with Yb atoms.

Laser microwave double-resonance experiment on trapped /sup 113/Cd/sup +/ ions

The possibility of using Cd/sup +/ ions as a microwave frequency standard whose light source is an all-solid state UV laser system is presented. The ground-state hyperfine splitting of trapped /sup 113/Cd/sup +/ ions is measured using an RF trap technique. The transition is detected using a laser microwave double-resonance method in the presence of He buffer gas. The splitting is determined to be 15 199 862 858(2) Hz. The preciseness of the value was improved over that in previous data by seven orders of magnitude. A light source of 214.5 nm is being developed by the authors for optical pumping and laser-cooling of Cd/sup +/ ions whose fundamental oscillator is based on diode lasers.

Deflection of a Velocity Compressed Yb Atomic Beam by a Multi-Mode Spectral Laser

We have generated a continuous, monovelocity Yb atomic beam based on a technique combining velocity compression and beam deflection. Two single-mode lasers were used to compress the thermally broadened velocity distribution, and a multi-mode spectrum of a mode-locked laser was used to extract the compressed part as a deflected beam. The observed deflection angles were compared with the calculations. Deflection angles up to 12° were obtained.