Study on high density and monochromatic atomic beam by ultra-high speed frequency modulation laser

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In general, atomic beam is generated by eruption of a small part of thermally generated gas from a small aperture. However, this method has a drawback that the velocity distribution is broad because the atomic source is in thermal equilibrium. Thus, this feature of the thermal atomic beam is a problem when used as a functional beam such as a probe of material surface and an energetic beam source. The purpose of this project is to realize a monochromatic atomic beam by using a high-speed modulation semiconductor laser.Conventional lasers have many narrow spectra called transverse mode, which are not a single broad spectrum required for atomic motion control by the laser light. Therefore, we developed an ultra-high speed frequency modulation semiconductor laser, of which the oscillation frequency varies faster than the reciprocal of the natural lifetime of the atom. High frequency current modulation and frequency-shifted feedback techniques are applied and compared.These laser sources were applied to control the atomic velocity by irradiating to an atomic beam. The atomic velocity distribution was obtained by plotting luminescence intensity from the atoms sweeping the frequency of an another single mode laser. It was verified that the velocity distribution of the thermal atomic beam changes by the laser irradiation. By changing the center frequency and the spectral width of the ultra-high speed frequency modulation laser, the velocity distribution, the distribution change followed the change of the laser parameter. In other words, the velocity of the atoms which Doppler shift corresponds to the laser frequency decreased. As a result, a high density and monochromatic atomic source was achieved.