Narrow band, high power light from diode lasers

A 100 mW CW laser diode array has been used to amplify the light from a low power, single stripe diode laser. The input light was spectrally narrowed and frequency stabilized to less than 300 kHz using optical feedback from a Fabry-Perot cavity, and the amplified beam had the same spectral characteristics. Also, the 90 mW amplified beam had a single diffraction-limited spatial mode corresponding to the full 100-micron width of the array, indicating that all its stripes were coherent. A simple quantitative model of this process has been tested using counterpropagating beams light from this array to form a one-dimensional optical molasses perpendicular to an atomic beam of Rb-85 for active collimation. The minimum measured angular spread of the beam corresponds to a transverse rms speed of 3 cm/s. This low velocity was limited only by experimental geometry.