Generation of Laguerre-Gaussian modes in Nd:YAG laser using diffractive optical pumping

Authors:
  • JBJ-F Bisson
    J-F Bisson
  • YSYu Senatsky
    Yu Senatsky
  • KUKen-Ichi Ueda
    Ken-Ichi Ueda
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Abstract
A beam of pulsed laser radiation at the wavelength λ = 0.532 μm was diffracted at a circular diaphragm to produce a hollow-shape intensity distribution in the near field. This light distribution was used to pump an Nd:YAG laser, resulting in the formation of an inversion profile with a minimum at the laser resonator axis and enabling the suppression of the fundamental mode. Under this condition, the oscillation at λ = 1.064 μm of Laguerre-Gaussian modes (LG0m) with low and high values of the azimuthal indexmwas produced in the gain-switching regime. By changing the geometry of the resonator, the size of its waist parameter was changed, enabling the selection of the mode with an indexmthat best overlaps with the inversion profile. Oscillation of LG0mmodes with indices ranging fromm=1 to more thanm=200 was obtained. LG0mmodes withm≤ 50 were produced using the dependence of the waist parameter on the length of the resonator near the boundary of its stability region. A LG0mmode of the highest order,m≈ 240 was obtained by building a miniature laser resonator and using a pair of diaphragms in order to form a sharper ring-shape pumping distribution. Applications of diffractive optical pumping and ``hollow'' LG0mlaser beams are discussed.

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