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

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 (LG 0m ) with low and high values of the azimuthal index m was 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 index m that best overlaps with the inversion profile. Oscillation of LG 0m modes with indices ranging from m =1 to more than m =200 was obtained. LG 0m modes with m ≤ 50 were produced using the dependence of the waist parameter on the length of the resonator near the boundary of its stability region. A LG 0m mode 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'' LG 0m laser beams are discussed.