Jean-Francois BISSON, Akira SHIRAKAWA, Youhei SATO, Yuri SENATSKY¹ and Ken-Ichi UEDA

Institute for Laser Science, University of Electro-Communications, 1-5-1, Chofu-gaoka, Chofu, Tokyo 182-8585, Japan
¹P.N.Lebedev Physical Institute of the RAS, Leninsky pr.53, Moscow, Russia

(Received October 6, 2004; Accepted October 9, 2004)

A Nd:YAG rod active element placed inside a resonator was pumped by the second harmonic radiation (the wavelength λ=0.532 μm) of a Q-switched Nd:YAG laser diffracted at a circular aperture. Various distributions of pumping intensity in the Fresnel (near-field) region along the direction of the pump beam diffraction were produced. Inversion profiles with maxima or minima at the resonator axis were formed in the active element, depending on its distance from the circular aperture. Gain-switched operation of the Nd:YAG rod laser at λ=1.064 μm is reported at the fundamental mode and also at the TEM₀₁, TEM_01* and other higher-order modes for different positions of the active element in the near-field region. Applications of such diffractive optical pumping for the concentration of the pumping radiation into the active media and for laser beam profiling are discussed.

Key words: diffractive optical pumping, laser ceramics, mode selection, hollow beams