title: Birefringence-induced bifocusing for selection of radially or azimuthally polarized laser modes.
abstract: We develop a round-trip matrix diagonalization method for quantitative description of selection of radially or azimuthally polarized beams by birefringence-induced bifocusing in a simple laser resonator. We employ different focusing between radially and tangentially polarized light in thermally stressed laser rods to obtain low-loss stable oscillation in a radially polarized Laguerre-Gaussian, LG(0,1)*, mode. We derive a free-space propagator for the radially and azimuthally polarized LG(0,1)* modes and explain basic principles of mode selection by use of a round-trip matrix diagonalization method. Within this method we calculate round-trip diffraction losses and intensity distributions for the lowest-loss transverse modes. We show that, for the considered laser configuration, the round-trip loss obtained for the radially polarized LG(0,1)* mode is significantly smaller than that of the azimuthally polarized mode. Our experimental results, obtained with a diode side-pumped Nd:YAG rod in a flat-convex resonator, confirm the theoretical predictions. We achieved a pure radially polarized LG(0,1)* beam with M(2)=2.5 and tens of watts of output power.
authors.affiliation: Soreq Nuclear Research Center, Electro-Optics Division, Yavne 81800, Israel. galina@soreq.gov.il
authors.forename: Galina
authors.initials: G
authors.lastname: Machavariani
authors.forename: Yaakov
authors.initials: Y
authors.lastname: Lumer
authors.forename: Inon
authors.initials: I
authors.lastname: Moshe
authors.forename: Avi
authors.initials: A
authors.lastname: Meir
authors.forename: Steven
authors.initials: S
authors.lastname: Jackel
authors.forename: Nir
authors.initials: N
authors.lastname: Davidson