Magnetization In The Uniaxial Crystal Induced By Highly Focusing Laser Beam And All Optic-Magnetical Storage Researches In The Uniaxial Crystal

All-optic magnetic storage is a ultrafast storage technology. The paper have researched on the distributions on the magnetization that focused light is in or through the uniaxial crystal with the Inverse Faraday effect , to analyse the high density all-optic magnetic storage mechanism.Based on the vector diffraction theory, magnetization distributions induced by tightly focusing circularly polarized laser pulses are analyzed in the uniaxial crystal with the Inverse Faraday effect. The dependence of the magnetization distributions on the position of the interface is studied and the magnetization distributions in the uniaxial crystal with small birefringence effect and in the isotropic medium are compared. Numerical results show that when the interface is closed to the lens, the positions of the maximum magnetization intensity and the minimum magnetization spot shift along the optical axial direction. The magnetization intensity in the uniaxial crystal is bigger than that in the isotropic medium but the size of the magnetization spot in the uniaxial crystal is smaller than that in the isotropic medium. For larger ratio(which is defined as a ratio of the anisotropic optic-magneto constant to the isotropic optic-magneto constant in the uniaxial crystal),magnetization intensity is larger but the magnetization spot is smaller.The properties of circularly polarized beams tightly focusing through a uniaxial crystal film are investigated. The numerical results show that for the positive crystal, the focal is close to lens with the birefringence increasing. However, for the negative crystal, the focal shifts away from the lens and the size of the optical spot increases. With the thickness of the positive and negative crystal increasing, the focus is close to lens. However, the thickness increases little, the focal for the positive crystal film shifts more obviously than that for the negative crystal film. When the positive and negative crystal is close to lens, the focal is close to lens, too. However, the film shifts rapidly, the intensity for the positive crystal film decreases more rapidly than that for the negative crystal film.In the transverse direction, passing through the positive and negative uniaxial crystal, the intensity of the center spot increases compared with the intensity without the film, the intensity of the center spot is the biggest when the light is through the negative uniaxial crystal. The side intensity increases for the positive uniaxial crystal film, but for the negative uniaxial crystal film, the side intensity keeps unchanged. In any case, the size of the optical spot keeps unchanged.With optical axis varying in the different directions, the maximal of the intensity for the positive crystal film keeps stable from -90 angle with the system optical axis to 0 angle with the system optical axis, focal depth decreases from -90 angle to -15 angle, focal depth increases from -15 angle to 0 angle, the sidelobe intensity decreases from -90 angle to -40 angle, the sidelobe intensity increases from -40 angle to 0 angle. However, for the negative crystal film, the maximal of the intensity for the positive crystal film keeps stable from -30 angle to 20 angle, depth decreases from -30 angle to 20 angle, the sidelobe intensity decreases from -30 angle to 20 angle. The size of the magnetization spot keeps unchanged between beam passing through the positive or negative uniaxial film and without film.