We present the first observation of nonlinear optical response mediated by ultrafast magneto-electric (ME) rectification. The control of magnetic properties of materials by ultrafast optical field enable novel sensing technology, energy conversion, terahertz emission, and ultrafast data storage. However, the interaction of the magnetic field of light with materials is normally ignored due to low magnetic susceptibilities at high frequencies. Optical nonlinearities driven jointly by electric and magnetic field components of light provide a new route in controlling magnetic properties of bulk media. Several novel physical phenomena arise from curved motion of bound electrons driven jointly by electric and magnetic fields such as longitudinally polarized second harmonic radiation, induced transverse magnetization at the optical frequency, and charge separation along the propagation direction. We investigate an ME charge separation in pentacene semiconductors using a time-resolved second harmonic generation technique. A femtosecond laser beam acted as an optical pump with photon energy well below the bandgap of the material to induce ME charge separation. The DC electric field from the ME charge separation interacted with the optical field from a second laser beam, the probe, in a four-wave-mixing interaction that induced second harmonic (M-EFISH) generation. We also sought evidence of ME charge separation by searching for THz emission. By monitoring time-resolved M-EFISH and THz emission, we were able to study the ME charge separation dynamics for the first time.
In this work, we report three-dimensional memory by recording optical bits with irradiation of near-infrared femtosecond laser pulses and by reading photoluminescence change in the blue due to permanent reduction of Eu<sup>3+</sup> to Eu<sup>2+</sup> in sodium borate glasses. We produced a multilayered micro-bit pattern which was read out by detecting the blue emission from the 405 nm excitation with a high S/N ratio. The readout was performed by using a scanning reflection-type confocal microscope.
We report ultraviolet-induced transient and stable absorption and two-color holographic recording at 514, 633, and 830 nm in thulium doped stoichiometric LiNbO3 crystal. The gating light at 355 nm increased the diffraction efficiency and sensitivity. We found the optimum gating-recording intensity ratio for maximum diffraction efficiency and weak nonvolatile holographic storage with gating.
From the ultraviolet induced absorption, we have found a broad blue band and little involvement of Pr ions in ultraviolet illumination. Ultraviolet excited photoluminescence and the excitation spectra for visible emission were also measured in Pr:LiNbO<sub>3</sub>. We estimated photovoltaic constant and photoconductivity by measuring photovoltaic current and voltage with different boundary conditions. With ultraviolet gated short-circuit holographic recording, we have measured enhanced sensitivity and diffraction efficiency.