Three-dimensional (3-d) volumetric display is urgently needed in the fields of air-transportation management, computer-assistant design, imaging application, biophysics, and congratulatory or entertaining art. Recently the growing í#information highwayí# has been accelerating the requirement for 3-d displays to show fast and complex pictures. Frequency up-conversion 3-d volumetric display, abstracting especially in its self-spatial vision, has the advantages of total-solidification, high reliability and speedy operation so that it has a broad range of application. Two-frequency up-conversion 3-d volumetric display was evaluated as the latest achievement of 1996 in physics. This paper careful investigates the one-beam pumping upconversion 3-d volumetric display , which is based on erbium Er doped glass. The bright-light facula length of one-beam pumping upconversion luminescence is studied by diode LD laser. The upconversion luminescence spectrum of Er doped glass is measured also. The physics basis of one-beam pumping upconversion 3-d volumetric display based on Er doped glass is discussed. This interesting result illustrates that the property of one-beam pumping 3-d volumetric display could be improved so much to achieve practical application greatly. As our best knowledge, similar result has not been reported.
Upconversion luminescence of Yb3+-doped and Yb3+ Ho3+-codoped oxyfluoride vitroceramics when excited by a diode laser operating at a wavelength of 960 nm is investigated. A strong 479-nm upconversion cooperative radiation luminescence, attributed to the coupled states of Yb3+Yb3+ clusters, is discovered. This result suggests an interesting and effective path to achieve compact blue upconversion luminescence. The presence of holmium in the Yb3+Ho3+-codoped oxyfluoride vitroceramics substantially reduces intensity of the cooperative upconversion luminescence.
This paper studies upconversion luminescence of oxyfluoride glass codoped with holmium and ytterbium. When the sample was excited in the infrared at a wavelength of 960 nm, several visible luminescence peaks were observed. The two strongest upconversion luminescence peaks are located at 544 and 658 nm, which are due to the 5S2 to 5I8 and 5F5 to 5I8 transitions of Ho3+, respectively. Additional upconversion luminescence peaks are present at 485, 751, and 799 nm. The upconversion luminescence process is initiated by excitation of the codoped Yb3+ ions, followed by a transfer of energy from the excited Yb3+ ions to the Ho3+ ions. The dependence of the upconversion luminescence intensity with the excitation laser power obeys a power law with fractional exponent. This unusual saturation phenomenon is likely a result of energy diffusion.
A diode-pumped microchip laser is developed and achieves self Q-switched operation, which produces nanosecond pulses at a wavelength of 946 nm. The laser medium is a crystal of yttrium aluminum garnet (YAG) doped with both neodymium and chromium. The two surfaces of the NdCr:YAG crystal are coated with dielectric layers, which serve as the mirrors of the laser cavity. The Nd3+ ions in the NdCr:YAG crystal function as the gain medium while the Cr4+ ions act as a saturable absorber. The presence of the saturable absorber leads to self Q-switching, which produces laser pulses of 3.7-ns duration and 946-nm wavelength at a peak power of 240 W. When the laser output is focused onto a KNbO3 crystal, nanosecond pulses of blue color at 473 nm are obtained. The blue laser output has a single frequency and TEM00 transverse mode at a peak power of approximately 18 W.
Nondegenerate four-wave mixing technique has been used to investigate the third-order nonlinear susceptibility for nanocomposite material with Au nanocrystals formed inside a SiO2 glass matrix. High concentrations of encapsulated Au nanocrystals are formed by implantation of Au+ ions into fused silica glass substrates and thermal annealing. The size distribution and the depth profiles of the Au nanoparticles can be controlled by the implantation dose, energy and annealing temperatures. The high value of the third-order susceptibility approximately (0.26 - 1.3) X 10-7 esu was found in the range of the frequency detunings (Delta) (1/(lambda) ) -1 near the surface plasmon resonance. Two characteristic relaxation times, 0.66 ps and 5.3 ps, have been extracted from the detuning curve of the third-order susceptibility as the probe-beam frequency changes and the pump-beam frequency fixed at the plasmon resonance. The first relaxation time was attributed to electron-phonon relaxation, and the second to thermal diffusion to the host medium. The efficient nondegenerate conversion is attractive for optical processing.
KEYWORDS: Near field optics, Silver, Nanoparticles, Particles, Transmission electron microscopy, Fractal analysis, Laser ablation, Thin films, Laser beam diagnostics, Near field
Thin films of randomly distributed silver nanoparticles are studied experimentally using photon scanning tunneling microscopy and theoretically using real-space renormalization group method. The studies reveal large variations of local optical intensity at sub-wavelength scales. In addition, irradiation of the film by nanosecond laser pulses is observed to yield substantial changes in the local optical response. The threshold for the photomodification is less than 10 mJ/cm2. It is believed that particles within some areas of nanometer scales are restructured during nanosecond laser irradiation. The geometric changes in turn result in modification of the local optical intensity.
The technique of optical second harmonic generation is used to study phase transformations at 2D surfaces and interfaces. Examples are given to illustrate that changes in surface symmetry, adsorption configuration, and electronic structure can be detected by this nonlinear optical technique. An oscillatory phase transformation of potassium adsorbed atoms on Al(111) probed by second harmonic generation is analyzed in detail.
The dynamics of photocarrier diffusion was studied by a two color transient grating technique in reflection geometry. A single exponential decay feature was observed immediately following the electron excitation pulse and was attributed to band edge carrier diffusion.
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