Dispersive phase coupling induced superluminal Gaussian light pulses in BSO crystals at room temperature

2005 ◽  
Author(s):  
Fang Bo ◽  
Guoquan Zhang ◽  
Jingjun Xu
Keyword(s):  
Room Temperature ◽  
Phase Coupling ◽  
Light Pulses ◽  
Dispersive Phase

SLOW AND FAST LIGHTS WITH MOVING AND STATIONARY REFRACTIVE INDEX GRATINGS IN SOLIDS AT ROOM TEMPERATURE

2008 ◽  
Vol 22 (05) ◽  
pp. 447-468 ◽  
Author(s):  
GUOQUAN ZHANG ◽  
FANG BO ◽  
FENG GAO ◽  
RONG DONG ◽  
YANFEI TU ◽  
...  
Keyword(s):  
Refractive Index ◽  
Room Temperature ◽  
Coupling Effect ◽  
Buffer Layers ◽  
Volume Index ◽  
Phase Coupling ◽  
Dispersion Slope ◽  
Grating Structure ◽  
Potential Applications ◽  
Fast Light

We reviewed the recent progress on slow and fast lights in solids at room temperature based on moving and stationary refractive index gratings. A dispersive photorefractive phase coupling associated with moving gratings results in slow and fast lights. In principle, such phase-coupling-induced slow and fast lights can be observed in any nonlinear wave mixing process with a dispersive phase coupling effect. The slow and fast lights in the stationary gratings are also discussed. One advantage of the stationary gratings is the possibility to engineer the dispersion slope of the grating through designing the grating structure and parameters. As an example, we show that the dispersion slope of the gratings is enhanced significantly by stratifying a series of identical volume index gratings with homogeneous optical buffer layers sandwiched between every two neighboring grating layers. The slow and fast lights, therefore, can be controlled more effectively in such specifically designed grating structures than in the homogeneous gratings. Another advantage is the high transparency of the slow and fast lights with appropriate grating structure and parameters. Issues such as the pulse broadening effect and the pulse distortion are addressed. The slow and fast light techniques have many important potential applications such as optical delay lines and optical buffers.

Erzeugung von freien Defektelektronen in 2,3 Dimethylnaphthalin- Einkristallen mit schwach absorbiertem Licht/ Photo generation of Holes in 2,3-Dimethylnaphthalene by Weakly Absorbed Light

1975 ◽  
Vol 30 (10) ◽  
pp. 1315-1327
Author(s):  
W.-W. Falter
Keyword(s):  
Surface Layer ◽  
Room Temperature ◽  
Second Harmonic ◽  
Incident Light ◽  
Crystal Defects ◽  
Recombination Coefficient ◽  
Nitrogen Laser ◽  
Light Pulses ◽  
Electronically Excited ◽  
Current Densities

Abstract Irradiation of 2,3 DN single crystals by 5 nsec light pulses from a nitrogen laser (337 nm) and by 20 nsec light pulses from a Q-switched ruby laser (347 nm, second harmonic) respectively, causes generation of free holes. Centers which are most probably associated with crystal defects are electronically excited by the incident light directly or by energy transfer from the primary excited 2,3 DN. The excited centers are quenched by charge transfer interaction with 2,3 DN. Mobile holes are separated from the localized negatively charged centers subject to the applied electric field. The centers are distributed uniformly over most of the volume, but in a region closer than 1 μm to the surface the concentration increases rapidly. In this surface layer also a high density of hole traps are found to exist, which are responsible for the temperature dependent rise of the photocurrent pulses below room temperature. At high current densities recombination between ionized centers and drifting holes becomes important. The recombination coefficient is found to be 10-5 cm3 /sec. Analysation of the fast (60 nsec) rise of the photocurrent pulses above room temperature gives information about the lifetime of the excited centers and about the lifetime of the singlet excitons in the surface layer. Values of ≈ 30 nsec for the centers and ≲ 10 nsec for the excitons are found. The volume lifetime of the singlet excitons is measured to be 80 nsec.

scholarly journals ELECTRON–PHONON INTERACTIONS CAUSE HTSC

2001 ◽  
Vol 15 (24n25) ◽  
pp. 3153-3155 ◽  
Author(s):  
J. C. PHILLIPS
Keyword(s):  
High Temperature ◽  
Room Temperature ◽  
High Temperature Superconductivity ◽  
Temperature Conductivity ◽  
Room Temperature Conductivity ◽  
Light Pulses ◽  
Pressure Changes

What is the microscopic interaction responsible for high temperature superconductivity (HTSC)? Here data on temporal relaxation of T c and the room temperature conductivity in YBa2Cu3O 6+x after abrupt alteration by light pulses or pressure changes are analyzed. The analysis proves, independently of microscopic details, that only electron–phonon interactions can cause HTSC in the cuprates; all other dynamical interactions are excluded by experiment.

Dependence of Intergranular Fracture on Boundary Topography and Cohesion

1973 ◽  
Vol 31 ◽  
pp. 150-151
Author(s):  
J. E. Doherty ◽  
A. F. Giamei ◽  
B. H. Kear ◽  
C. W. Steinke
Keyword(s):  
Grain Boundary ◽  
Room Temperature ◽  
Nickel Base Superalloy ◽  
Boundary Shear ◽  
Room Temperature Ductility ◽  
Solid Solution Matrix ◽  
Nickel Base ◽  
Solution Matrix ◽  
Different Levels ◽  
Base Superalloy

Recently we have been investigating a class of nickel-base superalloys which possess substantial room temperature ductility. This improvement in ductility is directly related to improvements in grain boundary strength due to increased boundary cohesion through control of detrimental impurities and improved boundary shear strength by controlled grain boundary micros true tures.For these investigations an experimental nickel-base superalloy was doped with different levels of sulphur impurity. The micros tructure after a heat treatment of 1360°C for 2 hr, 1200°C for 16 hr consists of coherent precipitates of γ’ Ni3(Al,X) in a nickel solid solution matrix.

Hepatocyte Alterations in Guinea Pigs FED Polychlorinated Biphenyls (PCBs), Dibenzodioxins (PCDD), AND DIBENZOFURANS (PCDF)

1982 ◽  
Vol 40 ◽  
pp. 56-57
Author(s):  
J. N. Turner ◽  
D. N. Collins
Keyword(s):  
Guinea Pigs ◽  
Room Temperature ◽  
Dose Group ◽  
Methyl Cellulose ◽  
Uranyl Acetate ◽  
Target Organ ◽  
Office Building ◽  
Lead Citrate ◽  
Control Groups ◽  
Cooling Fluid

A fire involving an electric service transformer and its cooling fluid, a mixture of PCBs and chlorinated benzenes, contaminated an office building with a fine soot. Chemical analysis showed PCDDs and PCDFs including the highly toxic tetra isomers. Guinea pigs were chosen as an experimental animal to test the soot's toxicity because of their sensitivity to these compounds, and the liver was examined because it is a target organ. The soot was suspended in 0.75% methyl cellulose and administered in a single dose by gavage at levels of 1,10,100, and 500mgm soot/kgm body weight. Each dose group was composed of 6 males and 6 females. Control groups included 12 (6 male, 6 female) animals fed activated carbon in methyl cellulose, 6 males fed methyl cellulose, and 16 males and 10 females untreated. The guinea pigs were sacrificed at 42 days by suffocation in CO2. Liver samples were immediately immersed and minced in 2% gluteraldehyde in cacadylate buffer at pH 7.4 and 4°C. After overnight fixation, samples were postfixed in 1% OsO4 in cacodylate for 1 hr at room temperature, embedded in epon, sectioned and stained with uranyl acetate and lead citrate.

Domain Formation in Synthetic Quartz

1971 ◽  
Vol 29 ◽  
pp. 156-157
Author(s):  
Joseph J. Comer
Keyword(s):  
Electron Beam ◽  
Room Temperature ◽  
Domain Formation ◽  
Synthetic Quartz ◽  
Transmission Electron ◽  
Black Spots ◽  
Diffraction Mode ◽  
Domain Boundaries ◽  
Kikuchi Lines ◽  
Straight Lines

Domains visible by transmission electron microscopy, believed to be Dauphiné inversion twins, were found in some specimens of synthetic quartz heated to 680°C and cooled to room temperature. With the electron beam close to parallel to the [0001] direction the domain boundaries appeared as straight lines normal to <100> and <410> or <510> directions. In the selected area diffraction mode, a shift of the Kikuchi lines was observed when the electron beam was made to traverse the specimen across a boundary. This shift indicates a change in orientation which accounts for the visibility of the domain by diffraction contrast when the specimen is tilted. Upon exposure to a 100 KV electron beam with a flux of 5x 1018 electrons/cm2sec the boundaries are rapidly decorated by radiation damage centers appearing as black spots. Similar crystallographio boundaries were sometimes found in unannealed (0001) quartz damaged by electrons.

A Liquid Nitrogen Cooled Stage for STEM

1974 ◽  
Vol 32 ◽  
pp. 444-445
Author(s):  
Louis T. Germinario
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Liquid Nitrogen ◽  
Room Temperature ◽  
Objective Lens ◽  
Thermal Drift ◽  
Specimen Holder ◽  
Resolution Capability ◽  
Focal Position

A liquid nitrogen stage has been developed for the JEOL JEM-100B electron microscope equipped with a scanning attachment. The design is a modification of the standard JEM-100B SEM specimen holder with specimen cooling to any temperatures In the range ~ 55°K to room temperature. Since the specimen plane is maintained at the ‘high resolution’ focal position of the objective lens and ‘bumping’ and thermal drift la minimized by supercooling the liquid nitrogen, the high resolution capability of the microscope is maintained (Fig.4).

Cryogenic atomic force microscopy

1991 ◽  
Vol 49 ◽  
pp. 54-55
Author(s):  
K. A. Fisher ◽  
M. G. L. Gustafsson ◽  
M. B. Shattuck ◽  
J. Clarke
Keyword(s):  
Room Temperature ◽  
Rapid Freezing ◽  
Cryogenic Temperatures ◽  
Soft Or ◽  
Electrically Conductive ◽  
Force Microscopy ◽  
Flexible Molecules ◽  
Advantages And Disadvantages ◽  
Atomic Force ◽  
Chemical Perturbation

The atomic force microscope (AFM) is capable of imaging electrically conductive and non-conductive surfaces at atomic resolution. When used to image biological samples, however, lateral resolution is often limited to nanometer levels, due primarily to AFM tip/sample interactions. Several approaches to immobilize and stabilize soft or flexible molecules for AFM have been examined, notably, tethering coating, and freezing. Although each approach has its advantages and disadvantages, rapid freezing techniques have the special advantage of avoiding chemical perturbation, and minimizing physical disruption of the sample. Scanning with an AFM at cryogenic temperatures has the potential to image frozen biomolecules at high resolution. We have constructed a force microscope capable of operating immersed in liquid n-pentane and have tested its performance at room temperature with carbon and metal-coated samples, and at 143° K with uncoated ferritin and purple membrane (PM).

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