A few different Sodium borate glasses were made by the melt quenching technique. A sodium borate glass embedded with Dy3+ revealed white color when excited by a diode laser. A chromaticity diagram was developed which revealed color coordinates to be x=0.403 and y=0.426 for 375 nm diode laser excitation. A glass that was embedded with Dy3+, and Sm3+ revealed warm white light under diode laser excitation. However, another glass embedded with Dy3+, Sm3+, and Tb3+ revealed warm white light whose color coordinates are x=0.375 and y=0.455 and the coordinated color temperature is 5173 K.
We investigated terbium doped halide crystals. These materials were investigated by exposing them to blue and violet diode laser sources. Optical spectroscopy and lifetime measurements are performed for unambiguous assignment of spectral transitions and detect quenching phenomenon, if any. Terbium doped halide crystals revealed bright white light under low power diode laser excitation. Chromaticity diagrams are developed from spectral measurements. Color coordinates and color temperature are estimated. Our measurements indicate that terbium-doped fluorides are suitable for white-light generation under diode laser excitation.
Absorption spectrum of Er3+-dopedCaF2 revealed absorption peaks at 255, 365, 379, 407, 441, 449, 487, 522, 539, 652, and 798 nm. When the sample was excited with an 802-nm near-infrared laser, it revealed emissions at 390, 415, 462, 555, 665, and 790 nm due to stepwise excitation and energy transfer upconversion processes. The absorption and emission peaks are identified with Er3+ spectral transitions. The sample color appears to be either white or green under near-infrared laser excitation. Emission color was found to be dependent on the pump laser wavelength used and laser power. Excitation spectral recordings were made by tuning the pump laser wavelength. Excited state lifetimes are measured to analyze the data. Color coordinates and color temperatures are measured for 802- and 405-nm laser excitations. Our studies indicate that this sample is useful for solid-state lighting applications.
Sodium borate glass embedded with Tb3+, Sm3+ and Dy3+ was made by the melt quenching technique. The resulting glass is highly transparent. Absorption, and emission spectral measurements are performed. Under a diode laser excitation the glass emitted warm white light. Lifetimes of the excited levels are measured. CIE color co-ordinates and color temperature are measured.
CaF2 is a cubic material and Erbium enters the lattice in triply ionized state. Erbium occupies Ca sites in the material. Defects occur in the material because a trivalent dopant ion replaces a divalent host ion. Er3+ occupies several different sites. Absorption spectrum of Er3+-doped CaF2 revealed absorption peaks at 255, 365, 379, 407, 441, 449, 487, 522, 539, 652 and 798 nm. When the sample was excited with an 800 nm near-infrared laser it revealed emissions at 390, 415, 462, 555, 665 and 790 nm. The absorption and emission peaks are identified with Er3+ spectral transitions. The sample color appears to be either white or green under near-infrared laser excitation. Emission color was found to be dependent on the pump laser wavelength used and laser power. Excitation spectral recordings were made by tuning the pump laser wavelength. The sample emission appears to be white under near-infrared excitation as well as violet laser excitation. Excited state lifetimes are measured to analyze the data. Our studies indicate that this sample is useful in solid state lighting applications.
Extracellular Biosynthesis technique (EBS) for nanoparticles production has attracted a lot of attention as an
environmentally friendly and an inexpensive methodology. Our recent research was focused on the rapid approach of the
green synthesis method and the reduction of the homogeneous size distribution of nanoparticles using pulse laser
application. Noble nanoparticles (NNPs) were produced using various ethanol and water plant extracts. The plants were
chosen based on their biomedical applications. The plants we used were Magnolia grandiflora, Geranium, Aloe
‘tingtinkie’, Aloe barbadensis (Aloe Vera), Eucalyptus angophoroides, Sansevieria trifasciata, Impatiens scapiflora.
Water and ethanol extract, were used as reducing agents to produce the nanoparticles. The reaction process was
monitored using a UV-Visible spectroscopy. NNPs were characterized by Fourier Transfer Infrared Spectroscopy
(FTIR), Transmission Electron Microscopy (TEM), and the Dynamic Light Scattering technique (DLS). During the pulse
laser Nd-YAG illumination (λ=1064nm, 532nm, PE= 450mJ, 200mJ, 10 min) the blue shift of the surface plasmon
resonance absorption peak was observed from ~424nm to 403nm for silver NP; and from ~530nm to 520 nm for gold
NPs. In addition, NNPs solution after Nd-YAG illumination was characterized by the narrowing of the surface plasmon
absorption resonance band, which corresponds to monodispersed NNPS distribution. FTIR, TEM, DLS, Zeta potential
results demonstrated that NNPs were surrounded by biological molecules, which naturally stabilized nanosolutions for
months. Cytotoxicity investigation of biosynthesized NNPs is in progress.
Glasses embedded with Dysprosium and Samarium were made by the melt quenching technique. Dy3+ -doped glasses exhibited bright white luminescence under 10 mW of 405 nm diode laser excitation. Color rending index of the glass was improved by adding Sm3+ as a co-dopant to the glass. Spectroscopic results of the glasses are discussed.
There is a great need for rapid detection of bio-hazardous species particularly in applications to food safety and biodefense.
It has been recently demonstrated that the colonies of various bio-species could be rapidly detected using
culture-specific and reproducible patterns generated by scattered non-coherent light. However, the method heavily relies
on a digital pattern recognition algorithm, which is rather complex, requires substantial computational power and is
prone to ambiguities due to shift, scale, or orientation mismatch between the analyzed pattern and the reference from the
library. The improvement could be made, if, in addition to the intensity of the scattered optical wave, its phase would be
also simultaneously recorded and used for the digital holographic pattern recognition. In this feasibility study the
research team recorded digital Gabor-type (in-line) holograms of colonies of micro-organisms, such as Salmonella with
a laser diode as a low-coherence light source and a lensless high-resolution (2.0x2.0 micron pixel pitch) digital image
sensor. The colonies were grown in conventional Petri dishes using standard methods. The digitally recorded holograms
were used for computational reconstruction of the amplitude and phase information of the optical wave diffracted on the
colonies. Besides, the pattern recognition of the colony fragments using the cross-correlation between the digital
hologram was also implemented. The colonies of mold fungi Altenaria sp, Rhizophus, sp, and Aspergillus sp have been
also generating nano-colloidal silver during their growth in specially prepared matrices. The silver-specific plasmonic
optical extinction peak at 410-nm was also used for rapid detection and growth monitoring of the fungi colonies.
We discuss phenomena of the optical photons and charged particle channeling in the periodic structures. While particle (as protons) channeling is widely used for the characterization of defects in crystals, channeling of photons is less known. We have demonstrated feasibility of optical channeling method for copying of phase radial grating on the chalcogenide semiconductor glass film and photo-thermoplastic films (PTPF). Chalcogenide glassy semiconductors (CGS) as a medium for recording of optical information have some advantages such as the possibility of achieving a higher resolution power, stability, and a high photosensitivity. We report about recording of the radial phase grating in the doped As-S-Se (CGS). Radial grating was recorded by making copy from the master phase grating placed in the near-field zone and exposure to the CW green (λ=532 nm) low power (P=100 mW) solid-state laser or incoherent UV source. The exposure time has been varied from 15 to 30 min. The recording process could be explained by optical channeling. This phenomenon gives us an opportunity to create phase radial grating using coherent and incoherent illumination.
We have studied holographic grating recordings in Fe-doped photorefractive crystals LiNbO3 (LN), in doped As-S-Se chalcogenide glassy semiconductors (CGS), and in CGS based photothermoplastic structures (PTPS). Transmission gratings in a-cut crystals of LN were efficient enough to demonstrate the effect of optical channeling. Volume gratings recorded in LN crystals may be used as a parallel array of the planar waveguides. For CGS, slanted grating geometry was tested, with the goal being the creation of asymmetric blazed gratings. Asymmetry of non-Bragg diffraction orders was observed. For the first time, reflection volume grating were recorded in 2μm thick CGS by green solid-state laser. We have also tested the possibility of single beam contact recording in LN, using CGS with recorded grating as beam-splitter attached to the surface of LN.
We have studied holographic grating recording in Fe-doped photorefractive crystals LiNbO3 (LN) and in doped As-S- Se chalcogenide glassy semiconductor (CGS) films. Transmission gratings in (alpha) -cut crystals of LN are efficient enough to demonstrate effect of optical channeling. Volume gratings recorded in LN crystals may be used as a parallel array of the planar waveguides. For the CGS slanted grating geometry was tested, aiming on creation of asymmetric blazed gratings. Asymmetry of non-Bragg diffraction orders was observed and its was 12 times enhanced by a gold coating. For the first time reflection volume grating were recorded in 2 mm thick CGS by green solid state laser ((lambda) equals 532 nm, P equals 100 mW).
We discuss manifestation of the channeling effect in the visualization of hexagonal patterns in KNbO3 and phase gratings in LiNbO3. We have shown that visualization of the domain patterns, discovered earlier in the subharmonic beam in the photorefractive BSO crystal, may be explained by the channeling effect. A wave-packet description allows us to explain backward movement of domains due to the specific dispersion law for the space-charge waves. An analogy is discussed with domain formation in the charge-density-waves, known in quasi-1D conductors. Non-linear phase shift of the couple's waves may lead to discomensuration.
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