Results

Stage I/2012

Preliminary study was done related to obtaining method, structure and properties of MVMOVPR
Design, performing and experimentation of the laboratory method to prepare MVMOVPR

optical quality alumino-phosphate glasses containing rare-earth oxides were prepared by wet chemical method
Bulk glasses with low defects (bubbles, inclusions, crystals, striations) were obtained by using Alcoa (import USA) melting crucibles by comparison with the glass obtained in crucibles type ICEM, Romania
SEM-EDX analysis (scanning electron microscopy, energy dispersive X-ray) revealed the presence of bubbles and micro-crystals in the bulk glass. Some of the crystals were identified as having the similar chemical composition to that of aluminum phosphite
EDX elemental maps showed a good chemical homogeneity of the doped phosphate glasses due both to the wet chemical method used to prepare the mixture of raw materials and to the homogenization program by mechanical stirring applied to the glass melt
A simple and efficient method used to assess the optical homogeneity and the remnant stress in the final glass was adapted; in order to establish the bubble and striae content, a method based on polarized light was applied.
The refractive index and optical dispersion were determined for several wavelengths in the visible domain
Characterizing procedures magnetic and magneto-optical properties of vitreous samples with rare earth ions
Information regarding the type of magnetic order and range of the magnetic moment of the rare-earth ions were obtained by magnetic susceptibility measurements, depending on temperature and field dependent magnetization respectively, at constant temperature. In all cases, we took into account the contribution of the vitreous matrix, doped with rare-earth ions, to the level of the magnetic signal
MOKE equipment was adapted (Magneto-Optical Kerr) for measurements of Faraday effect (measured by light transmission) by special mounting samples with and without magnetic field
A standard procedure for the measurement of magneto-optical effect in transmission geometry was established (set-up)

The dependence of the polarization vector rotation on the sample rotation angle around the wave vector (that was permenently mentained perpendicular on the sample plan) was noticed
Due to the optical anisotropy of the vitreous matrix (most likely induced by the specific conditions of preparation), it was found that a complete measurement must necessarily be polar, that is to be defined by the evolution of the Kerr angle against sample rotation angle.
The experimental conditions were determined to maximize the Kerr angle for a given sample. The Kerr angles depend sensitively on the sample homogeneity, so the purpose of the subsequent research reportswill have to consideras essential to prepare high homogeneous glass samples
Magnetic and magneto-optical measurements were performed on vitreous samples doped with rare-earth ions (Dy, Tb, Me, Pr). Conclusive results both with respect to the magnetic measurements and magneto-optical glasses were obtained for Tb and Dy doped glasses.
It was found that the magneto-optical properties of the obtained glasses are dependent on melting, stirring and annealing applied programs
The dissemination of the research results developed within Stage I of the project was done by publication of five articles in professional journals (ISI), submissionof four articles for publication in professional journals and presentation of six scientific papers at international events

Stage II/2013

Phosphate glasses doped with Eu³⁺, Dy³⁺ and Tb³⁺ have been prepared applying homogenization system by mechanical stirring of the vitreous melt
Undoped phosphate glass (reference glass) and La³⁺ replaced by Y³⁺ glass have been prepared in order to investigate magnetic and magneto-optical properties that will be correlated with those of Dy³⁺ and Tb³⁺ doped glasses
Optical measurements (optical homogeneity and remanent strains) have been performed on undoped glass and La³⁺ replaced by Y³⁺ glass
A theoretical model was elaborated to establish the rotation of the polarization plan due to the remnant strains (birefringence) that will be verified by magnetic measurements
Approach of two complementary measurement methods: optical homogeneity measured by polarimetry and, respectively, interferometry (applied only after polarimetry)
Un-doped and Dy, Tb and Fe doped phosphate glasses were prepared (increased amount of dopant), by non-conventional wet route raw materials preparation followed by melt-quenching method
Physical measurements were performed on the as prepared glasses (density, thermal expansion, glass characteristic temperatures, chemical stability and viscosity)
Adapted measurement for validation of the nonstandard polarimetric method
Model and soft elaboration for striae deffects in the glass, both in polarized light
A correlation was established was established between optical and magnetic measurements related to the influence of the striae from the glass on the change of the light polarization direction
Faraday rotation is in close correlation with optical homogeneity of the doped glass
Trials reports were done comprising data obtained from different devices, for samples from different bunches
Magneto-optical characterization procedures were established for different rare-earth-doped glasses (magnetic susceptibility in dependency on temperature and magnetization in dependency on the magnetic field, at constant temperature)]
MOKE (Magneto-Optical Kerr Effect) equipment was adapted for Faraday measurements for sample mounting with and without magnetic field
A standard procedure to measure magneto-optical effect in transmission mode was set-up
The dependency of the polarization vector rotation on the rotation angle of the sample around the wave vector was established
Faraday rotation is in close correlation with glass sample homogeneity
In the case of iron-doped glasses, samples annealing will be apllied in order to get significant magneto-optical signals
Ellipsometric method will be used to measure Faraday rotation in dependency on wavelength of bulk glasses as well as refractive index and thickness of the rare-earth-doped films

Stage III/2014

Elaboration, design, performing and experimentation of the non-conventional wet-method to prepare MOBGT (Fe²⁺, Mn²⁺) and MOBGPT (Pb²⁺, Bi³⁺)
Performing and testing of a dedicated mechanical system to homogenize the melt by stirring in order to prepare an optical quality glass
Magneto-optical glasses were characterized as regards: optical homogeneity (refractive index changes), striae and birefringence (remnant stress)
Optical investigation of the transition (Fe, Mn) and post-transition (Bi, Pb)-doped glasses was performed by: visual investigation, polariscope, polarimeter, interferometer without and with polarization, shadow method
General physical characterization of MOBGT and MOBGPT: density, thermal expansion coefficient, characteristic temperatures, density, viscosity
Structural characterization of MOBGT and MOBGPT by FTIR and Raman spectroscopy
Two methodologies aimed at measuring low Faraday rotations (very thin glasses, d< 1 mm) and, high rotations (thick glasses), based on an existing equipment adapted to transmission measurements
An ellipsometric methodology was elaborated in order to determine the dispersion of Verdet constant and magneto-optical characterization
Ellipsometric method was applied to all the glasses elaborated and characterized in the frame of the previous research stages
The new phosphate glasses: (i) neither doping oxides nor adding compounds (La₂O₃, Y₂O₃); (ii) contains adding compounds but without doping oxides; (iii) contains doping oxides but no adding compounds, elaborated in the frame of the present project exhibit a high Faraday rotation (at 400 nm, V= 10.8 rad)
Embedding of La₂O₃ and Y₂O₃ into the vitreous network does not change significantly Verdet constant of the glass
The calculation of the effective wavelengths corresponding to the electronic transitions responsible for Faraday rotation of the glasses was done based on the experimental data processing in agreement with the theoretical models
In the case of Dy and Tb-doped glasses, where scientific data are known, the effective wavelengths are in agreement with the data presented in the project. Hence, it is possible to assess that Verdet constant for Fe, Mn, Bi and Pb-doped glasses is correct
Verdet constant for the doped glasses are the following: (i) V_{glass +3% mol Dy2O3}=-2.7 rad/T/m; (ii) V_{glass +6% mol Dy2O3}= -17.6 rad/T/m; (iii) V_{glass +3% mol Tb2O3}=-4.0 rad/T/m; (iv) V_{glass +6% mol Tb2O3}= -20.3 rad/T/m; (v) V_{glass +Bismut} = + 12.2 rad/T/m; (vi) V_{glass +Pb}= +10.7 rad/T/m; (vii) V_{glass +Fe}= +7.9 rad/T/m; (viii) V_{glass +Mn}= +10.12 rad/T/m
The doping ions Bi³⁺ si Pb²⁺ embedded in the glass enhance the diamagnetic Verdet constant of the glasses
The doping ions Fe²⁺ and Mn²⁺ reduce the diamagnetic Verdet constant due to their paramagnetic effect, the influence being more significant in the case of Fe²⁺ by comparison with Mn²⁺
The highest paramagnetic effect was found for Tb-doped glass

Stage IV/2015

An unconventional wet method for high concentration Dy³⁺ and Bi³⁺-doped glasses preparation was elaborated, designed, realized and experimented that aims at obtaining a Faraday demonstrator (with Verdet constants close to that of those international standard glasses).
A laboratory method for Ce³⁺, Pr3+, Tb³⁺ (MVMOFPR) and Fe2+ (MVMOFT) -doped films obtaining was elaborated, designed, realized and experimented, applying sol-gel technique, spin coating method (deposition on the rotative substrate).
To prepare optical homogeneous glasses a mechanical stirring system was improved.
The bulk obtained glasses were optical analyzed (refractive index variation, striae, birefringence).
The good quality regarding the stripes and remnant stress of Dy³⁺-doped bulk glass recommends it as part of the magneto-optical device working in polarization regime.
MVMOVPR and MVMOVPT glasses were analyzed related to their general physical properties: density, thermal expansion coefficient, characteristic temperatures and viscosity.
MVMOVPR and MVMOVPT glasses were characterized related to magneto and magneto-optical properties by ellipsometric method.
High Dy₂O₃ - doped glass presents paramagnetic behavior and -49,3 rad/T/m Verdet constant at 400 nm and -29,1 rad/T/m at 500 nm wavelength compared to the best glass obtained in previous stages.
Bi₂O₃ - PbO-doped glass presents diamagnetic behavior with paramagnetic impurities; the paramagnetic impurities give a contrary sign contribution to the Verdet constant compared to the paramagnetic Verdet constant (+29.5 rad/T/m at 400 nm and 16.24 rad/T/m at 500 nm).
High Dy³⁺concentration (MVMOVPR) and Bi³⁺-Pb²⁺ (MVMOVPT)-doped bulk glasses and Ce³⁺, Pr³⁺, Tb³⁺ (MVMOFPR)-doped films were morphologically characterized by SEM (Scanning Electron Microscopy), EDX (Energy-Dispersive X-ray Spectroscopy) and AFM (Atomic Force Microscopy).
Ce³⁺, Pr³⁺, Tb³⁺ (MVMOFPR), Pb²⁺ (MVMOFPT) and Fe²⁺(MVMOFT) - doped films were analyzed related to magneto and magneto-optical properties, by using Kerr method (light reflexion on the film surface in magnetic field).
Elaboration, design, performing and experimentation of a laboratory method to prepare Mn²⁺ and Fe²⁺ - doped films , applying sol-gel method, spin coating technique.
Pulsed laser deposition technique (PLD) was experimented to prepare films doped with high amount of Dy2O3 (MVMOVPR) and Bi³⁺-Pb²⁺ (MVMOVPT).
Sol-gel films doped with Mn²⁺ si Fe²⁺ (MVMOFPR) as well as those PLD containing Dy³⁺ (MVMOFPR)and, Bi³⁺-Pb²⁺ (MVMOVPT), respectively, have been investigated by point of view of magneto-optical properties.
PLD films doped with Dy³⁺ ions have been investigated related to optical homogeneity, uniformity and morphology by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and atomic force microscopy (AFM)
Magneto-optical properties (Verdet constant) of sol-gel films based on aluminophosphate glass doped with Fe and Mn as well as PLD films containing Bi-Pb ions have been investigated, after deposition on Si, glass, quartz and Al substrates.
Sol-gel films were nontransparent and could not been investigated regarding magneto-optical properties.
The best results related to magneto-optical properties (Verdet constant) have been obtained from Dy³⁺-doped films, deposited at different laser energy and pulses number, post annealed after deposition process.
Regarding Bi-Pb –containing PLD films, the best magneto-optical results (Verdet constant) have been obtained for the films deposited on quartz and glass substrates.
A comparative analysis on aluminophosphate glasses doped with different elements (rare-earth ions, transition ions and post-transition ions) has been done.
The best magneto-optical results related to Verdet constant have been obtained in the case of Dy³⁺-doped bulk glass as paramagnetic materials and in the case of PLD films containing high amount of Bi³⁺-Pb²⁺ ions, as diamagnetic materials.
The optical and chemical homogeneity of the PLD films have been investigated in polarized light, using a dedicated microscope-conoscope experimental set-up.

Results

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