Georgy Todorov | Bulgarian Academy of Sciences (original) (raw)

Papers by Georgy Todorov

SPIE Proceedings, Mar 2, 2007

We report new results on the light enhanced teeth whitening obtained in a research collaboration ... more We report new results on the light enhanced teeth whitening obtained in a research collaboration financed by the Medical Science Council of the Medical University of Sofia. The project is an extension of previous research and its basic goal is to develop new teeth bleaching substances and procedures, in which the activators are diode lamps (LED).

Journal of Physics: Conference Series, 2012

The ultra-narrow resonances achieved in coherent spectroscopy of alkali atoms originate from the ... more The ultra-narrow resonances achieved in coherent spectroscopy of alkali atoms originate from the destruction of the laser-induced coherence in the ground state. An anti relaxation cell coating preserves the coherence created and, consequently, the resonance narrows by almost two orders of magnitude. Coherence resonances are used in magnetic field sensors, atomic clocks, quantum informatics, ets. In this work, we investigate the features of the CPT resonance on the D1 87 Rb line obtained in fluorescence in paraffin coated cells. The transformation from a black to a bright resonance is found to depend on the laser power and the experimental geometry.

SPIE Proceedings, 1996

Resonances with complex shape have been obtained experimentally in the magnetic field dependence ... more Resonances with complex shape have been obtained experimentally in the magnetic field dependence of the optogalvanic signal induced in a Cu/Ne hollow cathode discharge by 632.8 nm laser radiation. Either population trapping or transfer of coherence are considered as possible mechanisms of formation of these resonances. Both of them, however, appear insufficient to obtain full qualitative explanation of the observed

Journal of the Optical Society of America B, 2006

Coherent-population-trapping resonances within the degenerate two-level system of the F=2→F'=1 tr... more Coherent-population-trapping resonances within the degenerate two-level system of the F=2→F'=1 transition of the 87 Rb D1 line were investigated in an uncoated Rb vapor cell by means of level-crossing-type experiments. Tuning over the two-photon resonance is achieved sweeping a magnetic field around zero value. The influence of transverse magnetic fields on the amplitude and the width of the resonances, recorded in fluorescence and absorption, were investigated in the cases of excitation with linear, circular, and elliptical laser light polarization. A theoretical analysis was performed for the case of linearly polarized excitation, the results of which are in good agreement with the experiment.

Eighth International Conference on Laser and Laser Information Technologies, 2004

Ninth International School on Quantum Electronics: Lasers--Physics and Applications, 1996

The intensity fluctuations of laser beam cross section caused by a local air turbulence have been... more The intensity fluctuations of laser beam cross section caused by a local air turbulence have been experimentally investigated. Registration of successive saturated images of the laser spot has been provided by imaging camera using a computer for image acquisition and processing. Evaluation of the state of turbulence by estimation of the refractive index structure parameters has been carried out.

12th International School on Quantum Electronics: Laser Physics and Applications, 2003

12th International School on Quantum Electronics: Laser Physics and Applications, 2003

13th International School on Quantum Electronics: Laser Physics and Applications, 2005

The purpose of this communication is to summarize and compare the results obtained under the proj... more The purpose of this communication is to summarize and compare the results obtained under the project" New all-optical systems and methods for magnetic and electromagnetic field measurement", financed by EC (contract G6RD-CT-2001-000642). The main aim of the ...

11th International School on Quantum Electronics: Laser Physics and Applications, 2001

ABSTRACT In the present work some results of the comparative measurements of the tooth whitening ... more ABSTRACT In the present work some results of the comparative measurements of the tooth whitening effect using a bleaching agent activated by Ar+ (emitting at 488 nm) and CuBr (emitting at 510 nm) lasers are reported. It is shown that the whitening effect is observed in both cases. Some of the peculiarities in application of CuBr laser in the field of aesthetic dentistry are discussed, as well as the possibility to replace the more expensive Ar+ laser. In order to ensure reliable results from a light-chemical treatment of the teeth, as spectroscopy method has been developed and applied. The method is based on the analysis of laser-induced fluorescence spectra of the teeth with different coloring.

13th International School on Quantum Electronics: Laser Physics and Applications, 2005

The absorption and fluorescence spectra of a submicron Cs vapour layer under resonant excitation ... more The absorption and fluorescence spectra of a submicron Cs vapour layer under resonant excitation on the D2 line are measured. Sub-Doppler features centered at the resonance frequency of the hyperfine (hf) transitions have been observed. Substantial changes in the amplitude and width of the sub-Doppler resonances for individual hf transitions were recorded in dependence on the intensity of the incident

Proceedings of …, Jan 1, 2005

The absorption and fluorescence spectra of a submicron Cs vapour layer under resonant excitation ... more The absorption and fluorescence spectra of a submicron Cs vapour layer under resonant excitation on the D line are measured. Sub-Doppler features centered at the resonance frequency of the hyperfine (hf) transitions have been observed. Substantial changes in the ...

Conference on Lasers and Electro-Optics Europe, 1994

Tenth International School on Quantum Electronics: Laser Physics and Applications, 1999

ABSTRACT

13th International School on Quantum Electronics: Laser Physics and Applications, 2005

In this work we discuss Hanle absorption resonances obtained in a room temperature NO2 cell, irra... more In this work we discuss Hanle absorption resonances obtained in a room temperature NO2 cell, irradiated by a single mode Ar+ laser. The method used is based on measuring the changes of polarization of the transmitted laser beam crossing the NO2 cell, placed in a transverse magnetic field. The resonant changes in the measured absorption signal, that occur in the

The present investigations are directed at a more detailed studying of methods for colour determi... more The present investigations are directed at a more detailed studying of methods for colour determination aimed at estimation of human teeth whiteness degree, sufficiently handy for common use in clinical practice. In order to be obtained unbiased results of the whitening, specific techniques for the degree of whiteness (coloration) determination had been developed on the basis of common colorimetric and

11th International School on Quantum Electronics: Laser Physics and Applications, 2001

ABSTRACT In the present work some results of the comparative measurements of the tooth whitening ... more ABSTRACT In the present work some results of the comparative measurements of the tooth whitening effect using a bleaching agent activated by Ar+ (emitting at 488 nm) and CuBr (emitting at 510 nm) lasers are reported. It is shown that the whitening effect is observed in both cases. Some of the peculiarities in application of CuBr laser in the field of aesthetic dentistry are discussed, as well as the possibility to replace the more expensive Ar+ laser. In order to ensure reliable results from a light-chemical treatment of the teeth, as spectroscopy method has been developed and applied. The method is based on the analysis of laser-induced fluorescence spectra of the teeth with different coloring.

11th International School on Quantum Electronics: Laser Physics and Applications, 2001

ABSTRACT Laser induced Galvanic Signals (LIGS) were observed in a Se- buffer gas hollow cathode (... more ABSTRACT Laser induced Galvanic Signals (LIGS) were observed in a Se- buffer gas hollow cathode (HC) discharge irradiated by He- Se+ or cw dye lasers. Radial and current dependences were studied. A similarity of the radial dependences for the two buffer gases He and Ne and maximum in the current dependences are registered. The possible mechanisms which form GS responses in Se HC discharge are discussed.

11th International School on Quantum Electronics: Laser Physics and Applications, 2001

ABSTRACT A simple theoretical description is proposed aiming at a qualitative explanation of the ... more ABSTRACT A simple theoretical description is proposed aiming at a qualitative explanation of the observed in 11 dependences of the fluorescence from the resonant Rb levels excited by a single frequency diode laser on the magnetic field, when Hanle effect configuration of the experiment is used. The components of the statistical tensor for population and longitudinal alignment are calculated by iteration method up to fourth order terms. The spontaneous emission transfer influence is taken into account. A good qualitative agrement between calculated and experimentally observed resonances is obtained.

SPIE Proceedings, Mar 2, 2007

We report new results on the light enhanced teeth whitening obtained in a research collaboration ... more We report new results on the light enhanced teeth whitening obtained in a research collaboration financed by the Medical Science Council of the Medical University of Sofia. The project is an extension of previous research and its basic goal is to develop new teeth bleaching substances and procedures, in which the activators are diode lamps (LED).

Journal of Physics: Conference Series, 2012

The ultra-narrow resonances achieved in coherent spectroscopy of alkali atoms originate from the ... more The ultra-narrow resonances achieved in coherent spectroscopy of alkali atoms originate from the destruction of the laser-induced coherence in the ground state. An anti relaxation cell coating preserves the coherence created and, consequently, the resonance narrows by almost two orders of magnitude. Coherence resonances are used in magnetic field sensors, atomic clocks, quantum informatics, ets. In this work, we investigate the features of the CPT resonance on the D1 87 Rb line obtained in fluorescence in paraffin coated cells. The transformation from a black to a bright resonance is found to depend on the laser power and the experimental geometry.

SPIE Proceedings, 1996

Resonances with complex shape have been obtained experimentally in the magnetic field dependence ... more Resonances with complex shape have been obtained experimentally in the magnetic field dependence of the optogalvanic signal induced in a Cu/Ne hollow cathode discharge by 632.8 nm laser radiation. Either population trapping or transfer of coherence are considered as possible mechanisms of formation of these resonances. Both of them, however, appear insufficient to obtain full qualitative explanation of the observed

Journal of the Optical Society of America B, 2006

Coherent-population-trapping resonances within the degenerate two-level system of the F=2→F'=1 tr... more Coherent-population-trapping resonances within the degenerate two-level system of the F=2→F'=1 transition of the 87 Rb D1 line were investigated in an uncoated Rb vapor cell by means of level-crossing-type experiments. Tuning over the two-photon resonance is achieved sweeping a magnetic field around zero value. The influence of transverse magnetic fields on the amplitude and the width of the resonances, recorded in fluorescence and absorption, were investigated in the cases of excitation with linear, circular, and elliptical laser light polarization. A theoretical analysis was performed for the case of linearly polarized excitation, the results of which are in good agreement with the experiment.

Eighth International Conference on Laser and Laser Information Technologies, 2004

Ninth International School on Quantum Electronics: Lasers--Physics and Applications, 1996

The intensity fluctuations of laser beam cross section caused by a local air turbulence have been... more The intensity fluctuations of laser beam cross section caused by a local air turbulence have been experimentally investigated. Registration of successive saturated images of the laser spot has been provided by imaging camera using a computer for image acquisition and processing. Evaluation of the state of turbulence by estimation of the refractive index structure parameters has been carried out.

12th International School on Quantum Electronics: Laser Physics and Applications, 2003

12th International School on Quantum Electronics: Laser Physics and Applications, 2003

13th International School on Quantum Electronics: Laser Physics and Applications, 2005

The purpose of this communication is to summarize and compare the results obtained under the proj... more The purpose of this communication is to summarize and compare the results obtained under the project" New all-optical systems and methods for magnetic and electromagnetic field measurement", financed by EC (contract G6RD-CT-2001-000642). The main aim of the ...

11th International School on Quantum Electronics: Laser Physics and Applications, 2001

ABSTRACT In the present work some results of the comparative measurements of the tooth whitening ... more ABSTRACT In the present work some results of the comparative measurements of the tooth whitening effect using a bleaching agent activated by Ar+ (emitting at 488 nm) and CuBr (emitting at 510 nm) lasers are reported. It is shown that the whitening effect is observed in both cases. Some of the peculiarities in application of CuBr laser in the field of aesthetic dentistry are discussed, as well as the possibility to replace the more expensive Ar+ laser. In order to ensure reliable results from a light-chemical treatment of the teeth, as spectroscopy method has been developed and applied. The method is based on the analysis of laser-induced fluorescence spectra of the teeth with different coloring.

13th International School on Quantum Electronics: Laser Physics and Applications, 2005

The absorption and fluorescence spectra of a submicron Cs vapour layer under resonant excitation ... more The absorption and fluorescence spectra of a submicron Cs vapour layer under resonant excitation on the D2 line are measured. Sub-Doppler features centered at the resonance frequency of the hyperfine (hf) transitions have been observed. Substantial changes in the amplitude and width of the sub-Doppler resonances for individual hf transitions were recorded in dependence on the intensity of the incident

Proceedings of …, Jan 1, 2005

The absorption and fluorescence spectra of a submicron Cs vapour layer under resonant excitation ... more The absorption and fluorescence spectra of a submicron Cs vapour layer under resonant excitation on the D line are measured. Sub-Doppler features centered at the resonance frequency of the hyperfine (hf) transitions have been observed. Substantial changes in the ...

Conference on Lasers and Electro-Optics Europe, 1994

Tenth International School on Quantum Electronics: Laser Physics and Applications, 1999

ABSTRACT

13th International School on Quantum Electronics: Laser Physics and Applications, 2005

In this work we discuss Hanle absorption resonances obtained in a room temperature NO2 cell, irra... more In this work we discuss Hanle absorption resonances obtained in a room temperature NO2 cell, irradiated by a single mode Ar+ laser. The method used is based on measuring the changes of polarization of the transmitted laser beam crossing the NO2 cell, placed in a transverse magnetic field. The resonant changes in the measured absorption signal, that occur in the

The present investigations are directed at a more detailed studying of methods for colour determi... more The present investigations are directed at a more detailed studying of methods for colour determination aimed at estimation of human teeth whiteness degree, sufficiently handy for common use in clinical practice. In order to be obtained unbiased results of the whitening, specific techniques for the degree of whiteness (coloration) determination had been developed on the basis of common colorimetric and

11th International School on Quantum Electronics: Laser Physics and Applications, 2001

ABSTRACT In the present work some results of the comparative measurements of the tooth whitening ... more ABSTRACT In the present work some results of the comparative measurements of the tooth whitening effect using a bleaching agent activated by Ar+ (emitting at 488 nm) and CuBr (emitting at 510 nm) lasers are reported. It is shown that the whitening effect is observed in both cases. Some of the peculiarities in application of CuBr laser in the field of aesthetic dentistry are discussed, as well as the possibility to replace the more expensive Ar+ laser. In order to ensure reliable results from a light-chemical treatment of the teeth, as spectroscopy method has been developed and applied. The method is based on the analysis of laser-induced fluorescence spectra of the teeth with different coloring.

11th International School on Quantum Electronics: Laser Physics and Applications, 2001

ABSTRACT Laser induced Galvanic Signals (LIGS) were observed in a Se- buffer gas hollow cathode (... more ABSTRACT Laser induced Galvanic Signals (LIGS) were observed in a Se- buffer gas hollow cathode (HC) discharge irradiated by He- Se+ or cw dye lasers. Radial and current dependences were studied. A similarity of the radial dependences for the two buffer gases He and Ne and maximum in the current dependences are registered. The possible mechanisms which form GS responses in Se HC discharge are discussed.

11th International School on Quantum Electronics: Laser Physics and Applications, 2001

ABSTRACT A simple theoretical description is proposed aiming at a qualitative explanation of the ... more ABSTRACT A simple theoretical description is proposed aiming at a qualitative explanation of the observed in 11 dependences of the fluorescence from the resonant Rb levels excited by a single frequency diode laser on the magnetic field, when Hanle effect configuration of the experiment is used. The components of the statistical tensor for population and longitudinal alignment are calculated by iteration method up to fourth order terms. The spontaneous emission transfer influence is taken into account. A good qualitative agrement between calculated and experimentally observed resonances is obtained.