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LABORATORY
OPTICS AND SPECTROSCOPY

HEAD: Prof. Minko Petrov, D.Sc.
tel: 875 70 95; e-mail: mpetrov@issp.bas.bg

TOTAL STAFF: 30
RESEARCH SCIENTISTS: 28

Prof. N.Kirov, D.Sc.
Prof. S.Rashev, D.Sc.
Prof. I.Savatinova, Ph.D.
Assoc.Prof. D.Angelov, Ph.D.
Assoc.Prof. E.Angelova, Ph.D.
Assoc.Prof. L.Tsonev, Ph.D.
Assoc.Prof. A.Andreev, Ph.D.
Assoc.Prof. S.Tonchev, Ph.D.
Assoc.Prof. K.Panayotov, D.Sc.
Assoc.Prof. A.Angelov, Ph.D.
Assoc.Prof. G.Dyankov, Ph.D.
Assoc.Prof. E.Keskinova, Ph.D.
Assoc.Prof. G.Hadjihristov, Ph.D.
Assoc.Prof. J.Rangelov, Ph.D.
Assoc.Prof. T.Tsvetkova, Ph.D.
Assoc.Prof. R.Peeva, Ph.D.
Asist.Prof. K.Antonova Ph.D.
Asist.Prof. B.Zafirova, Ph.D.
Asist.Prof. M.Kaneva, Ph.D
Asist.Prof. T.Tenev, Ph.D.
Asist.Prof. B.Panchev
Asist.Prof. H.Naradikian
Asist.Prof. B.Petrov
Asist.Prof. B.Bozhkov
Asist.Prof. E.Karakoleva
I.Savova PhD.
Asist.Prof. E.Vlaikova
B.Katranchev, Ph.D. student
Y.Velkova


RESEARCH ACTIVITIES:

I. OPTICS AND SPECTROSCOPY OF WAVEGUIDES

Proton exchanged planar optical waveguides in LiNbO3 and LiTaO3

    1. A new proton source - LiHSO4 vapours at low temperature - was used in forming optical waveguides in LiNbO3 and LiTaO3. The proton-exchanged layers were investigated by mode spectroscopy and IR absorption spectroscopy. An estimate of the optical losses and phase contents of the waveguides was made. The diffusion parameters were determined for both types of crystal, and were compared to those obtained when benzoic acid melt was used as a proton source. The results presented could contribute to the realization of waveguides with controlled phase compositions. The method proposed allows the use of a very simple and safe chamber construction, and the production of low-loss waveguides in a single technological step.

    Proton exchanged planar waveguides on Z-cut lithium niobate crystals have been fabricated by using a proton source formed by a mixture of benzoic and adipic acids. Optical characteristics have been obtained at different values of the adipic/benzoic acid dilution ratio. The samples have been structurally characterized by IR absorption spectroscopy. The influence of dilution ratio on the crystallographic phases, wavelength dispersions, diffusion coefficients and index profiles has been investigated in detail. The effect of annealing procedure has been also verified.

    The influence of hydrogen diffusion on the Raman spectra of highly protonated LiNbO3 waveguides was studied. Vibrations in the lowest frequency range (30 - 150 cm-1) in various scattering configurations are reported. An attempt to clarify the structural changes, which take place during the proton exchange process, has been made. On the basis of the detected mixing of A1(zz) and E(zx) type of phonons, we showed that the formation of off-axis HxLi1-xNbO3 waveguide layers on X-cut LiNbO3 substrates is confirmed by Raman scattering measurements.

    2. Er:Y2O3 thin films grown by pulsed laser deposition
Deposition of thin films by pulsed laser ablation from an Er2O3:Y2О3 ceramic target is reported. Erbium-doped yttrium oxide (Er:Y2O3) thin films are grown on c-cut sapphire under optimised deposition parameters. The effects of (UV)-assisted annealing of thin Er:Y2O3 films on the structural properties and the morphology are investigated. The films exhibit better crystalline structure and smoother surface after post-deposition treatment. The optical transmission spectra and the waveguiding properties of the thin films are reported. The films exhibit lower absorption and scattering losses after UV-assisted annealing. The light is guided to the end of the treated films with propagation losses ~2 dB/cm.

    A study of hydrogen bonding and structural order in a-Si:H prepared with hydrogen diluted silane was carried out by means of nuclear reaction analysis and infrared and Raman spectroscopy. It was established that the increase in the film thickness leaded to an improved ordering of the amorphous network on the short and medium range scale. The concentration of the silicon-bonded hydrogen was uniformly distributed along the growth direction.

II. FIBER OPTICS

    It was developed and experimental researched an optical scheme for in-situ control of the thickness of amorphous Si, coated on the side polished optical fiber, through the output intensity radiation control from the optical fiber.

    The characteristics of the channel-dropping spectral filters, resulting in interaction of the side polished single mode polarization maintaining optical fiber and planar waveguide consisted of amorphous Si layer have been researched. A high sensitive of the structure , operating as refractometric sensors element- ~5.103 nm/URI have been experimentally carried out. The applicability of this structure for the spectral region near 850nm has been demonstrated.

    The software/A computing program for the approximate calculation of the vectors wavelength equations, calculating the propagation constants and the optical waveguides' field distribution has been elaborated and precised. A better coincidence with the exact analytical solutions, as well as with the experimental data have been demonstrated in the investigations of the refractometric sensors based on inscribed Bragg Gratings

    The work on the improving of the fibre optics components' parameters for the lights polarization states control in the optical fibres, such as a polarizers with polarization maintaining optical fibres and polarizers with isotropic input optical fibre and anisotropic output optical fibre, has been continued.

III. HOLOGRAPHIC DIFFRACTION GRATINGS

    In the indicated book we address the development of modelling the propagation and diffraction of light in periodic media during the last 20 years. Special attention is paid to the class of differential methods. The 15 chapters include basic principles of the differential theory of gratings; stacks of gratings; fast Fourier factorisation method; Maxwell equations in truncated Fourier space; rigorous coupled-wave method; coordinate transformation methods; gratings made of anisotropic materials; crossed, x-ray, and transmission gratings; photonic crystals; grating couplers and resonant excitation of guided modes; differential theory of non-periodic media; and Fourier factorisation of Maxwell equations in nonlinear optics. The book describes the latest developments in differential theory for applications in spectroscopy, information processing, and astronomy.

    Using a rigorous electromagnetic analysis of two-dimensional (or crossed) gratings, we account, in a first step, for the enhanced transmission of a sub-wavelength hole array pierced inside a metallic film, when plasmons are simultaneously excited at both interfaces of the film. Replacing the hole array with a continuous metallic film, we then show that resonant extraordinary transmission can still occur, provided the film is modulated. The modulation may be produced in both one-dimensional and two dimensional geometries either by periodic surface deformation or by adding an array of high-index pillars. Transmittance higher than 80% is found when surface plasmons are excited at both

    Low polarization dependent, high diffraction efficiency grating for wavelength demultiplexer is proposed, manufactured by standard crystallographic etching of Si surface. Light is incident and diffracted inside the wafer, which is covered with reflecting metal. Optimised groove form results in a flat spectral response for TE and TM polarizations.

    Development and fabrication of sensor elements based on resonant interaction of waveguides with diffraction gratings as well as investigation of multilayer coatings by diffraction gratings are in progress.

IV. MICRO- AND NANO-PHOTONICS "Georgy Zartov"

    Polarization and intensity all-optical bi- and tri-stability in interference structures that include both a birefringent LiNbO3 layer of different crystallographic orientation and an absorbing layer has been theoretically investigated. The origin of this bi- and multistability is the thermo-optical nonlinearity present in the structures. Electrically induced bistable response, electrical control of the bi- and tristable action and regenerative oscillations are demonstrated using the electro-optical and the photorefractive properties of the LiNbO3 crystal. A mirror image of the multistable curve for specific angles of the obliquely incident input beam is also observed. The unstable dynamical behaviour is explained heuristically as the result of competing nonlinearities.

    The temporal, polarization and power characteristics of the transmitted light in the structures with different orientation and at different focusing of the incident light are experimentally investigated.

    The experimental investigations of the transverse mode and polarization behavior of Vertical-Cavity Surface-Emitting Lasers (VCSELs) with different structures are going on.

    The VCSELs properties have been investigated at the switching gain regime.

    The statistical properties of the polarization-mode jumping in a new dynamical regime in VCSELs caused by optical feedback have been investigated. Both the oscillation behavior of the residence time and the coherent resonans have been demostrated.

    The theoretical investigations of the bifurcation scenarios of new dynamics in semiconductor laser with optical feedback, namely regular packets of fast pulsations of the intensity are going on.

    The spectral, dynamical and electrical characteristics of semiconductor lasers with optical feedback possessing very small delay have been investigated.

V. OPTICS AND SPECTROSCOPY OF THERMOTROPIC LIQUID CRYSTALS

    A mechanism (on molecular and supramolecular levels) for oriented dendrite texture in nematic with short range smectic order is reported. We assume that the building 'blocks' of the dendrites are oligomers, or mixture of oligomers with 'free' closed and open dimers, constituting a detached crystalline layered state, named by us smectic X. The study of the dynamics of the dendrite growth demonstrates a scaling relationship typical for non-equilibrium systems. The observed dendrites can be considered as patterns formed in complex non-linear dissipative systems, driven outside of equilibrium.

    An electrohydrodynamic convective (EC) dendrites (parabolic type) in the nematic (N) with short range smectic order was observed. The driving of the dendrites by lateral d.c. and a.c. electric field parameters in the nematic temperature range was carried out. The dynamics of the dendrite growth was studied and analysis by two-dimensional solution of the diffusion equation. Using various combination of blocked and unblocked electrodes, we studied dependences between the dimensionless electric field parameter and product of the dendrite parabolic radius and the velocity of the dendrite growth and found that kind of the electrodes, as well as the temperature, significantly modifies these basic dependences. We refer this effect to the possible opposite ion propagation (gradient of electric field in direction opposite to that of the charge injection). A possible mechanism of EC dendrite growth is suggested. A comparison with the thermal dendrites is presented.

    A new liquid crystal complex-mixtures: 4,n-alkyloxybenzoic acids (n-OBA) and 4-hydroxypyridine (HOPY) are investigated using FT-Far IR spectroscopy and polarisation optical microscopy. n-OBA operated as H-bonding donor and HOPY served as H-bonding acceptor in this complex. A pronounced liquid crystal (LC) (characterized with fluid chains) - gel (rigid chains) transition was observed. The transition from an achiral (racemic) to chiral liquid crystal state, on the microscopic and macroscopic levels was studied. The induced chirality in achiral LC was explained by symmetry lowering of the system due to temperature or surface action variations. An aggregation mechanism of the complex realization is suggested.

VI. THEORETICAL METHODS IN MOLECULAR PHYSICS

    We have derived a general formula for the vibrational energy levels of a polyatomic molecule, which is a generalization of the conventional Dunham spectroscopic expansion. Calculations were performed on the vibrational level density in S0 D2CO, H2C2 and NO2 at excitation energies in the vicinity of the dissociation limit, using the newly derived formula. The results from the calculations are in reasonable agreement with the experimentally measured data.

    It has been done one attempt to explain the collected experimental date about nucleonics mutual binding energy and its dependence on type and number of nucleonics within the nucleus. It has been shown that a very strong relation exists between nucleonics mutual binding energy and nucleonics number in the nucleus. We have proposed a possibility of significantly alteration in the structure of the neutrons. Indeed, as a result of the interaction between the neutrons and mean-field potential of nucleus, created by all nucleonics within it, it appears a significantly alternation in the neutron structure, e.g. the neutrons within the nucleus could be expressed as a pair of protons and the negative pi-mesons. We suggest in the frame of the mean-field a physical model where the nucleus could be expressed as an aggregate of protons and continually moved between protons negative pi-mesons. In this model the intensity and the space size of the mean-field potential of the protons within the nucleus will be strongly depend on the quantity of the negative pi-mesons, e.g. on the neutrons,the whole amount of the nucleonics consisting within the nucleus.

VII. MANYPHOTONIC PROCESSES. NONLINEAR OPTICS

    The rotational and translational contribution to the quasielastic neutron scattering, particularly elastic incoherent structure factor (EISF) in uniaxial systems are considered theoretically. New approaches for determination of diffusion coefficients and orientational order parameters <P2> and <P4> are proposed, taking into account the molecular biaxiality or the steric hindrance for the molecular long axis reorientation. New experiments, not exploited so far, are proposed to clarify the mechanism of translational and rotational dynamics of the molecules in unixially aligned molecules.

    Coherent anti-Stikes Raman scattering is applied to obtain data for the cubic optical nonlinearity of siloxane polymer preparated in layers. By analysis of the real and imaginary parts of the recorded spectra, the values (modulus and the sign) of the parameters of interest for nonlinear optical applications are obtained. The experiments show that this material is suitable for integral optics.

VIII. LASER SPECTROSCOPY APPLIED TO BIOLOGICAL SYSTEMS

    Evidence was provided that the incorporation of the unusual histone variant macro H2A in reconstituted nucleosomes impedes the SWI/SNF - induced remodeling and sliding. In vitro transcription assay on chromatin template containing macro H2A confirmed the repressive role of this histone variant. Since macro H2A is known to preferentially accumulate on inactive female X-chromosomes, our results give explanation of the selective transcription silencing within these regions.


PUBLICATIONS:
  1. M. K. Kuneva, S. Tonchev, and P.S. Dimitrova, Planar optical waveguides obtained in Z-cut LiNbO3 and LiTaO3 by proton exchange in LiHSO4, Journal of Materials Science - Materials in Electronics, 14, 859-861 (2003).
  2. A.Og. Dikovska, P.A. Atanasov, R.I. Tomov, S.H. Tonchev, D.Ts. Sapunjiev, Er:Y2O3 thin films grown by pulsed laser deposition, VACUUM, 69, 273-276 (2003).
  3. B. Pantchev, P. Danesh, K. Antonova, B. Schmidt, D. Grambole, J. Baran, Effect of film thickness on hydrogen content in a-Si:H, Journal of Material Science: Materials in Electronics, 14, 751-752 (2003).
  4. P. Danesh, B. Pantchev, E. Liarokapis, B. Schmidt, Raman study of ion-implanted hydrogenated amorphous silicon, Journal of Material Science: Materials in Electronics, 14, 753-754 (2003).
  5. R. Djulgerova, B. Pantchev, V. Mihailov, V. Gencheva, J. Flaga, Concentration profiles of ion exchanged optical waveguides in glass: analysed in hollow cathode plasma, Surface and Coatings Technology, 166, 201-205 (2003).
  6. P. Danesh, B. Pantchev, I. Savatinova, E. Liarokapis, B. Schmidt, Effect of ion implantation on the structural properties of a-Si:H films, Vacuum, 69, 83-86 (2003).
  7. V. M. N. Passaro, M. N. Armenise, I. Savova, B. Jordanov, P. Kircheva, I. T. Savatinova, B. Pantchev, "Characterization of Z-cut LiNbO3 Optical Waveguides Formed in a Mixed Proton Source", Journal of Lightwave Technology
  8. P. Danesh, B. Pantchev, U. Kreissig, B. Schmidt, Elastic recoil detection analysis of soda-lime glass substrates for a-Si:H devices, Vacuum, 69, 289-293 (2003).
  9. E. Kowalska, J. Radomska, P. Byszewski, K. Antonova, R. Diduszko, H. Lange, P. Dluzewski, Morphology and properties of carbon nanotubes with Fe catalyst, J.Mater.Res., 18, 2451-58, (2003).
  10. L.Bischoff, J.Teichert, S.Kitova and T.Tsvetkova: "Optical pattern formation in a-SiC:H films by Ga+ ion implantation", Vacuum, 69, 73 (2003).
  11. J.Romanek, A.P.Kobzev, M.Kulik, T.Tsvetkova and J.Zuk: "RBS and optical studies of ion implanted silicon carbide layers", Vacuum, 70, 457 (2003).
  12. T. Tsvetkova, O. Angelov, D. Dimova - Malinovska, M. Sendova - Vassileva, L. Bischoff, G.J.Adriaenssens, W.Grudzinski and J.Zuk: "Structural and optical properties modification of a-SiC:H by Ga+ ion implantation", Vacuum, 70, 467 (2003).
  13. T.Tsvetkova, S.Balabanov, E.Skordeva, S.Kitova, J.Sielanko, D.Maczka and J.Zuk: "Ion implantation induced surface morphology changes in thin As3Se2 films", Vacuum, 70, 471 (2003).
  14. S. Rashev, 'Empirical Determination of The Harmonic Force Constants in Benzene. 2. The C-H Stretch System, J. Phys. Chem., A 107, 2160-2171 (2003).
  15. S. Rashev and D.C. Moule, Calculations on the Vibrational Level Density in Formaldehyde, Chem. Phys., 295, 109-117 (2003).
  16. N.Bonod, L.Li, S.Enoch, M.Neviere, and E.Popov: "Resonant optical transmission through thin metallic films with and without holes," Opt. Ex. 11, 482-490 (2003)
  17. D. Angelov, A. Molla, P.-Y. Perche, F. Hans, J. Cote, S. Khochbin, P. Bouvet, S. Dimitrov - The histone variant macroH2A interferes with transcription factor binding and SWI/SNF nucleosome remodeling, Mol. Cell, 11, 1033-1041 (2003).
  18. D. Angelov, M. Charra, C. W. Muller, J. Cadet, S. Dimitrov - Solution study of the NF-kB p50-DNA complex by UV laser protein-DNA crosslinking, Photochem. Photobiol. 77, 592-596 (2003).
  19. Z.Shaqiri, A.Veseli, N.Shaqiri, E.Vidolova-Angelova, D.Angelov - Laser direct biphotonic photolysis of guanines within DNA. Fizika A 11, 131-138 (2003).
  20. J.P.Marcerou, M.P. Petrov, H. Naradikian and H.T. Nguyen, Dendrite-like texture growth in the nematic liquid crystal state of 4,n-heptyl and 4,n-octyloxybenzoic acids aligned by polyimide coating, Liq. Cryst. (UK), 31, (2003).
  21. B.P. Katranchev, M.P. Petrov, J.P.Marcerou, Development of an oligomeric supramolecular structure in the nematic phase, constituted by hydrogen bonded in dimers molecules of 4,n-alkyloxybenzoic acids. A dendrite texture observation. in Proceed. of the European conf. of dendrimers, York, 2003.
  22. G. Diankov, H. Naradikian, T. Angelov, R. Tomova, Optical properties of polymer stabilized liquid crystal indicator, Nanoscience & Nanotechnology, Heron Press, 241, (2003).
  23. Diankov G. Naradikian H. Angelov T., Polymer stabilized liquid crystal indicator used in thermometry, Journal of Materials Science: Materials in Electronics, 14, 831-832, (2003).
  24. G. Diankov, H. Naradikian, T. Angelov, R. Tomova, Optical properties of polymer stabilized liquid crystal indicator, Nanoscience&Nanotechnology, Eds. E.Balabanova, I. Dragieva, Heron Press Science Series, 241-242 (2003).
  25. M. Sciamanna, K. Panajotov, P. Megret, H. Thienpont, M. Blondel, I. Veretennicoff, Optical feedback induces polarization mode-hopping in vertical-cavity surface-emitting lasers, Opt. Lett., 28, 1543, (2003).
  26. M. Sciamanna, A. Valle, P. Megret, M. Blondel, K. Panajotov, Nonlinear polarization dynamics in directly modulated vertical-cavity surface-emitting lasers, Phys. Rev. E, 68, 016207, (2003).
  27. B. Nagler, M. Peeters, J. Albert, G. Verschaffelt, K. Panajotov, H. Thienpont, I. Veretennicoff, J. Danckaert, S. Barbay, G. Giacomelli, and F. Marin, Polarization-mode hopping in single-mode vertical-cavity surface-emitting lasers: Theory and experiment, Phys. Rev. A, 68, 013813, (2003).
  28. M.C. Larciprete, C. Sibilia, S. Paoloni, G. Leahu, R. Li Voti, and M. Bertolotti, K. Panajotov, Photothermal induced variations in the optical transmission of a photonic band gap structure, Rev. Scient. Instrum., 74, 860-862, (2003).
  29. B.Katranchev and M.Petrov, 'Surface memorization driven by surface polar angle values in achiral and induced by mixture chiral liquid crystals', Bul. J. Phys., 30, 2003.
  30. H. Naradikian, B.Katranchev, E. Keskinova, J.P.Marcerou and M.P. Petrov, 'Thermal and elecroconvective dendrites in the nematic phase with short range smectic order of 4,n-heptyl and 4,n-octyloxybenzoic acids', Bul. J. Phys., 30, (2003).
  31. H. Naradikian, B.Katranchev, T.Angelov, R.Ugrinov, 'Optical properties in polymer stabilized liquid crystal indicator used in the thermometry', Bul. J. Phys., 30, (2003).
  32. I. Savova, P. Kircheva, I. Savatinova, Relaxation of Raman Polarization Rules in H:LiNbO3, Applied Physics A, accepted.
  33. K. Panajotov, M. Sciamanna, A. Tabaka, P. Megret, M. Blondel, G. Giacomelli, F. Marin, H. Thienpont, and I. Veretennicoff, Residence time distribution and coherence resonance of optical feedback induced polarization mode hopping in vertical-cavity surface-emitting lasers, Phys. Rev. A, accepted.
  34. T. K. Tenev, G. D. Zartov, R. A. Peyeva, H. Thienpont, I. Veretennicoff, and K. P. Panajotov, Electrical and polarization controlled bistability and oscillations in photorefractive birefringent Fabry-Perot resonators, Opt. Commun., accepted.
  35. V. Badilita, J.-F. Carlin, M. Ilegems, M. Brunner, G. Verschaffelt, K. Panajotov, Control of Polarization Switching in Vertical Coupled-Cavities Surface Emitting Lasers, IEEE Photonics Technology Letters, accepted.
  36. G. Van der Sande, K. Panajotov, M. Peeters, I. Veretennicoff, J. Danckaert, and T. Erneux, Nonlinear waveguiding for self-pulsing in VCSELs, Opt. Lett., accepted.
  37. S. Rashev, Determination of an improved set of harmonic force constants for benzene, Int. J. Quant. Chem., accepted.
  38. S. Rashev and D.C. Moule, Empirical Determination of The Harmonic Force Constants in Benzene. 3. The Harmonic Frequencies, J. Phys. Chem. A, accepted.
  39. G.Zartov, R.Peyeva and B.Bozkov, All-optical self-oscillations in an interference filter, Bulg. J.of Physics, accepted.
  40. P. Pavlova, E. Borisova, H. Naradikian, T. Angelov, Temperature dependence of chromacity in Polymer Stabilized Cholesteric Liquid Crystal, Nanoscience & Nanotechnology, Heron Press Science Series, 2003, accepted.
  41. H. Naradikian, B. Katranchev, E.Keskinova and M. Petrov, Helicity in hydrogen bonded in dimers achiral liquid crystals, Nanoscience & Nanotechnology, Heron Press Science Series, 2003, accepted.
  42. I.Gutzow, B.Petroff and J.W.P.Schmelzer, Thermodynamic Phase Transition and Glass Transition: A New Geometric Approach, XXIV. (11.) Arbeitstagung 08. bis 11. September 2003, Wolfersdorf.
  43. I.Gutzow and B.Petroff, The glass transition in terms of Landau`s phenomenological approach, X International Conference on the Physics of Non-Crystalline Solid, Parma (Italy), 13-17 July 2003.
  44. D.Angelov et al. - Mapping of DNA-protein contacts through oxidative damage induced by UV laser photochemistry, VI Winter Research Conferences on Free Radical in Biology "Oxidative Damage to DNA: Formation and Biological Features", Les Houches, 22 - 28 March 2003.
  45. E.Vidolova-Angelova - Properties of highly excited states, Международна конференция по лазери, приложения и технологии ILLA2003, Смолян 27.08 - 1.09.2003.
  46. K. Panajotov, M. Sciamanna, P. Megret, H. Thienpont, M. Blondel, I. Veretennicoff, Polarization mode hopping in vertical-cavity surface-emitting lasers, induced by optical feedback, Physics and Simulation of Optoelectronic Devices XI, SPIE (2003).
  47. M. Sciamanna, A. Valle, K. Panajotov, P. Megret, M.Blondel, Nonlinear polarization dynamics of current-modulated vertical-cavity surface-emitting lasers, Physics and Simulation of Optoelectronic Devices XI, SPIE (2003).
  48. K. Panajotov, M. Camarena, M.-C. Moreno, H.J. Unold, R. Michalzik, H. Thienpont, J. Danckaert, I. Veretennicoff, and G. Verschaffelt, Polarization behavior and mode structure of Vertical-Cavity Surface-Emitting Lasers with elliptical surface relief, Vertical-Cavity Surface-Emitting Lasers, SPIE (2003).
  49. T. K. Tenev, G. D. Zartov, R. A. Peyeva, H. Thienpont, I. Veretennicoff, and K. P. Panajotov, Dynamical effects in photorefractive Fabry-Perot resonators, 7-th International Conference on Optics 'ROMOPTO 2003' Constanta, Romania, September 8-11 (2003).
  50. A.Tabaka, M. Sciamanna, I. Veretennicoff and K. Panajotov, Bifurcation study of regular pulse packages in laser diodes subject to optical feedback, IQEC, Munich (2003).
  51. M.Sciamanna, K. Panajotov, G. Monticelli, A. Tabaka, H. Thienpont, I. Veretennicoff, P. Megret, M. Blondel, S. Bandyopadhyay, Y. Hong and K.A. Shore, Polarization dynamics in VCSELs subject to optical injection, IQEC, Munich (2003).
  52. M. Camarena, G. Verschaffelt, M.-C. Moreno, L. Desmet, H. J. Unold, R. Michalzik, H. Thienpont, J. Danckaert, I. Veretennicoff, K. Panajotov, Polarization Behavior and Mode Structure of Elliptical Surface Relief VCSELs, CLEO, Munich (2003).
  53. K. Panajotov, M. Sciamanna, A. Tabaka, H.Thienpont, I. Veretennicoff, P. Megret, M. Blondel, G. Giacomelli, and F. Marin, Residence time distribution of noise induced hopping in bistable system with delay, IQEC, Munich (2003).
  54. K. Panajotov, I. Veretennicoff, Recent progress in the polarization dynamics of VCSELs, XI Conference on Laser Optics, St. Petersburg, invited talk, (2003).
  55. M. Neviere and E. Popov: Light Propagation in Periodic Media: Diffraction Theory and Design, Marcel Dekker, New York, (2003).

ONGOING RESEARCH PROJECTS:

Chirality and polarisation in thermotropic liquid crystals - CNRS France-BAS joint research project ( Prof. M.Petrov, D.Sc.).

The research of achiral and with induced chirality thermotropic liquid crystals- National grant for science Ф1307 (Prof. M.Petrov, D.Sc.).

Instabilities in HxLiMO3 (M=Nb, Ta) planar optical waveguides-National grant for science (Prof. I. Savatinova, Ph.D.).

Nonlinear optical phenomena in periodical and anisotropic structures-National grant for science (Assoc. Prof. R. Peeva Ph.D.).

Spectroscopical investigations of materials for new liquid crystal displaies- PAS Poland-BAS joint research project ( Prof. M. Petrov, D.Sc.).

INVESTIGATION OF THE ROLE OF THE LIGHT POLARIZATION IN PHOTONIC DEVICES FOR OPTICAL PROCESSING OF INFORMATION- BRUSSELS, BELGIUM-ISSP CONTRACT (ASSOC. PROF.K. PANAYOTOV D.SC.).

Growth of amorphous silicon layers with low values of the mechanical tension (Asist. Prof B. Panchev).


COLLABORATION:
  1. Universite de Bordeaux 1, Centre de Recherche Paul Pascal- France
  2. Institute of Low Temperature and Structural Research, Polish Academy of Sciences, Wroclaw, Poland.
  3. Free University of Brussels, Departmet of Photonics, Belgium
  4. Forschungszentrum Rossendorf, Institut fuer Ionenstralphysik und Materialforschung, Germany.
TEACHING ACTIVITIES:

Boyko Katranchev, Ph.D. students - thesis in liquid crystals field.


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