ACADEMICIAN EMIL DJAKOV INSTITUTE OF ELECTRONICS
BULGARIAN ACADEMY OF SCIENCES

72, Tzarigradsko chaussee blvd, 1784-Sofia, Bulgaria


 

LABORATORY LASER SYSTEMS

ÁÃ-åçèêEnglish
   
Activities Staff Publications Projects Posters Laser Spectroscopy Group Atomic spectroscopy
in Extremely Thin Cells (ETC)

    

RESEARCH ACTIVITIES

    

Since 2000, the investigations in the Laser Systems Lab are on the topic of Coherent interactions of laser light with alkali metal vapours and their applications for development of atomic clocks and frequency standards, optical laser magnetometry and quantum memory, quantum entanglement of atomic states, narrow-band spectral filtering, etc.

Last years, in collaboration with our colleagues from Armenia, England, France, India, Israel, Italy, Russia, and Poland, a complementary experimental and theoretical research in the field of coherent interaction of laser light with alkali vapours in optical cells with and without AR coating, as well as in unique cells with micro- and nano-metric dimensions is performed. The main results are:

nanostructures

Tunable and polarization-controlled high-contrast bright and dark EIT resonances in potassium. A novel approach in the so called Hanle configuration was proposed, and demonstrated for potassium vapour contained in an AR coated cell. The registered Electromagnetically Induced Transparency and Absorption (EIT/EIA) resonances are spectrally narrow and with very high contrast. The method allows easy control and fast switching between transparency and absorption, as well as realization of intermediate states of the atomic medium with different degrees of transparency.

Coherent population trapping resonances (CPT) registered in the fluorescence of AR coated 87Rb cell in transverse magnetic field. The influence of the transverse magnetic fields on the CPT resonances in an AR coated vacuum cell was investigated experimentally and the role of the different-rank polarization moments in the formation of the fluorescence signal was analyzed.

Light-induced atomic desorption (LIAD) physics and applications in coherent spectroscopy and for optical characterization. LIAD was investigated for homogeneous and inhomogeneous irradiation of Rb vapour in uncoated and paraffin coated cells. It has been shown that the homogeneous irradiation not only improves the LIAD yield, but increases the desorption and adsorption rates of the atoms. The experimentally obtained dependences are compared with the theoretical ones. The results are of interest not only for the better understanding of the LIAD process, but also for development of novel atomic devices, optical light control, optical sensors miniaturization, novel methods for diagnostics of surfaces and coatings, nanostructuring, etc.

Interaction of laser radiation with alkali atoms confined in a thin cells. Different approaches to decrease the depolarization due to atomic collisions with the cell walls in conventional (cm sized) optical cells have been proposed. Surprisingly, the strong reduction in length (to the order of the resonant light wavelength) in a low-pressure cell also leads to strong narrowing of some of the resonances. The registration of the optical signal from atoms moving in a thin optical cell (longitudinal dimension along the laser beam 60 μm and transverse size 2 cm) yields new information on the velocity distribution of the atoms. We have measured precisely the velocity distribution of Cs atoms moving almost parallel to the optical cell windows, i.e. they have almost zero velocity projection along the laser beam. The theoretical analysis of the experimentally measured nonlinear spectra of Cs in an extremely thin optical cell have shown that the spontaneous decay from the excited atomic levels of a closed transition leads to a change in the amplitude and sign of the nonlinear absorption resonance.

   

These investigations are supported by:
   
Grant DO08-19/2016 "New coherent and cooperative effects in hot alkali vapour" of the National Scientific Fund of Bulgaria,
   
Grant DNTS/Russia 01/5/2017 "Nonlinear spectroscopy of spatially restricted alkali vapour: methodology and applications" of the National Scientific Fund of Bulgaria,
   
Grant DFNP-17-76/2017 "LIAD influence on the properties of the AR coatings and CPT resonances" of the Bulgarian Academy of Sciences.

    

    

    

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