Laboratory of Laser Spectroscopy

Institute for Physical Research, NAS RA

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Head of the Laboratory of Laser Spectroscopy

Sarkisyan David

e-mail: david@ipr.sci.am
homepage: http://person.ipr.sci.am/david
phone : (374 10) 288150 (office)
fax : (374 232) 31172

 


Dr. Sarkisyan has been involved in development of unique extremely thin cells and carrying out research of physical processes in these cells filled with alkali metals and with smoothly controllable thickness of the atomic vapour layer in the range of 30-3000 nm.

Author of more than 100 publications.


Scientific activity of our group

Doctor of Science David Sarkisyan within last several years has been involved in development and study of physical processes in unique extremely thin cells filled with alkaline metals and with smoothly controllable thickness of the atomic vapour column in the range of 30-3000 nm. New and previously unknown behaviour of the absorption, fluorescence and magneto-optical processes for the case when the vapour column length L is of order of the resonant laser wavelength has been studied in collaboration with scientists from Paris-Nord University (as well as with other collaborators). Dramatic difference of these processes in extremely thin cells has been revealed compared with the cells of a usual length (1-100 mm). Also with the help of extremely thin cells filled with alkaline metals with the thickness below 100 nm it was possible to study atom-surface interactions.

Scientific activity and research carried out by Dr. D. Sarkisyan is connected with Laser Physics and Laser Spectroscopy. In 1978 he was one of the first scientists who had observed so called “picosecond or white continuum” generation in solids and liquids. At the present time “white continuum” generated by femtosecond pulses is widely used in many laboratories. In 1980 tunable picosecond pulses in the range of 300 -700 nm has been generated employing this effect by frequency mixing in nonlinear crystals.

During the last two decades Dr. Sarkisyan’s group is concerned with development and applications of unique high temperature sealed-off all-sapphire cells (ASC) in different aspects of Laser Physics, Atomic & Molecular Laser Spectroscopy. Some types of developed ASC allow one to provide principally new experimental investigations (for example observation of Selective Reflection from the interface of dielectric and dense atomic vapors) which are impossible to realize with widely used glass-made, fused silica and/or metallic cells. These ASC can be heated up to 500-1000 degrees of Celsius and can be used to enclose highly corrosive hot alkali vapors (Na, K, Rb, Cs) as well as In, Bi, Cd, Zn, Pb and others.

In 1989 with the help of ASC (40 cm-long) filled with Cs, efficient frequency converters of laser radiation (of nano- and pico- second pulse duration) from visible region to infra-red and UV region based on Stimulated Electronic Raman Scattering (Stokes and Antistokes pulse generation) have been developed. In 1993 Third Harmonic Generation employing ring-shape laser radiation and ASC filled with Rb has been demonstrated which allows one to realize a new type of “ring” phase-matching. In 1994 it has been demonstrated that with the help of ASC with Brewster windows (1 cm-long), containing Cs or Rb molecular vapors passive intra-cavity Q-switching of widely used YAG:Nd laser could be realized and laser pulses as short as 0.5 nsec could be efficiently generated. In 1996 it has been demonstrated that with the help of ASC and determined amount of alkaline metal it is possible to realize very efficient thermal dissociation of alkaline molecular vapors and thus to generate pure atomic vapor of alkali inside the ASC at high temperatures.

In 2000, for the first time lasing in optically pumped pure Na molecular vapor in a 1-mm long ACS has been demonstrated.

In 2001-2005 unique extremely thin cells filled with metallic alkaline and with smoothly controllable thickness of atomic vapor column in the range of 30-3000 nm have been developed. For the first time the unusual (and unknown) behavior of the absorption and fluorescence processes for the case when the atomic system is confined in a gap with thickness L of the order of optical light wavelength l have been studied in collaboration with the group of M. Ducloy and D. Bloch (France). Dramatically different behavior of absorption and fluorescence processes compared to that when the thickness L is much larger than l has been demonstrated. It was also revealed that the ratio L/l is very important parameter that influences the line-shape, line-width and the magnitude of the resonant absorption (where l is the laser wavelength - 780nm or 890nm, resonant with atomic transitions of Rb or Cs correspondingly). The following unusual peculiarities have been revealed: i) at the length L=l/2 absorption and fluorescence spectra have the narrowest line-width; ii) oscillating behavior of absorption line-width and magnitude is observed - the line-width has minimum value at L=(2n+1)l/2 (meanwhile the magnitude of the absorption reaches maximum), and maximum value when L = nl (meanwhile the magnitude of absorption decreases to its minimal value), here n is an integer. This effect we have called “collapse and revival of Dicke-type coherent narrowing”. In contrary to absorption, the sub-Doppler line-width and magnitude of fluorescence are monotonically increasing with L; iii) it is demonstrated that an ETC with thickness of vapor column L=l (780nm) allows one to provide a new frequency reference source for Rb atomic transitions, which is more convenient in exploitation than widely used one based on Saturation Absorption technique; iv) an ETC with thickness of the vapour column of L=l (780nm) allows one to separate numerous atomic transitions between Zeeman sublevels on D1 and D2 lines by applying moderate magnetic fields. Interaction between Rb atoms and ETC’s windows which is caused by van der Waals atom-wall interaction has been studied in the Fluorescence spectra when the thickness is below 100 nm and the parameter determining the frequency red shift of atomic transition has been measured for the first time.

Very recently the effect of Electromagnetically Induced Transparency (EIT) has been observed using a bichromatic laser radiation and ETC filled with pure Rb with smoothly controllable thickness L of atomic vapor layer in the range ~ 780 – 1600 nm. Note that L is by the order of 2 smaller than that of previously reported EIT observation (in 2004) by scientists from NIST, Boulder.

It is demonstrated that size- conditioned strongly anisotropic contribution of atoms with different velocities in an ETC causes several dramatic differences of the EIT and VSOP resonances formation in the ETC as compared with an ordinary 1–10 cm long cell. Particularly, in the case of the ETC, the EIT linewidth and contrast dramatically depend on the coupling laser detuning from the exact atomic transition. The theoretical model developed by Yu.Malakyan, Y.Pashayan-Leroy, C.Leroy well describes the experimental results. Recently we have developed a technique which we call “L =
l  Zeeman technique” (LZT) for investigation of the transitions between the Zeeman sublevels of the hfs structure of alkali metal atoms in external magnetic fields. The technique is based on the employment of a nanocell with the thickness of the Rb atom vapor column equal to the wavelength of the laser radiation, 780 nm, resonant with the atomic rubidium D2 transition. At the laser intensities of about 1 mW/cm2 in the transmission spectrum of the nanocell narrow (~ 10 MHz) resonant peaks of reduced absorption appear localized exactly on the atomic transitions(so called VSOP resonance). In magnetic fields VSOP resonance are split and their amplitudes (due to the modification of the atomic transition probability) and frequency positions depend on the magnetic field strength. The theoretical model developed by the group of Marcis Auzinsh well describes the experimental results.

In the experiments and theoretical modelling of the processes in ETCs are actively involved: Dr. of Sc. A.Papoyan, Dr. of Sc. Yu.Malakayan, Ph.D. A.Sarkisyan, Ph.D. T.Varzhapetyan, Ph.D.Y.Pashayan-Leroy, A.Sargsyan, A.Nersisyan, V.Babushkin.

Professional Activities

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The member of Ph.D. honour Council in the field of Quantum Electronics and Optics in Institute for Physical Research of NAS.
 

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The member of an editorial board of Journal of Contemporary Physics (NAS Armenia).
 

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The member of Program Committee of Intern. Conf. ICONO/LAT,11-15 May, St. Petersburg, Russia, 2005 and of Program Committee of Intern. Conf. Europhysics CLEO/ Europe -EQEC, 12-17 June , Munich, Germany, 2005.
 

Awards

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2007 INTAS South-Caucasus Project 06-1000017-9001 “Study of atomic vapor layers of nanometric thickness and atom-surface interaction”.
 

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2006 ANSEF award PS-opt-0813-233 “Formation of Ultra-Narrow Resonances in Optical Domain”.
 

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2005 SCOPES award IB 7320-110684/1 ”Tunable locking of diode laser radiation frequency to atomic resonance lines using atomic vapor nanolayers”.
 

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2005 ANSEF award PS-eng-728-31” Atomic Ensemble of Free Rubidium Atoms Confined in an Optical Nano-cell”.
 

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2003 Prize of the President of the Republic of Armenia for Scientific Researches in the Field of Natural Sciences, Physics, Gold medal.
 

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2002 ANSEF award PS18-01 “Laser spectroscopy by Sub-Micron thickness atomic vapor Layer”.
 

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1994 International Science Foundation Award RY 7000.
 

 


Contact Information

Telephone

(374 10) 288150

Fax

(374 232) 31172

Postal address

Ashtarak-2, 0203, Ashtarak, Republic of Armenia

Electronic mail

General information: david@ipr.sci.am

 

Designed by V. Babushkin, 2009.

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Last modified: 05/23/13