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Head of the Laboratory of Laser Spectroscopy
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.
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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.
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Contact Information
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Telephone
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(374 10) 288150
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Fax
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(374 232) 31172
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Postal
address
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Ashtarak-2, 0203, Ashtarak, Republic of
Armenia
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Electronic
mail
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General information:
david@ipr.sci.am
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