0000000000276397
AUTHOR
Michal Zawada
showing 13 related works from this author
Free-fall expansion of finite-temperature Bose-Einstein condensed gas in the non Thomas-Fermi regime
2008
We report on our study of the free-fall expansion of a finite-temperature Bose-Einstein condensed cloud of 87Rb. The experiments are performed with a variable total number of atoms while keeping constant the number of atoms in the condensate. The results provide evidence that the BEC dynamics depends on the interaction with thermal fraction. In particular, they provide experimental evidence that thermal cloud compresses the condensate.
Matter-wave interference versus spontaneous pattern formation in spinor Bose-Einstein condensates
2013
We describe effects of matter-wave interference of spinor states in the $^{87}$Rb Bose-Einstein condensate. The components of the F=2 manifold are populated by forced Majorana transitions and then fall freely due to gravity in an applied magnetic field. Weak inhomogeneities of the magnetic field, present in the experiment, impose relative velocities onto different $m_F$ components, which show up as interference patterns upon measurement of atomic density distributions with a Stern-Gerlach imaging method. We show that interference effects may appear in experiments even if gradients of the magnetic field components are eliminated but higher order inhomogeneity is present and the duration of t…
Laser frequency stabilization by magnetically assisted rotation spectroscopy
2011
Abstract We present a method of Doppler-free laser frequency stabilization based on magnetically assisted rotation spectroscopy (MARS) which combines the Doppler-free velocity-selective optical pumping (VSOP) and magnetic rotation spectroscopy. The stabilization is demonstrated for the atomic rubidium transitions at 780 nm. The proposed method is largely independent of stray magnetic fields and does not require any modulation of the laser frequency. Moreover, the discussed method allows one to choose between locking the laser exactly to the line center, or with a magnetically-controlled shift to an arbitrary frequency detuned by up to several natural linewidths. This feature is useful in ma…
Line shape measurements of rubidium 5S-7S two-photon transition
2014
We report the use of a digital lock to measure the line profile and center frequency of rubidium 5S-7S two-photon transitions with a cw laser referenced to an optical frequency comb. The narrow, two-photon transition, 5S-7S (760 nm), insensitive to first-order in a magnetic field, is a promising candidate for frequency reference.
Absolute frequency and isotope shift measurements of mercury 1S0–3P1 transition
2019
We report the measurement of the absolute frequencies of the 6s2 1S0−6s6p 3P1 transition (253.7 nm) and the relevant isotope shifts in five mercury isotopes 198Hg, 199Hg, 200Hg, 202Hg, and 204Hg. The Doppler-free saturated absorption measurements were performed in an atomic vapour cell at room temperature with a four-harmonic generated (FHG) continuous-wave (cw) laser digitally locked to the atomic transition. It was referenced with a femtosecond optical frequency comb synchronized to the frequency of local representation of the International Atomic Time to provide traceability to the SI second by the 330 km-long stabilized fibre optical link. The transition frequencies and isotope shi…
Interactions of Ultra-cold Alkaline-earth-like and Alkali Atoms with Light
2019
This paper presents the experimental results of photoionization and photoassociation experiments performed with both ultra-cold alkaline-earth-like and alkali atoms. Photoionization cross-section was studied for 88Sr at the blue magic 390 nm wavelength as well as for 87Rb at 254 nm. We also present preliminary results of photoassociation spectroscopy of the molecular line detected near the dissociation threshold of the excited Rb*Hg molecule at D1 Rb line (795 nm).
Photoionization cross sections of the 5S1/2 and 5P3/2 states of Rb in simultaneous magneto-optical trapping of Rb and Hg
2018
We report the measurement of the photoionization cross sections of the $5{S}_{1/2}$ and $5{P}_{3/2}$ states of $^{87}\mathrm{Rb}$ in a two-species Hg and Rb magneto-optical trap (MOT) by the cooling laser for Hg. The photoionization cross sections of Rb in the $5{S}_{1/2}$ and $5{P}_{3/2}$ states at 253.7 nm are determined to be ${1}_{\ensuremath{-}1}^{+4.3}\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}20}\phantom{\rule{0.28em}{0ex}}{\text{cm}}^{2}$ and $4.63(30)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}18}\phantom{\rule{0.28em}{0ex}}{\text{cm}}^{2}$, respectively. To measure the $5{S}_{1/2}$ and $5{P}_{3/2}$ state fractions in the MOT we detected the photoionization rat…
Absolute frequency measurement of rubidium 5S-7S two-photon transitions.
2013
We report the absolute frequency measurements of rubidium 5S-7S two-photon transitions with a cw laser digitally locked to an atomic transition and referenced to an optical frequency comb. The narrow, two-photon transition, 5S-7S (760 nm) insensitive to first order in a magnetic field, is a promising candidate for frequency reference. The performed tests yield the transition frequency with accuracy better than reported previously.
Production and study of spinor condensates of <sup>87</sup>Rb released from a magnetic trap
2009
We report on our study of spinor condensates in the F=2 state of 87Rb produced in an atomic cloud expanding after releasing from a magnetic trap. The experiments are conducted in the setup described in Ref. [1].
Analysis and calibration of absorptive images of Bose-Einstein condensate at non-zero temperatures
2008
We describe the method allowing quantitative interpretation of absorptive images of mixtures of BEC and thermal atoms which reduces possible systematic errors associated with evaluation of the contribution of each fraction. By using known temperature dependence of the BEC fraction, the analysis allows precise calibration of the fitting results. The developed method is verified in two different measurements and compares well with theoretical calculations and with measurements performed by another group.
Optimal geometry for efficient loading of an optical dipole trap
2009
One important factor which determines efficiency of loading cold atoms into an optical dipole trap from a magneto-optical trap is the distance between the trap centers. By studying this efficiency for various optical trap depths (2--110 mK) we find that for optimum dipole trap loading, longitudinal displacements up to 15 mm are necessary. An explanation for this observation is presented and compared with other work and a simple analytical formula is derived for the optimum distance between the trap centers.
Dual Hg-Rb magneto-optical trap
2017
We present a two-species laser cooling apparatus capable of simultaneously collecting Rb and Hg atomic gases into a magneto-optical trap (MOT). The atomic sources, laser system, and vacuum set-up are described. While there is a loss of Rb atoms in the MOT due to photoionization by the Hg cooling laser, we show that it does not prevent simultaneous trapping of Rb and Hg. We also demonstrate interspecies collision-induced losses in the ${}^{87}$Rb-${}^{202}$Hg system.
Experiments on the dynamics of the Bose–Einstein condensate at finite temperatures
2009
This paper presents the results of our recent experiments on the finite-temperature Bose?Einstein condensate of 87Rb atoms in a magnetic trap, and is devoted to the study of the hydrodynamic properties and dynamics of an ultra-cold atomic gas near the critical temperature. Measurements of the aspect ratio of an expanding atomic cloud allow for verification of the condensate models and study of the interaction between condensed and non-condensed fractions of a finite-temperature sample.