arXiv subjects

Mateusz Bocheński

Publications and source records attributed to Mateusz Bocheński.

4 recordsLinked to original sources

arXiv2026

Simultaneous sub-Doppler laser cooling and optical trapping of bosonic $^{39}$K-$^{133}$Cs and $^{41}$K-$^{133}$Cs mixtures

We report simultaneous sub-Doppler cooling and optical dipole trapping of $^{39}$K-Cs and $^{41}$K-Cs mixtures. Both mixtures are cooled to temperatures $\sim10$ $\mathrmμ$K, achieving performance comparable to that obtained with each species individually. To the best of our knowledge, this constitutes the first realization of a laser-cooled and optically trapped $^{41}$K-Cs mixture. For the $^{39}$K-Cs mixture, we additionally implement parallel spin-resolved Feshbach spectroscopy enabled by Stern-Gerlach separation. For potassium isotopes, we implement sub-Doppler cooling with $D_1$-line gray molasses, while for cesium the entire cooling sequence is implemented using $D_2$ transitions. We spin-polarize the atoms and confine Bose-Bose mixtures in a 1064 nm optical dipole trap. Using the resulting $^{39}$K-Cs samples, we observe 14 heteronuclear Feshbach loss features. Five agree with resonances reported previously, while nine have, to the best of our knowledge, not been observed experimentally before, including $p$-wave features and resonances in additional spin channels. The shorter lifetime of the $^{41}$K-Cs mixture in the optical dipole trap currently hinders systematic Feshbach spectroscopy, which we therefore do not pursue in this work. To characterize this limitation quantitatively, we study the decay dynamics of $^{39}$K-Cs and $^{41}$K-Cs mixtures under comparable temperature and density conditions, revealing a substantially stronger nonexponential loss in the $^{41}$K-Cs mixture. The demonstrated preparation of ultracold $^{41}$K-Cs mixtures provides a starting point for Feshbach-resonance and photoassociation spectroscopy of this previously unexplored isotopologue. Such measurements are essential for identifying suitable pathways for magnetoassociation and coherent optical transfer, and ultimately for the production of ultracold ground-state $^{41}$KCs molecules.

physics.atom-ph↗

arXiv2024

Sub-Doppler laser cooling and magnetic trapping of natural-abundance fermionic potassium

We report on reaching sub-Doppler temperatures of $^{40}$K in a single-chamber setup using a dispenser-based potassium source with natural (0.012$\%$ of $^{40}$K) isotopic composition. With gray molasses cooling on the $D_1$-line following a standard $D_2$-line magneto-optical trap, we obtain $3\times10^5$ atoms at $\sim$10~\textmu K. We reach densities high enough to measure the temperature via absorption imaging using the time-of-flight method. Directly after sub-Doppler cooling we pump atoms into the $F=7/2$ hyperfine ground state and transfer a mixture of $m_F=-3/2,-5/2$ and $-7/2$ Zeeman states into the magnetic trap. We trap $5\times10^4$ atoms with a lifetime of 0.6~s when the dispensers are heated up to maximize the atom number at a cost of deteriorated background gas pressure. When the dispensers have been off for a day and the magneto-optical trap loading rate has been increased by light induced atomic desorption we can magnetically trap $\sim$$10^3$ atoms with a lifetime of 2.8~s. The background pressure-limited lifetime of 0.6~s is a reasonable starting point for proof-of-principle experiments with atoms and/or molecules in optical tweezers as well as for sympathetic cooling with another species if transport to a secondary chamber is implemented. Our results show that unenriched potassium can be used to optimize experimental setups containing $^{40}$K in the initial stages of their construction, which can effectively extend the lifetime of enriched sources needed for proper experiments. Moreover, demonstration of sub-Doppler cooling and magnetic trapping of a relatively small number of potassium atoms might influence experiments with laser cooled radioactive isotopes of potassium.

physics.atom-ph↗

arXiv2024

Magnetic trapping of an ultracold $^{39}$K-$^{40}$K mixture with a versatile potassium laser system

We present a dual isotope magneto-optical trap (MOT), simultaneous sub-Doppler laser cooling, and magnetic trapping of a spin-polarized $^{39}$K-$^{40}$K Bose-Fermi mixture realized in a single-chamber setup with an unenriched potassium dispenser as the source of atoms. We are able to magnetically confine more than $2.2\times10^5$ fermions ($F=9/2\,m_F=9/2$) and $1.4\times10^7$ bosons ($F=2\,m_F=2$) with a lifetime exceeding 1.2 s. For this work, we have developed a versatile laser tailored for sub-Doppler cooling of all naturally occurring potassium isotopes and their mixtures. This laser system incorporates innovative features, such as the capability to select an isotope by activating or deactivating specific acousto-optic modulators that control the light seeding tapered amplifiers. Switching between isotopes takes $\sim$1 $\mathrmμ$s without any mechanical adjustment of the components. As a final step in characterizing the laser system, we demonstrate sub-Doppler cooling of $^{41}$K.

physics.atom-ph↗

arXiv2021

Bidirectional, Analog Current Source Benchmarked with Gray Molasses-Assisted Stray Magnetic Field Compensation

In ultracold-atom and ion experiments, flexible control of the direction and amplitude of a uniform magnetic field is necessary. It is achieved almost exclusively by controlling the current flowing through coils surrounding the experimental chamber. Here, we present the design and characterization of a modular, analog electronic circuit that enables three-dimensional control of a magnetic field via the amplitude and direction of a current flowing through three perpendicular pairs of coils. Each pair is controlled by one module, and we are able to continuously change the current flowing thorough the coils in the $\pm$4 A range using analog waveforms such that smooth crossing through zero as the current's direction changes is possible. With the electrical current stability at the 10$^{-5}$ level, the designed circuit enables state-of-the-art ultracold experiments. As a benchmark, we use the circuit to compensate stray magnetic fields that hinder efficient sub-Doppler cooling of alkali atoms in gray molasses. We demonstrate how such compensation can be achieved without actually measuring the stray fields present, thus speeding up the process of optimization of various laser cooling stages.

physics.atom-ph↗