Molecular Spectroscopy and Ultracold Quantum Gases Laboratory (QGL)
We use laser technique of polarization labelling spectroscopy to study excited states of diatomic molecules, particularly these states which are important in experiments on ultra-cold matter. For this reason we focus our research on homo- and heteronuclear alkali dimers and alkali atom - alkaline earth atom molecules. Basing on experimental observations the potential energy curves of investigated states are constructed using the pointwise Inverted Perturbation Approach method developed in our group.
We also focus on several intertwined topics of modern AMO physics, in particular on the development of new laser cooling methods and formation of ultracold ground state molecules of cesium and potassium. In a project “Cold atom-based quantum simulators” financed by the Foundation for Polish Science’s Homing grant we investigate the possibility of direct laser cooling of cesium to quantum degeneracy. This would speed up the time required to obtain quantum degenerate gas (laser cooling is orders of magnitude more efficient than evaporative cooling).
The main objective of spectroscopy of diatomic alkali metal molecules has always been to compare the structure of their electron states with theoretical predictions. Interest in this structure has been greatly revived by recent advances in the fabrication of cold alkali metal molecules, as detailed knowledge of the electron states of the molecules is particularly important for the realisation of this process.
Polarisation labelling spectroscopy (PLS) is an efficient method for simplifying complex molecular spectra, combining the principles of polarisation spectroscopy and double optical resonance. The basic idea of the method is to monitor polarisation changes of a weak sample laser beam, which are induced by the optical anisotropy of the sample produced by a strong pumping laser beam. In contrast to the classical PLS scheme, in our experiments we use a sampling laser with a fixed frequency, while the pump laser light is tuned in the spectral interval under study.
The frequencies of the observed spectral lines are converted into energies of oscillation-rotation levels. The excited state is then represented by a potential energy curve determined numerically using our unique implementation of the Inverse Perturbation Approach (IPA) method. This method allows the construction of potentials even with exotic shapes for which traditional description methods fail. To date, we have studied more than 90 excited states in the alkali dimers Li2, Na2, K2, Rb2, Cs2, LiCs, NaCs, NaRb, NaK and KLi using the PLS technique.
Laser cooling of caesium and potassium for quantum degeneration
We use Raman cooling in an optical network to increase the density of atoms in the phase space using only optical methods. In this approach, cooling is a more on an order of magnitude faster process than in evaporative cooling approaches. Developed experimental methods will allow efficient production of ultra-cold particles trapped in optical networks and, thus, they will contribute to the onset of a new generation of analog quantum simulators for the simulation of properties of the strongly interacting matter.
Boson-fermion mixture of potassium isotopes
The ultra-cold mixture of potassium-39 and potassium-40, which we have received, allows us to attempt to observe the p-wave superfluidity in quantum gases, thus it gives us a tool to study properties of exotic superconductors. We expect that this achievement will contribute to a better understanding of existing theoretical models describing this phenomenon and will guide the development of these models, allowing us to develop realistic systems of technological significance.
As a part of the NLPQT project, we are working on a construction of a mobile station for atomic interferometry. The use of matter waves of ultra-cold atoms will allow us to construct a gradiometer enabling absolute measurement of gravitational field intensity. Thus, the device will be a sensor, which will not require any calibration and allow the detection of objects below the surface of the earth, such as minerals, abandoned shafts or military objects. With absolute measurements, the device will enable inertial navigation using gravitational field maps without the need for the use of the GPS.