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We present the measurements of the photoionization cross sections of the excited 1 P 1 and 3 S 1 states of ultracold 88 Sr atoms at 389.889 nm wavelength, which is the magic wavelength of the 1 S 0 - 3 P 0 clock transition. The photoionization cross section of the 1 P 1 state is determined from the measured ionization rates of 88 Sr in the magneto-optical trap in the 1 P 1 state to be 2.20(50)×10 -20 m 2 , while the photoionization cross section of 88 Sr in the 3 S 1 state is inferred from the photoionization-induced reduction in the number of atoms transferred through the 3 S 1 state in an operating optical lattice clock to be 1.38(66) ×10 -18 m 2 . Furthermore, the resulting limitations of employing a blue-detuned magic wavelength optical lattice in strontium optical lattice clocks are evaluated. We estimated photoionization induced loss rates of atoms at 389.889 nm wavelength under typical experimental conditions and made several suggestions on how to mitigate these losses. In particular, the large photoionization induced losses for the 3 S 1 state would make the use of the 3 S 1 state in the optical cycle in a blue-detuned optical lattice unfeasible and would instead require the less commonly used 3 D 1,2 states during the detection part of the optical clock cycle.

We have identified magic wavelengths for 1 S 0  ↔  3 P 1,2 (m J  = 0) transitions and zero-magic wavelengths for the 3 P 1,2 (m J  = 0) states of 200 Hg atoms, analysed the robustness of the magic conditions with respect to wavelength and polarization imperfections. We show that the most experimentally feasible magic wavelength for the 1 S 0  ↔  3 P 2 transition is 351.8 nm of π polarized light. Relevant transition wavelengths and transition strengths are calculated using the state-of-the-art Complete Active Space Self-Consistent-Field (CASSCF) method with a perturbative inclusion of spin-orbit coupling. The transition wavelengths are a posteriori corrected for the dynamical energy using the second-order perturbation theory.

Superradiant active clocks operating on narrow linewidth clock transitions are predicted to achieve precision orders of magnitude higher than any currently existing optical atomic clocks. We introduce a theory of superradiant lasing and implement it for the example of 40 Ca atoms. The presented model, however, is valid for any two- or three-level system in an optical lattice. We perform a feasibility analysis and suggest a set of parameters for the experimental fulfillment of superradiant lasing in Ca. Moreover, we present an overview of different magic wavelengths for the 4s 2 1 S 0  ↔ 4s4p 3 (m 1 (m J  = 0) transition in Ca for different polarizations and a robustness analysis of these magic conditions. We also report the magic-zero wavelengths for the 4s4p 3 , m 1 , m J  = 0 state.

We report the measurement of the absolute frequencies of the 6s 2 1 S 0 -6s6p  3 P 1 transition (253.7 nm) and the relevant isotope shifts in five mercury isotopes   198 Hg,   199 Hg,   200 Hg,   202 Hg, and   204 Hg. 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 shifts have been determined with an accuracy of a few hundred kHz, at least one order of magnitude better than any previous measurement. By making a King plot with the isotope shifts of 6s6p  3 P 2 -6s7s  3 S 1 transition (546 nm) we determined the accurate value of the ratio of the electronic field-shift parameters E 546 /E 254 and estimated the electronic field-shift term E 254 .

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.

We explore a cavity-enhanced spectroscopic technique based on determination of the absorbtion coefficient from direct measurement of spectral width of the mode of the optical cavity filled with absorbing medium. This technique called here the cavity mode-width spectroscopy (CMWS) is complementary to the cavity ring-down spectroscopy (CRDS). While both these techniques use information on interaction time of the light with the cavity to determine absorption coefficient, the CMWS does not require to measure very fast signals at high absorption conditions. Instead the CMWS method require a very narrow line width laser with precise frequency control. As an example a spectral line shape of P7 Q6 O₂ line from the B-band was measured with use of an ultra narrow laser system based on two phase-locked external cavity diode lasers (ECDL) having tunability of ± 20 GHz at wavelength range of 687 to 693 nm.