Georgy A. Kazakov

Active optical frequency standards using cold atoms: Perspectives and challenges

We consider various approaches to the creation of a high-stability active optical frequency standard, where the atomic ensemble itself produces a highly stable and accurate frequency signal. The short-time frequency stability of such standards may overcome the stability of lasers stabilized to macroscopic cavities which are used as local oscillators in the modern optical frequency standard systems. The main idea is to create a “superradiant” laser operating deep in the bad cavity regime, where the decay rate of the cavity field significantly exceeds the decoherence rate of the lasing transition. Two main approaches towards the realization of an active optical frequency standard have been proposed already: the optical lattice laser, and the atomic beam laser. We consider these and some alternative approaches, and discuss the parameters for atomic ensembles necessary to attain the metrology relevant level of short-time frequency stability, and various effects and main challenges critical for practical implementations.

Magic radio-frequency dressing for trapped atomic microwave clocks

It has been proposed to use magnetically trapped atomic ensembles to enhance the interrogation time in microwave clocks. To mitigate the perturbing effects of the magnetic trap, near-magic-field configurations are employed, where the involved clock transition becomes independent of the atoms potential energy to first order. Still, higher order effects are a dominating source for dephasing, limiting the performance of this approach. Here we propose a simple method to cancel the energy dependence to both first and second order, using weak radio-frequency dressing. We give values for dressing frequencies, amplitudes, and trapping fields for 87Rb atoms and investigate quantitatively the robustness of these second-order-magic conditions to variations of the system parameters. We conclude that radio-frequency dressing can suppress field-induced dephasing by at least one order of magnitude for typical experimental parameters

Feasibility study of measuring the Th 229 nuclear isomer transition with U 233 -doped crystals

We propose a simple approach to measure the energy of the few-eV isomeric state in Th-229. To this end, U-229 nuclei are doped into VUV-transparent crystals, where they undergo alpha decay into Th-229, and, with a probability of 2%, populate the isomeric state. These Th-229m nuclei may decay into the nuclear ground state under emission of the sought-after VUV gamma, whose wavelength can be determined with a spectrometer. Based on measurements of the optical transmission of U:CaF2 crystals in the VUV range, we expect a signal at least 2 orders of magnitude larger compared to current schemes using surface-implantation of recoil nuclei. The signal background is dominated by Cherenkov radiation induced by beta decays of the thorium decay chain. We estimate that, even if the isomer undergoes radiative de-excitation with a probability of only 0.1%, the VUV gamma can be detected within a reasonable measurement time.

Towards a measurement of the nuclear clock transition in 229Th

We investigate a potential candidate for a future optical clock: the nucleus of the isotope 229Th. Over the past 40 years of research, various experiments have found evidence for the existence of an isomeric state at an energy of a few eV. So far, neither the energy nor the lifetime of the isomer have been determined directly. As the scene is not yet prepared for direct laser excitation, other means of populating the isomer need to be explored. We investigate three different approaches, all of which rely on CaF2 crystals doped with 229Th or 233U. Various kinds of crystal luminescence are discussed in detail.

On an attempt to optically excite the nuclear isomer in Th-229

We aim to perform direct optical spectroscopy of the

Stability analysis for bad cavity lasers using inhomogeneously broadened spin-1/2 atoms as a gain medium

^{229}\mathrm{Th}

Prospects for an active optical clock using forbidden transition in trapped ions

nuclear isomer to measure its energy and lifetime, and to demonstrate optical coupling to the nucleus. To this end, we develop

A Laser Excitation Scheme for Th-229m

^{229}\mathrm{Th}

A laser excitation scheme for

-doped

^{229\text{m}}

{\mathrm{CaF}}_{2}