Femtosecond frequency comb based distance measurement in air

Interferometric measurement of distance using a femtosecond frequency comb is demonstrated and compared with a counting interferometer displacement measurement. A numerical model of pulse propagation in air is developed and the results are compared with experimental data for short distances. The relative agreement for distance measurement in known laboratory conditions is better than 1

Guidelines for developing optical clocks with 10−1810^{-18} fractional frequency uncertainty

There has been tremendous progress in the performance of optical frequency standards since the first proposals to carry out precision spectroscopy on trapped, single ions in the 1970s. The estimated fractional frequency uncertainty of today's leading optical standards is currently in the $10^{-18}$ range, approximately two orders of magnitude better than that of the best caesium primary frequency standards. This exceptional accuracy and stability is resulting in a growing number of research groups developing optical clocks. While good review papers covering the topic already exist, more practical guidelines are needed as a complement. The purpose of this document is therefore to provide technical guidance for researchers starting in the field of optical clocks. The target audience includes national metrology institutes (NMIs) wanting to set up optical clocks (or subsystems thereof) and PhD students and postdocs entering the field. Another potential audience is academic groups with experience in atomic physics and atom or ion trapping, but with less experience of time and frequency metrology and optical clock requirements. These guidelines have arisen from the scope of the EMPIR project "Optical clocks with $1 imes 10^{-18}$ uncertainty" (OC18). Therefore, the examples are from European laboratories even though similar work is carried out all over the world. The goal of OC18 was to push the development of optical clocks by improving each of the necessary subsystems: ultrastable lasers, neutral-atom and single-ion traps, and interrogation techniques. This document shares the knowledge acquired by the OC18 project consortium and gives practical guidance on each of these aspects

Guidelines for developing optical clocks with 10-18 fractional frequency uncertainty

There has been tremendous progress in the performance of optical frequency standards since the first proposals to carry out precision spectroscopy on trapped, single ions in the 1970s. The estimated fractional frequency uncertainty of today's leading optical standards is currently in the 10−18 range, approximately two orders of magnitude better than that of the best caesium primary frequency standards. This exceptional accuracy and stability is resulting in a growing number of research groups developing optical clocks. While good review papers covering the topic already exist, more practical guidelines are needed as a complement. The purpose of this document is therefore to provide technical guidance for researchers starting in the field of optical clocks. The target audience includes national metrology institutes (NMIs) wanting to set up optical clocks (or subsystems thereof) and PhD students and postdocs entering the field. Another potential audience is academic groups with experience in atomic physics and atom or ion trapping, but with less experience of time and frequency metrology and optical clock requirements. These guidelines have arisen from the scope of the EMPIR project "Optical clocks with 1×10−18 uncertainty" (OC18). Therefore, the examples are from European laboratories even though similar work is carried out all over the world. The goal of OC18 was to push the development of optical clocks by improving each of the necessary subsystems: ultrastable lasers, neutral-atom and single-ion traps, and interrogation techniques. This document shares the knowledge acquired by the OC18 project consortium and gives practical guidance on each of these aspects.EU/Horizon2020/EMPIR/E

Frekvenční stabilizace laserů a měření optických frekvencí

Katedra chemické fyziky a optikyDepartment of Chemical Physics and OpticsFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult

Linking the optical and the mechanical measurements of dimension by a Newton's rings method

Optical (e.g. interferometric or laser focus probe) measurement of dimensions must be corrected to take into account phase change on reflection and the influence of surface roughness in order to be compatible with mechanical dimension measurement methods (e.g. tactile probes). One typical example is interferometric measurement of a gauge block; while a correction of only a few nanometres is needed for standard interferometric measurement of a gauge block wrung on a platen made of the same material, a correction of tens of nanometres is needed when different materials are used (e.g. a steel gauge block on a glass platen) and even a total correction of up to a hundred nanometres is needed for some gauges when a double-ended interferometer is used. Here we describe and evaluate a Newton's rings method that enables direct estimation of such correction. The implementation of this method is described, the sensitivities to experimental adjustments are discussed, and the results are compared with standard measurements within EURAMET project No. 1272. The resulting central length measured with a double-ended interferometer and corrected using the Newton's rings method agrees well with the standard measurement results within a total uncertainty of ±20 nm for both steel and ceramic gauges. Unlike the stack method, the Newton's rings method enables measurement of the correction for an individual sample (e.g. gauge block) and can easily be done for both short and long gauges with equal speed and uncertainty