Iodine Absorption Cells Purity Testing.

This article deals with the evaluation of the chemical purity of iodine-filled absorption cells and the optical frequency references used for the frequency locking of laser standards. We summarize the recent trends and progress in absorption cell technology and we focus on methods for iodine cell purity testing. We compare two independent experimental systems based on the laser-induced fluorescence method, showing an improvement of measurement uncertainty by introducing a compensation system reducing unwanted influences.

Spectral properties of molecular iodine in absorption cells filled to specified saturation pressure.

We present the results of measurement and evaluation of spectral properties of iodine absorption cells filled at certain saturation pressure. A set of cells made of borosilicate glass instead of common fused silica was tested for their spectral properties in greater detail with special care for the long-term development of the absorption media purity. The results were compared with standard fused silica cells and the high quality of iodine was verified.

Optical phase locking of two infrared continuous wave lasers separated by 100 THz.

We report on phase locking of two continuous wave IR laser sources separated by 100 THz emitting around 1029 and 1544 nm, respectively. Our approach uses three independent harmonic generation processes of the IR laser frequencies in periodically poled MgO:LiNbO3 crystals to generate second and third harmonics of those two IR sources. The beat note between the two independent green radiations generated around 515 nm is used to phase lock one IR laser to the other, with tunable radio frequency offset.

Lasers for coherent optical satellite links with large dynamics.

We present the experimental realization of a laser system for ground-to-satellite optical Doppler ranging at the atmospheric turbulence limit. Such a system needs to display good frequency stability (a few parts in 10) while allowing large and well-controlled frequency sweeps of ±12  GHz at rates exceeding 100  MHz/s. Furthermore it needs to be sufficiently compact and robust for transportation to different astronomical observation sites, where it is to be interfaced with satellite ranging telescopes.

Coherent optical link through the turbulent atmosphere.

We describe the realization of a 5 km free-space coherent optical link through the turbulent atmosphere between a telescope and a ground target. We present the phase noise of the link, limited mainly by atmospheric turbulence and mechanical vibrations of the telescope and the target. We discuss the implications of our results for applications, with particular emphasis on optical Doppler ranging to satellites and long-distance frequency transfer.