New Magnetometer

We summarize here the main practical results obtained in the Institute of Electronics at the Bulgarian Academy of Sciences under the project: “New alloptical systems and methods for magnetic and electromagnetic field measurement”, financed by EC (contract G6RD-CT-2001-00642). The project Consortium consists of the following partners: Department of Physics, University of Siena, Italy, Project Coordinator Prof. L. Moi Optela Optical Technologies JSC, Plovdiv, Bulgaria, Team leader Dr. V. Ribarov Institute of Experimental Physics, Technical University of Graz, Austria, Team leader Prof. L. Windholz Institute of Electronics, Bulgarian Academy of Sciences, Bulgaria, Team leader Dr. S. Cartaleva Optella Ltd, Sofia, Bulgaria, Team leader Dr. L Avramov The Institute of Electronics’ staff working on the project: Dr. Stefka Cartaleva, Dr. Sanka Gateva, Dr. Emilia Alipieva, Dr . Andrey Yanev, Dr. Georgy Todorov, Dr. Dimitar Slavov, Dr. Christina Andreeva, PhD Student Todor Karaulanov, PhD Student Elena Taskova, PhD Student Lyubomir Petrov, Physicist Valentina Sarova, Physicist Nikolay Petrov The aim of the project was investigation of the potential of different approaches for application of the effect of Coherent Population Trapping (CPT) for magnetic field (MF) measurement. The CPT consists in the accumulation of atoms in a coherent superposition of two or more atomic sublevels, resulting in the registration of a resonance whose width is determined by the superposed levels width. This in alkali atoms determines a very narrow resonance because its width is set by ground-state hyperfine (hf) levels lifetime. CPT resonance linewidths smaller than 1 kHz have been measured. With Rb or Cs atomic vapour, simple, and not expensive CPT experiments can be set and portable practical devices can be developed using diode lasers. CPT is produced by simultaneous excitation of the two ground-states levels by laser light whose spectral profile is modified by frequency modulation obtained through direct diode current modulation. CPT resonances appear either when the modulation frequency matches the splitting between Zeeman sublevels of the two ground-state hf levels or the splitting of two Zeeman sublevels of the same hf level. In the second case, the laser light is modulated at a much lower frequency. The high precision achieved is due to the CPT resonance linewidth and because the MF is determined by frequency measurement. In the Institute of Electronics three approaches have been developed for CPT phenomenon investigation and its application for MF measurement: