Picotesla magnetometer based on coherently prepared thermal alkali atomic vapors

Summary form only given. We have experimentally investigated the potential of narrow coherent population trapping (CPT) resonances for precision magnetometry. CPT can be observed in /spl Lambda/ systems where two ground states are coupled to a common excited state by two near-resonant light fields. On resonance, effective formation of long-lived ground state coherences which do not couple in the light fields leads to reduced absorption in the medium ("electromagnetically induced transparency") and thus reduced fluorescence intensity ("dark resonance"). Extremely narrow CPT resonances can be observed when the light fields have fixed phase and frequency difference and time-of-flight broadening is suppressed by the use of a buffer gas, making this type of system a promising candidate for precision applications.