טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentBen-Aroya Ido
SubjectCoherent Phenomena in Hot Three-Level Lambda-Systems and
Atomic Clocks
DepartmentDepartment of Electrical Engineering
Supervisor Professor Emeritus Gad Eisenstein
Full Thesis textFull thesis text - English Version


Abstract

    The world of atomic clocks is undergoing a revolution as a new class of compact devices whose power consumption is sufficiently low to enable battery driven operation has emerged. Atomic clocks are implemented by locking a local oscillator to an atomic resonance by a frequency-locking loop. The new small-scale clocks are based on an atomic resonance known as Coherent Population Trapping, or CPT, of hot alkali atoms which is induced by a directly modulated diode laser. This technique provides very narrow atomic resonances but their contrasts are in general low, of the order of only 1%. Therefore, they require sophisticated and complex locking schemes for obtaining a proper, even if limited, clock performance.

    In this thesis, we explore this problem and discuss its possible solutions from two different aspects: the engineering aspect which deals with an optimization of the overall system and the physics aspect in which a new, large contrast atomic resonance is introduced.

   

    In the first part of the thesis we introduce a novel ultra-sensitive spectroscopic technique which we have developed. This technique which is termed the Double-field FM Spectroscopy or DFFMS is presented, analyzed, and demonstrated by utilizing a two-photon process - the CPT resonance which is induced by a directly modulated diode laser.

    The DFFMS is then harnessed for closing the frequency-locking loop of a small-scale CPT based atomic clock. Our clock architecture which potentially enables miniaturization is presented and optimized systematically. Finally, the locked system, namely, the atomic clock is tested and exhibiting state-of-the-art performance.

   

    A novel atomic resonance which is based on a three-photon coherent effect in hot alkali vapor is introduced in the second part of the thesis. The new effect which is termed the Population Transfer Resonance or PTR avails a large contrast resonance. Moreover, the implementation of the setup which enables the PTR requires only a slight modification of the CPT based small-scale atomic clock architecture. Therefore, it can potentially serve as the basis for vastly improved small-scale atomic clocks. In this part, we demonstrate the three-photon effect and analyze the physical process behind it by introducing a microscopic coupling model. The last chapter of this part summarizes preliminary experimental results in which an anti-symmetric resonance was obtained by employing an electromagnetic field containing five components. The anti-symmetric resonance allows, in principle, a new concept in which the local oscillator is locked on the atomic resonance directly.