Laser frequency stabilizations using electromagnetically induced transparency

Abstract

We present two techniques to lock a laser frequency on an atomic transition line by using an electromagnetically induced transparency (EIT) signals, which give optical and electric feedback. We employed these methods to the D2 line of Rb87 atoms. Spectral characteristics of subnatural linewidth EIT allow us to improve frequency stability. By optical feedback of EIT signals, we were able to obtain locking bandwidths of 12 MHz, while frequency stability was 5×10−13 at best after 100 s of integration using a frequency modulation technique.

Linewidths below 100 kHz with external cavity diode lasers

“…For an ECDL, external noise sources such as thermal and mechanical fluctuations broaden the timeaveraged effective linewidth to the extent that changes to the intrinsic cavity-determined linewidth are difficult to observe. Feedback stabilization techniques [31][32][33] can be used to compensate such disturbances, but perturb measurement of the intrinsic cavity-determined linewidth. For our measurements of the intrinsic linewidth, only passive isolation and decoupling from the environment were used.…”

Laser frequency offset-locking using electromagnetically induced transparency spectroscopy of 85 Rb in magnetic field

“…The technique of cavity-assisted frequency locking [14,15] can synchronically lock the lasers with different wavelengths to one common cavity, where a stable cavity system with a precise cavity length should be guaranteed. The third method is using atomic spectroscopy, such as electromagnetically induced transparency (EIT), [16][17][18][19] where the frequency difference can be determined by the EIT resonance. With the aid of the Raman process, the two lasers are differentially locked to an atomic hyperfine splitting.…”

Laser frequency offset locking via tripod-type electromagnetically induced transparency

“…Due to its quantum interference origin, EIT resonance spectrum can be much narrower than the usual atom transitions spectrum, with greater dispersion and the potential for lower relative frequency uncertainty. Many studies have been done to offset lock one laser frequency to another using the EIT dip signal since its early demonstration in [29]. S. C. Bell and co-workers have offset locked the lasers frequency via Lambda-type EIT and achieved less than 1 kHz spec-tral width of microwave beat frequency via high bandwidth feedback [30].…”