Laser frequency stabilization on 5P → 5D transition by double resonance optical pumping and two-photon transition spectroscopy in rubidium

Abstract

We present a laser frequency locking scheme for the high excited transition of rubidium, which cannot be directly referenced by atomic absorption spectroscopy. Double resonance optical pumping spectroscopy and two-photon transition spectroscopy of a 5S → 5P → 5D transition are obtained in a room temperature vapor cell and employed as the reference sources. An Allan deviation of 1.71 × 10−12 at an averaging time of 2048 s with a residual frequency fluctuation of ±0.2 MHz over 7000 s is obtained by two-photon transition spectroscopy. The case of double resonance optical pumping spectroscopy presents an Allan deviation of 4.86 × 10−12 at an averaging time of 2048 s with a residual frequency fluctuation of ±0.4 MHz over 7000 s. One distinct advantage of two-photon transition spectroscopy method is demonstrated by the analysis of the fast Fourier transform of error signal. A narrower full width at half-maximum of two-photon transition spectroscopy and a higher zero crossing slope by using a frequency modulation method lead to a better frequency stabilization. This work provides a technical basis for the laser frequency stabilization based on atomic and molecular transition spectroscopy, and it also supplies a new frequency standard for optical telecommunication applications.