Investigation of waveguide frequency doubling crystals for interrogation of a two-photon transition in rubidium

An excellent candidate for a high-quality portable frequency standard at the telecommunication region is the 5S1/2 (F = 3) –5D5/2 (F = 5) two-photon transition of rubidium (85) at 778 nm. The interrogation of the two-photon transition needs efficient second harmonic conversion of a laser at 1556 nm. In the present work, a comparison is made between the conversion efficiencies of bulk and waveguide periodically polled lithium niobate (PPLN) crystals. In order to acquire the optimum operating conditions, the frequency doubled power is measured as a function of crystal temperature and laser wavelength. The conversion efficiency of the bulk PPLN crystal is found to be smaller than that of the waveguide PPLN for input powers less than 150 mW.

Keywords:

Frequency doubling , Bulk PPLN , Waveguide PPLN , Rubidium