Blue fluorescence as a frequency offset reference in the rubidium 5S-5P-5D transition

Area of Science:

• Atomic Physics
• Laser Spectroscopy
• Quantum Optics

Background:

• Frequency offset references are crucial for high-precision spectroscopy.
• Blue fluorescence in atomic systems can arise from specific excitation and decay pathways.
• Understanding optical pumping and splitting phenomena is key to controlling atomic transitions.

Purpose of the Study:

• To evaluate the suitability of blue fluorescent light from Rb85 atoms as a frequency offset reference.
• To investigate the influence of double resonance optical pumping (DROP) and Autler-Townes splitting on blue light generation.
• To assess the stability of a laser system stabilized using this blue fluorescence.

Main Methods:

• Pump-probe spectroscopy on the 5S_1/2→5P_3/2→5D_3/2 ladder transition in Rb85.
• Generation of blue light (420 nm) via spontaneous decay (5D_3/2→6P_3/2→5S_1/2).
• Coherence-induced modulation transfer spectroscopy for laser stabilization.

Main Results:

• Blue fluorescence exhibits a narrow linewidth under the DROP regime, making it an effective frequency reference.
• Laser stabilization to the blue fluorescence peak was achieved.
• Analysis revealed probe laser fluctuations transferred to the pump laser due to two-photon coherent coupling.

Conclusions:

• Blue fluorescence from Rb85 atoms is a viable and stable frequency offset reference, especially in the DROP regime.
• The study demonstrates a method for laser stabilization using this atomic fluorescence.
• Coherent coupling effects must be considered in precision laser stabilization schemes.