Rubidium Fluorescence and Diode Laser Spectroscopy

Thumbnail Image
Garai, Máté
Peterson, Dr. Randolph
Issue Date
Scholarship Sewanee 2023 , University of the South , Diode Laser , Spectroscopy , Fluorescence , Optics , Rubidium
The invention of inexpensive, tunable, narrow-bandwidth semiconductor diode lasers has opened up many spectroscopic analysis techniques to individual use, undergraduate research, and advanced laboratories. In this study, a finely tunable ~780 nm AlGaAs diode laser is used to observe the resonant absorption effects in the fine and hyperfine structure of Rb vapor. In particular, the 5S1/2 to 5P3/2 D2 transition line is explored and quantitatively measured. The hyperfine structure energy levels are separated by <100 MHz (∆λ = ~0.1 pm) and are revealed only through saturated absorption spectroscopy which eliminates the previously Doppler-broadened absorption peaks. Saturated absorption is achieved using a single-mode, time-dependent pump beam through the cell which saturates nearby Rb molecules, allowing the much less intense probe beam to distinguish the absorption features of stationary molecules. The temperature-dependent complex index of refraction of the vapor was also modeled using a simplified, but approximate model, assuming the 5s electron as a harmonic oscillator. This dependence was observed using a Mach-Zehnder interferometer. The behavior of the beam suggests that the index of refraction has a strong temperature dependence. The Zeeman effect of the energy levels was also observed using a controlled parallel magnetic field. The project explores a multitude of topics from linear and nonlinear optics, classical electrodynamics, and electronics, and also incorporates ideas from quantum physics.