Utilizing a two-photon absorption scheme in an alkali-metal vapor cell, we suggest a technique where a strong laser beam switches off another laser beam of different wavelength in femtosecond time scales.
We report the fabrication of alkali-metal vapor cells using femtosecond laser machining. This laser-written vapor-cell (LWVC) technology allows arbitrarily-shaped 3D interior volumes and has potential for integration with photonic structures and optical components. We use non-evaporable getters both to dispense rubidium and to absorb buffer gas. This enables us to produce cells with sub-atmospheric buffer gas pressures without vacuum apparatus. We demonstrate sub-Doppler saturated absorption spectroscopy and single beam optical magnetometry with a single LWVC. The LWVC technology may find application in miniaturized atomic quantum sensors and frequency references.
A laser beam with left-/right-handed circular polarization is generally used to create the oriented atomic spins for precision measurements in a spin-exchange relaxation-free (SERF) co-magnetometer. The fluctuation of laser polarization interferes with the spin polarization of alkali metal atoms, leading to the system performance degradation. Here, we report a method for real-time polarization state measurement by using the transmitted light intensity of the pump beam passing through the vapor cell. Based on the principle of circular dichroism, the optical absorption model of polarized alkali metal atoms is established. The simulation results of the transmittance of the pump laser with different polarization states through the alkali metal vapor cell are given and verified by experiments. The experimental results show that the circularly polarized beam has the weakest absorption, while the linearly polarized laser beam is absorbed the strongest. The achieved measurement accuracy stands at an impressive 98.83 %. This work provides a simple and easy-to-use way to measure the polarization state of the laser beam used in the vapor cell devices, particularly the microfabricated prototypes with limited space.
Abstract : An absorption spectrum of a rubidium alkali metal dispenser (AMD) cell was obtained in order to determine the system s suitability for use in a diode pumped alkali laser (DPAL) and use in high-temperature spectroscopic studies. The AMD produced a concentration of 3.65 0.16 1010 cm-3, which is in the ideal range for Beer s Law region absorption spectroscopy, but too low to make a high-power DPAL in a 10 cm cell with a poor Q resonator. Before AMDs can be used to determine pressure broadening and shifting coefficients, issues concerning contamination and producing rubidium vapor at pressure must be resolved. A separate portion of this study focused on a sealed rubidium Pyrex cell with neon buffer gas. A continuous wave titanium sapphire beam was focused into the cell with various lenses to maximize pump intensity through the cell. Images were taken of the side fluorescence of the cell to determine the bleached regions. The total horizontal propagation of the bleached region for each image was proportional to the pump laser power and the inverse of the rubidium vapor density. Disparity between the bleached volume estimated from the beam parameters and the theoretical bleached volume suggested the beam intensity had a strong radial dependence. When the pump wavelength was changed, visible side fluorescence occurred in regions where the laser intensity was at least 0.125 times the saturation intensity and therefore not in the regions where the decay was determined by Beer s Law.