Brian Neyenhuis

Testing Nonclassical Theories of Electromagnetism with Ion Interferometry

We discuss using a tabletop ion interferometer to search for deviations from Coulombs inverse-square law. Such deviations would result from nonclassical effects such as a nonzero photon rest mass. We discuss the theory behind the proposed measurement, explain which fundamental, experimentally controllable parameters are the relevant figures of merit, and calculate the expected performance of such a device in terms of these parameters. The sensitivity to deviations in the exponent of the inverse-square law is predicted to be a few times 10(-22), an improvement by 5 orders of magnitude over current experiments. It could measure a nonzero photon rest mass smaller than 9 x 10(-50) grams, nearly 100 times smaller than current laboratory experiments.

High-temperature calcium vapor cell for spectroscopy on the 4s2S01–4s4pP13 intercombination line

We have demonstrated a high-temperature vapor cell for absorption spectroscopy on the Ca intercombination line. The cell uses a dual-chamber design to achieve the high temperatures necessary for an optically dense vapor while avoiding the necessity of high-temperature vacuum valves and glass-to-metal seals. We have observed over 50% absorption in a single pass through the cell. Although pressure broadening in the cell prevented us from performing saturated-absorption spectroscopy, the broadening resulted in higher signal-to-noise ratios by allowing us to probe the atoms with intensities much greater than the 0.2μW∕cm2 saturation intensity of the unbroadened transition. The techniques presented in this article could easily be applied to study other transitions in a variety of atomic species.

Identification and Control of a Grating-Stabilized External-Cavity Diode Laser

Diode lasers have many useful properties and have found a variety of uses including CD and DVD players, barcode scanners, laser surgery, water purification, quantum-key cryptography, spectroscopic sensing, etc. Nevertheless, their intrinsic linewidth or the precision of their emitted wavelengths, is not good enough for many cutting-edge applications such as atomic interferometry or high-performance atomic clocks. Using active feedback control, we can narrow the linewidth of a diode laser by not allowing the frequency of emitted light to drift away from a reference value. Nevertheless, such feedback designs are challenging because of a lack of first principles models and difficult sensor dynamics. This brief describes our diode laser system and reports our results identifying the system using black-box techniques, validating the empirical models, and designing controllers to achieve desired performance while preserving stability and satisfying implementation constraints.

Black-Box Identification of a Grating-Stabilized External-Cavity Diode Laser

Diode lasers have many useful properties and have found a variety of uses including CD and DVD players, barcode scanners, laser surgery, water purification, quantum-key cryptography, spectroscopic sensing, etc. Nevertheless, their intrinsic linewidth, or the precision of their emitted wavelengths, is not good enough for many cutting-edge applications such as atom interferometry or high-performance atomic clocks. Using active feedback control we can narrow the linewidth of a diode laser, not allowing the frequency of emitted light to drift away from a reference value. Nevertheless, such feedback designs are challenging because of a lack of first principles models and difficult sensor dynamics. This paper describes our diode laser system and reports our results identifying the system using black-box techniques.