Christopher J. Erickson

An ultrahigh stability, low-noise laser current driver with digital control

We present a low-noise, high modulation-bandwidth design for a laser current driver with excellent long-term stability. The driver improves upon the commonly used Hall-Libbrecht design. The current driver can be operated remotely by way of a microprocessing unit, which controls the current set point digitally. This allows precise repeatability and improved accuracy and stability. It also allows the driver to be placed near the laser for reduced noise and for lower phase lag when using the modulation input. We present the theory of operation for our driver in detail, and give a thorough characterization of its stability, noise, set-point accuracy and repeatability, temperature dependence, transient response, and modulation bandwidth.

Note: Updates to an ultra-low noise laser current driver

We describe updates to our current driver design allowing for higher output currents, both positive and negative currents, and updated digital interfacing to the microcontroller. We also discuss measurement of the noise spectral density of the driver with a better technique, showing that the drivers actual current noise density is about an order of magnitude lower than the upper limit we previously determined.

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.

Ex vacuo atom chip Bose-Einstein condensate

Ex vacuo atom chips, used in conjunction with a custom thin walled vacuum chamber, have enabled the rapid replacement of atom chips for magnetically trapped cold atom experiments. Atoms were trapped in >2 kHz magnetic traps created using high power atom chips. A thin walled vacuum chamber allowed the atoms to be trapped ≲1 mm from the atom chip conductors which were located outside of the vacuum system. Placing the atom chip outside of the vacuum simplified the electrical connections and improved the thermal management. Using a multi-lead Z-wire chip design, a Bose-Einstein condensate was produced with an external atom chip. Vacuum and optical conditions were maintained while replacing the Z-wire chip with an atom chip with a cross-wire design. The atom chips were exchanged and an initial magnetic trap was achieved in less than 3 h.

Precision Metrology with a Strontium Ion Interferometer

We present a strontium ion interferometer for use as an electromagnetic field sensor with unprecedented sensitivity. Applications include measurements of fringing fields, studies of image charge scattering in superconductors, and ultra-precise tests of electromagnetism.

Achieving High Precision with a Thermal Beam Atom Interferometer

We report on the progress of a thermal calcium-beam Ramsey-Borde atom interferometer. Our efforts have led to the development of precision electronic and laser systems whose design allows them to be implemented as lab standards.