Simultaneous two-photon resonant optical laser locking (STROLLing) in the hyperfine Paschen-Back regime.

We demonstrate a technique to lock simultaneously two laser frequencies to each step of a two-photon transition in the presence of a magnetic field sufficiently large to gain access to the hyperfine Paschen-Back regime. A ladder configuration with the 5S1/2, 5P3/2, and 5D5/2 terms in a thermal vapor of Rb87 atoms is used. The two lasers remain locked for more than 24 h. For the sum of the laser frequencies, which represents the stability of the two-photon lock, we measure a frequency instability of less than the Rb D2 natural linewidth of 6 MHz for nearly all measured timescales.

Optimized ultra-narrow atomic bandpass filters via magneto-optic rotation in an unconstrained geometry.

Atomic bandpass filters are widely used in a variety of applications, owing to their high peak transmission and narrow bandwidths. Much of the previous literature has used the Faraday effect to realize these filters, where an axial magnetic field is applied across the atomic medium. Here we show that by using a non-axial magnetic field, the performance of these filters can be improved in comparison to the Faraday geometry. We optimize the performance of these filters using a numerical model and verify their performance by direct quantitative comparison with experimental data. We find excellent agreement between experiment and theory. These optimized filters could find use in many of the areas where Faraday filters are currently used, with little modification to the optical setup, allowing for improved performance with relatively little change.

Automated translating beam profiler for in situ laser beam spot-size and focal position measurements.

We present a simple and convenient, high-resolution solution for automated laser-beam profiling with axial translation. The device is based on a Raspberry Pi computer, Pi Noir CMOS camera, stepper motor, and commercial translation stage. We also provide software to run the device. The CMOS sensor is sensitive over a large wavelength range between 300 and 1100 nm and can be translated over 25 mm along the beam axis. The sensor head can be reversed without changing its axial position, allowing for a quantitative estimate of beam overlap with counter-propagating laser beams. Although not limited to this application, the intended use for this device is the automated measurement of the focal position and spot-size of a Gaussian laser beam. We present example data of one such measurement to illustrate device performance.

A single-mode external cavity diode laser using an intra-cavity atomic Faraday filter with short-term linewidth <400 kHz and long-term stability of <1 MHz.

We report on the development of a diode laser system - the "Faraday laser" - using an atomic Faraday filter as the frequency-selective element. In contrast to typical external-cavity diode laser systems which offer tunable output frequency but require additional control systems in order to achieve a stable output frequency, our system only lases at a single frequency, set by the peak transmission frequency of the internal atomic Faraday filter. Our system has both short-term and long-term stability of less than 1 MHz, which is less than the natural linewidth of alkali-atomic D-lines, making similar systems suitable for use as a "turn-key" solution for laser-cooling experiments.

Electromagnetically induced absorption in a nondegenerate three-level ladder system.

We investigate, theoretically and experimentally, the transmission of light through a thermal vapor of three-level ladder-type atoms, in the presence of two counterpropagating control fields. A simple theoretical model predicts the presence of electromagnetically induced absorption in this pure three-level system when the control field is resonant. Experimentally, we use (87)Rb in a large magnetic field of 0.62 T to reach the hyperfine Paschen-Back regime and realize a nondegenerate three-level system. Experimental observations verify the predictions over a wide range of detunings.

Atomic Faraday filter with equivalent noise bandwidth less than 1 GHz.

We demonstrate an atomic bandpass optical filter with an equivalent noise bandwidth less than 1 GHz using the D1 line in a cesium vapor. We use the ElecSus computer program to find optimal experimental parameters and find that, for important quantities, the cesium D1 line clearly outperforms other alkali metals on either D-lines. The filter simultaneously achieves a peak transmission of 77%, a passband of 310 MHz, and an equivalent noise bandwidth of 0.96 GHz, for a magnetic field of 45.3 G and a temperature of 68.0°C. Experimentally, the prediction from the model is verified. The experiment and theoretical predictions show excellent agreement.