We have performed quantitative measurements of the variation of the on-resonance absorption coefficients ${\kappa }_0$ of the four hyperfine components of the Cs $D_1$ transition as a function of laser power $P$, for pumping with linearly and with circularly polarized light. Sublevel populations derived from rate equations assuming isotropic population relaxation (at a rate ${\gamma }_1$) yield algebraic ${\kappa }_0\left(P\right)$ dependences that do not reproduce the experimental findings from Cs vapor in a paraffin-coated cell. However, numerical results that consider spin-exchange relaxation (at a rate ${\gamma }_{\mathrm{se}}$) and isotropic relaxation fit the experimental data perfectly well. The fit parameters, viz., the absolute value of ${\kappa }_0$, the optical pumping saturation power $P_{\mathrm{sat}}$, and the ratio ${\gamma }_{\mathrm{se}}/{\gamma }_1$, are well described by the experimental conditions and yield absolute values for ${\gamma }_1$ and ${\gamma }_{\mathrm{se}}$. The latter is consistent with the previously published Cs-Cs spin-exchange relaxation cross section.

We report on broad instantaneous bandwidth microwave spectrum analysis with hot Rb 87 atoms in a microfabricated vapor cell in a large magnetic field gradient. The sensor is a MEMS atomic vapor cell filled with isotopically pure Rb 87 and N 2 buffer gas to localize the motion of the atoms. The microwave signals of interest are coupled through a coplanar waveguide to the cell, inducing spin-flip transitions between optically pumped ground states of the atoms. A static magnetic field with large gradient maps the frequency spectrum of the input microwave signals to a position-dependent spin-flip pattern on absorption images of the cell recorded with a laser beam onto a camera. In our proof-of-principle experiment, we demonstrate a microwave spectrum analyzer that has ≈ 1 GHz instantaneous bandwidth centered around 13 GHz, 3 MHz frequency resolution, 2 kHz refresh rate, and a − 23 dBm single-tone microwave power detection limit in 1 s measurement time. A theoretical model is constructed to simulate the image signals by considering the processes of optical pumping, microwave interaction, diffusion of Rb 87 atoms, and laser absorption. We expect to reach more than 25 GHz instantaneous bandwidth in an optimized setup, limited by the applied magnetic field gradient. Our demonstration offers a practical alternative to conventional microwave spectrum analyzers based on electronic heterodyne detection. Published by the American Physical Society 2024

In a recent article in this journal Grewal and Pattabiraman reported on the splitting of ground state Hanle resonances (recorded with linearly polarized light) by a transverse field. They claimed a “linearly proportional” dependence on the transverse field strength and supported this observation with results from numerical simulations. In this comment we argue that the splitting occurs only beyond a certain threshold field value and that it has a strong non-linearity near threshold. We base this claim on our previously published algebraic expressions for the line shapes and support this by experimental evidence.

Based on a low-noise cesium spectral lamp, a high-sensitivity self-oscillating cesium atomic magnetometer with a wide operating temperature range has been developed, solving problems with existing sensors such as a limited operating temperature range and difficult startup at low temperatures. The temperature feedback mechanism is used to make adjustments to any fluctuations in the cesium lamp’s excitation source in real time, improving the magnetometer’s stability and operating temperature range. Herein, the design and optimization of the cesium atomic magnetometer are presented, and a prototype of the magnetometer is described. The quantum limit sensitivity of the cesium atomic magnetometer is estimated by evaluating the intrinsic relaxation rate in the geomagnetic field. A test demonstrates that the cesium atomic magnetometer’s sensitivity in the geomagnetic background is around $140\mathrm{f}\mathrm{T}/\sqrt{\mathrm{H}\mathrm{z}}$ at 1 Hz at room temperature, and the operating temperature range is from −50 °C to 70 °C, surpassing most of the commercial products of its kind in terms of sensitivity and operating temperature range.