We present an approach allowing an optically pumped magnetometer (OPM) to be operated within the Earth’s magnetic field as a vector magnetometer, the sensitive axis of which can be freely defined. This approach enables the measurement of any vector component of the Earth’s magnetic field with the same sensitivity. The OPM is realized by a microfabricated cesium-vapor cell with nitrogen buffer gas, which is immersed in a constant homogeneous bias field of approximately 730 μ T . Since this bias field is about one order of magnitude stronger than the Earth’s magnetic field, it defines the sensitive axis of the OPM. The bias field is generated by solid-state magnets and has been designed to exhibit a very low relative inhomogeneity ( < ± 10 − 4 in relative units) within the vapor-cell dimensions as well as a point of vanishing temperature dependence at around 40 ∘ C . The OPM utilizes the light-narrowing effect, which enables effective suppression of spin-exchange relaxation even in such a large magnetic field amplitude. Based on this implementation, we demonstrate a white-noise floor of below 60 fT / Hz in the frequency interval between 100 Hz and 600 Hz and a 3-dB sensor bandwidth of > 5 kHz . Our approach enables unshielded ultrasensitive vectorial measurement capabilities that are relevant in many important applications.

In mobile applications such as geomagnetic surveying, two major effects hamper the use of optically pumped magnetometers: dead zones, sensor orientations where the sensors signal amplitude drops; and heading errors, a dependence of the measured magnetic field value on the sensor orientation. We present a concept for an omnidirectional magnetometer to overcome both of these effects. The sensor uses two cesium vapor cells, interrogated by circularly-polarized amplitude-modulated laser light split into two beams propagating perpendicular to each other. This configuration is experimentally investigated using a setup wherein the laser beam and magnetic field direction can be freely adjusted relative to each other within a magnetically shielded environment. We demonstrate that a dead-zone-free magnetometer can be realized with nearly isotropic magnetic-field sensitivity. While in the current configuration we observe heading errors emerging from light shifts and shifts due to the nonlinear Zeeman effect, we introduce a straightforward approach to suppress these systematic effects in an advanced sensor realization.

The transparent conducting oxides ZnO and ZnO:Al are interesting materials for a wide range of applications. Several of these applications need a large area, single crystalline, and specially doped thin layers. A common technique for the fabrication of those layers is RF (radio frequency) -magnetron sputtering. The investigation of the crystal quality of such layers requires methods of analysis that are destruction free and that are able to obtain information about the concentration and type of defects versus depth. One such option is the Rutherford backscattering spectroscopy (RBS) in channelling mode. In this work, we exploit the channelling effect and its energy dependence, which are sensitive to the type of defects. By using appropriate software and measuring RBS channelling spectra with different beam energies, we were able to determine the depth distribution of point defects and dislocation loops. The presence of dislocation loops was proven using other previously applied analysis methods. The main advantage of RBS in channelling mode is the quantification of point defects, which can be important for defining the electrical and optical properties of such layers. The technique demonstrated is applicable to other defective crystals or thin crystalline layers.

Measurements of weak magnetic fields demand a small distance between the sensor and the to-be-measured object. Optically pumped magnetometers (OPMs) utilize laser light and the Zeeman effect in alkali vapor cells to measure those fields. OPMs can be used in transmission or reflection geometry. A minimization of the distance between active volume and magnetized source calls for reflection geometry with integrated mirrors. Unfortunately, cesium reacts chemically with most materials, especially high-performing materials, such as gold. Herein, we show the first functional OPM cell using a gold mirror inside the cell. We fabricated the gold mirrors with and without a passivation layer in order to evaluate the feasibility of expanding on the limited list of possible mirror materials. A comparison of this implementation revealed that mirrors without a passivation layer only reach a reflectivity of about 6% while mirrors with a passivation layer retain reflectivity values of about 90% in the visible light to near-infrared spectrum. This result and the proof of elemental cesium in the alkali vapor cell demonstrates the feasibility of passivated gold mirrors for applications in alkali vapor cells for OPMs.

Stray-light reduction is critical for the operation of optical components in space. Here, we report on the testing of high performance plasmonic broadband absorbing black coatings for space applications fabricated by metastable atomic layer deposition (MS-ALD). For this purpose, humidity testing, thermal cycling, exposure to atomic oxygen, and adhesion testing were used as testing methods. The results show that the films with thickness greater than 9 μm are able to withstand the humidity tests, thermal cycling, and exposure to atomic oxygen without significant loss of their broadband absorption. However, it was also observed that the adhesion of the films has not yet been sufficient to meet the requirements posed by the space environment. Therefore, the authors conclude that further fine-tuning of the films with respect to increasing adhesion is required to make the films suitable for space applications. Therefore, the authors propose to investigate the coating of the MS-ALD films with high refractive index coatings.

In mobile applications such as geomagnetic surveying, two major effects hamper the use of optically pumped magnetometers: dead zones, sensor orientations where the sensors signal amplitude drops; and heading errors, a dependence of the measured magnetic field value on the sensor orientation. We present a concept for an omnidirectional magnetometer to overcome both these effects. The sensor uses two cesium vapor cells, interrogated by circularly-polarized amplitude-modulated laser light split into two beams running perpendicular to each other. This configuration is experimentally investigated using a setup wherein the laser beam and magnetic field direction can be freely adjusted relative to each other within a magnetically shielded environment. We demonstrate that a dead-zone free magnetometer can be realized with nearly isotropic magnetic-field sensitivity. While in the current configuration we observe heading errors emerging from light shifts and due to the nonlinear Zeeman effect, we introduce a straightforward approach to suppress these systematic effects in an advanced sensor realisation.