Heading errors in all-optical alkali-metal-vapor magnetometers in geomagnetic fields

Laser-written vapor cells for chip-scale atomic sensing and spectroscopy

“…However, due to the planar bonding or lithographic strategy, all these cells do not show 3D versatility and have limited optical access. Many atomic sensors like those based on multipass cells [34][35][36], cell arrays [37], dual-beam [38], triple-beam [39,40] or cavity-enhanced [41,42] geometries, do require greater flexibility and optical access. Various strategies have been also developed for the integration of vapor cells with photonic waveguides.…”

Heading-error-free optical atomic magnetometry in the Earth-field range

“…However, the dependence of the (nominally scalar) magnetometer reading on the direction of the magnetic field, known as heading error, may be a limiting factor in the performance of such devices [7]. Depending on the type of the atomic sensor, there are mainly three physical sources of heading error: the nonlinear Zeeman effect (NLZ) due to the coupling between electron spin and nuclear spin [9][10][11], the different gyromagnetic ratios of the two ground hyperfine states due to the linear nuclear Zeeman effect (NuZ) [11,12], and the magnetic-field-direction-dependent light shift (LS) [10]. The first two effects lead to the direction-dependent asymmetry of the magnetic resonance curve, and the third one leads to the direction-dependent shift of the magnetic resonance frequency.…”

“…Various methods to suppress the NLZ-related heading error have been attempted, including synchronous optical pumping with double modulation [15], excitation of high-order atomic polarization [16], compensation with tensor light shift [17], push-pull pump [18], spin-locking with synchronous optical pumping and radio-frequency (RF) [9] or modulated optical [19] field, pumping with light of opposite circular polarization [10], and using a high-power pump and correcting with theoretical predictions [11]. In some cases, heading errors due to NuZ [11] or LS [10] effect are suppressed together with the NLZrelated effect at the same time.…”

A femtotesla quantum-noise-limited pulsed gradiometer at finite fields

“…This goal is important for a wide spectrum of applications, including space magnetometry [8][9][10], magnetic navigation [11,12], archeological mapping [13,14], biomagnetism detection [15][16][17], mineral exploration [18,19], searches for unexploded ordnance [20,21], as well as for tests of fundamental physics [22,23]. In general, total-field OPMs can operate in geomagnetic fields (10-100 µT) [24] and they are better suited for applications in challenging environments [25]. Under continuous operation, finite field sensors based on Bell-Bloom (BB) [26], modulated nonlinear magneto-optical rotation (NMOR) and M z operation modes, have enabled sensitivity typically at the pT/ √ Hz [27][28][29] or slightly below that level [30][31][32].…”

“…The high CMRR is suitable for applications in unshielded and challenging environments [25,40]. The sensitivity could be further improved with higher VCSEL laser power and by using two pump lasers for hyperfine re-pumping [34,58], while a technique reducing heading errors due to the orientation of a total-field sensor has been recently developed [24]. The operation mode of the described quantum-noise-limited gradiometer is compatible with quantum enhancement techniques using spin or polarization squeezing [44,59] in geomagnetic fields.…”