High-performance atomic magnetometers (AMs) rely on the measurement of optical rotation, which requires a set of bulky polarization optics that limit their applications in scenarios where portability and compactness are necessary. In this study, a miniaturized AM is constructed based on a cubic 87 Rb vapor cell and monolithic metalens, which provides an integrated scheme to achieve optical rotation detection induced by the circular birefringence of polarized atoms. The designed metalens achieves polarization splitting with deflection angles of ±10 ∘ and focusing with efficiencies of approximately 30% for orthogonal linear polarizations. The sensitivity of our compact device is ∼30 fT/Hz 1/2 with a dynamic range of around ±1.45 nT. We envision that the presented approach paves the way for the chip integration of emerging atomic devices, which are in demand for applications such as biomagnetic imaging and portable atomic gyroscopes.
High-performance atomic magnetometers (AMs) rely on the measurement of optical rotation, which requires a set of bulky polarization optics that limit their applications in scenarios where portability and compactness are necessary. In this study, a miniaturized AM is constructed based on a cubic 87 Rb vapor cell and monolithic metalens, which provides an integrated scheme to achieve optical rotation detection induced by the circular birefringence of polarized atoms. The designed metalens achieves polarization splitting with deflection angles of ±10 ∘ and focusing with efficiencies of approximately 30% for orthogonal linear polarizations. The sensitivity of our compact device is ∼30 fT/Hz 1/2 with a dynamic range of around ±1.45 nT. We envision that the presented approach paves the way for the chip integration of emerging atomic devices, which are in demand for applications such as biomagnetic imaging and portable atomic gyroscopes.
Emerging atomic magnetometers (AMs) are among the most advanced sensors for detecting and characterizing magnetic fields. Recently, there has been growing interest in the miniaturization and integration of AMs due to the urgent demand for portability and compactness in various fields such as biomagnetism imaging. While conventional AMs require a bulky setup of optical devices for the pumping and optical readout of atomic spin, here, a novel chip-scale single-beam AM scheme is proposed by leveraging extreme transmissive circular polarization dichroism (TCPD) and geometric phase manipulation of spin-selective interference meta-optics. This is achieved through silicon-based metasurfaces that enable the realization of arbitrary-to-circular polarization conversion and wavefront modulation within a monolithic chip at Rb D1 transition wavelength (λ = 795 nm). Two spin-selective interference metasurfaces, i.e., meta-circular-polarizer (MCP) and meta-circular-polarizer-lens (MCPL), are fabricated and characterized, with a measured TCPD of 0.68 for the MCP as well as focusing efficiency and TCPD of around 70.67% and 0.69 for the MCPL, respectively. As a proof of concept, a 4 × 4 × 4 mm 3 Rb vapor cell is combined with our metasurface to construct a miniaturized single-beam AM. The sensitivity of our compact metasurface-based system is about 15 fT/Hz 1/2, with a dynamic range near zero-field of ± 2.2 nT. We envision that this work could facilitate the development of burgeoning chip-scale quantum sensors, which hold great potential for high-spatial-resolution biomagnetic imaging, on-chip nuclear magnetic resonance, and so forth.
ABSTRACT Atomic magnetometers (AMs) are among the most sensitive magnetic field sensors, with uses in magnetic anomaly detection, geosciences, and fundamental physics research. Despite notable progress, developing highly integrated, miniaturized components with high resolution, sensitivity, and efficiency for chip‐scale AMs remains a significant challenge. Here, we present a novel integrated polarization detection scheme based on a bifocal liquid‐crystal polarization metalens (LCPM) for chip‐scale AMs. By leveraging geometric phase and holographic synthesis principles, the LCPM efficiently separates and focuses left‐ and right‐handed circularly polarized light at the rubidium D1 transition wavelength (795 nm), achieving a high focusing efficiency of up to 80% and extinction ratios of 104 and 134 for the two channels. We demonstrate a prototype AM operating in the spin‐exchange relaxation‐free regime, achieving a high magnetic‐field sensitivity of 17 fT/Hz 1/2 and a dynamic range of ±4.8 nT. The proposed LCPM‐based scheme reduces the optical‐path volume by 94% compared to traditional polarization detection systems. Importantly, our method is compatible with large‐scale, cost‐effective production through established liquid‐crystal manufacturing lines, paving the way for high‐throughput fabrication of chip‐scale AMs. This innovation enables compact, affordable polarization detection with enhanced sensitivity of atomic sensors, opening new opportunities for high‐resolution biomagnetic imaging and quantum precision measurements.
We demonstrate atomic magnetometry using a metasurface polarizing beamsplitter fabricated on a silicon-on-sapphire (SOS) platform. The metasurface splits a beam that is near-resonant with the rubidium atoms (795 nm) into orthogonal linear polarizations, enabling the measurement of magnetically sensitive circular birefringence in rubidium vapor through balanced polarimetry. We incorporated the metasurface into an atomic magnetometer based on nonlinear magneto-optical rotation and measured subnanotesla sensitivity, which is limited by low-frequency technical noise and transmission loss through the metasurface. To our knowledge, this work represents the first demonstration of SOS nanophotonics for atom-based sensing and paves the way for highly integrated, miniaturized atomic sensors with enhanced sensitivity and portability.
Abstract Emerging miniaturized atomic sensors such as optically pumped magnetometers (OPMs) have attracted widespread interest due to their application in high‐spatial‐resolution biomagnetism imaging. While optical probing systems in conventional OPMs require bulk optical devices including linear polarizers and lenses for polarization conversion and wavefront shaping, which are challenging for chip‐scale integration. In this study, an integrated optical probing scheme based on localized‐interference metasurface for chip‐scale OPM is developed. Our monolithic metasurface allows tailorable linear polarization conversion and wavefront manipulation. Two silicon‐based metasurfaces namely meta‐polarizer and meta‐polarizer‐lens are fabricated and characterized, with maximum transmission efficiency and extinction ratio (ER) of 86.29 % and 14.2 dB for the meta‐polarizer as well as focusing efficiency and ER of 72.79 % and 6.4 dB for the meta‐polarizer‐lens, respectively. A miniaturized vapor cell with 4 × 4 × 4 mm 3 dimension containing 87 Rb and N 2 is combined with the meta‐polarizer to construct a compact zero‐field resonance OPM for proof of concept. The sensitivity of this sensor reaches approximately 9 fT/Hz 1/2 with a dynamic range near zero magnetic field of about ±2.3 nT. This study provides a promising solution for chip‐scale optical probing, which holds potential for the development of chip‐integrated OPMs as well as other advanced atomic devices where the integration of optical probing system is expected.
Abstract The chip-scale hybrid optical pumping spin-exchange relaxation-free (SERF) atomic magnetometer with a single-beam arrangement has prominent applications in biomagnetic measurements because of its outstanding features, including ultrahigh sensitivity, an enhanced signal-to-noise ratio, homogeneous spin polarization and a much simpler optical configuration than other devices. In this work, a miniaturized single-beam hybrid optical pumping SERF atomic magnetometer based on a microfabricated atomic vapor cell is demonstrated. Although the optically thin Cs atoms are spin-polarized, the dense Rb atoms determine the experimental results. The enhanced signal strength and narrowed resonance linewidth are experimentally proven, which shows the superiority of the proposed magnetometer scheme. By using a differential detection scheme, we effectively suppress optical noise with an approximate five-fold improvement. Moreover, the cell temperature markedly affects the performance of the magnetometer. We systematically investigate the effects of temperature on the magnetometer parameters. The theoretical basis for these effects is explained in detail. The developed miniaturized magnetometer has an optimal magnetic sensitivity of 20 fT/Hz 1/2 . The presented work provides a foundation for the chip-scale integration of ultrahighly sensitive quantum magnetometers that can be used for forward-looking magnetocardiography (MCG) and magnetoencephalography (MEG) applications.
Optically pumped magnetometers (OPMs) have undergone rapid development in recent years. The optical probing system, which plays a crucial role in interrogating quantum state of atoms under external perturbations, is an essential component in OPMs. However, conventional optical probing schemes rely on bulky optical components and tedious adjustment procedures, which hinder their applications in portable or compact scenarios. In this study, a method has been proposed in order to overcome these limitations by a metasurface, which is based on localized - interference effects. With the metasurface, we can simultaneously convert any incident polarized light into linearly polarized light and manipulate its wavefront. It achieves a maximum transmission efficiency of 91.7 % and a focusing efficiency of 91.3 %. Since the fabrication process of our metasurface is compatible with current complementary-metal-oxide-semiconductor (CMOS) fabrication technology, it can be integrated with a vapor cell, which is the core sensing element for many advanced atomic devices. Our study proposes an optical probing scheme suitable for chip-scale OPMs, and laying the foundation for the mass production of other chip-scale atomic devices.