Abstract Optical magnetometers based on alkali vapors, such as rubidium, are among the most sensitive technologies for detecting and characterizing magnetic fields. Following the recent effort in miniaturizing atomic-based quantum technologies, the last years were marked by a growing interest in developing integrated quantum nanophotonic circuits for a vast range of applications. Motivated by the attractiveness of such chip-scale integration, we present and experimentally demonstrate an integrated magnetic sensing platform, based on a nanophotonic-chip interfaced to a microfabricated alkali vapor cell. Magnetically induced circular dichroism in rubidium vapor is measured using a planar structure that spatially resolves the handedness of incoming photons depending on their spin. The presented approach paves the way toward further integration of highly sensitive magnetometers, with potential for future applications, such as in high-spatial resolution magnetic vectorial imaging.
Abstract Optical magnetometers based on alkali vapors, such as rubidium, are among the most sensitive technologies for detecting and characterizing magnetic fields. Following the recent effort in miniaturizing atomic-based quantum technologies, the last years were marked by a growing interest in developing integrated quantum nanophotonic circuits for a vast range of applications. Motivated by the attractiveness of such chip-scale integration, we present and experimentally demonstrate an integrated magnetic sensing platform, based on a nanophotonic-chip interfaced to a microfabricated alkali vapor cell. Magnetically induced circular dichroism in rubidium vapor is measured using a planar structure that spatially resolves the handedness of incoming photons depending on their spin. The presented approach paves the way toward further integration of highly sensitive magnetometers, with potential for future applications, such as in high-spatial resolution magnetic vectorial imaging.
Recently, there has been growing interest in the miniaturization and integration of atomic-based quantum technologies. In addition to the obvious advantages brought by such integration in facilitating mass production, reducing the footprint, and reducing the cost, the flexibility offered by on-chip integration enables the development of new concepts and capabilities. In particular, recent advanced techniques based on computer-assisted optimization algorithms enable the development of newly engineered photonic structures with unconventional functionalities. Taking this concept further, we hereby demonstrate the design, fabrication, and experimental characterization of an integrated nanophotonic-atomic chip magnetometer based on alkali vapor with a micrometer-scale spatial resolution and a magnetic sensitivity of 700 pT/√Hz. The presented platform paves the way for future applications using integrated photonic-atomic chips, including high-spatial-resolution magnetometry, near-field vectorial imaging, magnetically induced switching, and optical isolation.
The designs of microfabricated alkali vapor cells play an important role when the atomic magnetometers are developing toward on-chip integration. This paper presents microfabricated spherical alkali vapor cells with improved sensitivity for chip-scale atomic magnetometers. A microfabricated spherical rubidium vapor cell and a traditional microfabricated planar rubidium vapor cell are designed for comparison, which are of the same volume and interconnected by a microchannel to acquire equal inner buffer gas pressure. In chip-scale spin-exchange relaxation-free (SERF) atomic magnetometers, the rubidium polarization lifetimes of three pairs of spherical and planar vapor cells at different buffer gas pressures of 0.35, 0.73, and 2.00 amg are measured, respectively. The sensitivity of SERF atomic magnetometers using the vapor cells at a 0.35-amg buffer gas pressure is also measured. The results show that the transverse polarization lifetime of the spherical vapor cell is 2.46, 1.44, and 1.05 times that of the planar one at 0.35-, 0.73-, and 2.00-amg buffer gas pressures, respectively. Combining the improved polarization lifetime and increased optical path length, chip-scale SERF atomic magnetometer using the microspherical vapor cell has the sensitivity of 60 fT/Hz1/2from 5 to 15 Hz, while that based on the planar one is demonstrated with the sensitivity of 400 fT/Hz1/2from 5 to 15 Hz.
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.
Quantum sensing is an ever-evolving research field describing the use of a quantum phenomenon to perform measurement of a physical quantity. Amongst different types of quantum sensors, atomic vapor-based quantum effects are extensively used to measure quantities such as time, velocity, acceleration, electric, and magnetic fields. Here, we propose and demonstrate remote quantum sensing using a chip-scale atomic vapor cell. Specifically, we remotely interrogate millimeter-scale micromachined vapor cells, and measure the ambient Earth’s magnetic field at a standoff distance of ∼10 m and a sensitivity of ∼1 pT/√Hz. We further spatially map different magnetic fields in the presence of a noisy ambient environment. Simultaneously we are able measure the distance between a micro-cell and the interrogating system by means of time-of-flight measurements, thus correlating between position and magnetic field. Utilizing micromachined vapor cells for remote magnetometry offers substantial advantages in scalability, planar photonic integration, cost, and size. Consequently, we provide a novel toolset to deploy, measure, and map arbitrary, remote, and hard-to-access magnetic fields in unshielded environments with high sensitivity and spatial resolution, paving the way to a variety of novel applications in diverse fields such as medicine, communication, defense, space-exploration, and quantum technologies.
Abstract Discrete optical system in optically pumped magnetometers (OPMs) presents a significant challenge to their integration into high‐spatial‐resolution magnetic field detection. Here, the electron spin polarization of atoms using a fiber‐coupled silicon nitride () photonic integrated circuit (PIC) is demonstrated, by the way of delivering arrayed elliptically polarized light (EPL) into a vapor cell. Specifically, the photonic integrated circuit (PIC) transforms fiber‐coupled 795 nm pump light via optical waveguides to eight divergent free‐space beams, simultaneously converting linear polarized light (LPL) into EPL with an average polarization conversion efficiency of 71%. The PIC‐enabled OPM has detected the weak magnetic field with an optimal sensitivity of 0.53 pT at 70Hz. This work presents an effective approach for manipulation of alkali atoms using a chip and, crucially, introduces a chip‐based pump solution for OPMs. This approach contributes to the integration of nanophotonics with atomic systems, paving the way for future advancements in quantum sensing.