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We report on the design and the construction of a sounding rocket payload capable of performing atom interferometry with Bose-Einstein condensates of 41 K and 87 Rb. The apparatus is designed to be launched in two consecutive missions with a VSB-30 sounding rocket and is qualified to withstand the expected vibrational loads of 1.8 g root-mean-square in a frequency range between 20–2000 Hz and the expected static loads during ascent and re-entry of 25 g. We present a modular design of the scientific payload comprising a physics package, a laser system, an electronics system and a battery module. A dedicated on-board software provides a largely automated process of predefined experiments. To operate the payload safely in laboratory and flight mode, a thermal control system and ground support equipment has been implemented and will be presented. The payload presented here represents a cornerstone for future applications of matter wave interferometry with ultracold atoms on satellites. [ABSTRACT FROM AUTHOR]

The Atomic, Molecular, and Optical Sciences Gateway (AMOSGateway) enables novice and experienced users to utilize state-of-the-art software suites for tackling problems central to atomic, molecular, and optical science. This international collaboration provides a free platform and coordinated approach for computational research, allowing the community to produce new scientific results on an unprecedented scale. Currently hosting 10 software packages, the advanced cyberinfrastructure of AMOSGateway impacts many areas, including quantum information, cold atoms/molecules, plasma physics, and astrophysics. Future updates will further simplify these complex tools through graphical user interfaces, fundamentally transforming how practitioners gain expertise in cutting-edge computational research. [ABSTRACT FROM AUTHOR]

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Deep UV radiation is commonly used as a disinfectant with an appropriate dose for better efficacy. However, continuous monitoring of UV radiation is required to have appropriate dose exposure for proper disinfection. This article reports a low-cost solution-processed fabrication method of the UV photodetector (PD) with a device geometry of Al/MoS2 quantum dots (QDs)/Al on Si/SiO2 substrate, which is sensitive to deep UV radiations ~275 nm, commonly used for water and surfaces disinfection technologies. Colloidal MoS2 QDs with an average size of 1.99 nm have been synthesized by an inexpensive hydrothermal method. The surface ligand of MoS2 QDs has been replaced by a shorter ligand 1, 2-ethanedithiol (EDT) to reduce dot-to-dot distance. The fabricated device shows high responsivity (21.62 mA/W), external quantum efficiency (EQE) (9.74%), and detectivity ($3.57\times 10$ 10 Jones) under the deep UV irradiation of ~275 nm. The PD has a good photoresponse speed of rise and decay times of 173 and 92 ms, respectively. [ABSTRACT FROM AUTHOR]

Progress made in optical references, including ultrastable Fabry–Perot cavities, optical frequency combs, and optical atomic clocks, has driven the need for ultrastable optical fiber networks. Telecom-wavelength ultrapure optical signal transport has been demonstrated on distances ranging from the laboratory scale to the continental scale. In this article, we present a Doppler-cancellation setup based on a digital phase-locked loop (PLL) for ultrastable optical signal dissemination over fiber. The optical phase stabilization setup is based on a usual heterodyne Michelson-interferometer setup, while the software-defined radio (SDR) implementation of the PLL is based on a compact commercial board embedding a field-programmable gate array and analog-to-digital and digital-to-analog converters. Using three different configurations, including an undersampling method, we demonstrate a 20-m-long fiber link with residual fractional frequency instability as low as 10−18 at 1000 s and optical phase noise of −70 dBc/Hz at 1 Hz with a telecom frequency carrier. [ABSTRACT FROM AUTHOR]

A reflected atomic magnetometer with single beam is described in this study. A single beam propagates forward for polarizing the atoms and backward for detecting Larmor precession after reflection. The feasibility of the system was studied theoretically and experimentally and compared with the single beam with ellipticity. In reflected scheme, high pump efficiency ensures a reduced power and more flexible operating wavelength considering the AC Stark shift, pump efficiency, and probe signal. The nonuniform optical rotation distribution along the cell was also analyzed. The wavelength of the system was optimized to 795.3 nm. The magnetic field sensitivity of the system is achieved to be 600 fT/Hz1/2 and the experimental bandwidth was 17 Hz. The compact design enables new possibility of the atomic magnetometer for magnetoencephalography systems. [ABSTRACT FROM AUTHOR]

In recent years, significant developments have occurred in the field of optically pumped magnetometers (OPMs), which are widely used in biomagnetic measurements. In this study, we propose a temperature optimization model for a single-beam miniaturized atomic magnetometer. Based on this model, we find that there is an optimal operating temperature for each individual vapor cell, under which the OPM achieves optimal performance. We construct a single-beam zero-field modulation OPM to prove this model. The sensitivity of the magnetometer reaches 18 fT/Hz1/2 (close to the theoretical sensitivity) when we adjust the temperature of the vapor cell through our model, and a detection bandwidth of more than 160 Hz is achieved. It is also discovered that the system bandwidth is reduced when the temperature is increased, whereas the sensitivity of the system does not show notable variation during this process. Our model enables a quick definition of the best working temperature for each individual magnetometer, ensuring the best performance at the lowest operating temperature. This model is especially advantageous for miniaturized OPMs and can also be further applied to arrayed integration for biomagnetic measurement in the future work. [ABSTRACT FROM AUTHOR]

An in situ method has been proposed for measuring all nonorthogonal angles of the beams and triaxial coils in a three-axis vector optically pumped magnetometer (OPM). Based on the combination and alignment of two pump beams, each of which can achieve biaxial transverse measurement in a time-sharing regime under modulated magnetic fields, a 3-D orthogonal coordinate measurement system is obtained, and the measurement models for three categories (six types) of nonorthogonal angles are established theoretically. On this basis, we experimentally measured the nonorthogonal angles along with related uncertainties at different modulated frequencies and strengths of the magnetic fields. The nonorthogonal angles were (3.65° ± 0.52°) between the two pump beams before compensation. They were (7.05° ± 0.23°) between the $X$ - and $Y$ -axis coils, (8.89° ± 0.21°) between the $Y$ - and $Z$ -axis coils, (5.23° ± 0.27°) between the $X$ - and $Z$ -axis coils, (7.24° ± 0.24°) between the $x$ -direction pump beam and $X$ -axis coil, and (9.10° ± 0.22°) between the $z$ -direction pump beam and the $Z$ -axis coil. This study measures the magnitudes of six types of nonorthogonality, without making an assumption of ideal orthogonality or using auxiliary calibration equipment. Moreover, this method can be extended to several other kinds of OPMs with simple modifications. This study is critical for evaluating and reducing the misalignment error to improve the accuracy of three-axis vector OPMs. [ABSTRACT FROM AUTHOR]

Traditional practice of suppressing low-frequency noise in atomic magnetometers is mainly through the application of magnetic field modulation, while magnetic fields of this kind introduce extra transverse relaxation, which results in a decrease of sensitivity. In this study, a novel method of measuring relaxation rate induced by spin-destruction, wall collisions and modulation magnetic fields is proposed. The optical pumping model is studied both in optical-thin and optical-thick vapor cell through the analysis of total relaxation, thus the optical pumping rate can be separated from total relaxation by analyzing the optical depth. Furthermore, based on the analysis of optical pumping rate and relaxation rate, the polarization of the electron ensemble was evaluated. A compact magnetometer with single-beam configuration is developed for the proof of concept, and the experimental results show good agreements with theoretical calculation. Our method provides a simple and feasible approach to in-situ measurement of transverse relaxation rate and optical pumping rate with physical structure of the device untouched, which is especially advantageous for designing and optimizing compact atomic magnetometers. [ABSTRACT FROM AUTHOR]

We present a portable Rydberg-atom-based radio frequency (RF) electric ($E$) field measurement instrument (Rydberg field measurement system or RFMS). The RFMS comprises an atomic RF field probe (RFP) connected by a ruggedized fiber-optic patch cord to a portable mainframe control unit. The unit includes a software interface providing self-calibrated SI-traceable RF measurement and analysis, including real-time field and measurement uncertainty readout and spectral RF waveform visualization. We characterize the RFP and measure polar field and polarization patterns along primary axes of the RFP at 12.6 GHz, obtained by rotations of the RFP in the far-field of a standard gain horn antenna. Field pattern measurements at 2.5 GHz are also presented. The measured field patterns are in good agreement with finite-element simulations of the RFP, establishing that the atom-based RF $E$ -field probe is well-suited for SI-traceable RF measurements over multiple bands. A one-time calibration procedure and an uncertainty analysis are introduced and implemented, as required for practical atomic probe designs to realize absolute-standard SI-traceable measurement capability. This includes uncertainty contributions from the atomic-spectroscopy measurement method and analysis and from the material, geometry, and hardware design. Simultaneous RF field and polarization measurements are demonstrated. RF waveform measurement is demonstrated using example pulsed and modulated RF signals. [ABSTRACT FROM AUTHOR]

Atomic frequency standards are used to generate accurate and precise time and frequency, enabling many communications, synchronization, and navigation systems in modern life. GPS and other satellite navigation systems, voice and data telecommunications, and timestamping of financial transactions all rely on precise time and frequency enabled by atomic frequency standards. This review provides a snapshot and an outlook of commercial and emerging atomic frequency standards. We provide a concise summary of the performance and physics of operation of current atomic frequency standards. In addition, we discuss examples of emerging frequency standard technologies and prototype demonstrations with a focus on technologies expected to provide commercial or military utility within the next decade. We include a comparison of performance versus size and power for current atomic frequency standards. We develop and discuss an empirical relationship between frequency standard performance and product size. [ABSTRACT FROM AUTHOR]

Radio reception relies on antennas for the collection of electromagnetic fields carrying information, and receiver elements for demodulation and retrieval of the transmitted information. Here, we demonstrate an atom-based receiver for AM and FM microwave communication with a 3 dB bandwidth in the baseband of ~100 kHz that provides optical circuit-free field pickup, multiband carrier capability, and inherently high field sensitivity. The atom-based receiver exploits field-sensitive cesium Rydberg vapors in a centimeter-sized glass cell, and electromagnetically induced transparency, a quantum-optical effect, as a readout of baseband signals modulated onto carriers with frequencies ranging over four octaves, from C-band to Q-band. Receiver bandwidth, dynamic range and sideband suppression are characterized, and acquisition of audio waveforms of human vocals demonstrated. The atomic receiver is a valuable receiver technology because it does not require antenna structures and is resilient against electromagnetic interference, while affording multiband operation in a single compact receiving element. [ABSTRACT FROM AUTHOR]

Microgravity eases several constraints limiting experiments with ultracold and condensed atoms on ground. It enables extended times of flight without suspension and eliminates the gravitational sag for trapped atoms. These advantages motivated numerous initiatives to adapt and operate experimental setups on microgravity platforms. We describe the design of the payload, motivations for design choices, and capabilities of the Bose-Einstein Condensate and Cold Atom Laboratory (BECCAL), a NASA-DLR collaboration. BECCAL builds on the heritage of previous devices operated in microgravity, features rubidium and potassium, multiple options for magnetic and optical trapping, different methods for coherent manipulation, and will offer new perspectives for experiments on quantum optics, atom optics, and atom interferometry in the unique microgravity environment on board the International Space Station. [ABSTRACT FROM AUTHOR]

Micro-expressions are the rapid movements of facial muscles that can be used to reveal concealed emotions. Recognizing them from video clips has a wide range of applications and receives increasing attention recently. Among existing methods, the main directional mean optical-flow (MDMO) feature achieves state-of-the-art performance for recognizing spontaneous micro-expressions. For a video clip, the MDMO feature is computed by averaging a set of atomic features frame-by-frame. Despite its simplicity, the average operation in MDMO can easily lose the underlying manifold structure inherent in the feature space. In this paper we propose a sparse MDMO feature that learns an effective dictionary from a micro-expression video dataset. In particular, a new distance metric is proposed based on the sparsity of sample points in the MDMO feature space, which can efficiently reveal the underlying manifold structure. The proposed sparse MDMO feature is obtained by incorporating this new metric into the classic graph regularized sparse coding (GraphSC) scheme. We evaluate sparse MDMO and four representative features (LBP-TOP, STCLQP, MDMO and FDM) on three spontaneous micro-expression datasets (SMIC, CASME and CASME II). The results show that sparse MDMO outperforms these representative features. [ABSTRACT FROM AUTHOR]

The strong confined electromagnetic field in the micro/nano photonic structures brings new opportunities for the research of interaction between light and matter. By designing optical modes, light can be controlled to realize reversible or inreversible energy exchange between photons and emitters at the micro/nano scale. Here, we review the basic principles of the interaction between light and matter in cavity quantum electrodynamics and their recent advances in strong coupling based on micro/nano photonic structures such as plasmon nanostructures, whispering gallery resonators and photonic crystals. These works opening the research of quantum nanophotonics will have great influence on the on-chip quantum devices and quantum informations. [ABSTRACT FROM AUTHOR]

The distribution and dissipation of neutral atoms are crucial for understanding the dielectric recovery process after interrupting direct current (DC) vacuum arcs. This article aims to investigate the dissipation of copper atoms after a forced extinction of the vacuum arc experimentally, adopting the plane laser-induced fluorescence method. The change in the 2-D distribution of copper atoms with time is presented. The results show that the magnetic fields, the axial magnetic field (AMF), and the transverse magnetic field (TMF) have a limited effect on the initial density of copper atoms. For both the AMF and the TMF, the copper atom densities at current zero (CZ) vary in the range (6– $8) \times 10^{17}\,\,\text{m}^{-3}$ when 3-kA vacuum arcs are forced to 0 in 0.2 ms. Contrary to the TMF case, in the AMF case, the evaporation on the anode after the CZ results in long-existing atoms near it. Consequently, the atom density of the TMF decays faster than that of the AMF, which indicates that a vacuum interrupter with the TMF contacts has a better performance when interrupting a DC load. The difference between the two magnetic fields originates from the arc control patterns. Namely, the AMF tends to keep vacuum arcs in a stable mode, which is unfavorable for a DC interruption; on the contrary, the TMF drives the vacuum arcs to move at high velocities resulting in faster dissipation of copper atoms after the CZ. In addition, the composition proportion of CuCr contacts has a limited effect on the diffusion of copper atoms when a low-vacuum arc is interrupted. [ABSTRACT FROM AUTHOR]

In the past decade, colloidal quantum wells, also known as 2-D semiconductor nanoplatelets (NPLs), have been added to the colloidal nanocrystal (NC) family. Through the unique control of the thickness with monolayer precision, these novel materials exhibit strong 1-D quantum confinement that offers unique optical properties along with the possibility of fabricating advanced heterostructures, which are not possible with other quantum-confined nanostructures. The 2-D CdX (X = Se, S)-based NPLs provide high color purities, fast fluorescence lifetimes, and large exciton binding energies. This review covers the latest developments in the successful utilization of these flat NCs in different nanophotonic device applications. The synthesis of the advanced heterostructures of flat 2-D NCs (e.g., core–shell, core–crown, and core–crown–shell) has matured very rapidly, and new exciting optical and electronic applications are emerging. Doping of these atomically thin NCs also offers new possibilities for their utilization in different solar light harvesting, magnetic, electronic, and lasing applications. This review also includes the recent advancements in the understanding of their unique optical properties that are of utmost importance for their practical implementation in light-emitting devices and lasers. Finally, we present a future perspective on their successful utilization in different nanophotonic applications. [ABSTRACT FROM AUTHOR]

Precision measurements represent a cornerstone in fundamental science. The capability of observing and quantifying subtle phenomena and events allows new discoveries and it confirms or confutes the theories describing our understanding of nature. The optical frequency comb, providing hundreds of thousands of phase-locked and evenly spaced laser lines, is one of the most fascinating enabling optical technologies and it is the result of a continuous pursuit for precision. Within the two decades from its inception, it has become a key instrument in many laboratories and has revolutionized numerous fields, spanning from time, frequency and length metrology to attosecond physics, gas-sensing and molecular fingerprinting. In this letter we summarize some steps of an exciting journey started 20 years ago, with a certain focus on the authors’ contribution, finally leading to the demonstration of frequency measurements at the 20th decimal digit, and we show some prospective developments. [ABSTRACT FROM AUTHOR]

Measuring the field strength of an electromagnetic wave based on atomic quantum mechanics is expected to be an innovative method to realize stable and reliable measurements. However, the major issue of atomic measurements is that the measurable frequency is limited to the resonant frequency of atoms. Therefore, in this paper, we demonstrate the measurement at arbitrary frequencies using the Zeeman effect in a static magnetic field. A cesium vapor cell is placed in a static magnetic field of approximately 40 mT, which causes the resonant frequency of the cesium atom to shift from 9.2 to 8.2 GHz. In addition, the Rabi frequency due to the interaction between cesium atoms and microwaves is measured at the frequency of 8.2 GHz in this experiment. [ABSTRACT FROM AUTHOR]

Following the major revision of four SI units in 2018, the redefinition of the second on the basis of optical clocks is becoming foreseeable. In this paper, how optical frequency standards have made progress to surpass microwave frequency standards and the level they are presently at are shown. Future redefinition also requires advances: 1) in remote frequency comparison to confirm the frequency reproducibility of standards and 2) in the capability of maintaining International Atomic Time compatible with an optical definition. Such issues to be resolved prior to the redefinition are also discussed. [ABSTRACT FROM AUTHOR]

The paper describes a Raman-laser system with high performance for an absolute gravimeter that was based on 87Rb atom interferometer. As our gravimeter is a part of the standard acceleration of gravity of China, the Raman lasers’ characteristics should be considered. This laser system includes two diode lasers. The master laser is frequency locked through the frequency-modulation (FM) spectroscopy technology. Its maximum frequency drift is better than 50 kHz in 11 h, which is measured by home-made optical frequency comb. The slave laser is phase locked to the master laser with a frequency difference of 6.8346 GHz while using an optical phase lock loop (OPLL). The phase noise is lower than −105 dBc/Hz at the Fourier frequency from 200 Hz to 42 kHz. It is limited by the measurement sensitivity of the signal source analyzer in low Fourier frequency. Furthermore, the power fluctuation of Raman lasers’ pulses is also suppressed by a fast power servo system. While using this servo system, Raman lasers’ pulses could be fast re-locked while its fast turning on again in the pulse sequence. The peak value fluctuation of the laser power pulses is decreased from 25% to 0.7%, which is improved over 35 times. This Raman-laser system can stably operate over 500 h, which is suited for long-term highly precise and accurate gravity measurements.

In this paper, a single-fiber Sagnac-like interferometer is proposed and experimentally demonstrated for detecting atomic spin precession in an atomic magnetometer. The single-fiber Sagnac-like interferometer has a reciprocal optical structure, which is insensitive to environmental disturbances. The fiber system is more flexible for implementation in miniature atomic magnetometers, which has potential for application in magnetoencephalography systems. The sensitivity and the bandwidth of the system are also discussed. The thermal and bending disturbances to fiber system are observed, whereas the long-term stability is analyzed and compared with the Faraday modulation scheme. [ABSTRACT FROM AUTHOR]

Here, we discuss a novel, mixed mode 3D XYZ scanner built within a single foundry process. The device has a large range of motion in X, Y, and Z ($14.1~\mu \text{m}$ in X and Y and $97.9~\mu \text{m}$ in Z) and can also rotate about two axes (7.4°), making it a 5 degree of freedom scanner. Vertical actuation can be accomplished with both thermal actuators, which have a larger range of motion, and capacitive actuators, which are faster, responding fully up to 3.2 kHz. Although useful for many applications, including scanning probe microscopy, micrometer scale optical microscopy, and manipulation of biological objects, the device was designed to be a 3D scanner for spray-painting atoms upon a surface with nanoscale precision and resolution for nanofabrication. Demonstrating the ability to combine the device with other complicated MEMS systems, it is integrated with an XY scanner designed to serve as a shutter of atomic flux. The full system has 7 degrees of freedom and 12 actuation motors, and because it is built in a low cost commercial foundry with a robust and stable process, it is easy and inexpensive to fabricate multiple copies or integrate into other complicated systems, making a system of systems. [2018-0213] [ABSTRACT FROM AUTHOR]

The light shift is an important error source for atomic magnetometers. It would vanish if the frequency of the circularly polarized light is tuned to the optical resonance center. For high-density alkali-metal atomic magnetometers, the vapor cell has a large optical depth near the resonance, resulting in the difficulty in obtaining the exact resonance center by measuring the optical absorption line. In order to solve this problem, we propose a method to tune the pump light to a frequency where the shift is minimum based on the magnetic field zeroing technique. In addition, we also compare our results with the fitting center of the optical absorption line based on the measurement data far detuned from the resonance. The experimental results show that our method achieves a better suppression result of the light shift. [ABSTRACT FROM AUTHOR]

Monolayer 2-D transition metal dichalcogenide (TMDC) field-effect transistors (FETs) have excellent scaling properties due to an extremely thin body and reduced quantum-mechanical tunneling. High-field and ballistic carrier transport can play an important role in aggressively scaled TMDC FETs. A compact model is developed to describe carrier transport in 2-D monolayer FETs based on a TMDC material. The model has the following features: 1) it treats high-field transport and velocity saturation; 2) it can be applied from ballistic to quasi-ballistic to diffusive transport regimes; and 3) it incorporates analytical expressions for carrier mobility values based on examining physical carrier scattering mechanisms in TMDC materials. Monte Carlo simulation, which solves the Boltzmann transport equation stochastically, is used to validate the model. The carrier transport model is further integrated with a virtual-source model to calculate the ${I}$ – ${V}$ characteristics of 2-D monolayer FETs. Based on the model, the effects of phonon scattering and ionized impurity scattering on the average carrier injection velocity and transistor ballisticity are discussed. [ABSTRACT FROM AUTHOR]

Narrow-band filtering of light is widely used in optical spectroscopy. Atomic filters, which rely on the Faraday effect, allow for GHz-wide transmission spectra, which are intrinsically matched to an atomic transition. We present an experimental realization and a theoretical study of a Faraday filter based on cesium and its D1-line-transition ($6^{2}S_{1/2}\rightarrow 6^{2}P_{1/2}$) around 894 nm. We also present the prospects and visions for combining this filter with the single photon emission of a single quantum dot, which matches with the atomic transition. The option to lock the spectral position of a quantum dot is discussed at the end of this letter. [ABSTRACT FROM AUTHOR]

The erosion of the accelerator grid affects the life of the ion thruster. One of the most important reasons for accelerator grid erosion is the bombardment of charge exchange (CEX) ions to the accelerator grid. There are two types of erosions caused by CEX ions: barrel erosion and pits and grooves erosion. The erosion mechanism of pits and grooves erosion is the CEX ion back flowed from the downstream of the optics. However, there is no unified conclusion on the erosion mechanism of barrel erosion since the erosion mechanism of barrel erosion developed in most of the current research is only applicable to the specific conditions set up in each research. In this paper, the 3-D IFE-PIC-MCC algorithm is used to simulate the beam ion motion, the CEX collision, and the erosion of CEX ion on the accelerator grid under different operation conditions. The erosion mechanism of barrel erosion under different operation conditions is studied. The results indicate that the main production areas of CEX ions which cause the barrel erosion are different under different operation conditions. [ABSTRACT FROM AUTHOR]

This paper aims to review the technology, developments, and applications of spin exchange relaxation free (SERF) atomic magnetometers. The generalized comparisons between the SERF magnetometer and the other types of weak magnetic sensors are elaborated. Further, the fundamental composition and operational principle of the SERF atomic magnetometer are elucidated. The development history and recent technological developments with respect to several aspects, including the alkali metal vapor source, atom heating method, pump and probe lasers, and magnetic shielding system, are presented. The classification and respective advantages and disadvantages of these technologies are described in detail. Finally, the existing and potential applications, as well as the prospective future development trends are presented. [ABSTRACT FROM AUTHOR]

We report an experiment about the transformation of radical and azimuthal information of high-order Laguerre-Gaussian beam from the probe beam to dressing four-wave mixing beam. During this process, dressing Kerr nonlinear dispersion causes a spatial splitting on output Laguerre-Gaussian beam. We found that the number of split spots can be controlled by frequency detuning and power of the dressing field. The potential application of such modulated spatial splitting phenomenon on optical switching of the multi-channel router in atomic ensembles is discussed. [ABSTRACT FROM AUTHOR]

Active optical clocks (AOCs) have the intrinsic suppression of the influence of the cavity’s noise on the output frequency, giving rise to the potentially ultranarrow linewidth. To break the cavity’s thermal noise limitation by taking full advantage of the AOC’s principle, as well as to achieve a long-term instability, we propose a scheme of cavity-stabilized active optical clock. The system consists of two key procedures. The dual-wavelength (DW) output signals share the same cavity and work in the good- and the bad-cavity regime, respectively. Then, the good-cavity signal is locked to a reference cavity by the Pound–Drever–Hall (PDH) technique to stabilize the main-cavity length. By doing this, the main-cavity’s noise is expected to be reduced to the thermal noise floor of the reference cavity. Hence, the frequency stability of the bad-cavity signal will break this noise floor due to the suppression of the cavity-pulling effect. Experimentally, we realize the DW good–bad-cavity laser system by taking the Nd:YAG 1064 nm and Cs 1470 nm transitions as the good- and bad-cavity gain medium. The power and linewidth characteristics of the DW output are studied. Limitation factors of the clock frequency as well as the feasibility of the PDH cavity stabilization are analyzed. [ABSTRACT FROM AUTHOR]

An induced-dichroism-excited atomic line (IDEAL) filter at 1529 nm operating on the transition of 87Rb 52P3/2-42D3/2 is realized. Its peak transmittance achieves 63.8% at 80 °C by a 13.4 mW/mm2 laser pumping at 780 nm and the equivalent noise bandwidth is 546 MHz. Detailed experiments show that, compared with the excited-state Faraday anomalous dispersion optical filter and excited-state Voigt atomic line filters which are realized by the same atomic vapor cell, operating on the same transition and under the same pumping intensity, the IDEAL filter achieves the same performance level without the magnetic field. This letter provides a new solution to ultra-narrow optical filtering at 1529 nm, and it is particularly useful in applications which require non-magnetic environments. [ABSTRACT FROM AUTHOR]

This paper reports a dedicated theoretical and experimental study on the properties (signal amplitude and linewidth) of coherent population trapping resonances detected in vacuum vapor cells. Results are presented for conventional single-lambda schemes of atomic energy levels but also for double-lambda schemes, now widely used in various applications including atomic clocks and magnetometers. Approximate compact analytical expressions, valid for a wide range of light-wave intensities, i.e., beyond the low intensities or pump-probe regime, have been obtained. Analytical results are found to be in excellent agreement with exact numerical solutions based on the optical Bloch equations. Experimental results, obtained in a Cs vapor microfabricated cell, are reported and found to be in correct agreement with theoretical expressions. [ABSTRACT FROM AUTHOR]

We report on the characterization of two fiber-coupled 1.5- $\mu \text{m}$ diode lasers, frequency-doubled and stabilized to Rubidium (Rb) atomic resonances at 780 nm. Such laser systems are of interest in view of their implementation in Rb vapor-cell atomic clocks, as an alternative to lasers emitting directly at 780 nm. The spectral properties and the instabilities of the frequency-doubled lasers are evaluated against a state-of-the-art compact Rb-stabilized laser system based on a distributed-feedback laser diode emitting at 780 nm. All three lasers are frequency stabilized using essentially identical Doppler-free spectroscopy schemes. The long-term optical power fluctuations at 780 nm are measured, simultaneously with the frequency instability measurements done by three beat notes established between the three lasers. One of the frequency-doubled laser systems shows at 780 nm excellent spectral properties. Its relative intensity noise <10−12 Hz−1 is one order of magnitude lower than the reference 780-nm laser, and the frequency noise <106 Hz2/Hz is limited by the laser current source. Its optical frequency instability is $< 4 \times 10^{-12}$ at $\tau = 1$ s, limited by the reference laser, and better than $1 \times 10^{-11}$ at all timescales up to one day. We also evaluate the impact of the laser spectral properties and instabilities on the Rb atomic clock performance, in particular taking into account the light-shift effect. Optical power instabilities on long-term timescales, largely originating from the frequency-doubling stage, are identified as a limitation in view of high-performance Rb atomic clocks. [ABSTRACT FROM AUTHOR]

Spin-exchange-relaxation-free (SERF) optical atomic magnetometers are facing the challenges of dramatic decrease of sensitivity when the alkali vapor cells become small. This paper focuses on the sensitivity improvement of the chip-scale atomic magnetometer (CSAM) by changing buffer-gas pressures inside the microfabricated vapor cells. The rubidium vapor cells with three different buffer-gas pressures were tested in the SERF magnetometer. The influences of vapor cell temperature and pumping laser power on the device sensitivity are also characterized for further optimization. Results show that the three atomic vapor cells, with N2 buffer-gas pressure of 0.20, 0.88, and 2.35 amg, have sensitivities of 900, 500, and 150 fT/Hz1/2, respectively. Results indicated that when the alkali vapor cells continue to be smaller, high buffer-gas pressure would provide an effective way to reduce the wall collision and improve the performance of CSAMs. [ABSTRACT FROM AUTHOR]

In this letter, we report the first experimental realization of purely two-dimensional-material-based hot electron transistor (2D-HET) by the van der Waals stacking. We used ultra-thin graphene as the base, and WSe2 or h -BN as the emitter-base or base-collector barriers. We quantitatively determined that the transport mechanism through the 2D barrier changes from the Fowler?Nordheim tunneling to the thermionic emission with the increase of temperature. In our 2D-HET, the dangling-bond-free 2D materials provide atomically sharp interfaces to suppress the hot electron scattering, which along with the optimization of the barriers, gives a relatively large collection efficiency of 99.95% and a relatively high current density of 233 A/cm2 in the family of graphene-base HETs. [ABSTRACT FROM AUTHOR]

Phase collapse and revival for Bose–Einstein condensates are nonlinear phenomena appearing due to atomic collisions. While it has been observed in a general setting involving many modes, for one-mode condensates its occurrence is forbidden by the particle number superselection rule (SSR), which arises because there is no phase reference available. We consider a single mode atomic Bose–Einstein condensate interacting with an off-resonant optical probe field. We show that the condensate phase revival time is dependent on the atom–light interaction, allowing optical control on the atomic collapse and revival dynamics. Incoherent effects over the condensate phase are included by considering a continuous photo-detection over the probe field. We consider conditioned and unconditioned photo-counting events and verify that no extra control upon the condensate is achieved by the probe photo-detection, while further inference of the atomic system statistics is allowed leading to a useful test of the SSR on particle number and its imposition on the kind of physical condensate state. [ABSTRACT FROM AUTHOR]

We describe a fiber-optic solution for simultaneous distribution of all signals generated at today’s most advanced time and frequency laboratories, i.e., an ultrastable optical reference frequency derived from an optical atomic clock, a radio frequency precisely linked to a realization of the SI-Second, and a realization of an atomic timescale, being the local representation of the virtual, global UTC timescale. In our solution both the phase of the optical carrier and the delay of electrical signals (10-MHz frequency reference and one-pulse-per-second time tags) are stabilized against environmental perturbations influencing the fiber link instability and accuracy. We experimentally demonstrate optical transfer stabilities of 5 \times 10^-19 and 2 \times 10^-15 for 100 s averaging period, for optical carrier and 10-MHz signals, respectively. [ABSTRACT FROM PUBLISHER]

In atomic force microscopy (AFM), the exchange and alignment of the AFM cantilever with respect to the optical beam and position-sensitive detector (PSD) are often performed manually. This process is tedious and time consuming, and sometimes damages the cantilever or tip. To increase the throughput of AFM in industrial applications, the ability to automatically exchange and align the cantilever in a very short time with sufficient accuracy is required. In this paper, we present the development of an automated cantilever exchange and optical alignment instrument. We present an experimental proof of principle by exchanging various types of AFM cantilevers in 6 s with an accuracy better than 2 μm. The exchange and alignment unit is miniaturized to allow for integration in a parallel AFM. The reliability of the demonstrator has also been evaluated. Ten thousand continuous exchange and alignment cycles were performed without failure. The automated exchange and alignment of the AFM cantilever overcome a large hurdle toward bringing AFM into high-volume manufacturing and industrial applications. [ABSTRACT FROM PUBLISHER]

Defects in CdSe nanoparticles (NPs) have been studied within the framework of density functional theory (DFT) and time dependent DFT. Both vacancies and substitutional defects were examined and their energy levels as well as their excitations were calculated. The energy gap of the NPs is significantly affected and reduced upon the introduction of Se vacancies, substitution of Cd with either Al, Ga, In, and substitution of Se with either Cl, or Br, or I. This leads to excitations with significantly lower energies compared to chemically and phase pure NPs in a wide range of the visible spectrum. Such derived CdSe NPs may be used in solar cells and biosensing applications. [ABSTRACT FROM PUBLISHER]

A new electromagnetic sensor using the atomic Rabi frequency is presented. Gaseous cesium-133 atoms enclosed in a compact glass cell work as an electromagnetic sensor by detecting the Rabi frequency. In this paper, we measured the electromagnetic field radiated from a standard gain horn antenna using the new sensor. This result was compared with a numerical simulation based on the method of moments. Both results were in good agreement. Moreover, a hypothesized reduction in electromagnetic perturbation caused by the glass cell was investigated using a numerical simulation. [ABSTRACT FROM AUTHOR]