Atomic Spin Gyroscope Research Articles

Quadrupolar interaction induced frequency shift of nuclear spins on the surface of silicon

The combination of micro-machined technology with atomic spin gyroscope (ASG) devices can be used to fabricate a chip-scale atomic spin gyroscope (CASG). The core of the gyroscope is a micromachined vapour cell, which contains alkali metal and isotope-enriched noble gases, such as and . The quadrupolar frequency shift of is a key parameter that can affect the drift of the ASG and is related to the material of the cell in which they are contained. In micromachining technology, the utilised material is silicon. In this study, we investigated the electric quadrupolar frequency shift of atoms with the silicon wall of a micro-machined vapour cell. A cylindrical micromachined vapour cell was utilised in the experiment, and a large part of the inner cell surface comprised silicon material. We studied the temperature dependence of the spin relaxation and frequency shifts to evaluate the interaction of the nuclear spin with the container wall and alkali metal atoms. The results show that the average twisted angle of the nuclear spins as they collided with the silicon wall was measured as rad. The desorption energy required for the nuclear spin to escape from the silicon surface was . This study could help improve the bias stability of the CASG, which is a key parameter for the gyroscope, and may help to develop a method to study the surface properties of various materials.

Bandwidth Expansion of Atomic Spin Gyroscope With Transient Response

Atomic spin gyroscopes have ultra-high sensitivity on inertial measurement, but the narrow bandwidth limits its application. We describe a bandwidth expansion method for atomic spin gyroscope based on the transient response of electron spin. The gyroscope is modeled as a four inputs two outputs linear state-space system by commonly used linearization. As the transverse component of electron spin polarization decays much faster than that of nuclear spin, a quasi-steady-state approximation on electron spin is proposed to estimate the transverse polarization component of nuclear spin in real-time. In experiment, the system matrix, input matrix, and output matrix of the state-space model are decided with a series of calibrations. A bandwidth expansion method is proposed to solve the rotation input with the transient response of the electron spin. The proposed method shows strong rotation tracking ability compared with the steady-state method. The bandwidth of atomic spin gyroscope is extended and 3 dB/Oct lower signal attenuation in the frequency range of 0.4~5 Hz is obtained with the proposed method.

Investigation on magnetic field response of a 87Rb-129Xe atomic spin comagnetometer.

The magnetic field response of a 87Rb-129Xe atomic spin comagnetometer operated in the spin-exchange relaxation-free (SERF) regime was investigated. The response model of the comagnetometer to the transverse magnetic fields along the y-axis and the x-axis considering the couple of electron spin and nuclear spin is presented. In the experiment, a high hybrid resonance peak near low-frequency was observed. By fitting the hybrid resonance with the presented response model, a pair of poles at 0.62 Hz and 1.8 Hz were obtained which correspond to the nuclear spin resonance and the electron spin resonance, respectively. The magnetic field response characteristic of the 87Rb-129Xe comagnetometer with different nuclear magnetic fields and electronic magnetic fields was simulated and analyzed. The simulation results indicate that the hybrid resonance frequency can be right-shifted by the larger nuclear magnetic field while the magnetic field suppression factor can be decreased by the larger electron magnetic field. This study is helpful to improve the performance of the atomic spin gyroscope based on the 87Rb-129Xe comagnetometer.

Measuring scale factor of atomic spin gyroscope and closed-loop operation

The response of an atomic spin gyroscope to the AC magnetic field shows a dispersion-like signal as the field frequency. When a system rotates, the curve shifts with a unit scale factor. We used natural Xe and enriched 87Rb gas to construct an atomic spin gyroscope, and we experimentally measured its scale factor by calculating the amount of curve-shift when the system rotates. The scale factor in the range of ±360°/Hz was measured to be 0.99 ± 0.008 for Xe-129 and −0.993 ± 0.003 for Xe-131. We also operated the system with close-loop control of AC frequencies to compensate the frequency shift by a rotation sensor. Herein, we introduce our system and its signal processing for an atomic spin gyroscope.

Optimal design of a high homogeneous and small-size shim coil for atomic spin gyroscope based on 0-1 linear programming

It is necessary to develop a high homogeneous, low power consumption, high frequency and small-size shim coil for high precision and low-cost atomic spin gyroscope (ASG). To provide the shim coil, a multi-objective optimization design method is proposed. All structural parameters including the wire diameter are optimized. In addition to the homogeneity, the size of optimized coil, especially the axial position and winding number, is restricted to develop the small-size shim coil with low power consumption. The 0-1 linear programming is adopted in the optimal model to conveniently describe winding distributions. The branch and bound algorithm is used to solve this model. Theoretical optimization results show that the homogeneity of the optimized shim coil is several orders of magnitudes better than the same-size solenoid. A simulation experiment is also conducted. Experimental results show that optimization results are verified, and power consumption of the optimized coil is about half of the solenoid when providing the same uniform magnetic field. This indicates that the proposed optimal method is feasible to develop shim coil for ASG.

Theoretical simulation of a signal for a scheme of an atomic spin gyroscope with optical detection

An operation scheme of an atomic spin gyroscope with optical detection is described, in which two noble gas isotopes, 129 Xe and 131 Xe, are used as carriers of the spin of an atomic nucleus. Based on this scheme, we construct a theoretical model of the dynamics of the spin polarisation of an alkali metal and the magnetisation of a noble gas under conditions of spin-exchange interaction and optical pumping. This model allows one to simulate the pumping and signal readout in the gyroscope scheme. The time dependences of this signal are plotted, the analysis of which shows that the signal has a sophisticated complex structure. Thus, the problem arises of demodulating this signal based on the improvement of demodulation methods and algorithms.

Investigation on Rotation Response of Spin-Exchange Relaxation-Free Atomic Spin Gyroscope

Spin-exchange relaxation-free atomic spin gyroscope (SERF gyro) has ultrahigh theoretical sensitivity and is regarded as one of the most potential atomic gyroscopes. To investigate its rotation response, a high linear atomic spin precession detection module was developed firstly by modifying the fiber reflective Sagnac interferometer for atomic spin precession detection and operating it in closed-loop mode. The SERF gyro based on K-Rb- 21 Ne comagnetometer was built and tested and appeared obvious nonlinear response feature. The nonlinear rotation response model was deduced by assuming the rotation-induced nuclei spin procession detecting as an in-situ magnetometer inside the SERF gyro and the fitting curves are in good agreement with the experimental results. The optimized pump power for maximum sensitivity and measurable dynamic range were analyzed theoretically and demonstrated experimentally. The investigation results show that the nonlinear rotation response is an intrinsic property of SERF gyro and its measurable dynamic range is limited due to the saturation characteristic of the sum of pumping and relaxation rate. This indicates that SERF gyro is propitious to a position gyroscope with high sensitivity.

A parametrically modulated dual-axis atomic spin gyroscope

We describe a dual-axis atomic spin gyroscope based on an alkali metal-noble gas comagnetometer. Alkali metal vapor is optically pumped, and then the noble gas is hyperpolarized along the z axis. When sensing a transverse rotation, the polarized noble gas will be induced to precess and produce an effective magnetic field in the x – y plane for alkali metals to precess under. Operating in the spin-exchange relaxation-free regime, alkali atoms are modulated by the z axis magnetic field and serve as an integrated in-situ dual-axis magnetometer to detect the gyroscopic precession in the x and y axes simultaneously, using a single probe beam. By using the parametric modulation technique, the low frequency drift is effectively suppressed and a bias instability of less than 0.05 deg/h has been achieved in our dual-axis atomic spin gyroscope.

Common-mode noise reduction in an atomic spin gyroscope using optical differential detection.

Optical rotation of linearly polarized light is used to measure atom spin precession in an atomic spin gyroscope (ASG). However, the common-mode noise in the polarization measurement seriously affects the performance of the sensitive ASG. Here we propose an optical differential detection method based on the photoelastic polarization modulation, which could effectively eliminate the light power fluctuation of the laser source and optical elements, while removing the polarization noise and the residual birefringence. The feasibility and efficiency of this method have been verified experimentally. The rotation sensitivity of the ASG is an order of magnitude better, and the long-time stability is significantly improved. In addition, this method is easier to implement because noise sources do not need to be strictly distinguished.

Inertial rotation measurement with atomic spins: From angular momentum conservation to quantum phase theory

Rotation measurement in an inertial frame is an important technology for modern advanced navigation systems and fundamental physics research. Inertial rotation measurement with atomic spin has demonstrated potential in both high-precision applications and small-volume low-cost devices. After rapid development in the last few decades, atomic spin gyroscopes are considered a promising competitor to current conventional gyroscopes—from rate-grade to strategic-grade applications. Although it has been more than a century since the discovery of the relationship between atomic spin and mechanical rotation by Einstein [Naturwissenschaften, 3(19) (1915)], research on the coupling between spin and rotation is still a focus point. The semi-classical Larmor precession model is usually adopted to describe atomic spin gyroscope measurement principles. More recently, the geometric phase theory has provided a different view of the rotation measurement mechanism via atomic spin. The theory has been used to describe a gyroscope based on the nuclear spin ensembles in diamond. A comprehensive understanding of inertial rotation measurement principles based on atomic spin would be helpful for future applications. This work reviews different atomic spin gyroscopes and their rotation measurement principles with a historical overlook. In addition, the spin-rotation coupling mechanism in the context of the quantum phase theory is presented. The geometric phase is assumed to be the origin of the measurable rotation signal from atomic spins. In conclusion, with a complete understanding of inertial rotation measurements using atomic spin and advances in techniques, wide application of high-performance atomic spin gyroscopes is expected in the near future.

High precision estimation of inertial rotation via the extended Kalman filter

Recent developments in technology have enabled atomic gyroscopes to become the most sensitive inertial sensors. Atomic spin gyroscopes essentially output an estimate of the inertial rotation rate to be measured. In this paper, we present a simple yet efficient estimation method, the extended Kalman filter (EKF), for the atomic spin gyroscope. Numerical results show that the EKF method is much more accurate than the steady-state estimation method, which is used in the most sensitive atomic gyroscopes at present. Specifically, the root-mean-squared errors obtained by the EKF method are at least 103 times smaller than those obtained by the steady-state estimation method under the same response time.

Modeling and optimizing of the random atomic spin gyroscope drift based on the atomic spin gyroscope.

In order to improve the atom spin gyroscope's operational accuracy and compensate the random error caused by the nonlinear and weak-stability characteristic of the random atomic spin gyroscope (ASG) drift, the hybrid random drift error model based on autoregressive (AR) and genetic programming (GP) + genetic algorithm (GA) technique is established. The time series of random ASG drift is taken as the study object. The time series of random ASG drift is acquired by analyzing and preprocessing the measured data of ASG. The linear section model is established based on AR technique. After that, the nonlinear section model is built based on GP technique and GA is used to optimize the coefficients of the mathematic expression acquired by GP in order to obtain a more accurate model. The simulation result indicates that this hybrid model can effectively reflect the characteristics of the ASG's random drift. The square error of the ASG's random drift is reduced by 92.40%. Comparing with the AR technique and the GP + GA technique, the random drift is reduced by 9.34% and 5.06%, respectively. The hybrid modeling method can effectively compensate the ASG's random drift and improve the stability of the system.

Dynamics of an all-optical atomic spin gyroscope

We present the transfer function of an all-optical atomic spin gyroscope through a series of differential equations and validate the transfer function by experimental test. A transfer function is the basis for further control system design. We build the differential equations based on a complete set of Bloch equations describing the all-optical atomic spin gyroscope, and obtain the transfer function through application of the Laplace transformation to these differential equations. Moreover, we experimentally validate the transfer function in an all-optical Cs-Xe129 atomic spin gyroscope through a series of step responses. This transfer function is convenient for analysis of the form of control system required. Furthermore, it is available for the design of the control system specifically to improve the performance of all-optical atomic spin gyroscopes.

A novel Cs-129Xe atomic spin gyroscope with closed-loop Faraday modulation

We report a novel Cs-(129)Xe atomic spin gyroscope (ASG) with closed-loop Faraday modulation method. This ASG requires approximately 30 min to start-up and 110 °C to operate. A closed-loop Faraday modulation method for measurement of the optical rotation was used in this ASG. This method uses an additional Faraday modulator to suppress the laser intensity fluctuation and Faraday modulator thermal induced fluctuation. We theoretically and experimentally validate this method in the Cs-(129)Xe ASG and achieved a bias stability of approximately 3.25 °∕h.

Atomic spin gyroscope based on 129Xe-Cs comagnetometer

Atomic spin gyroscope (ASG) based on comagnetometer is a high sensitive and compact gyroscope for future inertial navigation applications. The start-up time was several hours of the demonstrated ASGs based on 3He-K or 21Ne-Rb-K comagnetometer, and only a few inertial navigation applications allow such a long time for preparation. We report the demonstration of an ASG based on 129Xe-Cs comagnetometer, which decreases the start-up time to 10 minutes and decreases the operation temperature by 40% as well. By operating this ASG in spin exchange relaxation free regime, a sensitivity of 7×10−5 °/(s Hz1/2) was achieved.

Drift Error Analysis of Atomic Spin Gyroscope

With the rapid development of quantum manipulation technique, atomic spin gyroscope has been demonstrated in recent years. Understanding the sources and the influence of error on the performance of atomic spin gyroscope is important during the design of such devices. The basic principle of atomic spin gyroscope was reviewed and the analysis of error sources presented began with the coupled Bloch equations describing the dynamics of atomic spin gyroscope including magnetic field, light shift and pump-probe non-orthogonality. It was shown analytically that the first order effects of the transverse magnetic fields and imperfections can be eliminated by turning the longitudinal magnetic field on the magnetic field compensation point. The effects of longitudinal magnetic field and light shift imperfections with other terms zeroed contributed only to scale factor of the atomic spin gyroscope. Furthermore, the effects magneto-optical crystal and magnetic shielding due to temperature drift were described and according approaches to suppress these errors were also proposed.

Light-shift measurement and suppression in atomic spin gyroscope

We present a method to determine and suppress the light shift in an atomic spin gyroscope. This method doesn't require additional drive source or frequency modulation, and it is based on the dynamics of an atomic spin gyroscope to determine a clean curve as a function of the frequency of the pump beam that predicts the zero light shift. We experimentally validate the method in a Cs-(129)Xe atomic spin gyroscope and verify the results through numerical simulations. This method can also be applied to an atomic spin magnetometer based on the spin-exchange relaxation-free exchange that experiences light shift. The method is useful for atomic spin devices because it can improve long-term performance and reduce the influence of the laser.

Advances in Atomic Gyroscopes: A View from Inertial Navigation Applications

With the rapid development of modern physics, atomic gyroscopes have been demonstrated in recent years. There are two types of atomic gyroscope. The Atomic Interferometer Gyroscope (AIG), which utilizes the atomic interferometer to sense rotation, is an ultra-high precision gyroscope; and the Atomic Spin Gyroscope (ASG), which utilizes atomic spin to sense rotation, features high precision, compact size and the possibility to make a chip-scale one. Recent developments in the atomic gyroscope field have created new ways to obtain high precision gyroscopes which were previously unavailable with mechanical or optical gyroscopes, but there are still lots of problems that need to be overcome to meet the requirements of inertial navigation systems. This paper reviews the basic principles of AIG and ASG, introduces the recent progress in this area, focusing on discussing their technical difficulties for inertial navigation applications, and suggests methods for developing high performance atomic gyroscopes in the near future.