Search

We theoretically propose a high-resolution biomolecules mass sensor based on a spinning resonator with a coherent phonon pump. When the resonator spins along the clockwise and counterclockwise directions, the resonator undergoes a different Sagnac effect, which combines the phonon pump with tunable amplitude and phase results in significantly enhanced probe transmission. If the mass of external biomolecules (such as baculovirus or coronavirus) deposited on the resonator, they can be measured by tracking the resonance frequency shifts in the transmission spectrum. Therefore our study presents a means to classify different viruses, and can also be used to identify 2019-nCoV.

In this paper, the uncertainty of time transfer based on a bidirectional time division multiplexing transmission over a single fiber with the same wavelength (BTDM-SFSW) is investigated via theoretical models and experimental measurements. According to the principle and system architecture, the uncertainty evaluation schemes for BTDM-SFSW based time transfer are presented and the uncertainty sources are identified accordingly. In order to avoid the effect of the temperature-dependent fiber delay, the measured time intervals at two sites are regarded as a whole to obtain an overall uncertainty of time interval measurements. For the uncertainty of time transfer modem calibration, aside from the type A uncertainty obtained under the applied calibration scheme, the system reproducibility against practical operation and the contribution of optical power-dependent receiving delays are also included. A mathematical model considering fiber dispersion, polarization mode dispersion (PMD) and the Sagnac effect is established to evaluate the uncertainty from the fiber link. The characteristics of the uncertainty sources in a long-distance fiber-optic time transfer testbed are then explored in detail. The combined expanded uncertainties with a coverage factor of 2 are calculated and experimentally validated over various non-calibrated fiber extensions.

Light propagating in opposite directions around the same loop in general shows a relative phase shift when recombined. This phenomenon is known as the Sagnac effect after Georges Sagnac who, in 1913, demonstrated with an interferometer on a rotating table that the phase shift depended on the angular velocity of the table. In previous work we have given a very general formula for the Sagnac effect, valid in full general relativity. The relativistic effect not only contains the `classical' contribution from the rotation of the laboratory but also contributions due its acceleration and due to incoming gravitational waves. Here, we point out a major consequence of this gravitational effect which may have implications for third generation gravitational wave detectors. We describe an `antenna' design which picks out specific components of the Weyl tensor describing the incident gravitational waves., Comment: 5 pages, 2 figures

Speedmeters are known to be quantum non-demolition devices and, by potentially providing sensitivity beyond the standard quantum limit, become interesting for third generation gravitational wave detectors. Here we introduce a new configuration, the sloshing-Sagnac interferometer, and compare it to the more established ring-Sagnac interferometer. The sloshing-Sagnac interferometer is designed to provide improved quantum noise limited sensitivity and lower coating thermal noise than standard position meter interferometers employed in current gravitational wave detectors. We compare the quantum noise limited sensitivity of the ring-Sagnac and the sloshing-Sagnac interferometers, in the frequency range, from 5 Hz to 100 Hz, where they provide the greatest potential benefit. We evaluate the improvement in terms of the unweighted noise reduction below the standard quantum limit, and by finding the range up to which binary black hole inspirals may be observed. The sloshing-Sagnac was found to give approximately similar or better sensitivity than the ring-Sagnac in all cases. We also show that by eliminating the requirement for maximally-reflecting cavity end mirrors with correspondingly-thick multi-layer coatings, coating noise can be reduced by a factor of approximately 2.2 compared to conventional interferometers.

A model based on Lamb's theory of gas lasers is applied to a He-Ne ring laser gyroscope in order to estimate and remove the laser dynamics contribution from the rotation measurements. The intensities of the counter-propagating laser beams exiting one cavity mirror are continuously observed together with a monitor of the laser population inversion. These observables, once properly calibrated with a dedicated procedure, allow us to estimate cold cavity and active medium parameters driving the main part of the nonlinearities of the system. The parameters identification and noise subtraction procedure has been verified by means of a Monte Carlo study of the system, and experimentally tested on the G-Pisa ring laser oriented with the normal to the ring plane almost parallel to the Earth rotation axis. In this configuration the Earth rotation-rate provides the maximum Sagnac effect while the contribution of the orientation error is reduced at minimum. After the subtraction of laser dynamics by a Kalman filter, the relative systematic errors of G-PISA reduce from 50 to 5 part in 10^3 and can be attributed to the residual uncertainties on geometrical scale factor and orientation of the ring., corrected typos

The phenomenon of interference has great importance in understanding the wave properties of light. Here, we demonstrate the effect of a moving reference frame on an interference pattern by building a simple Sagnac interferometer, without the burden of using optical fibres. A generalized theoretical derivation for an arbitrarily shaped interferometer is given, and the Sagnac effect is demonstrated in a simple laboratory setup.

A semiconductor ring laser (SRL) with a radiation wavelength of 1540 nm and a fibre ring cavity is developed and studied in several main lasing regimes. An SRL design based on a semiconductor optical travelling-wave amplifier and a ring cavity, composed of a single-mode polarisation-maintaining fibre, is considered. The SRL is studied in the regime of a rotation speed sensor, in which the frequency shift of counterpropagating waves in the SRL is proportional to its rotation speed. The minimum rotation speed that can be detected using the SRL under consideration depends on the cavity length; in our experiment it turned to be 1deg s-1. The changes in the threshold current, emission spectrum, and fundamental radiation wavelength upon closing and opening the SRL ring cavity and with a change in its radius are also investigated.

Presented in this paper is a novel digital demodulation method for fiber-optic interferometric sensors. The method controls the modulation depth at π/2 radians and uses only five key points sampling values every modulation period. Both an automatic accurate sampling method and a modulation depth control method are introduced. Fewer resources are needed for the calculation processes to obtain the phase shift. High speed A/D converter is not necessary, which results in significant reduction of the manufacturing cost of fiber-optic interferometric sensors. A bias stability of 0.64 deg (i.e. 2.23 µrad) is demonstrated after using this method on an interferometric fiber-optic gyroscope (IFOG) based on the Sagnac effect.

The whispering gallery mode optical microresonator offers a high quality factor, which enables it to act as the core component of a high sensitivity resonator optic gyro; however, nonreciprocal noise limits its precision. Considering the Sagnac effect, i.e. mode splitting in high-quality optical micro-resonators, we derive the explicit expression for the angular velocity versus the splitting amount, and verify the sensing mechanism by simulation using finite element method. Remarkably, the accuracy of the angular velocity measurement in the whispering gallery mode optical microresonator with a quality factor of 108 is 106 °/s. We obtain the optimal coupling position of the novel angular velocity sensing system by detecting the output transmittance spectra of different vertical coupling distances and axial coupling positions. In addition, the reason for the nonreciprocal phenomenon is determined by theoretical analysis of the evanescent distribution of a tapered fiber. These results will provide an effective method and a theoretical basis for suppression of the nonreciprocal noise.

We offer an elementary proof, within a classical model, that the beat frequency produced in an active optical Sagnac interferometer, in which clockwise (CW) and counterclockwise (CCW) waves are mixed, is proportional to its vector area A divided by its perimeter P. We aim to fill a gap in the literature, since alternative proofs are usually incomplete or rather more complicated. Our observations in various large ring laser interferometers support this A/P dependence and allow the observed Sagnac frequencies from Earth rotation to be predicted to very high accuracy.

The optic-bound effect on fibre optic gyro (FOG) precision is analysed theoretically, and formulas describing the change of FOG light power under the action of optic-bound effect are given. It is confirmed that optic-bound effect is a main instantaneous non-reciprocity effect of FOG in addition to the Sagnac effect and can lead to a dynamic error of FOG in practical environments. An approach to suppressing or eliminating the error due to the optic-bound effect is presented and verified experimentally. The result shows that the approach is valid and the precision of FOG is improved observably.

It is shown that the rotation of the polarization plane of rays induced by a rotating body can be accumulated by means of a long baseline optical cavity. Theoretical analysis shows that the presently proposal experimental scheme is possible to test this gravitational Faraday rotation effect on the Earth, especially including how to effectively suppress the dominant part of the Sagnac effect due to the rotation of the Earth with a reasonable experimental configuration.

We describe a method to create a circular magnetic waveguide for deBroglie waves on a microchip. The guide is a two-dimensional magnetic minimum for trapping weak-field seeking states of atoms or molecules with a magnetic dipole moment. It is created completely by electric currents in wires that are lithographically patterned on a multi-level chip. We describe the geometry and time-dependent currents of the wires and show that it is possible to wrap the waveguide in a complete circle with minimal perturbations due to the leads or wire crossings. This maximal area geometry is suited for rotation sensing with atom interferometry via the Sagnac effect using either cold thermal atoms and molecules or Bose-condensed systems.

With the development of manufacturing technology, the propagation loss of the planar waveguide is getting lower and lower, and the shot-noise-limited sensitivity of an IIOG will be greatly improved. When the propagation loss is getting lower, improper coupling-out waveguide in the waveguide coil may lead to non-ignorable bending loss and crosstalk because of the small radius of curvature and X-junction. In this paper, different coupling-out waveguides have been designed. After calculation and optimization by the beam propagation method, we found the proper coupling-out waveguide having relatively low propagation loss, which can improve the sensitivity of the IIOG.

Interference resides deeply in our understanding of the wave properties of light. In this paper, the century famous Sagnac effect is demonstrated to be independent of the rotation axis position, using a rotating ring optical fiber in a straightforward laboratory experiment. A simple theoretical explanation for this result is given for any arbitrary closed loop interferometer. The level of this discussion should be suitable for undergraduate physics or engineering courses where electromagnetic theory and optics are discussed. The experiment described utilizes basic and important aspects in modern optics which every science student should acquire.

We proposed a two-coupled microsphere resonator structure as the element of angular velocity sensing under the Sagnac effect. We analyzed the theoretical model of the two coupled microspheres, and derived the coupled-resonator-induced transparency (CRIT) transfer function, the effective phase shift, and the group delay. Experiments were also carried out to demonstrate the CRIT phenomenon in the two-coupled microsphere resonator structure. We calculated that the group index of the two-coupled sphere reaches n g = 180.46, while the input light at a wavelength of 1550 nm.

We reports improvements to our Sagnac effect matter-wave interferometer gyroscope. This device now has a short-term rotation-rate sensitivity of 6×10−10 rad s−1 over 1 s of integration, which is the best publicly reported value to date. Stimulated Raman transitions are used to coherently manipulate atoms from counterpropagating thermal beams, forming two interferometers with opposite rotation phase shifts, allowing rotation to be distinguished from acceleration and laser arbitrary phase. Furthermore, electronically compensating the rotation-induced Doppler shifts of the Raman lasers allows operation at an effective zero rotation rate, improving sensitivity and facilitating sensitive lock-in detection readout techniques. Long-term stability is promising but not yet fully characterized. Potential applications include inertial navigation, geophysical studies and tests of general relativity.

It is shown that the Maxwell–Heaviside theory is incomplete and limited, for example, it is unable to describe the Sagnac effect, either with platform at rest or in motion. An electrodynamical theory based on a physical internal O(3) gauge space is shown to provide the correct explanation in classical electrodynamics for the Sagnac effect, and for interferometry in general, for example Sagnac and Michelson interferometry. The U(1) sector of unified field theory must therefore be replaced by an SU(2) sector broken to O(3). This has numerous consequences for unified field theory.

A method is proposed for observation of the polarisation nonreciprocity of fibre ring interferometers (FRIs) by placing a rotating polariser at the output of an interferometer ahead of a photodetector. It is demonstrated theoretically and experimentally that the absence of a signal for any position of the transmission axis of the polariser at the FRI output is a criterion of the absence of the polarisation nonreciprocity. It is suggested that the coaxial alignment of the anisotropic FRI components be monitored during assembly to ensure the polarisation nonreciprocity on the basis of the absence of a signal at the output of a rotating polariser. It is also shown that, when the conditions for the polarisation nonreciprocity are fulfilled, the signal from the output of a beam splitter located flush against the fibre loop output carries information about the phase characteristics of the beam splitter.

A fibre-optic resonant ring interferometer with a low-coherent light source was investigated experimentally. The feasibility of measuring the parameters of ring cavities characterised by very narrow lines (of the order of tens of kilohertz) was demonstrated by using a broad-band light source and a retroreflecting Doppler mirror. The Sagnac effect was first observed in a ring resonant interferometer with a low-coherence light source. Modulation and compensation of the phase nonrecriprocity in a low-coherence resonant interferometer with the aid of an optical frequency shifter located outside a sensing fibre loop were observed experimentally.

It is shown that higher symmetry (O(3)) electrodynamical considerations lead to a straightforward explanation of the Sagnac effect in terms of the topological phase and Aharonov Bohm effect. The method is extended to interferometry and physical optics in general, using the Sagnac, Michelson and Young interferometers as examples.

According to the triangle Sagnac experiment, between point A and point B that are moving in a circular motion, the travel times for light or radio signals from A to B and from B to A are different. The difference Δt, i.e. the Sagnac effect, equals 2VDL/c2, where D is the foot of the altitude to AB, VD is the speed of point D and L is the distance from A to B. The Sagnac effect exists whether the radius of the circle is as small as only few centimeters, e.g., in fiber-optic gyroscopes, or as big as twenty thousand kilometers, e.g., in GPS. Therefore, if we mount an atomic clock and signal transmitter and receiver on each of two objects moving at the same speed in a circular motion (it is not necessary to synchronize the two clocks beforehand), we will find such a time difference. Practically, using sufficiently large L and VD, this time difference can reach around 1 ns, which is relatively easy to detect with current technology. This experiment would yield both practical applications and theoretical implications. First, it can be used as a verification of Sagnac corrections in GPS. Second, a theoretical problem arises when these two objects change their paths to a straight line. Would the time difference still exist (then it contradicts the principle of the constancy of the speed of light) or does the time difference "jump" to zero? The result of the experiment will be of great interest.

The frequency splitting due to the Sagnac effect is considered in the active laser gyro with a ring cavity filled with a medium having the high refraction index and nonzero dispersion. It is shown that the medium reduces the gyro-factor by n* times, where n* is the group refractive index. However, in the case of dynamic anomalous dispersion, it is possible in principle to increase the gyro-factor without increasing the ring cavity size.

By means of a formal analogy with the Aharonov–Bohm effect, the Sagnac time delay and the corresponding Sagnac phase shift in the Kerr–Newman and Reissner–Nordstrom spacetimes are discussed. We find that the effect depends on the properties of the source of the gravitational field. The contributions made by the electric charge of the gravitational source can be employed to weaken it in the Kerr–Newman spacetime, even if a phase shift and a time delay still appear. This is due to the properties of the rotating source of the gravitational field.

HeNe ring-laser gyros are standard sensors in inertial guidance; mirror reflectances now reach 99.9999%. Present research instruments have an area of , a passive quality factor of , and a resolution of the frequency difference of counter-rotating optical beams approaching microhertz. In the Sagnac effect, this difference is proportional to the angular velocity. Present resolution is limited by thermal drifts in frequency pulling, itself reflecting mirror backscatter. The capability of ring lasers for measurements of geodesic interest, including seismometry and earth tides, and for detection of other sources of non-reciprocal refractive indices, including axions and CP violation, are discussed. In standard polarization geometries the observable is necessarily time-reversal odd. Scaling rules for dimensions, finesse etc summarizing past progress and suggesting future potential are given.

We propose a scheme to realize rotation sensing through the use of optical lattices with laser-assisted tunneling. We theoretically demonstrate that competition between the rotation and the spin-orbit coupling governs the spin-dependent response of the cyclotron dynamics of the spin-orbit coupled bosons. The Sagnac-type cumulative phase can be read out from the envelope of a beat-frequency time evolution of the population imbalance in the spin-balanced system and enhanced by cyclotron motion. We also theoretically show that the sensitivity limit of the spin-orbit–coupled system to rotational motion can reach .

Experiments involving quantum interference of neutron de Broglie waves, having a wavelength A , extending over macroscopic distances of order are described. In particular I discuss interference induced by the Earth's gravitational field and by its rotation (Sagnac effect), the topological phase shifts resulting from the diffraction of the neutron, carrying its magnetic moment , around a charged electrode (Aharonov--Casher effect) and then finally during its passage through a pulsed magnetic field (scalar Aharonov--Bohm effect).

A preferred-frame test theory formulated for accelerated frames is obtained by adapting the differential geometric analysis of an accelerated observer. This analysis explicitly incorporates the conventionality of the one-way speed of light resulting from the freedom in clock synchronization, allowing a discussion of the role of synchrony in test theories. The Sagnac effect is investigated within the test theory, enabling the use of a precision ring laser to bound parameters of the theory and thus to test local Lorentz invariance.

Squeezed light from a Sagnac fibre ring may be used to test Bell's inequality. This system is analogous to the original EPR thought experiment. The authors show that Bell's inequality can be tested with homodyne detection of such light when the photon numbers of the squeezed vacuum and the local oscillator are small.

We report here the possibility of controlling the position of the standing-wave pattern in a ring-laser cavity at rest thanks to diffraction. Modulating the position of the aperture along the beam axis induces a beat frequency between the two counterpropagating waves in the motionless ring laser, the so-called reverse Sagnac effect. This effect permits us to observe rotation rates like the Earth's one, several orders of magnitude smaller than the width of the locking region, by purely internal measurements.

Physics and experimental results of atom interferometry are reviewed and several realizations of atom interferometers are summarized. As a typical example of an atom interferometer utilizing the internal degrees of freedom of the atom, we discuss the separated field excitation of a calcium atomic beam using four traveling laser fields and demonstrate the Sagnac effect in a rotating interferometer. The sensitivity of this interferometer can be largely increased by use of slow atoms with narrow velocity distribution. We therefore furthermore report on the preparation of a laser cooled and deflected calcium atomic beam.

An investigation was made of the characteristics of a laser with a new active medium in the form of neodymium-activated gadolinium scandium gallium garnet (GSGG:Nd3+), containing chromium and emitting ultrashort pulses in the case of passive mode locking. Statistical dependences of the duration, energy, and reproducibility of the output pulses on the position of a cell with a saturable absorber (dye 3274 in ethanol) in an interferometer and on the initial transmission of the cell were determined. A new resonator configuration with an asymmetric position of the active element inside an interferometer ring was used: it ensured simple emission of the lowest transverse mode without additional spatial selection. A comparison of the main parameters of the ultrashort pulses emitted by YAG and GSGG lasers demonstrated characteristic advantages of the new active medium in generation of picosecond pulses.

The authors consider the Sagnac effect from the point of view of a co-rotating observer. They give for both matter and light waves the fully relativistic evolution equations in the rotating frame of reference. In the nonrelativistic limit the Sagnac effect is similar to the Aharonov-Bohm effect. This similarity shows that the Sagnac effect is a manifestation of Berry's phase.