Ultrahigh sensitivity of rotation sensing beyond the trade-off between sensitivity and linewidth by the storage of light in a dynamic slow-light resonator
We propose to employ the storage of light in a dynamically tuned add-drop resonator to realize an optical gyroscope of ultrahigh sensitivity and compact size. Taking the impact of the linewidth of incident light on the sensitivity into account, we investigate the effect of rotation on the propagation of a partially coherent light field in this dynamically tuned slow-light structure. It is demonstrated that the fundamental trade-off between the rotation-detection sensitivity and the linewidth will be overcome and the sensitivity-linewidth product will be enhanced by two orders of magnitude in comparison to that of the corresponding static slow-light structure. Furthermore, the optical gyroscope employing the storage of light in the dynamically tuned add-drop resonator can acquire ultrahigh sensitivity by extremely short fiber length without a high-performance laser source of narrow linewidth and a complex laser frequency stabilization system. Thus the proposal in this paper provides a promising and feasible scheme to realize highly sensitive and compact integrated optical gyroscopes by slow-light structures.
We propose to employ the storage of light in a dynamically tuned add-drop resonator to realize an optical gyroscope of ultrahigh sensitivity and compact size. Taking the impact of the linewidth of incident light on the sensitivity into account, we investigate the effect of rotation on the propagation of a partially coherent light field in this dynamically tuned slow-light structure. It is demonstrated that the fundamental trade-off between the rotation-detection sensitivity and the linewidth will be overcome and the sensitivity-linewidth product will be enhanced by two orders of magnitude in comparison to that of the corresponding static slow-light structure. Furthermore, the optical gyroscope employing the storage of light in the dynamically tuned add-drop resonator can acquire ultrahigh sensitivity by extremely short fiber length without a high-performance laser source of narrow linewidth and a complex laser frequency stabilization system. Thus the proposal in this paper provides a promising and feasible scheme to realize highly sensitive and compact integrated optical gyroscopes by slow-light structures.
We describe a resonator-based optical gyroscope whose sensitivity for measuring absolute rotation is enhanced via use of the anomalous dispersion characteristic of superluminal light propagation. The enhancement is given by the inverse of the group index, saturating to a bound determined by the group velocity dispersion. We also show how the offsetting effect of the concomitant broadening of the resonator linewidth may be circumvented by using an active cavity. For realistic conditions, the enhancement factor is as high as 106. We also show how normal dispersion used for slow light can enhance relative rotation sensing in a specially designed Sagnac interferometer, with the enhancement given by the slowing factor.
We discuss the relationship between Sagnac effect and "slow light" phenomenon, and point out that although the medium and waveguide dispersion can in no way affect the magnitude of Sagnac effect, the highly dispersive structure is still beneficial to the enhancement of Sagnac effect and can be utilized to detect absolute rotation for navigation purpose. Based on the EIT-like property of coupled resonator structure, a miniature highly sensitive gyroscope is possible. This EIT-like phenomenon occurs through a classical mean in a coupled resonator structure due to all-optical classical interference, called coupled resonator induced transparency (CRIT). With the analogy between optical and atomic parameters, we treat Sagnac effect as a phase perturbation to resonators' optical parameters, and then analyze Sagnac effect in a CRIT structure with a transfer function approach and derive the explicit expression of relative Sagnac phase shift. We find that Sagnac effect is enhanced as a factor as light slows, and can be tailored by adjusting the optical parameters of structure. Furthermore, as a potential highly sensitive, compact size rotation sensor, some issues for the implementation of CRIT structure based gyroscope are discussed and considered, such as the fabrication possibility, line-width, shot noise limit sensitivity and integration issues. With the improvement of micro-fabrication technique, this gyroscope should have all-solid configuration, compact size and also be expected to achieve comparable sensitivity to common optic-fiber gyroscope. It would be easily integrated to all-optical application and construct a high performance rotation sensor.
Precise positioning and motion tracking are enabling development of key technologies in numerous fields of research and applications such as control, navigation, stabilization, and positioning systems for robotics, medical-imaging applications, virtual reality, computer games, and many more. While rotation sensing can be based on both mechanical and optical effects, optical gyroscopes provide the highest sensitivity and accuracy. Although the details may vary depending on the specific implementation, all optical rotation sensors exploit the Sagnac effect,1 i.e., the interference pattern resulting from the different phase shifts of waves propagating in a circular path along and opposite the direction of rotation. The classical Sagnac phase shift is determined solely by the angular velocity, the optical frequency, and the area enclosed by the closed-loop optical path, and completely independent of the medium’s other properties such as the index of refraction and its dispersion properties.2 This century-old result has been the subject of ongoing debate for several decades, both because of its fundamental nature and because it inherently limits the feasibility of attaining highly sensitive miniaturized rotation sensors. Specifically, it implies that the only ways to enhance the sensitivity and accuracy of optical gyroscopes are to either increase the optical frequency or enlarge the gyro’s area. In practice, both approaches are limited. Recent studies have pointed out the advantages of exploiting the Sagnac effect, generated by electronic resonances, in slow-3 and fast-light4 media (i.e., in which the group velocity is substantially smaller or larger than the speed of light) for fabrication of ultrasensitive optical gyroscopes. However, material properties based on slow/fast-light media suffer from inherent limitations and drawbacks. In particular, such systems are bulky, lossy, require very low temperatures, and are limited to specific wavelengths according to the material’s electronic andoptical properties. Instead, we have been focusing on photonic-resonance-based structures,5, 6 taking advantage of their flexibility, compact dimensions, and excellent optical Figure 1. Schematic of a coupled-resonator optical waveguide (CROW).
We report the experimental observation of enhanced rotation sensing in a slow-light structure. We demonstrate that the differential of the phase difference, introduced by rotation, between the counterpropagating waves is proportional to the group index, and thus we can obtain large rotation sensitivity in the slow-light structure with high dispersion (large group index). The results also predict the realization of highly sensitive and compact integrated rotation sensors and gyroscopes by using microwaveguides.
A high-sensitivity gyroscope is vital for both investigation of the fundamental physics and monitoring of the subtle variation of Earth’s behaviors. However, it is a challenge to realize a portable gyroscope with sensitivity approaching a small fraction of the Earth’s rotation rate. Here, we theoretically propose a method for implementing a table-top gyroscope with remarkably high sensitivity based on photon drag in a rotating dielectric object. By inserting an Er3+-doped glass rod in a Fabry–Pérot optical cavity with only 20 cm length, we theoretically show that the giant group refractive index and the narrowing cavity linewidth due to slow light can essentially increase the nonreciprocal phase shift due to the photon drag to achieve a rotation sensitivity of 26 frad/s/Hz. This work paves the way to accurately detect tiny variations of the Earth’s rotation rate and orientation and even can test the geodetic and frame-dragging effects predicted by the general relativity with small-volume equipment.