An integrated silicon photonic optical gyroscope achieves two orders of magnitude size reduction and a factor of thirty better phase-shift sensitivity using reciprocal sensitivity enhancement. Optical gyroscopes measure the rate of rotation by exploiting a relativistic phenomenon known as the Sagnac effect1,2. Such gyroscopes are great candidates for miniaturization onto nanophotonic platforms3,4. However, the signal-to-noise ratio of optical gyroscopes is generally limited by thermal fluctuations, component drift and fabrication mismatch. Due to the comparatively weaker signal strength at the microscale, integrated nanophotonic optical gyroscopes have not been realized so far. Here, we demonstrate an all-integrated nanophotonic optical gyroscope by exploiting the reciprocity of passive optical networks to significantly reduce thermal fluctuations and mismatch. The proof-of-concept device is capable of detecting phase shifts 30 times smaller than state-of-the-art miniature fibre-optic gyroscopes, despite being 500 times smaller in size. Thus, our approach is capable of enhancing the performance of optical gyroscopes by one to two orders of magnitude.

Nanophotonic optical gyroscope with reciprocal sensitivity enhancement

An Acousto-Optic Gyroscope (AOG) consisting of a photonic integrated device embedded into two inherently matched piezoelectric surface acoustic wave (SAW) resonators sharing the same acoustic cavity is presented. This constitutes the first demonstration of a micromachined strain-based optomechanical gyroscope that uses the effective index of the optical waveguide due to the acousto-optic effect rather than conventional displacement sensing. The theoretical analysis comparing various photonic phase sensing techniques is presented and verified experimentally for the cases based on a Mach-Zehnder interferometer, as well as a racetrack resonator. This first prototype integrates acoustic and photonic components on the same lithium niobate on insulator (LNOI) substrate and constitutes the first proof of concept demonstration of the AOG. This approach enables the development of a new class of micromachined gyroscopes that combines the advantages of both conventional microscale vibrating gyroscopes and optical gyroscopes.

Novel on chip rotation detection based on the acousto-optic effect in surface acoustic wave gyroscopes

An improving structure for resonance optical gyro inserting a Mach-Zehnder Interferomete (MZI) into coupler region between ring resonator and straight waveguide was proposed. The different reference phase shift parameters in the MZI arms are tunable by thermo-optic effect and can be optimized at every rotation angular rate point without additional phase bias. Four optimum paths are formed to make the gyroscope to work always at the highest sensitivity.

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On-chip modulation for rotating sensing of gyroscope based on ring resonator coupled with Mach-Zehnder interferometer.

Miniaturized and low-cost optical gyroscopes are urgently required for emerging applications in consumer electronics market. In this paper, we proposed a theoretical analysis and preliminary experiment results for integrated interferometric optical gyroscope based on the silicon-on-insulator (SOI) platform for the first time. The gyroscope is based on the Sagnac effect and composed of coiled multimode waveguides to reduce propagation loss and the footprint. The sensitivity of the sensing part is fully investigated in terms of waveguide loss, gyroscope footprint, crossing numbers for coiled waveguides, as well as the waveguide cross section. The experimental results show that gyroscope sensitivity is 51.3 deg/s with a footprint of 600 μm × 700 μm.

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Silicon Integrated Interferometric Optical Gyroscope.

We proposed a new readout scheme for an ultrasensitive gyroscope, which uses the physics of the exceptional points of a PT-symmetric system to enhance the device sensitivity. In particular, we demonstrated that the full-width at half-maximum linewidth (Δ ω FWHM ) of the light exiting the ring resonator system is proportional to the square root of the rotation rate (Ω). Moreover, we designed a PT-symmetric gyroscope, kept at the exceptional point (at rest) with two 100-μm-radius rings, obtaining a theoretical Δ ω FWHM of 3.37×104 rad/s for an angular velocity of 100 °/h. One algorithm capable to keep the system at the exceptional point and another one to identify the direction of rotation are also proposed.

Design Rules of a Microscale PT-Symmetric Optical Gyroscope Using Group IV Platform

We propose and analyze a gyroscope using active three-dimensional vertically coupled resonators (3D-VCRs), which allows for loss compensation, unidirectional propagation, and a larger sensing area while maintaining the same bulk volume. For the ideal uniform case, the minimum detectable rotation rate ΔΩmin of the active 3D-VCR gyroscope can be decreased by above three orders of magnitude after optimization compared with the passive case. The minimal measurable rotation rates of the 3D-VCR gyroscope, the loss-compensated coupled resonator optical waveguide (LC-CROW) gyroscope, and the equivalent resonant waveguide optical gyroscope (RWOG) decrease with a higher number N of the resonators. Finally, it is shown that the uniform active 3D-VCR gyroscope has a better resolution ΔΩmin than the equivalent LC-CROW and RWOG.

Miniaturized optical gyroscope using active three-dimensional vertically coupled resonators

We propose a configuration consisting of several passive ring resonators named as fast-light
enhanced ring resonator, coupled to an active ring laser for introducing anomalous dispersion.
Theoretical analysis indicates that the introduced anomalous dispersion allows the frequency shift to
be improved as large as one order of magnitude due to Sagnac effect when the structure is rotated,
namely having the same rotational sensitivity compared to a standard ring-laser gyroscope (RLG)
with tenfold size as that of the proposed structure. In this paper, the impact of passive ring resonator
number is discussed and deduced, which manifests that only odd number of passive rings will
produce effective anomalous dispersion, thus improve the rotational sensitivity. The configuration
proposed here will have broad prospect in realizing highly integrated on-chip laser gyroscope for
rotation sensing.

Fast-light enhanced integrated on-chip laser gyroscope for rotation sensing

Active coupled resonator optical waveguide (CROW) structure can significantly enhance the performance of optical gyroscope due to its loss compensation effect and highly dispersive properties. In this paper, we analyze the effect of optical gain and its induced noise, i.e. spontaneous emission noise, on the properties of the active CROWs. A thorough investigation of the impact of various disorder degrees on the performance of the active three dimensional vertically coupled resonators (3D-VCR) gyroscope has been performed. It shows how the disorder interacted with coupling coefficient affects the achievable resolution ΔΩmin of gyroscope, and the degree of disorder will supplant the propagation loss to become an ultimate limitation. Finally, it is shown that the active 3D-VCR gyroscope (the number of ring, N>6) has better resolution ΔΩmin than that of the equivalent resonant waveguide optical gyroscope (RWOG).

Optimization of gyroscope properties with active coupled resonator optical waveguide structures

We theoretically analyze the characteristics of scale factor in frequency sensitive integrated optical gyroscope consisting of a ring resonator coupled with double ring resonators. The impact of through coupling coefficients is investigated to decide the optimal parameters located at 0s-1 for improving the scale factor. It demonstrates that the scale factor enhancement in this frequency sensitive optical gyroscope, without increasing the overall footprint, can be improved compared with conventional single ring resonator gyroscope and presents the characteristic of better performance within low-rate range. It implies a broad prospect in highly integrated on-chip applications, especially in aeronautic and astronautic area.

Long Zhao

Papers

On-chip modulation for rotating sensing of gyroscope based on ring resonator coupled with Mach-Zehnder interferometer.

Miniaturized optical gyroscope using active three-dimensional vertically coupled resonators

Fast-light enhanced integrated on-chip laser gyroscope for rotation sensing

Optimization of gyroscope properties with active coupled resonator optical waveguide structures

Improving the scale factor for rotation sensing in a frequency sensitive integrated optical gyroscope