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

We show that a certain fundamental limit applies to the accuracy of all optical rotation sensors which use laser light as a probe. We derive this fundamental rotation-rate uncertainty from the Heisenberg uncertainty relations and Glauber's minimum uncertainty states. The same relationship is obtained from a spontaneous-emission noise formulation. We present experimental data on a (nondithered) four-frequency ring laser gyroscope for which this limit is attained.

Laser gyro at quantum limit

Whispering gallery mode (WGM) resonators have been exploited as a highly sensitive and efficient sensing technique in the past few years. They offer the advantages of ultra-high sensitivity, compact size and label-free sensing capability. More recently, with the rapid development of microfluidic technologies, many integrated WGM sensors, by combining the portability of lab-on-chip devices and the high sensitivity of WGM resonators, have emerged. The capabilities of efficient sample handling and multiplexed analyte detection offered by these systems have led to many biological and chemical sensing applications, especially for the detection of single particle or biomolecule. In this review, different sensing mechanisms based on integrated whispering gallery mode resonators are introduced. Various geometries of WGM cavities including solid, liquid and hollow resonators and a detailed discussion on their integration with microfluidic devices are also covered. Different types of packaging schemes and integration methods are compared in terms of ease of fabrication and device performance. Finally, recent applications of microfluidic-based WGM sensors for detecting biological and chemical target molecules are discussed, with a prospect on future challenges and trends of development in microfluidics for multiplexed detection.

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Microfluidic Whispering Gallery Mode Optical Sensors for Biological Applications

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.

A gyroscope structure with tailored local dispersion profile to enhance sensitivity is proposed, which uses lithium niobate (LiNbO3) thin film as the on-chip material of gyroscope’s resonator. A Mach–Zehnder interferometer (MZI) structure as a coupler, which induces a different reference phase shift in each arm, is inserted into the position between ring resonator and output bus waveguide. Through modulating reference phase shift in MZI, theoretical rotation sensitivity enhancement as large as one order of magnitude is presented.

On-chip tunable dispersion in a ring laser gyroscope for enhanced rotation sensing

Microcavities based on asymmetrical Fano resonance have great potential in the application of ultra-sensitive sensors. In this paper, a very sharp asymmetrical Fano resonance is achieved by indirectly coupled gain–loss cavities. The sensitivity for detecting temperature can be enhanced up to 107/K, 8 orders of magnitude greater than that for two indirectly coupled lossy cavities. The resolution of the thermal sensor reaches 10−13  K. A thermal sensing mechanism based on coupled gain–loss optical cavities is investigated theoretically. The integrated structure shows potential to be an ultra-sensitive temperature microsensor.

On-chip high-sensitivity temperature sensor based on gain–loss coupled microresonators

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

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).

Jian Lin

Papers

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

On-chip tunable dispersion in a ring laser gyroscope for enhanced rotation sensing

On-chip high-sensitivity temperature sensor based on gain–loss coupled microresonators

Miniaturized optical gyroscope using active three-dimensional vertically coupled resonators

Optimization of gyroscope properties with active coupled resonator optical waveguide structures