Aspects of the present disclosure are directed to process flow to fabricate a waveguide structure with a silicon nitride core having atomic-level smooth sidewalls achieved by wet etching instead of the conventional dry etching process. A mask is pre-biased to account for lateral etching during the wet-etching steps.

A system for fibre-optic Sagnac interferometry, the system comprising: an optical source; an optical splitter configured to split light from the optical source into a first optical beam and a second optical beam; an optical circuit comprising a first modulation unit, a second modulation unit, and an optical fibre operatively coupled between the first and second modulation units, wherein the optical circuit is operatively coupled to the optical splitter such that the first and second optical beams traverse the optical circuit in opposite directions, the first optical beam being modulated by the first modulation unit before being modulated by the second modulation unit, and the second optical beam being modulated by the second modulation unit before being modulated by the first modulation unit, wherein the first modulation unit is configured to modulate light passing through it with a first modulation code, and the second modulation unit is configured to modulate light passing through it with a second modulation code which is different from the first modulation code; an optical detector configured to detect the first and second optical beams after the first and second optical beams have traversed the optical circuit; and a processing system configured to receive from the optical detector an interference signal, which is indicative of an optical phase difference between the first and second optical beams, and to determine the optical phase difference by demodulating the interference signal based on the first and second modulation codes; wherein a correlation of the first modulation code with a time-shifted version of itself is maximum for a zero time shift; and wherein a correlation of the second modulation code with a time-shifted version of itself is maximum for a zero time shift.

Novel small-footprint integrated photonics optical gyroscopes disclosed herein can provide ARW in the range of 0.05°/√Hr or below (e.g. as low as 0.02°/√Hr), which makes them comparable to fiber optic gyroscopes (FOGs) in terms of performance, at a much lower cost. The low bias stability value in the integrated photonics optical gyroscope corresponds to a low bias estimation error (in the range of 1.5°/Hr or even lower) that is crucial for safety-critical applications, such as calculating heading for autonomous vehicles, drones, aircrafts etc. The integrated photonics optical gyroscopes may be co-packaged with mechanical gyroscopes into a hybrid inertial measurement unit (IMU) to provide high-precision angular measurement for one or more axes.

Novel small-footprint integrated photonics optical gyroscopes disclosed herein can provide ARW in the range of 0.05°/√Hr or below (e.g. as low as 0.02°/√Hr), which makes them comparable to fiber optic gyroscopes (FOGs) in terms of performance, at a much lower cost. The low bias stability value in the integrated photonics optical gyroscope corresponds to a low bias estimation error (in the range of 1.5°/Hr or even lower) that is crucial for safety-critical applications, such as calculating heading for autonomous vehicles, drones, aircrafts etc. The integrated photonics optical gyroscopes may be co-packaged with mechanical gyroscopes into a hybrid inertial measurement unit (IMU) to provide high-precision angular measurement for one or more axes.

A spherical multi-axis optical fiber sensing device is formed by a three-axis optical interference sensor composed of a multi-level opto-mechanical integrated unit kit. The opto-mechanical integrated unit kit is composed of three fiber rings, which are respectively a large fiber ring, a medium fiber ring and a small fiber ring. The multi-level opto-mechanical integrated unit kit is combined with the use of the mechanism component technology that can be freely rotated and positioned to achieve the functional purpose of establishing a three-axis orthogonal optical fiber sensing unit in a single sphere volume.

Aspects of the present disclosure are directed to process flow to fabricate a waveguide structure with a silicon nitride core having atomic-level smooth sidewalls achieved by wet etching instead of the conventional dry etching process.

Techniques for reducing the bias error present in optical gyroscopes is disclosed. Such techniques include at least one path length adjustment member placed in an optical gyroscope resonator, which are configured to modulate the optical path length of the resonator so that bias errors attributable to the optical path length are shifted outside of the bandwidth of the optical gyroscope. In some embodiments, the at least one path length adjustment member includes a plurality of microheaters coupled to the resonator, in which case optical path length modulation is achieved by heating the resonator via the microheaters. Alternatively, a plurality of piezo-electric regions can be placed in the resonator, which enables optical path length modulation through electric field gradients applied to the piezo-electric regions.

Systems and methods for embodiments having an extra thick ultraviolet durability coating are described herein. For example, a system may include a laser block assembly. The system may also include a cavity in the laser block assembly. Further, the system may include a plurality of multilayer mirrors in the cavity. In certain embodiments, at least one multilayer mirror of the plurality of multilayer mirrors may include a plurality of alternating layers of a first optical material having a high index of refraction and a second optical material having a first low index of refraction. Additionally, the at least one multilayer mirror may include a multilayer durability coating disposed on the plurality of alternating layers.

Improvements to optical power regulation in a gyroscopic system are described. The system can include an optical assembly (e.g., optical bench) which couples opposing optical signals to a resonator coil. The system can monitor the power of the optical signals through the resonator coil by including signal extraction optics in the optical assembly which are configured to extract a portion of the optical signals. The portions can be extracted via a single beamsplitter, wherein the beamsplitter reflects the portions at a single common surface, and can also reflect the portions to a respective photodetector in free space free from intervening optical components, such as polarizers or beamsplitters. One or more processors can be coupled to the optical assembly, wherein the processor(s) are configured to adjust the power of the optical signals in response to detecting a power difference between the optical signals.

Aspects of the present disclosure are directed to structural modifications introduced in a waveguide structure in order to more tightly pack adjacent waveguide turns in an optical gyroscope fabricated on a planar silicon platform as a photonic integrated circuit. Increasing number of turns of the gyroscope coil increases total waveguide length as well as enclosed area of the gyroscope loop, which translates to increased sensitivity to rotational measurement.