Integration of photonics optical gyroscopes with micro-electro-mechanical sensors
Aspects of the present disclosure are directed to monolithically integrating an optical gyroscope fabricated on a planar silicon platform as a photonic integrated circuit with a MEMS accelerometer on the same die. The accelerometer can be controlled by electronic circuitry that controls the optical gyroscope. Gaps may be introduced between adjacent waveguide turns to reduce cross-talk and improve sensitivity and packing density of the optical gyroscope.
1. An integrated photonics chip comprising:
a waveguide coil comprising a plurality of waveguide turns looping around a central area enclosed by the waveguide coil, each waveguide turn being parallel to adjacent waveguide turns, wherein the waveguide coil is used as a rotational sensing element of an optical gyroscope; and
a micro-electro-mechanical-systems (MEMS)-based motion sensing device monolithically integrated in the central area enclosed by the waveguide coil, wherein the waveguide coil and the MEMS-based motion sensing device are fabricated on a common platform,
wherein the common platform is a silicon photonics platform, wherein each waveguide turn comprises a waveguide core sandwiched between an upper cladding and a lower cladding, and the waveguide core comprises silicon nitride and the upper cladding and lower cladding comprise oxide.
2. The integrated photonics chip of claim 1 , wherein the optical gyroscope and the MEMS-based motion sensing device are packaged together as a modularized integrated inertial measurement unit (IMU).
3. The integrated photonics chip of claim 2 , wherein the MEMS-based motion sensing device provides coarse rotational sensing reading for all axes of motion, and the optical gyroscope provides a higher-precision rotational sensing reading for one or more selected axes of motion.
4. The integrated photonics chip of claim 2 , wherein the MEMS-based motion sensing device comprises an accelerometer for one or more axes of motion.
5. The integrated photonics chip of claim 1 , further comprising:
a structural modification introduced on either side of each waveguide turn to reduce crosstalk between the adjacent waveguide turns, thereby increasing a spatial density of waveguide turns that can be fabricated within a predetermined area of the integrated photonics chip, wherein the structural modification comprises a gap along a lateral dimension of an oxide layer that constitutes the upper cladding and the lower cladding sandwiching the waveguide core on the silicon photonics platform.
6. The integrated photonics chip of claim 5 , wherein the predetermined area depends on an exposure field of a reticle used to fabricate the waveguide coil and the MEMS-based motion sensing device.
7. The integrated photonics chip of claim 5 , wherein increasing spatial density of waveguide turns increases the central area enclosed within the waveguide coil, as well as increases a number of waveguide turns enclosing the central area, thereby increasing sensitivity of the rotational sensing element.
8. The integrated photonics chip of claim 5 , wherein the structural modification comprises a gap.
9. The integrated photonics chip of claim 8 , wherein the gap comprises one of: an air gap, a gap filled with metal, or, a gap filled with an inert gas or liquid.
10. The integrated photonics chip of claim 8 , wherein the gap is in a form of a high-aspect-ratio rectangular slit or trench with a longitudinal dimension of the gap being substantially higher than a lateral dimension of the gap, such that the gap extends substantially above and below the waveguide core along a direction of the longitudinal dimension.
11. The integrated photonics chip of claim 1 , wherein a first portion of the waveguide coil resides on a first plane and a second portion of the waveguide coil resides on a second plane, wherein the first plane and the second plane are vertically stacked above one another.
12. The integrated photonics chip of claim 11 , wherein light couples evanescently between the first portion of the waveguide coil on the first plane and the second portion of the waveguide coil on the second plane.