Active Waveguide Optical Gyroscope Using Rare-Earth Doping
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Solution Overview
Problem
Conventional optical gyroscopes are bulky, expensive, and limited by high background losses in silicon and silicon dioxide waveguides, which restrict their sensitivity and require lengthy waveguides to achieve desired sensitivity, making them unsuitable for compact and cost-effective applications.
Innovation Solution
The use of rare-earth doped waveguides with orthogonal connections formed by crossing elements reduces path interference and background losses, allowing for highly sensitive optical gyroscopes with a small footprint, achieved by employing substrates with doped waveguides and a system including a wavelength division multiplexer, photodetectors, and a lock-in amplifier to enhance sensitivity and compactness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional silicon and silicon dioxide waveguides are used, then the gyroscope can be manufactured with standard lithographic processes, but the background losses are very high (about 1 dB/cm) which limits sensitivity
Solution Approach 1:
The patent changes the material composition parameter of the waveguide by doping silicon with rare-earth materials (erbium, ytterbium, or thulium) at concentrations of 10^18 to 10^20 atoms/cm³. This parameter change transforms the waveguide from a passive high-loss structure to an active low-loss structure that can even amplify light signals, directly resolving the contradiction between manufacturability and sensitivity.
Solution Approach 2:
The patent creates a composite material system by combining silicon substrate with rare-earth dopants and silica cladding layers. This composite structure leverages the complementary properties of each material: silicon provides the waveguide core, rare-earth elements provide low loss and potential amplification, and silica provides protective cladding, together achieving performance superior to any single material.
2Measurement precision
If the waveguide length L is increased to reduce minimum detectable angular rotation, then sensitivity improves, but the device becomes bulky and expensive
Solution Approach 1:
By changing the material parameter (doping silicon with rare-earth materials), the patent achieves ultra-low background losses that enable short waveguide lengths (1-10 cm) to provide the same sensitivity that would otherwise require kilometer-length conventional waveguides, directly resolving the contradiction between sensitivity and device size.
3Measurement precision
If the loop diameter D is increased to improve sensitivity, then the gyroscope performance improves, but the device footprint increases
Solution Approach 1:
The patent changes the optical parameter of the waveguide material (refractive index and loss characteristics through rare-earth doping) to enable compact loop designs. The reduced losses allow light to complete many more circulation cycles within a small footprint, effectively increasing the optical path length without increasing the physical loop diameter, thus resolving the contradiction between sensitivity and device area.
4Measurement precision
If rare-earth doped waveguides are used to reduce background losses, then sensitivity improves and device size reduces, but the manufacturing process becomes more complex
Solution Approach 1:
The patent incorporates rare-earth materials into the silicon substrate during the initial lithographic fabrication process rather than as a separate post-processing step. This preliminary action integrates the doping process into the standard manufacturing flow, minimizing additional complexity while achieving the desired low-loss waveguide properties.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly improves sensitivity by increasing the product of waveguide length and diameter, achieving resolution better than 10°/h, and reduces the size of the gyroscope to less than 1 cm², making it suitable for high-performance angular velocity sensing in various applications, including inertial navigation.
Implementation Method 1
The waveguide is doped with a rare-earth material and has an active character in that the waveguide amplifies light
Implementation Method 2
The waveguide is doped with a rare-earth material and has an active character in that the waveguide amplifies light; it is believed that the dopant serves to reduce background losses in the waveguide and/or amplifies light passing through the waveguide
Implementation Method 3
a loop of the optical waveguide is employed in view of principles of the Sagnac effect to measure the interference of counter-propagating waves therein; Rotation about the axis normal to the waveguide either slows or speeds the propagation of light through the waveguide, resulting in a measurable shift in phase of the light
Implementation Method 4
An interferometric gyroscope is operated with a source at center wavelength λ0 and power P of photon energy hν that is detected by a photodetector with quantum efficiency h
Data Source
AI summary
The present application is directed an optical gyroscope. The optical gyroscope includes a substrate including a first and a second waveguide disposed thereon. One or both of the waveguides may be doped with a rare-earth material. A crossing element is disposed between the first and the second waveguides to form a substantially orthogonal connection therebetween. The application is also directed to a system including an optical gyroscope. The application is further directed to a method of observing characteristics of the optical gyroscope.