Porous Unclad Waveguide for Atomic Clock Frequency Noise Reduction
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Solution Overview
Problem
Hollow core planar optical waveguides used in atomic clocks suffer from high optical loss, leading to increased frequency noise in frequency-locked optical signals, which diminishes the accuracy of atomic clocks due to the demand for miniaturization and integrated spectroscopy systems.
Innovation Solution
A porous, unclad waveguide is implemented with a low index of refraction region and a cover, hermetically sealed to reduce optical loss by allowing the optical signal to propagate outside the waveguide, minimizing sidewall losses and using a low pressure environment to achieve a low index of refraction, thereby reducing frequency noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If hollow core planar optical waveguide is used for miniaturization, then device size is reduced, but optical loss increases
Solution Approach 1:
The patent employs a porous low index of refraction material (such as porous silicon dioxide) to form the waveguide core. The porous structure provides an effective index of refraction closer to that of vacuum, reducing optical confinement requirements and allowing the optical mode to extend further into the low-pressure environment where loss is minimized. This enables miniaturization while maintaining low optical loss.
Solution Approach 2:
The patent changes the physical and chemical parameters of the waveguide core material by creating a porous structure with controlled porosity (e.g., 60-95%). This parameter change reduces the effective index of refraction of the core material, allowing better mode matching with the low-pressure environment and reducing optical loss while maintaining compact dimensions.
2Device complexity
If hollow core planar optical waveguide is used, then device integration is improved, but frequency noise increases
Solution Approach 1:
The porous waveguide core material reduces optical loss by providing better index matching with the low-pressure environment, which directly reduces frequency noise in the generated optical signal while maintaining integration capabilities.
Solution Approach 2:
The patent creates a low-pressure (vacuum or near-vacuum) environment within the waveguide structure, which provides an inert medium with index of refraction close to unity. This environment minimizes optical absorption and scattering losses, thereby reducing frequency noise while allowing integrated operation.
3Stability of the object's composition
If optical signal propagates through hollow core waveguide, then signal confinement is improved, but sidewall losses increase
Solution Approach 1:
The porous core material provides gradual index transition at the waveguide boundaries, reducing abrupt sidewall reflections and scattering. The effective index of the porous material is closer to the surrounding low-pressure environment, reducing the index contrast and thereby minimizing sidewall losses while maintaining adequate signal confinement.
Solution Approach 2:
The patent applies different porosity levels or material compositions at different locations within the waveguide structure to optimize local confinement properties. The porous structure allows tailored index profiles that provide sufficient confinement while minimizing losses at critical interfaces.
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
The porous, unclad waveguide design reduces optical loss and frequency noise, enhancing the accuracy of atomic clocks by providing a more stable frequency-locked optical signal, addressing the limitations of hollow core planar waveguides.
Implementation Method 1
allowing the optical signal to propagate outside the waveguide, minimizing sidewall losses
Implementation Method 2
using a low pressure environment to achieve a low index of refraction, thereby reducing frequency noise
Data Source
AI summary
An apparatus is provided. The apparatus comprises a substrate; a low index of refraction region in or on the substrate; an optical waveguide; a cover; wherein at least a portion of the low index of refraction region and the optical waveguide are hermetically sealed under the cover; a chamber formed by the low index of refraction region and the cover; atoms; an environment, in the chamber, including the atoms and having a first index of refraction; a segment of the optical waveguide formed over the low index of refraction region and within the chamber; and wherein the segment has a second index of refraction which is substantially equal to the first index of refraction.