Integrated Optical Waveguide Atomic Clock for Thin Stable Packaging
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Solution Overview
Problem
Existing miniaturized atomic clocks face challenges in reducing size and maintaining temperature stability, with prior solutions being costly and prone to optical instability due to the use of discrete optical components and complex assembly processes.
Innovation Solution
A miniaturized atomic clock design featuring a substantially flat optical waveguide that expands a guided light beam through multiple internal reflections, allowing for a thickness of less than 15 mm, and utilizing a compact vapor cell with integrated optical waveguides and photo detectors for improved stability and reduced complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If discrete optical elements (beam splitters, lenses, prisms) are used to reduce the overall size of the optical system, then the device size is reduced, but the alignment and assembly complexity increases and optical stability deteriorates
Solution Approach 1:
The patent integrates multiple discrete optical elements (beam splitters, lenses, prisms) into a single monolithic optical component fabricated using microlithography techniques. This merging eliminates the need for separate alignment and assembly of multiple components, thereby reducing device complexity while maintaining the compact size. The integrated component performs multiple optical functions within a single structure, resolving the contradiction between size reduction and assembly complexity.
2Volume of moving object
If discrete optical elements are used to reduce device size, then the overall size is reduced, but optical stability deteriorates due to sensitivity to shocks and vibrations
Solution Approach 1:
By integrating all optical elements into a single monolithic component, the patent eliminates the interfaces and mounting structures that would be sensitive to shocks and vibrations. The unified structure maintains fixed optical paths without mechanical joints, thereby improving optical stability and reliability while keeping the device compact.
3Measurement precision
If a resonant cavity is used to confine microwaves for vapor-cell frequency references, then the atomic resonance excitation is achieved, but the minimum size is determined by half the wavelength of microwave radiation (several centimeters)
Solution Approach 1:
The patent replaces the traditional microwave resonant cavity (mechanical/electromagnetic system) with an optical-based detection system using integrated photonic components. This substitution allows for miniaturization because optical wavelengths are much shorter than microwave wavelengths, enabling the vapor cell to be significantly smaller while still achieving precise atomic resonance measurement through optical probing rather than microwave confinement.
4Measurement precision
If a large gas volume is used in standard vapor-cell frequency references, then the atomic resonance signal is sufficient, but the power required to maintain cell temperature increases (several watts for cubic centimeter volume)
Solution Approach 1:
The patent changes the detection parameter from microwave-based to optical-based, using integrated photonic detectors to measure atomic resonance. This parameter change allows for the use of smaller vapor cell volumes while maintaining sufficient signal strength, thereby reducing the power required for temperature control. The optical detection method is more efficient for small volumes compared to traditional microwave techniques.
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 design achieves significant size reduction and enhanced stability, reducing the overall thickness to less than 5 mm, while simplifying assembly and lowering costs by minimizing the use of discrete optical components and improving optical stability.
Implementation Method 1
The first optical waveguide is arranged to expand a guided light beam provided by a light source through multiple internal reflections
Implementation Method 2
CPT is a nonlinear phenomenon in atoms in which coherences (electromagnetic dipole moments) between atomic energy levels are excited by pairs of optical fields
Implementation Method 3
Atomic clocks based on CPT rely mainly on a vertical cavity surface emitting laser diode (VCSEL) as the light source
Implementation Method 4
said photo detector being adapted to detect said optical frequency reference signal and to generate at least one reference signal
Implementation Method 5
The atomic transition frequency is dependent on the temperature of the vapor-cell, therefore the cell temperature must be controlled to a fixed value and have a great stability
Data Source
Figure 1
Figure 2a~2b
Figure 3a~3b
AI summary
In the present invention a new atomic clock is proposed comprising: at least one light source adapted to provide an optical beam, at least one photo detector and a vapor cell comprising a first optical window, said optical beam being directed through said vapor cell for providing an optical frequency reference signal, said photo detector being adapted to detect said optical frequency reference signal and to generate at least one reference signal, wherein - said atomic clock comprises a first optical waveguide arranged to said first optical window, said first optical waveguide being arranged to incouple at least a portion of said optical beam, said first optical waveguide being sized and shaped so that said first guided light beam is expanded, - a first outcoupler is arranged to outcouple at least a portion of said guided light beam to said vapor cell, - the thickness t of the atomic clock is smaller than 15mm.