Folded-Path Alkali-Metal Vapor Cell for Compact Atomic Clocks
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Solution Overview
Problem
Current alkaline vapor cells for atomic clocks face challenges in compactness, frequency stability, power consumption, and component integration, with existing architectures being complex and costly, and not well-suited for large-scale industrial production.
Innovation Solution
An alkaline vapor cell design featuring upstream and downstream optical reflectors inclined relative to each other, with diffraction means to maintain circular polarization, and a compact housing with a dispenser cavity for cesium vapor, allowing for efficient laser beam path and precise assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the laser beam passes through the cell from one side to the other (transmissive architecture), then the optical path is simple, but the cell volume and housing area increase
Solution Approach 1:
The patent transitions from a linear one-dimensional optical path (entering and exiting through opposite sides) to a two-dimensional folded path within the same housing face. The laser beam enters through the upstream window, reflects off the upstream reflector at an angle, travels to the downstream reflector, reflects again, and exits through the downstream window on the same housing face. This dimensional reconfiguration reduces the cell's footprint while maintaining the necessary optical path length.
2Volume of moving object
If compact microcells are designed for chip-scale atomic clocks, then the device size and power consumption decrease, but the manufacturing precision and assembly difficulty increase
Solution Approach 1:
The patent combines multiple optical components (upstream reflector, downstream reflector, upstream window, downstream window) into a single integrated housing structure. The reflectors are positioned at specific angles relative to each other and to the windows, forming a compact folded optical path within a unified housing. This integration reduces the number of separate parts and simplifies assembly while maintaining precise optical alignment, making the design more suitable for industrial production of chip-scale atomic clocks.
3Volume of moving object
If the reflectors are inclined relative to each other to fold the optical path, then the cell compactness improves, but the optical alignment complexity increases
Solution Approach 1:
The patent employs asymmetric inclination angles for the upstream and downstream reflectors relative to the optical axis. The upstream reflector is inclined at a first angle, and the downstream reflector is inclined at a second angle, creating a folded optical path that efficiently returns the beam to the same housing face. This asymmetric configuration optimizes the compactness of the cell while maintaining manageable optical alignment requirements through careful geometric design.
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 design enhances compactness, frequency stability, and reduces power consumption while simplifying the assembly process, making it more suitable for industrial production and integration into atomic clocks.
Implementation Method 1
the incoming inner laser beam is reflected by the upstream reflector and deflected towards the downstream reflector to form an intermediate inner laser beam
Implementation Method 2
the intermediate inner laser beam is reflected by the downstream reflector and deflected towards the downstream window to form an outgoing inner laser beam
Implementation Method 3
The cell also includes means for diffracting the incoming outer laser beam upstream of the upstream reflector and means for diffracting the laser beam reflected by the downstream reflector downstream of the downstream reflector, so as to combine the deflection produced by the diffraction means with the deflection produced by the associated reflector
Implementation Method 4
The reflectors and the diffraction means are configured so as to maintain the circular polarization state of the laser beam during its path
Data Source
Figure 1A
Figure 1B~1C
Figure 2
AI summary
The invention relates to an alkali-metal vapour cell, especially for an atomic clock, and to its manufacturing process. The alkali-metal vapour cell (2) is able to be associated with a laser (3) for emitting an external input laser beam (5a) and a photodetector (4) for receiving an external output laser beam (5e), and comprises a housing (6) having an upstream optical window (9) and a downstream optical window (10) and forming an optical cavity (11) filled with an alkali-metal vapour such as a caesium-comprising vapour, and micro-optical means arranged in the optical cavity (11) and comprising an upstream optical reflector (14) and a downstream optical reflector (15) for reflecting the laser beam (5), which reflectors are inclined relative to each other, the upstream reflector (14) being inclined relative to the plane (P) of the upstream window (9) and to the axis of the input laser beam (5) so that the external input laser beam (5a) passes through the upstream window (9) in order to form an internal input laser beam (5b), the latter being reflected by the upstream reflector (14) and deviated towards the downstream reflector (15) so as to form an internal intermediate laser beam (5c) that is reflected by the downstream reflector (15) and deviated towards the downstream window (10) so as to form an internal output laser beam (5d), the internal output (5d) laser beam (5) passing through the downstream window (10) in order to form the external output laser beam (5e).