Folded-Path Alkali-Metal Vapor Cell for Compact Atomic Clocks
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing alkali-metal vapour cells for atomic clocks face challenges in compactness, frequency stability, power consumption, and integration of components, with complex and costly assembly processes that are not suitable for industrial-scale production.
Innovation Solution
An alkali-metal vapour cell design featuring inclined upstream and downstream optical reflectors within a housing with optical windows, allowing the laser beam to pass through the cell in a controlled path, maintaining polarization, and using anodic bonding for assembly, along with a dispenser cavity for alkali metal vapor generation, to enhance compactness and integration while reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the laser beam traverses the cell from side to side with VCSEL and photodetector located on either side, then the atomic clock achieves proper operation, but the device complexity and manufacturing complexity increase
Solution Approach 1:
The patent combines the VCSEL and photodetector into a single integrated assembly located at one end of the cell, rather than placing them on opposite sides. This merging reduces device complexity and the number of components while maintaining the necessary optical functionality for atomic clock operation.
Solution Approach 2:
The patent introduces a reflective surface at the second end of the cell, creating a folded optical path. The laser beam travels through the cell, reflects off the surface, and passes through the cell again in the opposite direction to reach the photodetector. This dimensional change in the optical path allows integration at one end while maintaining proper operation.
2Ease of operation
If the VCSEL produces a diverging laser beam passing through the cell twice in opposite directions, then the photodetector can receive the beam, but the manufacturing precision and assembly difficulty increase
Solution Approach 1:
The reflective surface is positioned and oriented to automatically return the diverging laser beam to the photodetector after it passes through the cell. The system uses the natural divergence of the laser beam and the geometry of the reflective surface to achieve proper beam reception without requiring high-precision manual alignment during assembly.
3Volume of moving object
If compact atomic clock components are integrated, then the volume is reduced, but the assembly process becomes more complex and costly
Solution Approach 1:
The VCSEL and photodetector are merged into a single integrated assembly that can be positioned and connected to the cell in fewer steps, reducing assembly complexity and cost while achieving compact dimensions.
Solution Approach 2:
The folded optical path using the reflective surface allows the compact integration of components at one end of the cell while maintaining the necessary optical path length, achieving volume reduction without proportionally increasing assembly complexity.
4Ease of operation
If the reflectors are inclined relative to the window plane and laser beam axis, then the laser beam path is controlled and polarization is maintained, but the manufacturing precision requirements increase
Solution Approach 1:
The reflectors are designed with specific asymmetric inclinations relative to the window plane and laser beam axis. This asymmetric geometry is optimized to control the laser beam path and maintain polarization while being manufacturable with standard precision capabilities, avoiding excessive precision requirements.
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 improves compactness, frequency stability, and power efficiency of alkali-metal vapour cells, facilitating easier and more precise assembly suitable for industrial-scale production of compact atomic clocks.
Implementation Method 1
micro-optical means arranged in the optical cavity and comprising an upstream optical reflector and a downstream optical reflector for reflecting the laser beam, said reflectors being inclined relative to one another
Implementation Method 2
anodic bonding
Implementation Method 3
which overcomes the problem of the conflict between the anodic bonding and the chemistry of cesium
Data Source
AI summary
The invention relates to an alkali-metal vapor cell, especially for an atomic clock, and to its manufacturing process. The alkali-metal vapor cell is able to be associated with a laser for emitting an external input laser beam and a photodetector for receiving an external output laser beam, and comprises a housing having an upstream optical window and a downstream optical window and forming an optical cavity filled with an alkali-metal vapor such as a caesium-comprising vapor, and micro-optical means arranged in the optical cavity and comprising an upstream optical reflector and a downstream optical reflector for reflecting the laser beam, which reflectors are inclined relative to each other, the upstream reflector being inclined relative to the plane (P) of the upstream window and to the axis of the input laser beam so that the external input laser beam passes through the upstream window in order to form an internal input laser beam, the latter being reflected by the upstream reflector and deviated towards the downstream reflector so as to form an internal intermediate laser beam that is reflected on the downstream reflector and deviated towards the downstream window so as to form an internal output laser beam, the internal output laser beam passing through the downstream window in order to form the external output laser beam.