Micro Atomic Clock Laser Relocking Without AC Stark Shift
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Solution Overview
Problem
Miniature atomic clocks face challenges in reducing clock bias and drift due to AC Stark shifts caused by external laser light during spectroscopy, requiring high attenuation and rapid frequency stabilization, which existing technologies struggle to achieve with minimal size, power, and insertion loss.
Innovation Solution
The method involves turning off the laser during atomic clock spectroscopy, then relocking it to an external reference cell before probing, using a feed-forward signal to compensate for temperature-induced frequency shifts and employing an etalon for robust locking, thereby eliminating AC Stark shifts without increasing footprint or power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If laser light is used to cool and probe atoms in the atomic clock, then atom cooling and probing functions are achieved, but AC Stark shifts cause clock bias and drift
Solution Approach 1:
The patent implements periodic switching of the laser between on and off states. The laser is turned off during spectroscopy to eliminate AC Stark shifts, then turned on for atom cooling and probing. This periodic action resolves the contradiction by temporarily removing the harmful laser light during critical measurement phases while maintaining its useful functions during other phases.
Solution Approach 2:
The patent extracts the harmful component (laser light) from the system during spectroscopy by turning the laser off. This separation allows the spectroscopy to proceed without AC Stark shifts, while the laser can be reactivated for its cooling and probing functions when needed.
2Object-affected harmful factors
If mechanical shutters are used to attenuate laser light during spectroscopy, then AC Stark shifts are reduced, but device size and mechanical complexity increase
Solution Approach 1:
The patent replaces the mechanical shutter system with an electronic control mechanism that turns the laser off during spectroscopy. This substitution eliminates the need for mechanical moving parts, reducing device complexity and improving reliability while achieving the same goal of eliminating AC Stark shifts.
Solution Approach 2:
The patent replaces the mechanical shutter system with an electronic control mechanism that turns the laser off during spectroscopy. This substitution eliminates the need for mechanical moving parts, reducing device complexity and improving reliability while achieving the same goal of eliminating AC Stark shifts.
3Object-affected harmful factors
If acousto-optic beam shifters are used to attenuate laser light, then 80 dB attenuation is achieved, but device footprint and power consumption increase
Solution Approach 1:
The patent extracts the harmful laser light by turning the laser off completely during spectroscopy, eliminating the need for acousto-optic beam shifters. This approach achieves infinite attenuation (complete blockage) while consuming zero power during spectroscopy, resolving the contradiction between attenuation performance and power consumption.
4Object-affected harmful factors
If laser frequency is shifted by more than 10 GHz to reduce Stark shift, then AC Stark shifts are reduced, but laser re-acquisition becomes difficult
Solution Approach 1:
The patent uses periodic switching of the laser instead of continuous frequency shifting. The laser is turned off during spectroscopy and then turned back on at its original frequency for probing. This approach eliminates AC Stark shifts without the need for large frequency excursions, making re-acquisition trivial since the laser frequency never changes.
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 effectively reduces or eliminates clock bias and drift, achieving stable frequency lock within 1 ms with minimal size and power, while maintaining low insertion loss and robust frequency stabilization.
Implementation Method 1
laser cooled atoms that enable narrow clock linewidths in a small size. Atoms are pre-cooled for a background atomic vapor into a magneto-optical trap (MOT) or optical molasses.
Implementation Method 2
the dominant clock shift caused by atoms interacting with the near resonance light via the AC Stark shift
Implementation Method 3
employing an etalon for robust locking
Data Source
AI summary
A method for reducing or eliminating clock bias in an atomic clock is provided. The method comprises cooling a population of atoms collected in the atomic clock using a laser locked at a predetermined frequency, turning off the laser, performing atomic clock spectroscopy, turning on the laser after the atomic clock spectroscopy, and relocking the frequency of the laser to an external reference cell. The population of atoms that are in each of two ground hyperfine levels is then probed using laser light that is on or near-resonant with a selected atomic transition.