Atomic Interferometric Accelerometer Vibrational Stability
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Solution Overview
Problem
Miniature atomic interferometric accelerometers face challenges in achieving vibrational stability and reducing size, weight, and cost due to the complexity of generating counter-propagating lightwaves, while existing techniques to break symmetry between lightwaves are difficult to implement in small systems.
Innovation Solution
A pulsed laser system with an electro-optic modulator and a piezo mirror structure that imparts a Doppler shift to retro-reflected lightwaves, creating non-symmetric counter-propagating pairs where one pair supports interferometry and the other is non-resonant, using a sawtooth waveform to drive the piezo mirror with constant velocity during each laser pulse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If velocity is imparted to atom waves prior to initiating the interferometer cycle to break symmetry between lightwaves, then only one pair of laser beams can be selected to avoid competition, but the technique is difficult to implement in small or miniature systems due to requiring additional lasers and reducing interrogation time
Solution Approach 1:
The patent changes the parameter being modulated from atom velocity to mirror position. By driving the retro-reflecting mirror with a sawtooth waveform at constant velocity during the laser pulse, the system imparts a Doppler shift to the retro-reflected lightwaves, breaking the symmetry between counter-propagating beams without requiring additional lasers or reducing interrogation time. This parameter substitution resolves the contradiction between achieving beam pair selection and maintaining system simplicity.
2Measurement precision
If a large lab-scale system with mirrors and opposing windows is used to direct lightwaves, then interferometry can be performed, but the beam-path adds significant size, weight, and cost as well as increasing sensitivity to vibrations
Solution Approach 1:
The patent merges the functions of multiple optical components into a single retro-reflecting mirror inside the vacuum chamber. Instead of using separate mirrors and opposing windows to direct lightwaves through a long beam-path, the system uses one mirror to retro-reflect both counter-propagating beams back through the same path, eliminating the need for additional optical components and reducing vibration sensitivity.
Solution Approach 2:
The patent inverts the conventional approach by having lightwaves retro-reflect off a mirror and return through the same path, rather than passing through opposing windows in a large chamber. This inversion of the beam-path geometry reduces the physical size of the system and minimizes exposure to external vibrations.
3Measurement precision
If two counter-propagating lightwaves with differing frequency are used to divide and recombine atomic waves, then phase shifts due to inertial forces can be read out, but competing interferometers are formed by two sets of counter-propagating lightwaves requiring selection of only one beam pair
Solution Approach 1:
The patent introduces asymmetry into the otherwise symmetric counter-propagating beam configuration by driving the retro-reflecting mirror with a sawtooth waveform. This creates a Doppler shift that breaks the symmetry between left-going and right-going lightwaves, allowing the system to maintain both beams while selectively enabling interferometry with only one beam pair, thus avoiding competition between competing interferometers.
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 results in a smaller, vibration-insensitive, and cost-effective design with improved robustness and performance by selectively tuning laser frequencies to avoid interference between lightwave pairs, enhancing the accuracy of the accelerometer.
Implementation Method 1
The piezo mirror structure is driven with substantially constant velocity during each individual laser beam pulse, thereby imparting a Doppler shift to the retro-reflected first and second optical signals
Implementation Method 2
an electro-optic modulator in optical communication with the laser device and configured to receive the pulsed laser beam at the first frequency, the electro-optic modulator configured to output a first optical signal corresponding to the pulsed laser beam at the first frequency and a second optical signal having a second frequency different from the first frequency
Implementation Method 3
a piezo mirror structure in optical communication with the vacuum cell and configured to retro-reflect the first and second optical signals back through the laser cooled atoms in a counter-propagating direction
Data Source
AI summary
An atomic interferometric accelerometer comprises a laser that emits a pulsed beam at a first frequency, an electro-optic modulator that receives the beam, and a vacuum cell in communication with the electro-optic modulator. The electro-optic modulator outputs a first optical signal corresponding to the beam at the first frequency and a second optical signal having a second frequency different from the first frequency. The vacuum cell has a chamber for laser cooled atoms. The vacuum cell receives the optical signals such that they propagate in a direction that passes through the atoms. A piezo mirror retro-reflects the optical signals back through the vacuum cell in a counter-propagating direction. The piezo mirror is driven with substantially constant velocity during a beam pulse, thereby imparting a Doppler shift to the retro-reflected optical signals to create two non-symmetric counter-propagating lightwave pairs. One of the lightwave pairs supports interferometry while the other is non-resonant.