Atomic Sensor System Wavelength Modulation

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Solution Overview

Problem

Current atomic sensor systems face challenges in accurately measuring rotation about a sensitive axis and the magnitude of external magnetic fields due to limitations in the modulation of optical beams and the separation of signal changes from environmental parameter changes.

Innovation Solution

The system employs a vertical-cavity surface-emitting laser to generate an optical beam that is modulated between on-resonance and off-resonance wavelengths to spin-polarize alkali metal in a vapor cell, using a quarter-wave plate and linear polarizer to facilitate Faraday rotation measurement, while polarization-insensitive photodetectors stabilize parameters like temperature and frequency to distinguish signal changes from environmental influences.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If optical beam modulation is used to measure rotation and magnetic field, then measurement capability is improved, but ability to separate signal changes from environmental parameter changes deteriorates

Engineering Contradiction:
Improvemeasurement capabilityVSAvoidsignal separation capability
Core Design Contradiction:
Measurement precisionVSLoss of information

Solution Approach 1:

The patent divides the optical beam modulation into separate functional segments: one segment measures rotation about the sensitive axis, another segment measures rotation about an axis perpendicular to the sensitive axis, and a third segment measures the magnitude of the magnetic field. By segmenting the measurement functions and using distinct modulation schemes for each, the system can separate signal changes from environmental parameter changes, resolving the contradiction between measurement capability and signal separation capability.

Inventive Principle:
Principle #1Segmentation

2Adaptability or versatility

If multiple measurement functions are integrated into a single atomic sensor system, then versatility is improved, but device complexity increases

Engineering Contradiction:
Improvemeasurement functionsVSAvoidsystem complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent implements a universal atomic sensor system that can perform multiple measurement functions using a single vapor cell and optical system. The system measures rotation about the sensitive axis, rotation about an axis perpendicular to the sensitive axis, and magnitude of the magnetic field through different modulation sequences of the same optical beam. This multi-functionality approach increases versatility while avoiding the complexity of separate sensor systems for each measurement type.

Inventive Principle:
Principle #6Universality (Multi-functionality)

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 enables precise measurement of rotation and magnetic field magnitude by effectively separating signal changes from environmental parameter changes, improving accuracy and stability in atomic sensor systems.

Implementation Method 1

an optical beam that is modulated between on-resonance and off-resonance wavelengths to spin-polarize alkali metal in a vapor cell

Methodology Applied
Scientific EffectSpin polarization:

Implementation Method 2

using a quarter-wave plate and linear polarizer to facilitate Faraday rotation measurement

Methodology Applied
Scientific EffectFaraday rotation: Faraday Effect

Implementation Method 3

polarization-insensitive photodetectors stabilize parameters like temperature and frequency to distinguish signal changes from environmental influences

Methodology Applied
Scientific EffectPolarization detection: Polarisation

Data Source

PatentEP2944971B1Atomic sensor system
Publication Date: 2020.07.22 NORTHROP GRUMMAN SYSTEMS CORP
  • EP2944971B1 patent drawingFigure 1~2
  • EP2944971B1 patent drawingFigure 3~4
  • EP2944971B1 patent drawingFigure 5

AI summary

One embodiment includes an atomic sensor system (10). The system includes a vapor cell (56) that is sealed to enclose an alkali metal that is spin-polarized by an optical beam. The vapor cell includes a mirror at a distal end. The system also includes an optical system including a photodetector system and a laser that generates the optical beam (54). The optical beam is provided into a proximal end of the vapor cell and is reflected back to the photodetector system via the mirror (60) as a reflected optical beam to generate at least one intensity signal. The optical system further includes a control system (24) that modulates a wavelength of the optical beam between an on-resonance wavelength and an off-resonance wavelength with respect to the alkali metal. The system also includes a processor (26) that calculates a measurable parameter associated with the atomic sensor system based on the at least one intensity signal.