Atomic Oscillator Mode Filtering for Clean EIT Signals

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Solution Overview

Problem

Atomic oscillators using quantum interference effects face issues with higher drive voltage, lower resistance to electrostatic discharge, and shorter lifespan due to the use of single-mode surface-emitting lasers, which are not as effective as multimode lasers in terms of structure and performance.

Innovation Solution

Incorporating a mode filter between the coherent light source and the atom cell to cut higher-order mode lights, allowing only zero-order mode lights to pass through, thereby reducing noise and improving the signal-to-noise ratio of the EIT signal, and using a multimode surface-emitting laser that outputs multiple lights.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a single-mode surface-emitting laser is used as the light source, then the EIT signal can be obtained, but the drive voltage is higher, resistance to electrostatic discharge is lower, and life is shorter

Engineering Contradiction:

Improvelaser life and electrostatic discharge resistanceVSAvoidEIT signal quality

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent extracts only the necessary zero-order mode light from the multimode laser output by using a mode filter, eliminating the harmful higher-order mode lights. This allows the use of more reliable multimode lasers while maintaining the EIT signal quality that would otherwise require single-mode lasers.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The mode filter acts as an intermediary component between the multimode laser and the alkali metal gas cell. It selectively transmits the zero-order mode light while blocking higher-order mode lights, enabling the use of multimode lasers without degrading the EIT signal.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If higher-order mode lights are not filtered, then the device structure is simpler, but the S/N-ratio of the EIT signal degrades due to unnecessary higher-order mode lights entering the light receiving unit

Engineering Contradiction:

ImproveEIT signal S/N-ratioVSAvoidoptical path structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The mode filter extracts and removes the harmful higher-order mode lights from the optical path, keeping only the useful zero-order mode light. This simple extraction approach maintains high EIT signal S/N-ratio without requiring complex optical systems.

Inventive Principle:

Principle #2Taking out (Extraction)

3Use of energy by moving object

If a multimode surface-emitting laser is used, then drive voltage is lower, resistance to electrostatic discharge is higher, and life is longer, but higher-order mode lights degrade the EIT signal S/N-ratio

Engineering Contradiction:

Improvelaser drive voltageVSAvoidEIT signal S/N-ratio

Core Design Contradiction:

Use of energy by moving objectVSMeasurement precision

Solution Approach 1:

The mode filter takes out the harmful higher-order mode lights from the multimode laser output, allowing the system to utilize the energy-efficient multimode laser while maintaining the measurement precision required for high-quality EIT signals.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The mode filter changes the spatial mode distribution parameter of the light by selectively transmitting only the zero-order mode, thereby transforming the multimode light into an effective single-mode equivalent for the EIT measurement while retaining the benefits of multimode laser operation.

Inventive Principle:

Principle #35Parameter 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 configuration enables the use of multimode surface-emitting lasers with lower drive voltage, higher resistance to electrostatic discharge, and longer lifespan, while maintaining high accuracy and reliability for atomic oscillators.

Implementation Method 1

a mode filter that cuts the higher-order mode lights is placed between the coherent light source and the atom cell

Methodology Applied

Scientific EffectOptical mode filtering: Filter (optical)

Implementation Method 2

a system using a quantum interference effect (CPT: Coherent Population Trapping) by two kinds of lights having different wavelengths

Methodology Applied

Scientific EffectCoherent Population Trapping:

Implementation Method 3

an electromagnetically induced transparency (EIT) phenomenon that, when the frequency difference between two kinds of resonance lights takes a specific value, none of the two kinds of resonance lights are absorbed by the alkali metal within the gas cell, but transmitted occurs

Methodology Applied

Scientific EffectElectromagnetically induced transparency:

Implementation Method 4

a photodetector (light receiving unit) that detects the resonance light transmitted through the gas cell

Methodology Applied

Scientific EffectPhotoelectric detection: Photoelectric Effect

Data Source

PatentUS10348317B2Quantum interference device, atomic oscillator, electronic apparatus, and moving object

Publication Date: 2019.07.09 MICROCHIP TECHNOLOGY INC

AI summary

A quantum interference device (atomic oscillator) includes a light source unit as a coherent light source, a unit that superimposes microwave on the light source unit to generate a side band, an atom cell in which an alkali metal gas is enclosed, and a light receiving unit that detects light transmitted through the atom cell, wherein the light source unit is a surface-emitting laser that outputs a zero-order mode light and a plurality of higher-order mode lights, and a mode filter that cuts the higher-order mode lights is placed between the light source unit and the atom cell.