Fiber-Based Thermal Property Probe Offset Configuration

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Solution Overview

Problem

Concentric fiber-based modulated optical reflectance (MOR) systems limit applications due to the inability to achieve an offset distance between the pump and probe beams, restricting the measurement of thermal diffusivity in bulk materials with reflective coatings.

Innovation Solution

A new fiber-based thermal properties probe configuration maintains the pump and probe lasers in close proximity at a fixed separation distance, allowing for the measurement of thermal diffusivity by detecting the phase of temperature changes at a known distance from the pump beam for a range of modulation frequencies.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If concentric fiber-based MOR systems are used, then the pump and probe beams are transmitted through a single fiber, but the offset distance between pump and probe beams cannot be achieved, limiting applications

Engineering Contradiction:

Improvefiber-based transmissionVSAvoidmeasurement capability

Core Design Contradiction:

Ease of operationVSAdaptability or versatility

Solution Approach 1:

The single fiber is divided into two separate fibers: a pump fiber for delivering the pump beam and a probe fiber for transmitting the probe beam. This segmentation allows the beams to be transmitted through separate pathways while maintaining close proximity at the sample, enabling offset configuration and broader measurement applications.

Inventive Principle:

Principle #1Segmentation

2Measurement precision

If the probe beam is positioned close to the pump beam, then the measurement of thermal diffusivity is enabled, but heat transfer through the fiber optic ferrule causes measurement errors

Engineering Contradiction:

Improvethermal diffusivity measurementVSAvoidheat transfer through ferrule

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The harmful heat transfer pathway through the ferrule is extracted and eliminated by positioning the probe fiber at a sufficient offset distance from the pump fiber. This separation removes the ferrule from the direct heat transfer path, preventing the harmful thermal conduction that caused measurement errors while maintaining the close proximity needed for effective thermal wave detection.

Inventive Principle:

Principle #2Taking out (Extraction)

3Measurement precision

If the probe beam is positioned away from the sample, then measurement errors are reduced, but the thermal wave detection sensitivity decreases

Engineering Contradiction:

Improveerror reductionVSAvoiddetection sensitivity

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The system dynamically adjusts the offset distance between the pump and probe fibers based on the specific measurement requirements. By varying this separation distance, the system can optimize the balance between minimizing ferrule heat transfer errors and maintaining sufficient thermal wave detection sensitivity for different sample types and measurement conditions.

Inventive Principle:

Principle #15Dynamics

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 accurate in-situ measurements of thermal diffusivity with improved precision, as demonstrated by measurements of Ge, SiC, and SiO2, with errors reduced to less than 2% when the probe is positioned away from the sample, addressing previous errors related to heat transfer through the fiber optic ferrule.

Implementation Method 1

One laser is used to produce a transient thermal response in the sample (pump)... The periodic heating of the pump beam induces a periodic thermal response in the sample which is often referred to as thermal waves

Methodology Applied

Scientific EffectOptical absorption: Absorption (EM radiation)

Implementation Method 2

The periodic heating of the pump beam induces a periodic thermal response in the sample... thermal wave propagation

Methodology Applied

Scientific EffectHeat conduction: Conduction (thermal)

Implementation Method 3

the change in optical reflectivity due to the change in surface temperature... the amplitude and phase of the probe beam, relative to the pump beam, is the measured quantity

Methodology Applied

Scientific EffectThermal wave detection through optical reflectance: Reflection

Implementation Method 4

A modulated optical reflectance (MOR) technique was first developed by Rosencwaig in 1985 when it was found that thermal waves could be detected using the change in optical reflectivity

Methodology Applied

Scientific EffectModulated optical reflectance:

Data Source

PatentUS10718673B2Thermal property probe

Publication Date: 2020.07.21 UTAH STATE UNIVERSITY

AI summary

A fiber-based thermal property probe is disclosed. In embodiments, the thermal property probe is a modulated optical reflectance system and includes a pump beam source configured to transmit a pump beam through a pump fiber, the pump beam configured to heat a sample and the pump fiber having a pump fiber sample end. The fiber-based thermal property probe further includes a probe beam source configured to transmit a probe beam through a probe fiber, the probe beam configured to measure the temperature of the sample and the probe fiber having a probe fiber sample end. Additionally, the system includes a ferrule configured to hold the pump fiber sample end and the probe fiber sample end at a fixed, known separation distance from each other.