Terahertz Measurement Device Coaxial Detection

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Solution Overview

Problem

Current optical measurement devices cannot accurately separate the optical axes of terahertz waves and coaxial lights, such as mid-infrared light, for simultaneous detection, leading to increased device size even when using a small-sized terahertz wave light source.

Innovation Solution

An optical measurement device that outputs terahertz waves and coaxial lights with different wavelengths coaxially, performs intensity modulation of both waves at a predetermined frequency, and uses a single light detection unit to synchronously detect the waves based on the modulation frequency, allowing for separate detection without axis separation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If both a terahertz wave and coaxial light are used in measurement with separate detection, then measurement capability is improved, but device size increases due to lack of optical axis separation elements

Engineering Contradiction:

Improvemeasurement capabilityVSAvoiddevice size

Core Design Contradiction:

Adaptability or versatilityVSVolume of moving object

Solution Approach 1:

The patent merges the detection paths of terahertz waves and coaxial light into a single optical axis, allowing both wavelengths to be detected by a single detector without requiring separate optical paths or additional separation elements, thereby maintaining measurement capability while reducing device size

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent employs periodic intensity modulation of the terahertz wave at a specific frequency, enabling temporal separation of signals from different wavelengths through frequency-based detection, which allows simultaneous measurement capability without spatial separation of optical axes

Inventive Principle:

Principle #19Periodic action

2Measurement precision

If intensity modulation and synchronous detection are used, then detection accuracy is improved, but device complexity increases

Engineering Contradiction:

Improvedetection accuracyVSAvoiddevice complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent applies periodic intensity modulation to the terahertz wave at a defined frequency, which when combined with synchronous detection, enables accurate signal extraction from noise while using relatively simple modulation and detection circuitry

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent implements synchronous detection that uses the modulation frequency as a reference, creating a feedback mechanism that selectively amplifies signals at the modulation frequency while rejecting other frequencies, thereby improving detection accuracy without requiring complex filtering

Inventive Principle:

Principle #23Feedback

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

Enables the use of both terahertz waves and coaxial lights in measurements while preventing the device from increasing in size, with accurate synchronous wave-detection and reduced noise through phase-switching and lock-in detection techniques.

Implementation Method 1

This quantum cascade laser is configured to generate first pumping light of a first frequency and second pumping light of a second frequency via intersubband light emission transition of electrons

Methodology Applied

Scientific EffectIntersubband light emission transition:

Implementation Method 2

to output a terahertz wave by using a difference frequency generation between the first pumping light and the second pumping light

Methodology Applied

Scientific EffectDifference frequency generation:

Implementation Method 3

an intensity modulation unit configured to perform intensity modulation of at least the terahertz wave of the terahertz wave and the coaxial light in a predetermined modulation frequency

Methodology Applied

Scientific EffectIntensity modulation: Phase Modulation

Implementation Method 4

a light detection unit configured to synchronously detects each of the terahertz wave and the coaxial light which have acted on a measurement subject via the intensity modulation unit based on the modulation frequency

Methodology Applied

Scientific EffectSynchronous wave-detection:

Implementation Method 5

the terahertz wave and the coaxial light which have acted on a measurement subject are synchronously detected based on the modulation frequency

Methodology Applied

Scientific EffectLock-in detection:

Data Source

PatentUS10809189B2Optical measurement device and optical measurement method

Publication Date: 2020.10.20 HAMAMATSU PHOTONICS KK

AI summary

An optical measurement device includes a light source configured to output a terahertz wave and coaxial light having a wavelength different from the wavelength of the terahertz wave, coaxially with the terahertz wave; an intensity modulation unit configured to perform intensity modulation of at least the terahertz wave of the terahertz wave and the coaxial light in a predetermined modulation frequency; and a light detection unit configured to synchronously detects each of the terahertz wave and the coaxial light which have acted on a measurement subject via the intensity modulation unit based on the modulation frequency.