Thz technolgy

8/9/2019 Thz technolgy

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Terahertz Technology

S. Prashanth kumar (06A71A0452)

Electronics and CommunicationSwami Vivekananda Institute of Technology


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What is Terahertz Technology?What is Terahertz Technology?

It refers to the research and development ofdevices operating at Terahertz frequencies.


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What are TWhat are T--rays?rays?

THz range is roughly defined as frequency 0.1 10 THz

wavelength 0.03 3 mm

energy 0.4 40 meV


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Technical characteristicsTechnical characteristics

Penetrating ability: THz wave has ability topenetrate a wide verity of non conductingmaterials like paper, plastic, wood andceramics.

T rays penetrate everything except

Metals which reflect them

Water which absorb them

Non-ionizing property: Meaning that unlike X-rays they do not do damage to human tissuesor DNA.


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THz imaging and SensingTHz imaging and Sensing

y THz imaging can be explained using the concept of

2D spectroscopy.

y The principle is based on scanning the sample

through the focus of a THz time domainspectroscopy transmission.

y THz-TDS directly measures the temporal electric

field.


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THzTHz--TDSTDS


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y THz spectroscopy can be used to find the

spectral features of a wide range of

molecules, once these features are known it

is possible to use these features to identifymolecules remotely.

y Explosive detection system uses these

process, could be placed at airports to

detect explosives.


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THz SourcesTHz Sources Incoherent thermal sources

Broad-band pulsed sources

Photo switches

Optical rectification

Accelerators

Narrowband CW sources

Molecular lasers

RF up conversion, optical

down conversion

Semiconductor cascade lasers


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Potential ApplicationsPotential Applications

y Security and Defense applications

y Chemical Analysis

y

Communicationsy Space applications

yAtmospheric Sensing(environmental

studies)

y Medical Applications


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Defense and Security applicationsDefense and Security applications

y The amazing ability of THz to penetrate through

food, package materials allows nondestructive and

non-ionization inspection(without opening them) for

e.g.. Food mail packages in post office and

luggage at airport security check points to find outconcealed drugs or pathogenic agents like anthrax.

y Detection and identification of explosives.


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Hidden weapon detection with THz wavesHidden weapon detection with THz waves


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The machine creates a 3-d image of the passenger'sbody

then sends it to a viewing station in another room

where a

TSA agent looks for potential threats.

Passenger imaging technology, so it allows us to see

the entire image of the passenger's body and anything

that might be hidden on the person.

The new technology includes new privacy protectionalso.

The screener in the viewing room can't see the

passenger's

face and the images from the machine are deleted,


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Chemical analysisChemical analysis

y Inspection of chemical mixtures is done by THz

spectroscopic imaging using known spectral

data of the pure chemical components.

y

This method, which is based on the principlecomponent analysis, can determine the

existence of chemicals, identifies them and

map the spectral distribution of each

component and measure their content in a

target.

y By using this method , we can determine

qualitatively and quantitatively the components

not only pure chemical samples but also

mixtures.


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CommunicationsCommunications

Frequencies higher than microwave offer many

benefits for the communication technology.

Broad bandwidth for high data rate information

transmission.

Small antenna and equipment size.

The obvious disadvantage of communication at

THz arises from the strong absorption through

atmosphere caused by water vapor as well as thelow power available from existing sources.


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Long distance atmospheric transmission is very challenging

(but possible for ~100 m or so).

THz light is heavily absorbed by theTHz light is heavily absorbed by the

atmosphere, and especially by water.atmosphere, and especially by water.

Note that the vertical axis is a log of a log scale!

Atmospheric absorption spectrum


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Despite these disadvantages, many

communications are possible.Satellite-to-Satellite communication

Indoor wireless communications

Wireless covert communication


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From: http://www.jpl.nasa.gov/news/news.cfm?release=2004-291

Environmental control: Ozone Hole


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Medical applicationsMedical applications

y THz waves ( meV photon energy) are

non-ionizing and so much safer than

X-rays(keV photon energy).


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Detection of a tumor, an application ofDetection of a tumor, an application of

TeraviewTeraview research into distinguishing types ofresearch into distinguishing types of

tissuetissue


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50 mm

paraffin

metastasis

healthy tissue

Optical image of a liver

sample containing tumorsTHz image: 0.2 - 0.5 THz

THz imaging for tumor detection

Tumors appear to have different THzabsorption properties from normal tissue.


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THz SensorsTHz Sensors

y Sensors also play an important role in THz

technology however they are far more developed

than sources at this time and so will not be

discussed in depth.

y A photo mixer can also be used to detect THzwaves by mixing them with a beam of known

frequency, the differences can be detected and the

source beam decoded.

y

Currently there are near-quantum-limited detectorsthat can measure both broadband or extremely

narrowband signals up to or exceeding 1 THz.


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ConclusionConclusion

Terahertz Technology is already being

marketed, mainly for medical and military

applications, and continuing advancements

in the field will see many new applicationsbeing realized and many industries being

revolutionized (particularly in terms of non-

destructive testing).


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