Possibility of the detection and identification of substance at long distance at using broad THz pulse

Terahertz Physics, Devices, and Systems IX: Advanced Applications in Industry and Defense

2015

Self Cite

We show possibility of the detection and identification of substance at long distance (several metres, for example) using the THz pulse reflected from the object under the real conditions: at room temperature and humidity of about 70%. The main feature of this report consists in a demonstration of the detection and identification of substance using the computer processing of the noisy THz pulse. Amplitude of the useful signal is less than the amplitude of a noise. Nevertheless, it is possible to detect "fingerprint" frequencies of substance if these frequencies are known and the SDA method is used together with new assessments for probability estimation for presence of detected frequencies. Essential restrictions of the commonly used THz TDS method for the detection and identification under real conditions (at long distance about 3.5 m and at a high relative humidity more than 50%) are demonstrated using the physical experiment with chocolate bar and thick paper bag. We show also that the THz TDS method detects spectral features of dangerous substances even in the THz signals measured in laboratory conditions (at distance 30-40 cm from the receiver and at a low relative humidity less than 2%); the n-Si and p-Si semiconductors were used as neutral substances. However, the integral correlation and likeness criteria, based on SDA method, allow us to detect the absence of dangerous substances in the samples. Current results show feasibility of using the discussed method of the THz pulsed spectroscopy for the counter-terrorism problem.

Section: Let ( )mentioning

confidence: 99%

Section: Spectral Properties Of Thick Bag and Chocolate Signals In Rementioning

confidence: 99%

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Possibility of the detection and identification of substance at long distance using the noisy reflected THz pulse under real conditions

Terahertz Physics, Devices, and Systems IX: Advanced Applications in Industry and Defense

2015

Self Cite

“…In our physical experiments, we exploit a THz spectrometer EKSPLA developed by Teravil Inc., Lithuania [32]. It uses a femtosecond fiber laser, which generates laser pulse with average power about 1 W, with 1030 nm centre wavelength, 75 MHz repetition rate, and its pulse duration is 80 fs.…”

Section: The Setupmentioning

confidence: 99%

“…Therefore, using of these spectral characteristics of the pulse (Fourier spectrum and absorbance) is equivalent for the detection problem. The Chocolate signal spectrum corresponding to the time interval t = [0, 110] ps is depicted in [32].…”

Section: Spectral Properties Of Chocolatementioning

confidence: 99%

False detection of dangerous and neutral substances in commonly used materials by means of the standard THz Time Domain Spectroscopy

J. Eur. Opt. Soc.-Rapid Publ.

2016

Essential limitations of the standard THz Time Domain Spectroscopy (TDS), which lead to false detection of dangerous and neutral substances in commonly used materials, are demonstrated using the physical experiment with chocolate under real conditions as well as with semiconductors under laboratory conditions. To overcome this disadvantage, we propose using the time-dependent spectrum of the THz pulse, transmitted through or reflected from a substance. For quality assessment of the standard substance absorption frequency presence in the signal under analysis, we use time-dependent integral correlation criteria. The influence of aperture placed in front of the sample on spectral properties of silicon wafers with different resistivity is demonstrated as well.

An Effective Method for Substance Detection Using the Broad Spectrum THz Signal: A "Terahertz Nose"

2015

Sensors

We propose an effective method for the detection and identification of dangerous substances by using the broadband THz pulse. This pulse excites, for example, many vibrational or rotational energy levels of molecules simultaneously. By analyzing the time-dependent spectrum of the THz pulse transmitted through or reflected from a substance, we follow the average response spectrum dynamics. Comparing the absorption and emission spectrum dynamics of a substance under analysis with the corresponding data for a standard substance, one can detect and identify the substance under real conditions taking into account the influence of packing material, water vapor and substance surface. For quality assessment of the standard substance detection in the signal under analysis, we propose time-dependent integral correlation criteria. Restrictions of usually used detection and identification methods, based on a comparison between the absorption frequencies of a substance under analysis and a standard substance, are demonstrated using a physical experiment with paper napkins.