The optical constants of some common low-loss polymers between 4 and 40 cm−1

Birch, J.R.; Dromey, J. D.; Lesurf, J. C. G.

doi:10.1016/0020-0891(81)90053-1

Cited by 112 publications

(41 citation statements)

References 14 publications

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“…From the data / f = 7.618 degrees/GHz, yielding a measured dielectric constant of 2.063. This is within 1% of the highly accurate measurements of [54]. The stability and dynamic range of the system is shown by the plot in Fig.…”

supporting

confidence: 64%

Terahertz Heterodyne Imaging Part II: Instruments

Siegel

Dengler

2007

Int J Infrared Milli Waves

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supporting

confidence: 64%

Terahertz Heterodyne Imaging Part II: Instruments

Siegel

Dengler

2007

Int J Infrared Milli Waves

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“…Figure 10 shows the index of refraction and the absorption coefficient of polyethylene. In contrast with the value found by Birch et al, 13 the measured index of refraction varies over the frequency range, rather than being fixed at 1.51. In addition, the absorption coefficient grows rapidly in the frequency range from 0.5 to 1.0 THz.…”

Section: Polyethylene Coatingcontrasting

confidence: 64%

“…non-absorption implies non-dispersion. 13 Some of the common transparent materials usually found in T-ray components are discussed below. Optical constants of these and other low-loss materials for T-ray frequencies were intensively reviewed in Lamb 14 and Simonis 15 and references therein.…”

Section: Transparent Materials For Antireflection Windowsmentioning

confidence: 99%

Retrofittable T-ray antireflection coatings

et al. 2006

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Terahertz time-domain spectroscopy (THz-TDS) is able to extract optical or dielectric properties of materials, whether in the solid, liquid, or gas phase, in the T-ray frequency region. Spectroscopy of a liquid or gas often requires a receptacle to confine the sample. In order to allow T-rays to probe the sample effectively, the receptacle must have T-ray transparent windows. However, even though windows are transparent to T-rays, attenuation exists, because of multiple reflections at air-window and window-air interfaces, which accounts for a major energy loss. Due to the recent emergence of T-ray technology, there has been very little work carried out to-date on the reduction of reflection losses. This paper analyses the reduction of T-ray reflection loss by means of an antireflection coating. Because T-ray wavelengths are much larger than visible wavelengths, the antireflection layer thickness for T-rays is much larger than the usual optical case. This creates an interesting opportunity for retrofittable antireflection layers in T-ray systems. In the experiment, a coating material made from polyethylene sheets is applied onto the surfaces of a silicon window. The coated window shows enhancement of the transmittance within a range of frequencies.

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“…Moreover, the refractive index of n= 1.53 [11] is almost constant over a very wide range of frequencies and, thus, the influence of dispersion is very small. Furthermore, such composites are used in manufacturing bulletproof jackets, helmets, and ballistic shields because of their high mechanical resistance.…”

Section: Introductionmentioning

confidence: 99%

Precise Determination of Thicknesses of Multilayer Polyethylene Composite Materials by Terahertz Time-Domain Spectroscopy

Pałka

Krimi

Ospald

et al. 2015

J Infrared Milli Terahz Waves

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The multilayer structure of an ultra-high molecular weight polyethylene (UHMWPE) composite material was investigated in the terahertz (THz) spectral range by means of time-domain spectroscopy (TDS) technique. Such structures consist of many alternating layers of fibers, each being perpendicular to the other and each having a thickness of about 50 μm. Refractive indices of two composite samples and of a sample composed of four single layers (plies) having the same fiber orientation were determined for two orthogonal orientations of the electric field in a transmission TDS system. The birefringence of a single layer was measured, and the origin of this phenomenon is discussed. Using the TDS system in reflection, the formation of many pulses shifted in time was observed originating from reflections from interfaces of successive layers caused by the periodic modulation of the refractive index along the propagation of the THz radiation. This phenomenon is theoretically described and simulated by means of a transfer matrix method (TMM). A time-domain fitting procedure was used to determine thicknesses of all layers of the composite material. The reconstructed waveform based on the optimized thicknesses shows very good agreement with the measured waveform, with typical differences between measurements and simulations J Infrared Milli Terahz Waves (2015) between 3 and 7 μm (depending on the sample). As a result, we were able to determine the thicknesses of all layers of two multilayer (~200 plies) structures by means of the reflection TDS technology with high accuracy.

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The optical constants of some common low-loss polymers between 4 and 40 cm−1

Cited by 112 publications

References 14 publications

Terahertz Heterodyne Imaging Part II: Instruments

Terahertz Heterodyne Imaging Part II: Instruments

Retrofittable T-ray antireflection coatings

Precise Determination of Thicknesses of Multilayer Polyethylene Composite Materials by Terahertz Time-Domain Spectroscopy

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