Optical Materials for the THz Range

Rogalin, V. E.; Kaplunov, I. A.; Кропотов, Г. И.

doi:10.1134/s0030400x18120172

Cited by 86 publications

(34 citation statements)

References 25 publications

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“…Diamond, for instance, meets this criterion. There is also an option of selecting cheaper polymer materials [30] having a transmission of nearly 100% in various parts of the farinfrared region. Solving this purely technical problem will allow emission spectroscopy to access the far-infrared and terahertz regions, the characteristic frequencies and energies of which contain information about intermolecular structure and dynamics [31,32].…”

Section: Resultsmentioning

confidence: 99%

Measurement of the Emission Spectra of Protein Solutions in the Infrared Range. Description of the Method and Testing Using Solution of Human Interferon Gamma as an Example

Penkov

Pen’kova

2020

Front. Phys.

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This paper describes a new method for measuring the spectra of infrared radiation emitted by protein solutions in the native state without any external excitation. Radiation is detected using a vacuum Fourier-transform infrared spectrometer, and the tested sample itself is a source of radiation. The necessary conditions for detecting radiation from a sample are the use of a highly sensitive cooled detector and the presence of a cold background. In this work, the background was a black body at the boiling point of nitrogen. It is also important to select the optimal vacuum pumping depth for the spectrometer and sample thickness. Radiation occurs due to spontaneous radiative transitions from excited vibrational energy states to the ground state of molecules. The intensity of radiation is determined by the population of the respective energy states, which, according to the Boltzmann distribution, depends on temperature and frequency. Using solution of human interferon gamma as an example, it has been shown for the first time that proteins have intrinsic radiation. The described method allows detecting spectral lines with a radiation power of about 10−8 W or even less. It has also been demonstrated that emission spectroscopy offers advantages in the signal-to-noize ratio compared to absorption spectroscopy and allows analyzing the structural characteristics of a protein, in particular, providing information about its secondary structure. Another significant advantage of the method described in the article is its noninvasiveness. At the sample temperature of 25°С, emission spectra can be detected in the range from 400 to 3,600 cm−1, which covers almost the entire frequency range of existing stretching and bending vibrations of molecules. At the same time, in the fingerprint region from 500 to 1,600 cm−1 (the most informative part of the infrared spectrum), the highest sensitivity of the method is demonstrated. There is also potential for extending the available frequency range into the far infrared and terahertz ranges. Being applicable to the study of protein solutions in low concentrations, the proposed approach is not only interesting from the point of view of fundamental science but also can have applied significance in biological and medical research.

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Section: Resultsmentioning

confidence: 99%

Measurement of the Emission Spectra of Protein Solutions in the Infrared Range. Description of the Method and Testing Using Solution of Human Interferon Gamma as an Example

Penkov

Pen’kova

2020

Front. Phys.

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“…Materials constituting the unit cell can be assumed lossless and the dispersion can be neglected in the considered frequency band, so the refractive indexes are n H = 2.25 (SiO 2 ) 25 and n L = 1.46 (TPX) 26 . All SiO 2 and TPX layers have the same optical thickness, that is, a quarter of the (vacuum) wavelength λ 0 = 59.96 μm, corresponding to the frequency f 0 = 5 THz, viz,

n_{H} d_{H} = n_{L} d_{L} = δ = \frac{λ_{0}}{4} .

…”

Section: Methodsmentioning

confidence: 99%

“…Other materials with features suitable for applications of multilayers include some polymers that show excellent transparency at terahertz. In particular, polymethylpentene (TPX, more precisely, poly‐4‐methylpentene‐1) is a semicrystalline polymer with negligible absorptance and with a refractive index which is practically constant in the range [3, 7] THz 26 . In addition, the TPX refractive index is particularly low (≈1.5), making it suitable for use in multilayers as the low refraction index medium.…”

Section: Introductionmentioning

confidence: 99%

“…In particular, polymethylpentene (TPX, more precisely, poly-4methylpentene-1) is a semicrystalline polymer with negligible absorptance and with a refractive index which is Abbreviations: InSb, indium antimonide; SiO 2 , silica; TPX, polymethylpentene practically constant in the range [3,7] THz. 26 In addition, the TPX refractive index is particularly low (≈1.5), making it suitable for use in multilayers as the low refraction index medium. Moreover, the material can be deposited on SiO 2 to make multilayers.…”

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confidence: 99%

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Temperature‐mediated excitation of defect modes in a periodic structure at terahertz frequencies

Simone

Chiadini

Scaglione

et al. 2020

Micro & Optical Tech Letters

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The dependence on temperature of a defect mode of a periodic dielectric multilayer is studied in the terahertz range by using the characteristic matrix method. The structure analyzed is composed of alternating layers of silica and polymethylpentene. The material of the defect is the indium antimonide (InSb), which has a permittivity that is temperature dependent causing a blueshift of the defect mode as the temperature rises. Although at terahertz frequencies, the InSb is a dissipative material, choosing appropriately the thickness of the defect results in a defect mode with a transmittance that, throughout the range explored, always remains above 0.9 with a maximum of 0.9914.

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“…It was shown that the film thickness limits the mobility of electrons. THz emission interacts better with the p-type materials [9], i.e., with the materials with positive Seebeck and Hall coefficients.…”

Section: Introductionmentioning

confidence: 99%

Effect of Antimony Buffer Layer on the Electric and Magnetic Properties of 200 and 600 nm Thick Bismuth Films on Mica Substrate

et al. 2020

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We report on the production of 200 and 600 nm thick Bi films on mica substrate with 10 nm thick Sb sublayer between Bi and mica. Two types of films have been studied: block and single crystal. Films were obtained using the thermal evaporation technique using continuous and discrete spraying. Discrete spraying allows smaller film blocks size: 2–6 μ m compared to 10–30 μ m, obtained by the continuous spraying. Single crystal films were made by the zone recrystallization method. Microscopic examination of Bi films with and without Sb sublayer did not reveal an essential distinction in crystal structure. A galvanomagnetic study shows that Sb sublayer results in the change of Bi films properties. Sb sublayer results in the increase of specific resistivity of block films and has no significant impact on single crystal films. For single-crystal films with Sb sublayer with a thickness of 200 nm the Hall coefficient has value 1.5 times higher than for the 600 nm thickness films at 77 K. The change of the Hall coefficient points to change of the contribution of carriers in the conductivity. This fact indicates a change in the energy band structure of the thin Bi film. The most significant impact of the Sb sublayer is on the magnetoresistance of single-crystal films at low temperatures. The increase of magnetoresistance points to the increase of mobility of the charge carriers. In case of detecting and sensing applications the increased carriers mobility can result in a faster device response time.

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Optical Materials for the THz Range

Cited by 86 publications

References 25 publications

Measurement of the Emission Spectra of Protein Solutions in the Infrared Range. Description of the Method and Testing Using Solution of Human Interferon Gamma as an Example

Measurement of the Emission Spectra of Protein Solutions in the Infrared Range. Description of the Method and Testing Using Solution of Human Interferon Gamma as an Example

Temperature‐mediated excitation of defect modes in a periodic structure at terahertz frequencies

Effect of Antimony Buffer Layer on the Electric and Magnetic Properties of 200 and 600 nm Thick Bismuth Films on Mica Substrate

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