Terahertz Spectrometer Based on Femtosecond Laser for a Scientific Research

2014 ◽  
Vol 9 (2) ◽  
pp. 6-12
Author(s):  
Sergey Mikerin ◽  
Kristina Poteshkina ◽  
Aleksandr Plekhanov
Keyword(s):  
Complex Refractive Index ◽  
Sapphire Laser ◽  
External Control ◽  
Thz Radiation ◽  
Absolute Calibration ◽  
Electrical Field ◽  
Apparatus Function ◽  
Emission Efficiency ◽  
Experimental Stand ◽  
Optical Media

Terahertz (THz) spectrometer using femtosecond titanium-sapphire laser was developed. Experimental stand of the multi-purpose application was realized by using this spectrometer. It was realized to obtaining of the complex refractive index spectra of a large aperture samples and to research of the emission efficiency of THz radiation in a nonlinear optical media. It was proposed a method of spectrometer's absolute calibration by THz electrical field through an external control of polarization of the probe radiation. The threshold sensitivity to polarization changes was measured. It was 1.4 ± 0.5 μrad. It allows to estimate the threshold of THz field strength ~ 0.1 V/cm when zinc telluride crystal is used to detection. Width of the apparatus function of spectrometer was 9 GHz and it was estimated from the width of narrow lines of the water vapor in absorption spectrum of air gap. It well agrees with the theoretical estimation

scholarly journals Broadband spectroscopy of astrophysical ice analogues

2019 ◽  
Vol 629 ◽  
pp. A112 ◽  
Author(s):  
B. M. Giuliano ◽  
A. A. Gavdush ◽  
B. Müller ◽  
K. I. Zaytsev ◽  
T. Grassi ◽  
...  
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Time Domain ◽  
Complex Refractive Index ◽  
Far Infrared ◽  
Infrared Region ◽  
Thz Radiation ◽  
The Real ◽  
Thz Range ◽  
The Time Domain

Context. Reliable, directly measured optical properties of astrophysical ice analogues in the infrared and terahertz (THz) range are missing from the literature. These parameters are of great importance to model the dust continuum radiative transfer in dense and cold regions, where thick ice mantles are present, and are necessary for the interpretation of future observations planned in the far-infrared region. Aims. Coherent THz radiation allows for direct measurement of the complex dielectric function (refractive index) of astrophysically relevant ice species in the THz range. Methods. We recorded the time-domain waveforms and the frequency-domain spectra of reference samples of CO ice, deposited at a temperature of 28.5 K and annealed to 33 K at different thicknesses. We developed a new algorithm to reconstruct the real and imaginary parts of the refractive index from the time-domain THz data. Results. The complex refractive index in the wavelength range 1 mm–150 μm (0.3–2.0 THz) was determined for the studied ice samples, and this index was compared with available data found in the literature. Conclusions. The developed algorithm of reconstructing the real and imaginary parts of the refractive index from the time-domain THz data enables us, for the first time, to determine the optical properties of astrophysical ice analogues without using the Kramers–Kronig relations. The obtained data provide a benchmark to interpret the observational data from current ground-based facilities as well as future space telescope missions, and we used these data to estimate the opacities of the dust grains in presence of CO ice mantles.

scholarly journals Organic crystal-based THz source for complex refractive index measurements of window materials using single-shot THz spectroscopy

2021 ◽  
Vol 127 (11) ◽  
Author(s):  
Lufan Du ◽  
Franz Roeder ◽  
Yun Li ◽  
Mostafa Shalaby ◽  
Burgard Beleites ◽  
...  
Keyword(s):  
Refractive Index ◽  
Complex Refractive Index ◽  
Accurate Determination ◽  
Laser Pulses ◽  
Thz Spectroscopy ◽  
Thz Radiation ◽  
Single Shot ◽  
Detection Scheme ◽  
Electro Optic

AbstractWe employed N-benzyl-2-methyl-4-nitroaniline (BNA) crystals bonded on substrates of different thermal conductivity to generate THz radiation by pumping with 800 nm laser pulses. Crystals bonded on sapphire substrate provided four times more THz yield than glass substrate. A pyrodetector and a single-shot electro-optic (EO) diagnostic were employed for measuring the energy and temporal characterisation of the THz pulse. Systematic studies were carried out for the selection of a suitable EO crystal, which allowed accurate determination of the emitted THz spectrum from both substrates. Subsequently, the THz source and single-shot electro-optic detection scheme were employed to measure the complex refractive index of window materials in the THz range.

Interfacing of a TEM/STEM System to a Computer

1981 ◽  
Vol 39 ◽  
pp. 250-251
Author(s):  
P. Hagemann
Keyword(s):  
Image Analysis ◽  
Transmission Rate ◽  
Analytical Electron Microscopy ◽  
Signal Beam ◽  
Automated Image Analysis ◽  
Beam Deflection ◽  
External Control ◽  
Computer Input ◽  
Instrument Control ◽  
Data Acquisition And Processing

The use of computers in the analytical electron microscopy today shows three different trends (1) automated image analysis with dedicated computer systems, (2) instrument control by microprocessors and (3) data acquisition and processing e.g. X-ray or EEL Spectroscopy.While image analysis in the T.E.M. usually needs a television chain to get a sequential transmission suitable as computer input, the STEM system already has this necessary facility. For the EM400T-STEM system therefore an interface was developed, that allows external control of the beam deflection in TEM as well as the control of the STEM probe and video signal/beam brightness on the STEM screen.The interface sends and receives analogue signals so that the transmission rate is determined by the convertors in the actual computer periphery.

Principles of Low-Vacuum SEM

1992 ◽  
Vol 50 (2) ◽  
pp. 1304-1305
Author(s):  
Klaus-Ruediger Peters
Keyword(s):  
New Technologies ◽  
High Vacuum ◽  
Optical Microscope ◽  
Specimen Surface ◽  
Electrical Field ◽  
Gaseous Environment ◽  
New Information ◽  
Gas Molecules ◽  
New Interactions ◽  
Gas Pressures

Only recently it became possible to expand scanning electron microscopy to low vacuum and atmospheric pressure through the introduction of several new technologies. In principle, only the specimen is provided with a controlled gaseous environment while the optical microscope column is kept at high vacuum. In the specimen chamber, the gas can generate new interactions with i) the probe electrons, ii) the specimen surface, and iii) the specimen-specific signal electrons. The results of these interactions yield new information about specimen surfaces not accessible to conventional high vacuum SEM. Several microscope types are available differing from each other by the maximum available gas pressure and the types of signals which can be used for investigation of specimen properties.Electrical non-conductors can be easily imaged despite charge accumulations at and beneath their surface. At high gas pressures between 10-2 and 2 torr, gas molecules are ionized in the electrical field between the specimen surface and the surrounding microscope parts through signal electrons and, to a certain extent, probe electrons. The gas provides a stable ion flux for a surface charge equalization if sufficient gas ions are provided.

An ultrastructural analysis of the sympathetic innervation of the rabbit ear artery and middle cerebral artery and their branches

1992 ◽  
Vol 50 (1) ◽  
pp. 934-935
Author(s):  
John T. Dodge ◽  
John A. Bevan
Keyword(s):  
Middle Cerebral Artery ◽  
Cerebral Artery ◽  
Sympathetic Innervation ◽  
Electrical Field Stimulation ◽  
Rabbit Ear Artery ◽  
Electrical Field ◽  
Functional Differences ◽  
Ear Artery ◽  
Rabbit Ear ◽  
Vascular Beds

Unlike many peripheral vascular beds, the sympathetic nervous system exerts little control on cerebral blood flow. The contractile response of isolated rabbit middle cerebral artery (MCA) segments to electrical field stimulation of its intramural nerves is less than in a similar-sized artery from the ear. This study was undertaken to characterize and compare the perivascular neuromuscular relationships and innervation density of similar-sized arteries varying in diameter from these two different regional arterial beds to see if there were structural correlates for these functional differences.

Impact of the Locus of Causality and Internal Control on the Social Utility of Causal Explanations

2010 ◽  
Vol 69 (3) ◽  
pp. 173-179 ◽  
Author(s):  
Samantha Perrin ◽  
Benoît Testé
Keyword(s):  
Internal Control ◽  
Three Dimensions ◽  
Social Utility ◽  
External Control ◽  
Job Interview ◽  
Locus Of Causality ◽  
Causal Explanations ◽  
Professional Success ◽  
The Social ◽  
Different Types

Research into the norm of internality ( Beauvois & Dubois, 1988 ) has shown that the expression of internal causal explanations is socially valued in social judgment. However, the value attributed to different types of internal explanations (e.g., efforts vs. traits) is far from homogeneous. This study used the Weiner (1979 ) tridimensional model to clarify the factors explaining the social utility attached to internal versus external explanations. Three dimensions were manipulated: locus of causality, controllability, and stability. Participants (N = 180 students) read the explanations expressed by appliants during a job interview. They then described the applicants on the French version of the revised causal dimension scale and rated their future professional success. Results indicated that internal-controllable explanations were the most valued. In addition, perceived internal and external control of explanations were significant predictors of judgments.

How to Measure and Control Corruption

2007 ◽  
pp. 4-10 ◽  
Author(s):  
G. Satarov
Keyword(s):  
Social Knowledge ◽  
External Control ◽  
Main Method ◽  
Economic Transformations ◽  
Business Corruption ◽  
And Control

Two aspects of the problem of corruption are discussed in the article. The first one concerns the evaluation of the level of corruption. The method of measuring the size of business corruption market is described. The specifics of its estimation as well as its relation with the main macroeconomic indexes are discussed. The second aspect regards the strategies of corruption reduction. The importance of establishing external control over the bureaucracy is noted. The failure of institutions transplantation as the main method of economic transformations is pointed out. The gaps in social knowledge are discussed, which decrease effectiveness of institutional borrowings.

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