scholarly journals Polarization-Sensitive Electro-Optic Sampling of Elliptically-Polarized Terahertz Pulses: Theoretical Description and Experimental Demonstration

Particles ◽  
2019 ◽  
Vol 2 (1) ◽  
pp. 70-89 ◽  
Author(s):  
Kenichi Oguchi ◽  
Makoto Okano ◽  
Shinichi Watanabe
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Probe Pulse ◽  
Polarization State ◽  
Frequency Component ◽  
Phase Mismatch ◽  
Pockels Effect ◽  
Electro Optic ◽  
Domain Description ◽  
Elliptically Polarized

We review our recent works on polarization-sensitive electro-optic (PS-EO) sampling, which is a method that allows us to measure elliptically-polarized terahertz time-domain waveforms without using wire-grid polarizers. Because of the phase mismatch between the employed probe pulse and the elliptically-polarized terahertz pulse that is to be analyzed, the probe pulse senses different terahertz electric-field (E-field) vectors during the propagation inside the EO crystal. To interpret the complex condition inside the EO crystal, we expressed the expected EO signal by “frequency-domain description” instead of relying on the conventional Pockels effect description. Using this approach, we derived two important conclusions: (i) the polarization state of each frequency component can be accurately measured, irrespective of the choice of the EO crystal because the relative amplitude and phase of the E-field of two mutually orthogonal directions are not affected by the phase mismatch; and, (ii) the time-domain waveform of the elliptically-polarized E-field vector can be retrieved by considering the phase mismatch, absorption, and the effect of the probe pulse width. We experimentally confirm the above two conclusions by using different EO crystals that are used for detection. This clarifies the validity of our theoretical analysis based on the frequency-domain description and the usefulness of PS-EO sampling.

Estimation of Eccentric Distance for Four-Tooth End Mills Based on Amplitude Spectrum

2013 ◽  
Vol 278-280 ◽  
pp. 207-211
Author(s):  
Can Liu ◽  
Jing Quan Wu ◽  
Guang Hui Li ◽  
Guang Yu Tan
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Mathematical Reasoning ◽  
Spectral Characteristics ◽  
Amplitude Spectrum ◽  
Frequency Component ◽  
Milling Force ◽  
End Mills ◽  
Domain Description ◽  
Eccentric Distance

Time-domain expressions of nominal component and eccentric component that composing horizontal peripheral milling force are derived from geometry of down milling, they are periodic functions with fundamental frequencies same as tooth-frequency and spindle-frequency respectively. By expanding these two time-domain expressions with Taylor series, the frequency-domain description of periheral milling force is obtained. Further mathematical reasoning is exerted on this frequency-domain description, and it proved that as for four-tooth end mills, even-order harmonics of eccentric milling force do not exist, and the amplitude of spindle-frequency component be linear with eccentric distance, but irrelevant with eccentric angle. Above research results imply that the tooth-frequency component of four-tooth end mills is irrelevant with eccentricity, and that eccentric distance can be estimated with amplitudes of tooth-frequency and spindle-frequency components. Results of milling experiment imply that this eccentric-distance estimating method be effective. Spectral characteristics of eccentric milling force for four-tooth end mills are revealed with theory deduction, and the estimation algorithm for eccentric distance with simple calculation is present. Study conclusions can be used in eccentric-geometry estimating and in milling-force modeling.

Study on Polarization Distribution of Polarization Encoder in Oblique Incidence

2011 ◽  
Vol 201-203 ◽  
pp. 1590-1595
Author(s):  
Mu Zhun Zhou ◽  
Yan Ru Chen ◽  
Qi Zhao ◽  
Yu Xin
Keyword(s):  
Theoretical Calculations ◽  
Incident Light ◽  
Polarization State ◽  
Polarized Light ◽  
Linbo3 Crystal ◽  
Polarization Distribution ◽  
Electro Optic ◽  
Measurement Results ◽  
Polarization Encoding ◽  
Elliptically Polarized

Principle of polarization encoding based on electro-optic effect of LiNbO3 crystal is analyzed, effact on polarization encoding optical field effects is studied when the incident light direction changes. Theoretical calculations show that, with the angle between the direction of incident laser beam and the main axis of LiNbO3 crystal increases, rotation angle of polarization ellipse remain unchanged,but ellipticity changes at any other position except in the center of the encoder,at the top and bottom of encoder,polarization state changes from circularly polarized to elliptically polarized,at other position of the encoder, polarization states are still elliptically polarized light but with different ellipticity angle. Experiment measurement results are in accord with ones of the calculation.

Time domain frequency stability calculated from the frequency domain description :

1991 ◽  
Author(s):  
F L Walls ◽  
John Gary ◽  
Abbie O'Gallagher ◽  
Roland Sweet ◽  
Linda Sweet
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Frequency Stability ◽  
Domain Description

scholarly journals Короткие импульсы нормальных мод электромагнитно индуцированной прозрачности

2019 ◽  
Vol 126 (4) ◽  
pp. 483
Author(s):  
О.М. Паршков
Keyword(s):  
Group Velocity ◽  
Probe Pulse ◽  
Polarization State ◽  
Normal Modes ◽  
Doppler Frequency ◽  
Resonant Medium ◽  
Probe Radiation ◽  
Significant Deterioration ◽  
Probe Field ◽  
Elliptically Polarized

AbstractThe process of propagation of short probe pulses of electromagnetically induced transparency has been analyzed theoretically in the case of elliptically polarized control radiation. As a model of a resonant medium, a Λ scheme of quantum transitions between the $$^{3}{{P}_{0}}$$ , $$^{3}P_{1}^{0}$$ , and $$^{3}{{P}_{2}}$$ degenerate levels of the ^208Pb isotope has been used. The situation in which the probe radiation is rather weak compared to the control radiation has been examined. In this case, the field of the probe pulse can be represented as a sum of the fields of two elliptically polarized pulses that propagate in the medium independently of one another without changing their polarization state, which makes it possible to interpret them as nonstationary normal modes. Numerical simulation has shown that the structure of normal modes depends on the ratio of the width of the spectrum of the input probe pulse to the Doppler frequency broadening of the quantum transition that is resonant to the probe field. If this ratio is small, each mode in the medium is a single pulse similar to the input probe pulse. Under these conditions, the propagation of each normal mode in the medium can be fairly well characterized by the group velocity depending on the intensity and the state of polarization of the control radiation. As this ratio increases, normal modes in the medium initially acquire the shape of a regular decaying train of pulses, and then their structure becomes chaotic. The described evolution is accompanied by an increase in the energy absorption of the probe radiation by the medium and by a significant deterioration in the applicability of the notion of group velocity for describing the propagation process of normal modes.

scholarly journals Analyses of Countermovement Jump Performance in Time and Frequency Domains

2021 ◽  
Vol 78 (1) ◽  
pp. 41-48
Author(s):  
Zhanxin Sha ◽  
Zhaoxian Zhou ◽  
Boyi Dai
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Frequency Component ◽  
Frequency Domain Analysis ◽  
American Football ◽  
Jump Height ◽  
Jump Performance ◽  
Additional Information ◽  
Frequency Domains ◽  
Time And Frequency Domains

Abstract This study aimed to analyze counter-movement jump (CMJ) performance in time and frequency domains. Fortyfour Division I American football players participated in the study. Kinetic variables were collected from both dominant and non-dominant legs using two force plates. Normalized peak power, normalized net impulse, and normalized peak force significantly correlated with jump height (r = .960, r = .998, r = .725, respectively with p < .05). The mean frequency component was significantly correlated with CMJ performance (r = .355 with p < .05). The reliability of the frequency variables was higher than the time domain variables. Frequency domain variables showed weaker correlations with jump height compared with time domain variables. Frequency domain analysis provides frequency components, which represent the rate of energy transmission from the eccentric phase to the end of the push-off phase. Frequency component information may provide additional information for the analyses of CMJ performance for athletes.

scholarly journals Time domain frequency stability calculated from the frequency domain description :

1989 ◽  
Author(s):  
F L Walls ◽  
John Gary ◽  
Abbie O'Gallagher ◽  
Roland Sweet ◽  
Linda Sweet
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Frequency Stability ◽  
Domain Description

JOINT INTERPRETATION OF AIRBORNE ELECTROMAGNETIC DATA IN THE TIME DOMAIN AND FREQUENCY DOMAIN

2018 ◽  
Vol 12 (7-8) ◽  
pp. 76-83
Author(s):  
E. V. KARSHAKOV ◽  
J. MOILANEN
Keyword(s):  
Fourier Transform ◽  
Frequency Domain ◽  
Time Domain ◽  
Frequency Interval ◽  
Single Spectrum ◽  
Simultaneous Inversion ◽  
Homogeneous Half Space ◽  
Time Domain Data ◽  
The Time Domain

Тhe advantage of combine processing of frequency domain and time domain data provided by the EQUATOR system is discussed. The heliborne complex has a towed transmitter, and, raised above it on the same cable a towed receiver. The excitation signal contains both pulsed and harmonic components. In fact, there are two independent transmitters operate in the system: one of them is a normal pulsed domain transmitter, with a half-sinusoidal pulse and a small "cut" on the falling edge, and the other one is a classical frequency domain transmitter at several specially selected frequencies. The received signal is first processed to a direct Fourier transform with high Q-factor detection at all significant frequencies. After that, in the spectral region, operations of converting the spectra of two sounding signals to a single spectrum of an ideal transmitter are performed. Than we do an inverse Fourier transform and return to the time domain. The detection of spectral components is done at a frequency band of several Hz, the receiver has the ability to perfectly suppress all sorts of extra-band noise. The detection bandwidth is several dozen times less the frequency interval between the harmonics, it turns out thatto achieve the same measurement quality of ground response without using out-of-band suppression you need several dozen times higher moment of airborne transmitting system. The data obtained from the model of a homogeneous half-space, a two-layered model, and a model of a horizontally layered medium is considered. A time-domain data makes it easier to detect a conductor in a relative insulator at greater depths. The data in the frequency domain gives more detailed information about subsurface. These conclusions are illustrated by the example of processing the survey data of the Republic of Rwanda in 2017. The simultaneous inversion of data in frequency domain and time domain can significantly improve the quality of interpretation.

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