scholarly journals Analysis of Hybrid Vector Beams Generated with a Detuned Q-Plate

2020 ◽  
Vol 10 (10) ◽  
pp. 3427 ◽  
Author(s):  
Julio César Quiceno-Moreno ◽  
David Marco ◽  
María del Mar Sánchez-López ◽  
Efraín Solarte ◽  
Ignacio Moreno
Keyword(s):  
Near Field ◽  
Far Field ◽  
Input Beam ◽  
Physical Explanation ◽  
Liquid Crystal Device ◽  
Different Types ◽  
Vector Beams ◽  
Quarter Wave ◽  
Gouy Phase ◽  
Standard Situation

We use a tunable commercial liquid-crystal device tuned to a quarter-wave retardance to study the generation and dynamics of different types of hybrid vector beams. The standard situation where the q-plate is illuminated by a Gaussian beam is compared with other cases where the input beam is a vortex or a pure vector beam. As a result, standard hybrid vector beams but also petal-like hybrid vector beams are generated. These beams are analyzed in the near field and compared with the far field distribution, where their hybrid nature is observed as a transformation of the intensity and polarization patterns. Analytical calculations and numerical results confirm the experiments. We include an approach that provides an intuitive physical explanation of the polarization patterns in terms of mode superpositions and their transformation upon propagation based on their different Gouy phase. The tunable q-plate device presents worthy advantages, since it allows a compact and efficient generation of pure and hybrid vector beams to study these effects.

scholarly journals NEAR AND FAR FIELD OPTICAL PATTERNS FORMATION BY ROTATIONAL SYMMETRY MASKS: APPLICATION TO OPTICAL SPATIAL SOLITON GENERATION

2012 ◽  
Vol 15 ◽  
pp. 113-119
Author(s):  
ANAHIT BADALYAN ◽  
PAYTSAR MANTASHYAN ◽  
VAHRAM MEKHITARYAN ◽  
VARSENIK NERSESYAN ◽  
RAFAEL DRAMPYAN
Keyword(s):  
Rotational Symmetry ◽  
Near Field ◽  
Single Mode ◽  
Optical Diffraction ◽  
Spatial Soliton ◽  
Far Field ◽  
Single Mode Laser ◽  
Beam Formation ◽  
Different Types ◽  
Soliton Generation

In this report we present the formation of necklace type optical beams from Gaussian beam by rotational symmetry masks. The detailed studies of space evolution of the optical beam formation from the near field to the far field by the use of 7-fold symmetry mask and a single mode laser beam were performed. Different types of necklace beams with different numbers of "pearls" periodically or quasi-periodically situated along the different radii rings were observed during the space evolution of the optical diffraction pattern.

Magnetic Tag Antenna for UHF Near-field and Far-Field RFID Applications

2015 ◽  
Vol 5 (2) ◽  
pp. 119
Author(s):  
Mondher Dhaouadi ◽  
M. Mabrouk ◽  
T. Vuong ◽  
A. Ghazel
Keyword(s):  
Near Field ◽  
Far Field ◽  
Rfid Applications

Far field modeling of the Mamala Bay outfalls

1998 ◽  
Vol 38 (10) ◽  
pp. 323-330
Author(s):  
Philip J. W. Roberts
Keyword(s):  
Field Model ◽  
Near Field ◽  
Far Field ◽  
Field Modeling ◽  
Visitation Frequency ◽  
Statistical Variation ◽  
Long Time ◽  
Harmonic Average ◽  
Ocean Outfall ◽  
Acoustic Doppler Current Profilers

The results of far field modeling of the wastefield formed by the Sand Island, Honolulu, ocean outfall are presented. A far field model, FRFIELD, was coupled to a near field model, NRFIELD. The input data for the models were long time series of oceanographic observations over the whole water column including currents measured by Acoustic Doppler Current Profilers and density stratification measured by thermistor strings. Thousands of simulations were made to predict the statistical variation of wastefield properties around the diffuser. It was shown that the visitation frequency of the wastefield decreases rapidly with distance from the diffuser. The spatial variation of minimum and harmonic average dilutions was also predicted. Average dilution increases rapidly with distance. It is concluded that any impact of the discharge will be confined to a relatively small area around the diffuser and beach impacts are not likely to be significant.

Direction of Arrival Estimation Under Near-Field Interference Using Matrix Filter

2015 ◽  
Vol 23 (04) ◽  
pp. 1540007 ◽  
Author(s):  
Guolong Liang ◽  
Wenbin Zhao ◽  
Zhan Fan
Keyword(s):  
Near Field ◽  
Direction Of Arrival ◽  
Doa Estimation ◽  
Direction Of Arrival Estimation ◽  
Far Field ◽  
Data Simulation ◽  
Estimation Algorithms ◽  
Simulation Results

Direction of arrival (DOA) estimation is of great interest due to its wide applications in sonar, radar and many other areas. However, the near-field interference is always presented in the received data, which may result in degradation of DOA estimation. An approach which can suppress the near-field interference and preserve the far-field signal desired by using a spatial matrix filter is proposed in this paper and some typical DOA estimation algorithms are adjusted to match the filtered data. Simulation results show that the approach can improve capability of DOA estimation under near-field inference efficiently.

scholarly journals Direction-of-Arrival Estimation of Far-Field Sources Under Near-Field Interferences in Passive Sonar Array

IEEE Access ◽  
2021 ◽  
Vol 9 ◽  
pp. 28413-28420
Author(s):  
Hojun Lee ◽  
Jongmin Ahn ◽  
Yongcheol Kim ◽  
Jaehak Chung
Keyword(s):  
Near Field ◽  
Direction Of Arrival ◽  
Direction Of Arrival Estimation ◽  
Far Field ◽  
Passive Sonar
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