Abstract
In a recent publication [Appl. Phys. Lett, 100, 051108 (2012)], a radially polarized (RP) beam with variable spatial coherence (i.e., partially coherent RP beam) was generated experimentally. In this paper, we derive the realizability conditions for a partially coherent RP beam, and we carry out theoretical and experimental study of the coherence and polarization properties of a partially coherent RP beam. It is found that after passing through a thin lens, both the degree of coherence and the degree of polarization of a partially coherent RP beam varies on propagation, while the state of polarization of the completely polarized part of such beam remains invariant. The variations of the degree of coherence and the degree of polarization depend closely on the initial spatial coherence. Our experimental results agree well with the theoretical predictions.
Highlights
After passing through a collimation thin lens L2 and a Gaussian amplitude filter (GAF), the transmitted beam becomes a linearly polarized Gaussian Schell-model (GSM) beam characterized by the cross-spectral density
The radial polarization converter (RPC) just alter the polarization state of the GSM beam, while it does not alter its spatial coherence and beam spot size, the beam waist size of the partially coherent radially polarized (RP) beam is approximately equal to that of the GSM beam, and the correlation radii of the partially coherent RP beam are approximated as δ xx = δ yy = δ xy = δ
Our results show that the degree of coherence of focused partially coherent RP beam becomes of non-Gaussian distribution, and the focused partially coherent RP beam is depolarized, while the state of polarization of its completely polarized part remains invariant, which is much different from that of an electromagnetic GSM beam
Summary
As a typical kind of cylindrical vector beam with spatially non-unifrom state of polarization [1], radially polarized beam has been studied extensively in both theory and experiment due to its interesting and unique focusing properties, and has been found wide applications in microscopy, lithography, free space optical communications, electron acceleration, proton acceleration, particle trapping, material processing, optical data storage, high-resolution metrology, super-resolution imaging, plasmonic focusing, and laser machining [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]. Characterization, generation and propagation of stochastic electromagnetic beam have been studied extensively due to its important applications in free-space optical communications, optical imaging, active laser radar systems and remote sensing [25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51]
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