We develop a method to synthesize any partially coherent source (PCS) with a genuine cross-spectral density (CSD) function using complex transmittance screens. Prior work concerning PCS synthesis with complex transmittance screens has focused on generating Schell-model (uniformly correlated) sources. Here, using the necessary and sufficient condition for a genuine CSD function, we derive an expression, in the form of a superposition integral, that produces stochastic complex screen realizations. The sample autocorrelation of the screens is equal to the complex correlation function of the desired PCS. We validate our work by generating, in simulation, three PCSs from the literature-none has ever been synthesized using stochastic screens before. Examining planar slices through the four-dimensional CSD functions, we find the simulated results to be in excellent agreement with theory, implying successful realization of all three PCSs. The technique presented herein adds to the existing literature concerning the generation of PCSs and can be physically implemented using a simple optical setup consisting of a laser, spatial light modulator, and spatial filter.

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Stochastic complex transmittance screens for synthesizing general partially coherent sources.

In this paper, we propose a numerical approach to simulate the degree of coherence (DOC) of a partially coherent beam (PCB) with a Schell-model correlator in any transverse plane during propagation. The approach is applicable for PCBs whose initial intensity distribution and DOC distribution are non-Gaussian functions, even for beams for which it is impossible to obtain an analytical expression for the cross-spectral density (CSD) function. Based on our approach, numerical examples for the distribution of the DOC of two types of PCBs are presented. One type is the partially coherent Hermite–Gaussian beam. The simulation results of the DOC agree well with those calculated from the analytical formula. The other type of PCB is the one for which it is impossible to obtain an analytical expression of CSD. The evolution of the DOC with the propagation distance and in the far field is studied in detail. Our numerical approach may find potential applications in optical encryption and information transfer.

Numerical Approach for Studying the Evolution of the Degrees of Coherence of Partially Coherent Beams Propagation through an ABCD Optical System

https://iopscience.iop.org/article/10.1088/2040-8986/ab2c48/pdf

Standard and elegant higher-order Laguerre-Gaussian correlated Schell-model beams

This paper presents the theory for controlling the spectral degree of coherence via spatial filtering Starting with a quasi-homogeneous partially coherent source, the cross-spectral density function of the field at the output of the spatial filter is found by applying Fourier and statistical optics theory The key relation obtained from this analysis is a closed-form expression for the filter function in terms of the desired output spectral degree of coherence This theory is verified with Monte Carlo wave-optics simulations of spatial coherence control and beam shaping for potential use in free-space optical communications and directed energy applications The simulated results are found to be in good agreement with the developed theory The technique presented in this paper will be useful in applications where coherence control is advantageous, eg, directed energy, free-space optical communications, remote sensing, medicine, and manufacturing

/pdf/controlling-the-spatial-coherence-of-an-optical-source-using-59f9b0a6sx.pdf

Controlling the Spatial Coherence of an Optical Source Using a Spatial Filter

We propose theoretically and numerically, for the first time, the generation of novel partially coherent truncated Airy beams (NPCTABs) with Airy-like distributions for both intensity and degree of coherence via Fourier phase processing. We demonstrate a clear link between the magnitude and frequency of intensity and degree of coherence distributions oscillations of generated beams, and the source coherence and the phase screen parameter. Thus, the source coherence and phase can serve as convenient parameters to control the intensity and degree of the coherence of NPCTABs. Furthermore, we discover that NPCTABs are more stable than the fully coherent truncated Airy beams (FCTABs) during their propagation in free space and can maintain their Airy-like profile for an extended propagation distance. The interesting and tunable characteristics of these novel beams may find applications in particle trapping, phase retrieval, and optical imaging.

Generation of novel partially coherent truncated Airy beams via Fourier phase processing

It is known that a 4f optical system with an amplitude filter can be adopted to shape the intensity of a coherent Gaussian beam. In this paper, we investigate the propagation of a typical kind of partially coherent beam called a Gaussian Schell-model (GSM) beam through a 4f optical system with an amplitude filter in the frequency plane. It is demonstrated both numerically and experimentally that the 4f optical system with an amplitude filter can be used to shape the intensity and degree of coherence of a GSM beam simultaneously. The shaped beam displays interesting properties and forms controllable far-field intensity lattices, which may be useful for particle trapping and information transfer.

https://iopscience.iop.org/article/10.1088/2040-8986/aa95d9/pdf

Tengfei Wu

Papers

Shaping the intensity and degree of coherence of a partially coherent beam by a 4f optical system with an amplitude filter