Direct object recovery from the Fraunhofer diffraction integral.

In this Letter, we present a novel, to the best of our knowledge, approach for recovering objects directly from the Fraunhofer diffraction integral, where the diffraction field of an object is approximated by the Fourier transform of this object augmented by an additional phase factor. This phase factor at the observation plane is universal for the diffraction fields generated by objects located at the same plane and illuminated by the same monochromatic plane wave. It can be first extracted from dividing the Fraunhofer diffraction field by the Fourier transform of an object reference.

Generation and propagation properties of Bessel-Gaussian beams with a rotationally symmetric power-exponent-phase vortex.

In this paper, the generation and propagation properties of Bessel-Gaussian (BG) rotationally symmetric power-exponent-phase vortex beam (RSPEPVBs) were demonstrated and discussed. The results showed that the BG-RSPEPVBs can be directly generated based on the spatial light modulator, of which the phase singularities were verified by the interference patterns with the plane wave. It can be found that the intensity distributions of the BG-RSPEPVBs, with different topological charges (TCs) and power orders, were fan-shaped and polycyclic, which possessed the characteristics of BG beams and RSPEPVBs, simultaneously.

Accurate method for correcting the translation position error of ptychography based on quantum particle swarm optimization.

In ptychography, the translation position error will cause the periodic grid deviation and tremendously decrease the reconstruction quality. It is crucial to attain the precise translation position of the probe with respect to the object. The current correction methods may fall into a local optimal value, and miss the better results.

Generation of rotationally symmetric power-exponent-phase vortex beams based on digital micromirror devices.

In this paper, what we believe to be a new method for the generation of rotationally symmetric power-exponent-phase vortex beams (RSPEPVBs) based on digital micromirror devices (DMD) was proposed and demonstrated. Based on the theory of binary amplitude holography and Lee method, the two-dimensional amplitude holograms for the generation of RSPEPVBs were obtained. Then, the experimental setup was established for the generation of RSPEPVBs based on DMD and to verify the phase structure of RSPEPVBs by the Mach-Zehnder interferometer.

Optical trapping of multiple particles based on a rotationally-symmetric power-exponent-phase vortex beam.

In this paper, the optical trapping of multiple particles based on a rotationally-symmetric power-exponent-phase vortex beam (RSPEPVB) was introduced and demonstrated. Based on the theories of tight focusing and optical force, the optical force model of RSPEPVB was established to analyze the optical trapping force of tightly focused RSPEPVB. Then, an experimental setup of optical tweezer, by utilizing the RSPEPVB, was built to demonstrate that the optical tweezer of RSPEPVBs can achieve the optical trapping of multiple particles, and the number of captured particles is equal to the topological charge l of RSPEPVB, which shows that the RSPEPVBs can achieve multi-particles trapping with controllable number.

Influences of salinity and temperature on propagation of radially polarized rotationally-symmetric power-exponent-phase vortex beams in oceanic turbulence.

In this paper, the propagation properties of radially polarized rotationally-symmetric power-exponent-phase vortex beams (RP-RSPEPVBs) in oceanic turbulence were theoretically and experimentally studied. Based on the extended Huygens-Fresnel diffraction integral and vector beams theories, the theoretical propagation model of RP-RSPEPVBs in the oceanic turbulence was established. Then, the numerical simulations were carried out to study the influences of the propagation distance z, the rate of dissipation of turbulence kinetic energy per unit mass of fluid ε, the temperature-salinity contribution ratio ω, and the dissipation rate of the mean-squared temperature χT on the optical intensity, spectral degree of polarization (DOP) and spectral degree of coherence (DOC) of RP-RSPEPVBs.

Controlled generation of mode-switchable nanosecond pulsed vector vortex beams from a Q-switched fiber laser.

We reported and demonstrated a ring Q-switched Ytterbium-doped fiber laser that can generate mode-switchable nanosecond pulsed vector vortex beams between two different orders. In the spatial optical path of the fiber laser, several cascaded Q-plates, divided into two Q-plate groups, are applied for intracavity mode conversion between LP mode and vector vortex beams. In one Q-plate group, two quarter-wave plates are inserted to achieve the addition and subtraction of the order of Q-plates.

Generalized shift-rotation absolute measurement method for optical surface shapes with polygonal apertures based on migration recognition by Radon transform.

A generalized shift-rotation absolute measurement method for optical surface shapes with polygonal apertures based on migration recognition by Radon transform is proposed. The rotation angles and translation distances of the test surface, measured three times, are calculated through migration recognition. The absolute shape of the test surface with the polygonal aperture is fitted by orthogonal Zernike polynomials.

Accelerated convergence extended ptychographical iterative engine using multiple axial intensity constraints.

The extended ptychographical iterative engine (ePIE) is widely applied in the field of ptychographic imaging due to its great flexibility and computational efficiency. A technique of ePIE with multiple axial intensity constraints, which is called MAIC-PIE, is proposed to drastically improve the convergence speed and reduce the calculation time. This technique requires that the diffracted light from the sample is propagated to the multiple individual axial planes, which can be achieved by using the beam splitter and multiple CCDs.

Real-time complex amplitude reconstruction method for beam quality M factor measurement.

We present a real-time complex amplitude reconstruction method for determining the beam propagation ratio M of laser beams based on the transport of intensity equation (TIE). In this work, a synchronous acquisition system consisting of two identical CCDs is established. Once two beam intensity images at different cross-section positions along the optical axis are captured simultaneously by the system, the complex amplitude of the laser beam can be rapidly reconstructed using TIE algorithm.

Generalized shift-rotation absolute measurement method for high-numerical-aperture spherical surfaces with global optimized wavefront reconstruction algorithm.

In this paper, a generalized shift-rotation absolute measurement method is proposed to measure the absolute surface shape of high-numerical-aperture spherical surfaces. Based on the wavefront difference method, the high order misalignment aberrations can be removed from the measurements. Our generalized shift-rotation absolute measurement process only needs one rotational measurement position and one translational measurement position.

Resolution enhancement of the microscopic imaging by unknown sinusoidal structured illumination with iterative algorithm.

Microscopy by sinusoidal structured illumination is a conventional method to improve resolution, which largely depends on accurate knowledge of the illumination pattern. Two steps are included in the reconstruction process of our proposed technique. The first step solves the parameters of the structured illumination in the spatial domain.

Focal length measurement based on the wavefront difference method by a Fizeau interferometer.

A method for measuring the focal length of the lens by a Fizeau interferometer is proposed. Based on the Gaussian imaging equation and the longitudinal displacements of the object point and image point, a precise formula for focal length calculation is deduced. The longitudinal displacement of the object points is determined by the wavefront difference method with a subnanometer resolution.