Zhaozhong Chen

Vectorial optical vortex filtering for edge enhancement

We propose to use a super-structured waveplate (called an S-waveplate) for vectorial optical vortex filtering, and experimentally demonstrate the radial Hilbert transform and selective edge enhancement. Based on the Jones calculus of polarization states and Fourier analysis, we calculate and analyze the point spread function of an optical 4-f system including an S-waveplate filter having the vectorial vortex of topological charge 1 (TC = 1). Numerical simulations and optical experiments demonstrate that a vectorial optical vortex filter can be used to implement selective edge enhancement with an analyzer before the output plane. The edge enhancement can be obtained even when the center of the filter is off-axis or the illuminating light is non-monochromatic.

Light field shaping by tailoring both phase and polarization.

We propose a method to generate a vectorial focal field with reconfigurable distributions for both the intensity and polarization state. The three-dimensional focal volume was configured by modulating the phase and polarization of the incident light. The incident light yielding the desired field was determined based on an iterative scheme involving vectorial diffraction calculations and fast Fourier transforms. Optical experiments on vectorial field shaping were performed to validate the feasibility of our method. This method may have applications in optical tweezers, such as for realizing the optical manipulation of particles via polarization modulation in addition to phase control.

Generalized phase-shifting for three-wave shearing interferometry

A generalized phase-shifting method for three-wave shearing interferometry is proposed. The phase-shifting algorithm is derived by an optimal process based on least-squares fitting. With this generalized algorithm, the steps of phase-shifting can be reduced to five, which greatly simplifies the measurement and decreases the burden of computation. Both the numerical simulation and the optical experiment are carried out to demonstrate the adaptability of the method.

Holographic optical tweezers obtained by using the three-dimensional Gerchberg–Saxton algorithm

An extension of the Gerchberg–Saxton algorithm from two dimensions to three is used to configure a continuous optical trap geometry. Intensity tailoring in a continuous, three-dimensional (3D) volume rather than in multiple discrete two-dimensional planes yields flexible 3D holographic optical tweezers. A numerical simulation and optical demonstrations of continuous 3D beam shaping and particle trapping confirm the capabilities of the method.