Complex Phase Filter Research Articles

The generation of ultra-long longitudinally polarized optical needle with multi-belt complex phase filter

In the paper, a multi-belt complex phase filter was optimized by increasing the number of belts and changing phase and amplitude parameters of the filter. By focusing radially polarized sinh-Gaussian beams in single objective system with high-NA lens, longitudinal polarized optical needles were obtained with super-resolution in focal plane. And the super-resolution optical needle owned 36.6λ depth of focus and 0.42λ of full–width at half-maximum. The aspect ratio of the obtained optical needle was 87.14. The beam quality reached to 87.7%. The results demonstrated that the optimized multi-belt complex phase filter can lengthen depth of focus and compress transverse size simultaneously. The obtained longitudinally polarization optical needles can be used in the fields of optical data storage, super-resolution imaging, particle trapping, nanolithography and so on.

Generation of 1D array of focal segments using spirally polarized beam and Complex Phase Filter

A new approach for generating and tuning 1D array of sub wavelength scale electric and magnetic spot, hole, flattop and bubble profiled segments using tightly focused spirally polarized beam phase and amplitude modulated with suitable complex phase filter is proposed and investigated numerically using vector diffraction theory. Numerical result shows that by using a well optimized single Complex Phase Filter (CPF), one can generated and tune the geometry of the 1D chain of electric and magnetic field distribution from sub wavelength scale hole to spot and then to a chain of flattop profiled or bubble structure segments by properly tuning the spirallity of incident spirally polarized beam. These focal field distributions may find potential applications in laser direct writing and optical microscopy, as well as multiple-particle trapping, alignment, and acceleration along the optical axis.

Creation of one dimensional array of magnetic field by tightly focused phase modulated azimuthal and radial variant vector beam

A new approach for generating sub wavelength scale one dimensional chain of magnetic spot, hole, flattop and bubble profiled segments using tightly focused phase modulated azimuthal and radial variant vector (ARVV) beam is proposed and investigated numerically using vector diffraction theory. Numerical result shows that by using a well optimized single Complex Phase Filter (CPF), one can generated and tune the geometry of the 1D chain of magnetic field distribution from sub wavelength scale hole to spot and then to a chain of flattop profiled and bubble structure segments by properly tuning the radial index of the incident azimuthal- and radial-variant vector beam. Such an approach is simple and usable for simulate condensed matter phenomena.

Tight focusing properties of phase modulated azimuthally polarized doughnut Gaussian vortex beam by high NA parabolic mirror

The intensity distribution in the focal region of a high NA parabolic mirror for the incident azimuthally polarized doughnut Gaussian vortex beam (DGVB) transmitted through a multi belt complex phase filter (MBCF) is studied using vector diffraction theory. By properly designing the phase of the incident beam using MBCF and by tuning the beam parameters of a DGVB, it is possible to switch the focal spot with sub wavelength dimension and long focal depth in to multiple focal spots suitable for particle acceleration, atom optical experiments, and near-field scanning optical microscopy.

Generation of ultra-long pure magnetization needle and multiple spots by phase modulated doughnut Gaussian beam

Based on vector diffraction theory and inverse Faraday effect (IFE), the light induced magnetization distribution of a tightly focused azimuthally polarized doughnut Gaussian beam superimposed with a helical phase and modulated by an optimized multi belt complex phase filter (MBCPF) is analysed numerically. It is noted that by adjusting the radii of different rings of the complex phase filter, one can achieve many novel magnetization focal distribution such as sub wavelength scale (0.29λ) and super long (52.2λ) longitudinal magnetic probe suitable for all optical magnetic recording and the formation of multiple magnetization chain with four, six and eight sub-wavelength spherical magnetization spots suitable for multiple trapping of magnetic particles are achieved.

Generating sub wavelength pure longitudinal magnetization probe and chain using complex phase plate

Based on inverse Faraday Effect, the three dimensional magnetization field distribution induced by the azimuthally polarized annular multi Gaussian transmitted through a multi belt complex phase filter (MBCPF) is investigated numerically using vector diffraction theory. Numerical results shows that by properly adjusting the radii of different rings of MBCPF, one can achieve sub wavelength (0.286λ) pure longitudinal magnetic probe with ultra-long focal depth of (35λ). We also noticed that magnetization chain composed of eight, four and two magnetic spots of subwavelength scale is also achieved by properly modulating the radii of MBCPF. The authors expects such a pure ultra-long subwavelength magnetic probe and magnetic chain can be used to realize all optical magnetic recording (AOMR), multilayer magneto-optical data storage, ultra-compact optomagnetic devices, magnetic particle trapping and transportation, fabricating magnetic lattices for spin wave operation, as well as confocal and magnetic resonance microscopy.

Creation of Multiple Subwavelength Focal Spot Segments Using Phase Modulated Radially Polarized Multi Gaussian Beam

Based on the vector diffraction theory, the effect of complex phase filters on intensity distribution of a radially polarized multi Gaussian beam in the focal region of high NA lens is theoretically investigated. It is observed that a properly designed multi belt complex phase filter can generate subwavelength novel focal patterns including splitting of focal spots and generation of multiple focal spot segments such as eight, six and four focal spots along the optical axis are obtained. We expect that such an investigation is useful for optical manipulation and material processing, multiple high refractive index particle trapping technologies.

Sharpening Minimum-Phase Interpolated Finite Impulse Response Filters

This paper presents a novel simple method for the direct design of low-pass minimum-phase (MP) filters. The method is based on a linear-phase (LP) finite impulse response (FIR) prototype, sharpening and IFIR (interpolated finite impulse response) techniques, usually used for the design of LP filters. As a result, a more complex minimum phase filter can be designed by using less complex filters. The paper presents the rules and the methodology of the design and illustrates them with an example. The advantage of the method is demonstrated by comparisons with some existing designs.

Generation of multiple focal spot and focal hole segments using phase modulated cylindrically polarized annular multi-Gaussian beam

We investigated the focusing properties of a cylindrically polarized annular multi Gaussian beam tightly focused with a high NA lens and a complex phase filter. It is observed that a properly designed complex phase filter can generate multiple focal spot and focal hole segments along optical axis its useful for the manipulation of multiple optical traps of low and high refractive index particles.

Tight focusing of phase modulated radially polarized hollow Gaussian beam using complex phase filter

We propose a new approach for generating multiple focal spot segment of sub wavelength size, by tight focusing of phase modulated radially polarized hollow Gaussian beam. The focusing properties are investigated theoretically by vector diffraction theory. We observed that focal segment with multiple focal spots structure separated with different axial distance can be generated by properly tuning the phase of the incident radially polarized hollow Gaussian (HGB) beam. Potential applications of this focal shaping technique are also discussed.

Generation of multiple sub wavelength focal spot segments using radially polarized Bessel Gaussian beam with complex phase filter

We propose a new approach for generating multiple focal spot segment of sub wavelength size, by tight focusing of phase modulated radially polarized Bessel Gaussian beam. The focusing properties are investigated theoretically by vector diffraction theory. We observed that focal segment with multiple focal spots structure separated with different axial distance can be generated by properly tuning the phase of the incident radially polarized Bessel Gaussian (BG) beam. Potential applications of this focal shaping technique are also discussed.

Generation of multiple focal spot and focal hole of sub wavelength scale using phase modulated LG (1,1) beam

Based on the vector diffraction theory, the effect of phase modulation on the intensity distribution on tight focusing of cylindrically polarized Laguerre–Gaussian beam in the focal region of high NA lens is investigated theoretically. It is observed that a properly designed complex phase filter can generate multiple focal spot and focal hole segments useful for the manipulation of optical traps.

Generation of multiple focal hole segment by tight focusing of azimuthally polarized double ring shaped beam

Based on the vector diffraction theory, the effect of phase modulation on the intensity distribution of TEM11 mode azimuthally polarized Laguerre-Gaussian beam in the focal region of high NA lens is investigated theoretically. It is observed that a properly designed complex phase filter can generate multiple focal hole segment and it is useful for the manipulation of optical traps.

Fringe detection in noisy complex interferograms

A new algorithm to estimate the two-dimensional local frequencies of phase interferometric data is described. With a complex sine-wave model, demonstration is given that a conventional multiple-signal classification (MUSIC) algorithm can be used in spite of multiplicative noise perturbations. A faster algorithm dedicated to the processing of interferograms is developed and a measure of confidence in the estimate is proposed. We studied numerical performances using synthetic fringes. As a result of the frequency estimation, knowledge of the fringe local width and orientation can be applied to restore noisy phase data. Results of a complex phase filter are presented for real interferograms obtained from synthetic aperture radar images.

Image Processing with Pure Phase Filters

Using two criteria for image quality leads to the derivation of two different pure phase optimal filters. One filter minimizes the difference between the original irradiance distribution in the image, before it has been smeared, and the resulting amplitude at the output of the coherent optical processor. The second filter minimizes the difference between the original irradiance distribution and the irradiance at the output of the coherent optical processor, while a coherent background illumination is added. As predicted by theory, the second filter causes a comparable improvement in resolution as a more complex amplitude and phase filter. However this filter suffers from noise introduced by the background illumination and the output imagery has inferior signal-to-noise ratio than that from the first filter. Experimental results support the theoretical predictions and demonstrate the ability of these filters to restore blurred pictures.