An approach for designing of interference filter is presented by using genetic algorithm (here after refer to as GA) here.
We use GA to design band stop filter and narrow-band filter. Interference filter designed here can calculate the optimal
reflectivity or transmission rate. Evaluation function used in our genetic algorithm is different from the others before.
Using characteristic matrix to calculate the photonic band gap of
one-dimensional photonic crystal is similar to electronic
structure of doped. If the evaluation is sensitive to the deviation of photonic crystal structure, the approach by genetic
algorithm is effective. A summary and explains towards some uncompleted issues are given at the end of this paper.
Focal shift plays an important in many optical fusing systems. In this article, focal shift of concentric piecewise
cylindrical vector beam is investigated by means of vector diffraction theory in detail. The section of the beam consists
of three concentric zones. The center circle zone and outer annular zone are radial polarized, and the inner annular zone
is generalized polarized. In addition the wavefront phase distribution of the vector beam is linear function to radial
coordinate. It is found that the parameter in phase distribution induces focal shift and can alter focal shift considerably.
However, radii of the inner annular zone and polarization angle do affect focal shift very slightly. So the phase parameter
can be used to alter big focal shift while the radii and polarization angle may be employed to adjust intensity distribution.
In focusing system, the focal shift and intensity distribution may be controlled separately, which improves the
application freedom of this kind of technique. Focal shift direction can also be altered by change the phase parameter.
The focusing properties of the hyperbolic-cosine-Gaussian beam induced by spiral phase plates are investigated
numerically. The phase plate may alter the wavefront phase of the hyperbolic-cosine-Gaussian beam by topological
charge which results in spiral optical vortex. Results show that the topological charge of the spiral phase plate influences
focal intensity distribution considerably, and some novel focal patterns, focal split appear in focal evolution with
different topological charge. The focal evolution differs for different parameters in cosh parts of the
hyperbolic-cosine-Gaussian beam. The optical gradient force is also illustrated to show promising application of the
hyperbolic-cosine-Gaussian beam containing the spiral optical vortex in optical tweezers array.
The focusing properties and focal depth of amplitude modulation Gaussian beams are investigated. Numerical results
show that the intensity in the focus plane is circle shape in the low numerical-aperture optical system, while the intensity
distribution in the focal plane is ellipse shape in high numerical-aperture optical system due to contribution of
depolarized longitudinal component. Focal spot size and focal depth can be adjusted by changing geometrical parameters
and the modulation amplitude power n of Gaussian beams. The tunable range of the focal depth is very considerable.
The evolution of the gradient force pattern of hyperbolic-cosine-Gaussian beams induced by a three-zone pure phase plate is numerically investigated. The pure phase plate consists of three concentric zones—the center circular zone, the inner annular zone—and the outer annular zone and the phase variance of inner annular zone is adjustable. The results show that the proposed plate may induce tunable gradient force on the particles in the focal region. The optical trap shape is obviously tunable and multiple traps may occur with changing geometrical parameters of the phase plate. An optical trap shift can be induced by changing the phase variance of the inner annular zone portion. The phase plate may be a very promising method of transporting trapped particles and can be used to construct controllable optical tweezers.