A radial sine phase filter is introduced in optical systems to control and alter the optical system focusing properties with
incident Gaussian beam. It was found that the radial sine phase filter can induce tunable multiple foci in focal region,
which means that the several field distances can be imaged clearly simultaneously with this kind of filter in imaging
optical system. And the point of absolute maximum intensity does not coincide with the geometrical focus but shifts
along the optical axis; this phenomenon is referred to as focal shift. Focal shift distance and direction can be altered by a
sine parameter in the sine term of the phase distribution function. In addition, focal shift may be accompanied by an
effective permutation of the focal point, namely, maximum intensity can jump from one position to other position for
certain sine parameter, this effect is referred to as focal switch, which also can also be used to adjust imaging clearly
field distance in-continuously. The radial sine phase filter can adjust and optimizing the focusing and imaging properties
of the optical systems considerably, waist width and section shape of incident Gaussian beam also affect multiple foci.
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.
Resolution and focal depth are very important parameters in optical data storage systems, and have attracted much
attention. In this article, focusing properties of concentric two-zone cylindrical vector beam are investigated theoretically
by means of vector diffraction theory. The phase shift of the center zone and outer annular zone are different. Simulation
results show that the focal pattern can be altered considerably by adjusting the radius of dividing circle between the two
concentric portions and the phase shift of each zone. For certain phase shifts for these two zone, focal spot broadens
along optical axis with increasing radius, and splits into two peaks, and then combine back into one peak again. In this
evolution process, some novel focal pattern may come into being. For certain geometrical parameter and phase shift, the
focal spot shrinks, which means superresolution effect appears, and at the same time, focal depth can also be widened,
high focal depth companies with resolution, which is very useful in optical data storage systems.
Superresolution is very important in imaging and optical storage systems, and has attracted much attention. In this
article, concentric three-zone phase plate with 0, pi, 0 phase variation has been investigated numerically to show that this
kind of phase plate can be used to obtain three dimensional superresolution. Focal depth, focal shift, full width half
maximum, superresolution effect are listed for different radii of the phase zones, which paves the way for design of the
phase plate, such as for purpose of radial superresolution with high focal depth in optical storage.
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.
This paper investigates the focusing properties by a single lens, based on the optically thinner medium (OTM). The lens
model is of a plano-concave shape, made from the OTM with a refractive index of 0.5 at the wavelength λ=6.328e-4mm,
named the plano-concave OTM thick lens. Any geometrical approximation is not included in the deducing process,
which ensures that the full geometrical aberrations are included. The intensity distribution, in its focal region, can be
calculated by the Huygens-Fresnel integral formula, using the phase and intensity distributions on the reference plane.
The on-axis intensity distribution in the focal region of the plano-convex optically denser medium (ODM) thick lens is
given correctly. The intensity distribution in the focal region of the plano-concave OTM thick lens is plotted in two
dimensions, no symmetry about the focal plane. The plano-concave OTM thick lens has smaller on-axis spherical
aberration than the plano-convex ODM thick lens has, when they have the same aperture radius, equal curvature radius
(not including the sign), and equal medium index difference quantity (not including the sign also) from the
environmental medium air. The radial resolution, around the near end peak in the focal region of the plano-concave
OTM thick lens with its total spherical aberration, breaks down the traditional diffraction limit. Therefore the planoconcave
OTM thick lens will exhibit its practical super resolution abilities, if the diffraction focused spot can be filtered
off, or further more if the energy outside the near end peak can be moved into it.
The trace H<sub>2</sub>S in range of 0-20ppm has been measured by means of off-axis integrated cavity output spectroscopy
(OA-ICOS) technology combined with tunable diode laser absorption spectroscopy (TDLAS) technology. The
instrument uses off-axis alignment geometry to eliminate the problem of mode matching between laser and optical
resonant cavity, in absenting the piezoelectric transducer. Combined with the high sensitivity of the TDLAS technology,
sensitivity of the instrument is improved. The repeatability of instrument in H<sub>2</sub>S measurement achieves to 0.303ppm
(3σ), linearity less than ±1% F.S., which meet the requirement of trace H<sub>2</sub>S measurement in petrochemical or natural gas industry.
Singular optics studying optical vortices, or phase singularities, has grown rapidly recently because optical vortices have
some interesting properties and promising applications, for instance, to construct highly versatile optical tweezers. In this
article, the focusing properties of hyperbolic-cosine-Gaussian beam, which contains a non-spiral optical vortex and a
spiral optical vortex, are investigated numerically. The phase plate may be used to construct non-spiral optical vortex by
putting phase plate in a half section part of hyperbolic-cosine-Gaussian beam. Results show that the parameters of nonspiral
optical vortex and spiral optical vortex influence focal intensity distribution considerably, and some novel focal
patterns, such as line focal spot, "H" shape focal spot, and intensity peaks array, may occur. Focal shift and focal split
may also appear in focal evolution with tunable parameters of vortices terms. The focal evolution differs for different
parameters in cosh parts of hyperbolic-cosine-Gaussian beam.
Static recording characteristics of super-resolution near-field structure with bismuth (Bi) mask layer and antimony (Sb) mask layer were investigated and compared. The experimental results show that Bi mask layer can also concentrate energy into the center of a laser beam at a low laser energy input similar to Sb, which may be because that Bi film exhibits giant nonlinearity at low laser intensity. The direct observation of laser-recording marks may help better understand the working mechanism of the super-RENS, super-resolution ablation, and other nonlinear switching phenomena.
Measurement technology plays an important role in the research of optical storage. Aiming at constructing research platform for blue-ray optical data storage, we designed and built a modularized static testing system, in which laser wavelength is 406.7nm. Modulation/demodulation technique is employed to weaken the test noise. The focus move mode decreases the requirement in size of samples. And Piezoeletronic nano-positioner is used to facilitate the relocation of recording marks and improve test repeatability. Experimental results are also given to verify the performance of the static testing system.
The axial intensity distribution and focal depth of an apodized focusing optical system are theoretically investigated with two kinds of incident light fields: a uniform-intensity-distribution beam and a Gaussian beam. Both a low-numerical-aperture and a high-numerical-aperture optical system are considered. Numerical results show that the depth of focus can be adjusted by changing the geometrical parameters and transmissivity of the apodizer in the focusing optical system. When a Gaussian beam is employed as the incident beam, the waist width also affects the depth of focus. The tunable range of the focal depth is very considerable.