We demonstrate a narrow-bandwidth tunable optical filter in the telecommunication wavelength region near 1550 nm
using photorefractive grating. Holographic gratings could be written by plane waves of green light using CW 532nm
laser as recording source. The filter could be tuned by changing the grating spacing by means of changing the incident
angle of the recording beams of grating. Through theoretically consideration, we get a diffractive efficiency up to 80%
and a bandwidth less than 0.1nm. Besides, we propose a holographic recording setup.
Annular binary filters that can fulfill the superresolution are designed and produced. The transverse and axial resolution
gains of the filters are defined. The transverse gain is optimized by genetic algorithm to obtain the optimal structure
parameters. The designed filter has a transverse gain of 1.37. The distributions of the transverse and axial intensity of the
designed filters and the general circular pupil is illustrated, from which we can see that the spot size of the former is
reduced by 30% and the depth of focus is increased compared with the latter. The optical system for testing the
performances of the binary annular filters was build. The experimental results show the binary annular filter has fulfilled
Experimental results are reported on temporal instability of phase conjugate beam in a self-pumped Ce: BaTiO3 phase conjugator at 532nm. The transition from stable output to unstable one is studied for various input powers, beam diameters and incident angles. Novel results that the phase conjugate output will be unsteady when control parameter PS is within a range of 2220~3897 mW/cm2 are presented. A qualitative analysis to temporal instability that instability behaviors result from competitions among the backscattering centers is given.
Photonic crystals have been widely studied in the fields of physics, material science and optical information technology.
In general, the standard rectangular FDTD method is used to predict the performances of photonic crystals even if it is
very time consuming and inefficient for the structures with non-orthogonal structures or inhomogeneous media. The
current authors developed a software called GCFE, which is based on non-orthogonal FDTD method .The upgraded
version of GCFE software can be used to calculate the photonic band structures, states density, transmission and
reflection coefficients of one dimensional to three dimensional photonic crystals. It has the characteristic of efficient
calculation and simple manipulation. In the present paper, the system structure of GCFE software is presented and the
implementation of the algorithm module and the result display module are described in detail. Finally the band
structures, transmission and reflection coefficients and photonic states density for the photonic crystal fibers with cube
structures are calculated by our GCFE software and the numerical application results are also shown and discussed.
A theoretical method for evaluating the three-dimensional focusing performances of the compound x-rays lenses is presented in the present paper. The relationship between the transverse and axial focusing behaviors is considered and a simple calculation that predicts the transverse and axial focusing behaviors of the compound x-ray lenses is also presented. As an example, the three-dimensional focusing performance of a compound x-ray lens with Al material is predicted. The dependences of the three-dimensional focusing performances on the compound lenses’ structural parameters are observed for the Al compound x-ray lens. Moreover, the approximate tolerances in the setting of the receiving planes are also considered for x-rays of 4.95keV, 14.99keV and 29.78keV.