Although there are several well -known methods such as RCWA, FMM, for analyzing the diffraction properties of
gratings, design of these optical elements with specified spectral properties is commonly a challenging problem. It is
relatively not easy for the researchers to design narrow line-with diffraction filters based on guided mode resonance
phenomenon with common diffraction algorithm.
Simulated Annealing (SA) method is evolutionary, robust technique that has been widely utilized to design optical
diffraction components. This method is inspired by the physical process of heating and controlled cooling of metal
material to increase the size of its crystals and reduce their defects. The most distinctive features of this method lie in its
powerful ability of convergence towards the global minimum in a reasonable computation time and the independence of
the initial parameter values.
In this paper, first, the physical basis of SA and its mathematical realization are introduced. Then, a Guided-Mode
Resonant Grating (GMRG) filters with single layer is designed by using SA algorithm. The central wavelength of
GMRG filter is locked at 532nm and its line-width is fixed at 1nm. The plane wave light radiates the grating from air
cover with normal incidence.
The optimized parameters are refractive indices and thicknesses of high and low material of grating, other parameters are
grating period and fill factor of the grating. It is shown from our calculation that an excellent reflection spectrum with
narrow line-width, high peak and low sideband can be obtained after optimizing the grating parameters. Next, a double
layered GMRG filter with line-width of 4nm, which is relatively easy fabrication in experiment, is designed at central
wavelength of 1064nm. The optimized parameters are grating period, groove depth, refractive index of waveguide layer
and fill factor respectively. The grating substrate and waveguide layer are Sio2 and Hfo2 respectively, the grating
structure is directly etched on the waveguide layer. The above grating values should be included in reasonable ranges in
consideration of grating fabrication in our experiment condition.
It is demonstrated from the calculations with the parameters obtained from SA optimization algorithm that the peak
diffraction efficiency is more than 99% at central wavelength 1064nm and the sideband reflection is depressed at the
level bellow 5% in a large wavelength range. Moreover, the parameters of a triple layer GMRG filter structure are also
provided with this powerful method. Meanwhile, the results found by SA method are compared with RCWA theory.
Hybrid Magneto-Optical Recording is a potential data storage technology in the future informational society. To
construct a research platform for hybrid recording, a dynamic testing system is designed and built in this paper, in which
406.7nm blue laser is used for recording and 655nm red laser for focus servo. With high modularization, the computer
serves as the control core for the laser external modulation, focus servo, and sample plate spinning. Each module and its
function are discussed in detail in the paper. Experimental results are also given to verify the stable and smooth
performance of the system, in which the key obstacle, vibration noise, is successfully surmounted.
Measurement technology plays an important role in the area of optical storage, a multifunctional quasi-dynamic static
optical recording tester, which can also be used as nanometer laser direct writing lithography system, is designed and
constructed for optical storage in this paper. The primary characteristics of the system are presented in detail, some
experimental results are also given to show that the tester perform successfully, acting as a research platform for both
optical storage and laser direct writing lithography.
A stratified model for scattering from multilayer coatings due to roughness of inhomogeneous interfaces is introduced in the paper. It assumes that a rough interface between two media of multilayer coatings consists of a series of very thin, homogeneous sub-layers and that there is an exponential increase in refractive indices of those sub-layers. Matrix method was used to deduce the formulation for calculating the total integrated scattering (TIS). ZrO<sub>2</sub> coatings were deposited on BK7 glass by electron beam evaporation, and their scattering properties were measured and calculated by the scatterometer, the stratified scattering model and the existing uncorrelated surface roughness model, respectively. It is shown that the calculated results based on predictions of the stratified scattering model are in closer correspondence with the experimental data than that obtained with uncorrelated surface roughness model.