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The design of a polarised optical filter is more complicated than that of a filter where the polarisation effect does not exist (at a normal angle of incidence). An error in the optical parameters, such as the physical thickness or refractive index of a layer, results in a change in the spectral performance of the multilayer structure. The correlation between error sensitivity and the polarisation effect of light in structures designed at an oblique angle was investigated. To illustrate the correlation, a perpendicular (S) and parallel (P) polarised beam splitter, at 0.9818 µm central wavelength, designed by genetic algorithm, was used. The beam splitter changes its state of polarisation according to the error in thickness simultaneously induced in each of the layers. The error was calculated by optimising the original design. The observation of the change of the state of polarisation as a result of error sensitivity leads to a different method of designing pure S-polarised or P-polarised optical filters.

We used a genetic algorithm in the design and optimisation of optical thin films and present the effects of the choice of variables, refractive index and optical thickness, in both applications of this algorithm, in this paper. The Fourier transform optical thin film design method was used to create a starting population, which was later optimised by the genetic algorithm. In the genetic algorithm design application, the effect of the choice of variable was not distinct, as it depended on the type of design specification. In the genetic algorithm optimisation application, the choice of refractive index as a variable showed a better performance than that of optical thickness. The results of this study indicate that a genetic algorithm is more effective in the design application than in the optimisation application of optical thin film synthesis.

An analysis was conducted to examine the transmission spectra through lamellar grating silicon wafers. Micromachining technique was utilized in the fabrication of grating structures on silicon wafers. Results revealed that the transmission in a smooth silicon wafer was almost independent from the wavelength while the transmission in lamellar gratings which were fabricated in a silicon wafer was dependent on the wavelength.

A Fourier-transform synthesis technique is applied to the design of inhomogeneous refractive-index optical thin films with dispersion of refractive index and absorption taken into account. Using measured properties of Si[O.sub.x][N.sub.y], we have designed a broadband reflector and two three-line filters with high reflectance. One of the three-line filters was manufactured by electron cyclotron resonance plasma-enhanced chemical vapor deposition from a mixture of Si[H.sub.4], [N.sub.2], [O.sub.2], and Ar. Good agreement between design and measured performance proves the feasibility of applying the Fourier-transform technique to the design of reflection filters even in the case of highly dispersive, absorbing material, if its optical properties are well characterized. Key words: Rugate filters, inhomogeneous thin films, Fourier-transform design technique, plasma-enhanced chemical vapor deposition.

The characteristics of GaAs grown by ion implantation were investigated using a novel fast nondestructive technique. The results showed that the technique was able to observe damage which cannot be detected by conventional transmission electron microscopy. The technique obtained results which were in good agreement with measurements obtained using the least-squares fit method and secondary ion mass spectroscopy.

A computerized in situ optical reflectivity measurement system for the quantitative determination of material parameter changes of a substrate during the process of ion implantation, is presented. These changes are related to the extent and nature of the induced crystal disorder in the substrate. The system comprises an optical reflectometer, with data acquisition and signal processing capabilities. For each sample a case history of the implant is obtained in the form of a continuous graph of reflectivity vs. a desired implantation parameter (e.g., dose). Examples regarding the implantation of 31P+, 40Ar+, and 14N+ are presented. Additional suggestions for further system development and applications are also made. Among the advantages of in situ measurements are the time-effort-expenses savings, higher yield of experimental data per sample, higher accuracy, repeatability, and various possibilities of process control.

In situ reflectometry during ion implantation of [sup.31][P.sup.+] into single crystal Si substrates at implantation energies between 50 and 240 keV, and using a dose rate of 0.2 [Mu]A/[cm.sup.2], has yielded new information, opening a new avenue for ion implantation research. The results show that the slope of the rapidly rising part of the reflectivity versus dose graph, and the amorphization dose are increasing functions of implantation energy. The total work up to the amorphization dose, and the work required for phase change, are calculated from the experimental data.

Presents a study which focuses on the physical performance of the lamellar gratings on silicon wafers as it relates to the zero angle of incidence transmission. Fabrication of gratings with feature sizes of the order of magnitude of the radiation wavelength; Reference to the oscillatory behavior; Information on theoretical simulation.