V.S. Mkrttchian.- State Engineering University of Armenia, 105 Terian Street Yereban 37009, Armenia

Before elaboration and designing of thin films growth (TFG) it is very important to carry out an appropriate computer modelling for their analysing and optimising.

To describe adequately the physical phenomenon taking place in TFG it is necessary to revise the existing methods of theoretical investigation and choose a suitable one.

For theoretical investigation of uniform TFG several methods have been developed. One of the widely used methods is the well-known coupled-wave theory, For periodical structure transfer matrix method and Bloch wave analysis have been used successfully. Other less employed methods have been devoted and developed for uniform TFG analysis. They are the Round's method; a discrete-time approach based on a digital signal processing formulation and a Hamiltonian formulation for coupled-wave equations.

For nonuniform TFG transmutative and reflective properties investigation the extension of the methods described above has been used. They are the extensions of transfer matrix method, Bloch wave analysis generalisation, coupled-wave theory and WKB methods extension. A variational technique and a Hamiltonian approach for nonuniform TFG analysis have been employed also.

The all generalised methods for nonuniform TFG have a restriction on the amplitude of modulation. The reason is that for these methods it's significant that the wave equation solution is searched as a superposition of counter-propagating waves. The last condition badly complicates the problem solving in the case of nonperiodically and strongly modulated media.

The proposed non-traditional method of theoretical investigation is free from the above-mentioned drawbacks. It is based on the fact, that a solution of the wave equation in a modulated media is searched in the form of a single expression, but not in the form of generally accepted counter-propagating waves. Such a form of wave equation solution has been proposed by a number of authors and further has been extended, basically, to investigate different types of multilayer structures. This method allows to solve the correct boundary problem not only for linear but for nonlinear media as well. Furthermore, this approach permits to carry out the investigation for media with losses (or gain) and doesn't need any preliminary assumptions concerning the form of wave equation solution (ie. the form of travelling waves, counter-propagating waves, exponentially increasing or decreasing waves or others in the case of nonlinearity).

Such a representation of wave equation solution is also very effective to investigate electromagnetic wave interaction with arbitrary modulated media (including nonlinear) and permits to solve numerically diverse problems easily and comparatively rapidly by using of a well-known Runge-Kutta method of numerical integration.

For computer modelling of desired type of TFG the non-traditional method of theoretical investigation is suggested.

Preliminary computer simulations for uniform TFG (taking into account losses and gain) have been carried out by using of the above-described non-traditional method of theoretical investigation .