Namig Alasgarzade

In the paraxial regime and neglecting back-reflections, the slow envelope A $A$ of a monochromatic wave at wavelength λ $\lambda$ propagates according to the paraxial Helmholtz equation 2 i k 0 n 0 ∂ A ∂ z + ∇ t 2 A + k 0 2 n 2 ( x , y , z ) − n 0 2 A = 0 $$\begin{equation} 2ik_0 n_0 \frac{\partial A}{\partial z} + \nabla ^2_t A + k_0^2 {\left(n^2(x,y,z) - n_0^2 \right)} A =0 \end{equation}$$ (1) where ∇ t 2 = ∂ x 2 + ∂ y 2 $\nabla ^2_t=\partial ^2_x+\partial ^2_y$ is the transversal...