AbstractThis paper describes the numerical results and derivation of the partial reflected waves from a square‐law medium in which a Gaussian beam is incident. First the WKB solution for the wave equation in the square‐law medium is presented along with approximate solution for the first, second and third reflected waves. The investigated partial reflected waves can not be found by means of the WKB solution. An approximate expression for the partial reflected waves between two reflected beams is derived by Bremmer series. It is found that the partial reflected waves do not depend on the spot size of the beam and are basically proportional to the gradient of the permittivity. The theoretical results are in good agreement with the experimental resu