Non-diffraction fringes produced by thin biprism

Thin biprism can form non-diffraction fringes when it is illuminated by coherent plane wave and the non-diffraction fringes have long focal length and uniform intensity distribution. Geometrical optics characteristic of thin biprism is analyzed. Non-diffraction field produced by thin biprism at the Fresnel zone is deduced with exact Fresnel integral and an approximation representation is obtained by the stationary phase method. Numerical calculation is utilized to investigate the properties of non-diffraction fringes and evaluate the influence of the diffractive field caused by rectangle aperture's square edge on the fringes. An experiment is setup to observe the intensity of the non-diffraction fringes.