Experimental investigation of the boundary wave pulse

The existence of the boundary (diffraction) wave pulse is demonstrated by measuring the spectrum and the radial intensity distribution of the diffracted femtosecond pulses behind a circular aperture. Our results confirm Thomas Young's assumption about the nature of diffraction which explains diffraction as the interference of the undisturbed (geometrical) wave and the boundary diffraction wave generated by the edge of the diffracting obstacle. It is experimentally demonstrated that two pulses propagate on the optical axis as it is predicted boundary diffraction wave theory. Because of the time (and path) difference between the geometrical pulse and the boundary wave pulse the spectrum becomes modulated. The radial intensity distribution in the vicinity of the axis can be described by the zero-order Bessel function if the two pulses do not overlap each other i.e., the time difference between the pulses is large enough compared to the pulse duration. (C) 2004 Elsevier B.V. All rights reserved.