Basic diffraction phenomena in time domain

Peeter Saari,Pamela Bowlan,Rick Trebino,Heli Valtna-Lukner,Peeter Piksarv,Madis Lõhmus

doi:10.1364/oe.18.011083

Abstract

Using a recently developed technique (SEA TADPOLE) for easily measuring the complete spatiotemporal electric field of light pulses with micrometer spatial and femtosecond temporal resolution, we directly demonstrate the formation of theo-called boundary diffraction wave and Arago's spot after an aperture, as well as the superluminal propagation of the spot. Our spatiotemporally resolved measurements beautifully confirm the time-domain treatment of diffraction. Also they prove very useful for modern physical optics, especially in micro- and meso-optics, and also significantly aid in the understanding of diffraction phenomena in general.

Highlights

The bending of light waves in the shadow region behind an opaque disk and the appearance of a bright “Spot of Arago” in the shadow centre are well-known manifestations of diffraction
Using a recently developed technique (SEA TADPOLE) for measuring the complete spatiotemporal electric field of light pulses with micrometer spatial and femtosecond temporal resolution, we directly demonstrate the formation of theo-called boundary diffraction wave and Arago’s spot after an aperture, as well as the superluminal propagation of the spot
Our spatiotemporally resolved measurements beautifully confirm the time-domain treatment of diffraction. They prove very useful for modern physical optics, especially in micro- and meso-optics, and significantly aid in the understanding of diffraction phenomena in general

Summary

Introduction

The bending of light waves in the shadow region behind an opaque disk and the appearance of a bright “Spot of Arago” in the shadow centre are well-known manifestations of diffraction. The boundary-diffraction wave (BDW) theory, as it was called, describes diffraction from openings in opaque screens in a mathematically simple manner. The BDW theory is especially intuitive when describing the formation of the diffracted field for the case of illumination with ultrashort laser pulses [4]. The formation of an ultrashort boundary-wave pulse just after a circular aperture has been theoretically studied [4], and experimental evidence for its existence was obtained by measuring modulations in the spectrum of the on-axis field, with CCD-recordings of the timeintegrated radial intensity distribution of the field, or using spatial interference [6,7,8]. Our aim has been to directly record, with simultaneous spatial and temporal resolution, the evolution and interference of the boundary waves behind an opaque disk and behind a circular opening. It reveals that the spots are decelerating versions of the superluminal Bessel-X pulse (see [9,10,11] and references therein)

Theoretical description of the boundary wave pulse

Experimental results in comparison with simulations

Conclusions