Metallic Slits Modify Laser Pulses

Calculations by Abdulhakem Y. Elezzabi and Anthony Dechant at the University of Alberta in Edmonton, Alberta, Canada, indicate that the design of arrays of subwavelength metallic slits can be used to control the temporal profile of femtosecond optical pulses. The team published its findings in the June 7 issue of Applied Physics Letters.

Considerable research has been devoted to the behavior of electromagnetic radiation that interacts with subwavelength periodic metal structures. Such work, however, generally has concentrated on CW radiation. The new research instead focused on the effects of 10-, 50- and 100-fs pulses of 800-nm radiation, such as from a Ti:sapphire laser.

Solving Maxwell's equations using the finite-difference-time-domain method for various periodicities of slits in a thin silver film, Elezzabi and Dechant determined that the geometry of such arrays affects their transmission and their dispersion. For some of the setups, the results indicated superluminal propagation of the pulses.