Results are presented on experimental and theoretical work performed to compare diffraction phenomena for ultrashort
pulses and continuous-wave propagation modes illuminating different-sized pinholes and slits. Results demonstrate that
pulses do not produce high-frequency diffraction like that produced with continuous-wave illumination. The diffraction through a
pinhole of temporally stretched pulses obtained by using fused silica plates whose frequency spectrum remains the same is compared with those of
pulses. The overall diffraction intensity profiles are, however, nearly identical in this case. The simulations of diffraction patterns for
incident pulse were compared theoretically for different aperture sizes and frequencies. Calculations indicate that the lack of high-frequency diffraction for the mode-locked case is due to the broadband nature of the ultrashort laser pulses; i.e., the distribution of the frequency contained in the pulse ends up washing out when objects are illuminated with pulses of broad frequency content. The results of this work have important application in biomedical imaging and remote imaging applications, to name only a few.
© 2005 Optical Society of America