Generation of femtosecond diffraction-compensated beam through an opaque disk

Abstract

The generation of a femtosecond diffraction-compensated beam through an opaque disk is presented: 100 fs pulses are focused in the vicinity of an opaque disk. A bright beam surrounded by concentric rings is generated. The beam can be collimated by a lens. A non-diffracting femtosecond beam which conserves a 500microm large central spot over more than 1.7m is then observed, without any nonlinear mechanism. Our theoretical analysis predicts well the results.

Non-Diverging Dark-Hollow Beam Generation With a Pigtailed Laser Diode

“…The adaptation of this method to femtosecond pulses will be further tested, as what could be done for the generation of femtosecond diffraction-compensated bright beams with an opaque disk. 14 …”

Analytical expressions for diffraction-free beams through an opaque disk

“…It is however possible to fit relatively well the experimental beam profile using the approached relation (29). In conclusion, the expression (29) represents a very important simplification of our previous numerical developments [15] which required long calculus times. It allows now the simple optimization of systems.…”

“…Diffraction is a linear, isotropic and homogeneous effect. The propagation of light can be described by a combination of Fresnel diffraction (for each spectral component) and a temporal filter (for proper superposition of monochromatic components) [14,15]. The pulse energy does not exceed a few tens of picojoules, such that there is no additional nonlinear effect in the substrate of the diffractive element.…”