Femtosecond spatial pulse shaping at the focal plane

Abstract

Abstract:Spatial shaping of ultrashort laser beams at the focal plane is theoretically analyzed. The description of the pulse is performed by its expansion in terms of Laguerre-Gaussian orthonormal modes. This procedure gives both a comprehensive interpretation of the propagation dynamics and the required signal to encode onto a spatial light modulator for spatial shaping, without using iterative algorithms. As an example, pulses with top-hat and annular spatial profiles are designed and their dynamics analyzed. The interference of top-hat pulses is also investigated finding potential applications in high precision pump-probe experiments (without using delay lines) and for the creation of subwavelength ablation patterns. In addition, a novel class of ultrashort pulses possessing non-stationary orbital angular momentum is also proposed. These exotic pulses provide additional degrees of freedom that open up new perspectives in fields such as laser-matter interaction and micro-machining.

Advances in ultrafast laser structuring of materials at the nanoscale

“…Applying propagation corrections and controlling the focal geometries [157,158] extrapolated to tight focusing will permit better control on the excitation gradients. Beyond the engineering of the shape of the focal plane [159], spatial phase control impacts particularly the field pattern in multibeam interference setups, determining flexibility in the pattern definition and hierarchical arrangements [160].…”

Multispectral Management of the Photon Orbital Angular Momentum

“…Optical pulse shaping is a mature technology having a huge range of applications, for instance, in spectroscopy and light wave communications [31] that still continue to be developed, as illustrated, for instance, by recent works on spatiotemporal focusing [32][33][34]. Situations involving the optical orbital angular momentum are also attractive in high-energy optics where techniques are developed towards space-time manipulation of optical pulses [35][36][37]. Hereafter, we discuss a case study illustrating how spectral vortex modulation is likely to impact this field.…”

Simulated propagation of ultrashort pulses modulated by low-Fresnel-number lenses using truncated series expansions

“…[7] was based on the numerical simulation of the pulselets; therefore, not enabling the potential efficiency of the expansion technique that could be obtained with closed expressions for the individual pulsed modes. Analytical formulation of the propagation of the LG pulselets will require the derivation of expressions for each unique spectral variation, Sω, but Martínez-Matos et al have recently augmented the potential of the LG expansion in pulse modeling with the derivation of a formula for the propagation of the LG pulselets with Gaussian spectra [19]. In contrast to [7] and [19], the LG expansion method is discussed here through the conventional model of a pulse as an integration of monochromatic fields [6], as in Eq.…”

“…( 7), illustrating the technique as an efficient alternative to the FDI. For pulses transformed by lenses, the concept of an ultrashort field propagating as a superposition of individual LG pulselets [7,19] would remain valid, with each individual pulselet subject to modulation. However, the spectral dependence of the mode coefficients, A m ω, in Eq.…”