Dynamic Control of Interference Effects Between Optical Filaments through Programmable Optical Phase Modulation

Abstract

Abstract-Light beams shaped by programmable megapixel spatial light modulators (SLMs) are key to broaden the applications of photonics. In this paper, we consider the application of a SLM for the generation of two mutually coherent white-light continuum optical sources by filamentation of infrared femtosecond pulses in bulk. We demonstrate that the inhomogeneity of the input beam and the longitudinal separation of the generated filaments are crucial parameters that break down the mutual coherence across neighboring filaments. We show that local control over the optical phase enables us to gain fine control over filament interference effects.

Diffractive control of 3D multifilamentation in fused silica with micrometric resolution

“…In addition, the energy coupled into the filaments could be also modified by decreasing the abovementioned phase parameter  associated with the diffraction efficiency of the lenses. However, owing to the homogeneous spatial sampling of the lenses throughout the DPE, all generated filaments are almost of the same energy, so the need from diffraction efficiency compensation i.e., for instance claimed in [24], is not an issue in the present experiment.…”

“…This kind of shaping of the energy distribution per filament may be very useful in situations when the amplitude of the laser beam at the DPE plane evidences clear inhomogeneities. In this case, if a conventional array of lenses is used to focus the pulse like in [24], the amount of energy coupled into the filaments could be quite different. In contrast, distributions of filaments shown in Fig.…”

“…For this reason, in this experiment corrections were only done in the focal lengths, but not in the diffraction efficiency of lenses. There are other well-known factors i.e., laser beam aberrations [21] or non-uniform spatial phase response [22][23][24] of the SLM, that also can change energies and positions of foci. However, in our experiment the high temporal stability of the obtained filaments suggests that possible effects introduced by time-dependent factors might be included into the scrambled distribution of filaments already shown in Fig.…”

“…Regarding this topic, the coherent nature of the filaments [20] has been investigated by means of several optical setups/devices such as a diffraction-grating-based interferometer [21], collinear geometries with time-delayed pulses [22], variable linear arrays of supercontinuum sources [23] or programmable liquid crystal SLMs [24]. In addition, the filamentation process in fused silica generated under femtosecond illumination has been studied by means of diffractive lenses [24][25][26]. In particular, conventional arrays of diffractive lenses have been implemented as a tool to generate multiple and predefined filaments in fused silica [24,27].…”

“…In addition, the filamentation process in fused silica generated under femtosecond illumination has been studied by means of diffractive lenses [24][25][26]. In particular, conventional arrays of diffractive lenses have been implemented as a tool to generate multiple and predefined filaments in fused silica [24,27]. At this point, we want to note that the utilization of a conventional array of diffractive lenses for multifilamentation has some drawbacks.…”