Ultrafast laser and electron pulses for high resolution imaging

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Lasers have impacted science, engineering and medicine in a transformative way. Lasers have opened new avenues for fundamental research and generated practical outcomes that have changed our daily life. Lasers have enabled new industrial processes and medical treatments and have triggered the present age of information. Lasers have allowed exploring new states of matter at unprecedented time scales. Laser systems generate powerful beams that can be positioned with sub-wavelength accuracy and have enabled microscopy tools with unmatched resolution. Nowadays laser science is moving towards fiber lasers that are compact and efficient. However propagation of optical signals in optical fibers leads to nonlinear effects that must be carefully managed, especially with pulses of short duration. The effective bandwidth of fiber lasers inhibits the generation of pulses of duration lasting a few optical cycles. In the coming mandate we will explore methods to resolve the issues raised by the latter effects that have limited the use of fiber laser systems. Our proposal will also address how properly structured laser signals can be used for high resolution imaging with laser scanning optical microscopes and laser accelerated electrons beams.***1. Shorter and more powerful pulses from fiber laser systems. We will use a cavity design with a pair of chirped fiber Bragg gratings to boost the energy of the pulses emitted by fiber laser oscillators. We will also design amplifiers based on Stimulated Raman Scattering to preserve the bandwidth of ultrashort pulses during amplification in order to make fiber laser systems competitive with their solid-state counterparts.***2. Superresolution in laser scanning optical microscopy. We will push the resolution limits of SLAM (Switching LAser Modes) microscopy well below the diffraction limit, down to 50 nm, using complex mode shapes and deconvolution methods. SLAM can be used with any type of modality in optical microscopy and its enhanced resolution does not require any specific laser sample interaction, contrary to most superresolution methods.***3. Particle acceleration using radially polarized laser pulses. We have introduced a scheme to directly accelerate electrons in free space using the longitudinal electric field component of ultrafast radially polarized laser pulses. We will exploit that scheme to produce electron beams suitable for high resolution imaging by means of ultrafast electron diffraction. We will explore how spatiotemporal shaping of laser pulses could be used to accelerate charged particles at laser focus in such a way as to produce a micrometer scale collider.***This research program will be realized in an environment suitable for student training. The students will benefit from many internal and external collaborations, as well as interactions with industry.**