Sub-3-cycle vortex pulses of tunable topological charge

Abstract

Novel types of reflective spiral micro-electro-mechanical systems were used to generate few-cycle vortex pulses of variable topological charge from a Ti:sapphire laser oscillator. The phase profile of these components was controlled by varying the temperature. The temporal properties of the pulses were characterized with spatially resolved nonlinear autocorrelation. The beam structure resembles a slightly distorted Laguerre-Gaussian distribution. The different topological charges were indicated by detecting Poynting-vector maps with a programmable Shack-Hartmann sensor of enhanced angular sensitivity.

Efficient generation of ultra-intense few-cycle radially polarized laser pulses

“…In this Letter, we focus on experimentally demonstrating a highly efficient linear-to-radial polarization mode conversion induced at the output of a few-cycle millijoule-level hollow-waveguide compressor where nearly transform-limited few-cycle pulses with radial polarization are achieved. This scheme results in a radially polarized ∼3-cycle laser centered at 800 nm routinely operating at peak and average power levels of 85 GW and 2 W, respectively, comprising the shortest pulse duration and the highest peak-and average-power radially polarized source reported to date [13][14][15]. Moreover, exploiting the intensity scalability in the few-cycle regime offers the additional benefit of reaching out to physical processes dependent on the carrier phase relative to the pulse envelope.…”

Singularities in the flying electromagnetic doughnuts

“…Our findings put forward the FD pulse as an ideal platform to study the instantaneous field singularities of ultrafast vector polarized pulses in both the paraxial and strongly focused regime without resorting to approximations. We anticipate that our results will be relevant to the experimental and theoretical efforts involving the generation, propagation properties and light matter interactions [17,18,[21][22][23][24][25][26]. We note that although a part of the fine topological structure in the FD pulse occurs at spatial regions of very low energy, a number of intriguing features manifest close to regions of relatively high energy (e.g.…”

Adaptive micro axicons for laser applications

“…The process for the thermally actuated devices proved to be amazingly flexible and thus allowed for the unique fabrication of a spiral phase plate (SPPs, Fig. 1 d) for the generation of vortex beams carrying an orbital angular momentum (OAM) of tunable topological charge [7]. Figure 2 shows as an example the fabrication, working principle, and a micrograph of a thermally tuned 2x2 axicon array.…”

“…1d to generate 7-fs vortex pulses with continuously tunable topological charge [7] as shown in Figure 5with a continuous phase profile of up to 14π. Compared to alternative solutions like high-power optical parametric oscillators (OPOs) as shapers, our approach allows us to work with much more compact systems.…”