Nonlinear propagation of necklace-shaped beams through gas-filled capillaries to generate few-cycle energetic pulses in the visible

There is a wide variety of schemes and setups to obtain ultrashort pulses in the visible region of the spectrum, but the complexity of some of them has motivated the search of other alternatives. One of the most compact setups to obtain ultrashort pulses from the ultraviolet to the infrared is by the dispersive wave (DW) generation from the soliton self-compression (SSC) inside a gas-filled capillary [1] . The energy of the DW depends on the input pulse energy, which is limited by the activation of the self-focusing and/or the photoionization inside the capillary, and the efficiency of the process usually lies between 10%-15%. In this work, we present another strategy to obtain ultrashort visible energetic pulses, which consists in propagating a specific combination of high-order capillary modes resulting in a linearly polarized necklace beam (NB), with an intensity spatial distribution similar to that shown in Fig. 1(a) [2] , [3] . The strong self-phase modulation (SPM) experienced by the NB in combination with the SSC effect inside the capillary, provide an ultrashort visible energetic pulse.