Decrease in laser ablation threshold for epithelial tissue microsurgery in a living Drosophila embryo during dorsal closure

In this work, we use a two-photon fluorescence microscope for combined imaging and laser tissue ablation of a living Drosophila Melanogaster embryo. By using tightly focused near-infrared femtosecond pulses at MHz repetition rate and of sub-nanojoule energy we are able to produce microsurgery on the epithelial tissue within a Drosophila embryo at the final stages of its embryonic development. Ablation was performed on labelled and unlabelled embryos during and after dorsal closure. We observed that ablation of GFP-labelled tissue required lower energy deposition than unlabelled tissue ensuring that the tissue ablation is mediated by multiphoton absorption of Green Fluorescent Protein (GFP). In addition, the energy deposition to produce ablation is further decreased during dorsal closure. These results show the presence of additional tensile forces on the tissue during dorsal closure. Furthermore, an increased activity of actin near the laser wounds was observed as the tissue heals.

Low-threshold femtosecond optical parametric oscillator based on chirped-pulse frequency conversion

We report what is to our knowledge the first demonstration of a femtosecond optical parametric oscillator based on chirped-pulse frequency conversion in a long crystal of aperiodically poled potassium titanyl phosphate. The minimum pump threshold power was 15 mW, and a signal slope efficiency of 35% was achieved. Continuous tuning from 1190 to 1450 nm was obtained for an average pump power of 800 mW.

Efficiency of quadratic soliton generation

We report what is believed to be the first experimental demonstration of soliton content as a function of the intensity of input light for multicolor quadratic solitons. Experiments were conducted with spatial solitons excited with Gaussian beams in a bulk crystal cut for second-harmonic generation. The effects introduced by the finite crystal length and by the scheme employed to elucidate the soliton energy are highlighted.