Palestrante
Descrição
Propagation of ultrashort laser pulses in gaseous media demands a precise knowledge of nonlinear (NL) effects and how their dependence on pulse characteristics. However, due to their low density, gases NL effects are relative weak if compared with solids (four orders of magnitude), and complex experimental setup must be employed to evaluate nonlinearities on them. The knowledge of NL effects on gaseous media is fundamental to several applications, such as: high harmonic generation, attosecond physics, filamentation, white light generation, terahertz production, compression of ultrashort pulses, LiDAR, among others.Very recently, our group have developed a new experimental setup to characterize gases NL refractive index ($n_2$) in simplified manner(1), when compared with the other methods (self-phase modulation (SPM), Kerr effect, four-wave mixing (FWM)). Ours experimental setup employed up to hundreds $\mu$J, tunable temporal pulse width (60 fs to 3 ps), at 800 nm in order to measure NL elliptical rotation (NER) effect in gaseous media confined on hollow core fiber (HCF). The use of an extended interaction length, provided by the HCF propagation, was necessary to overcome the gaseous weak NL effects. On this way, we were able to evaluate $n_2$, and its dependency with the excitation pulse width ($\tau_p$), for principal atmospheric constituting gases ($He$, $Ar$, $N_2$ and $O_2$). The sample $n_2$ fast (pure electronic, fs-scale) and slow (molecular orientation, ps-scale) contributions and their intermediate values were fully characterized varying $\tau_p$ from 60 fs to 3 ps. In addition, we have proposed an empirical model that allow one to obtain the gaseous $n_2$ for any pulse width constrained within the electronic and molecular contribution range.(2)Once the gaseous sample have been characterized, we employed the knowledge of the rare gases $n_2$ to better tailor the conditions to produce a wavelength tunable ultra-short and energetic source of deep ultraviolet (DUV) via soliton dispersive wave emission (DWE) in HCF.(3) That source is mainly desired for materials spectroscopy, opening a way for a new range of investigation. Consequently, we produced a soliton DWE propagating 1 mJ, sub-10 fs pulse in the IR (800 nm) through a 2 m long and flexible HCF filled with noble gases. Then, we were able to generate an energetic (tens of $mu$J), tunable (150 – 350 nm), and ultra-short (tens of fs) DUV beam through DWE.
Referências
1 MIGUEZ, M. L. et al. Accurate measurement of nonlinear ellipse rotation using a phase-sensitive method. Optics Express,v. 22, n. 21, p. 25530-25538,2014.
2 DE SOUZA, T. G. B. et al. Measurement of nonlinear refractive index of air, oxygen, and nitrogen in capillary by changing the temporal width of short laser pulses. Journal Optical Society of America B, v.34, n.10,p. 2233-2237,2017.
3 TRAVERS, J. C. et al. High-energy pulse self-compression and ultraviolet generation through soliton dynamics in hollow capillary fibres.Nature Photonics,** 2019.doi.org/10.1038/s41566-019-0416-4.
| Apresentação do trabalho acadêmico para o público geral | Sim |
|---|---|
| Subárea | Óptica e Lasers |
