Extending mechanism of femtosecond filamentation by double coaxial beams

We numerically investigated the interior connection dynamics of separated sub-filaments generated by the inner beam of double synchronous and coaxial beams. We demonstrated the critical differences from the case of sequential connection of two filaments generated by two asynchronous pulses. It shows that the background reservoir formed by the co-propagation beams has a secondary function of generation of wave-guide interlayer, resulting in a long continuous plasma channel.