Plasma expansion into a waveguide created by a linearly polarized femtosecond laser pulse

We demonstrate the efficient generation of 4 mm and 8 mm long plasma waveguides in hydrogen and helium. These waveguides have matching spots sizes for 13 to 34 mu m laser beams. The plasma waveguides are created by ultra-short laser pulses (sub-picosecond) of moderate intensities, similar to 10(15)-10(16) W cm(-2), that heat the plasma to initial temperatures of tens of eV in order to create a hot plasma column that will expand into a plasma waveguide. We have determined that the main heating mechanism when using fs laser pulses and plasma densities similar to 10(18-19) cm(-3) is Above Threshold Ionization. Detailed time and space electron density measurements are presented for the laser produced plasma waveguides. (C) 2013 AIP Publishing LLC.