Laser generated plasma using a dual pulse approach with Application to Laser Ignition

The present paper discusses an alternative approach to laser induced ignition using a dual pulse pre-ionization technique. The method uses a 266nm UV laser pulse to achieve initial gas pre-ionization followed by an overlapped 1064 nm NIR pulse for energy addition into the pre-ionized gas. The experimental and numerical studies presented here investigate the requirements for achieving ignition conditions using the overlapped pulses configuration without optical breakdown. Results have shown that the UV pulse is effective in achieving gas pre-ionization thus allowing good energy absorption through the subsequent NIR pulse. Even at a low intensity of the 266 nm pulse of ~1 GW/cm², the breakdown requirement for the 1064 nm beam drops ~25%, while 266 nm pulses of ~5 GW/cm² lead to a drop of ~50%. Rayleigh scattering has been employed for measuring the gas temperature increase due to the two laser pulses with preliminary results showing increase of ~200 K.