Laser plasma optical device comprising a laser system for outputting driving light pulses and signal light pulses, a vacuum target chamber, a gas target generating device for generating gas and forming a required plasma channel target through high voltage capillary discharge ionization (or through laser picosecond pre-pulse ablation) of gas, and a focusing element. The driving light pulse is focused on the generated plasma channel target through the focusing element to generate a density-modulated plasma wake; and after a predetermined delay time T, the signal light pulse is focused onto a leading edge region of a second plasma density cavitation bubble of the plasma wake through the focusing element, so that the frequency of the signal light pulse is red-shifted to generate an ultra-intense near-single-cycle mid-infrared pulse.