In the electrical field of a focused beam of a high‐power Q‐switched CO2laser a so‐called pulsed optical discharge (POD) can be sustained. Applying laser pulses with max. 104pulses/s, peak power 250 kW and pulse length 0.2 &mgr;s, the charge carrier density of a hydrogen plasma at a pressure of several MPa produced during the laser pulse is enhanced up to about the cut‐off density at &lgr;L=10.6 &mgr;m (&bartil;1025m−3) and the electron temperature is increased to about 105K. POD can be sustained very reproducibly by each individual laser pulse, because the optical discharge is ignited in the hot gas of the preceding laser pulse. Time and spatial resolved spectroscopic measurements yield Stark‐broadened Balmer H&bgr;‐line profiles from which, assuming partial local thermal equilibrium, the electron temperature and density can be derived. A numerical model was derived to calculate the time development of the electron density, temperature and plasma radius.