Abstract: A CO.sub.2 TEA laser utilizing an intra-cavity rotating prism Q-switch (70) for angularly switching the resonator gain by periodically causing the resonator mirrors (54, 56) to be in alignment. An opto-electronic timing device (79), which includes a graded index glass rod (76) rotating with the Q-switch prism, generates a pulse to initiate the laser discharge at the proper time before the mirrors are aligned so that the laser output pulse occurs when peak gain is achieved. The Q-switch speed of rotation is chosen such that the time interval in which the mirrors are aligned is not long enough to support the tail portion of the pulse typical of the gain switched CO.sub.2 TEA laser.