Forced CO2 Laser Oscillation by Injection of a Weak External Optical Signal

A forced or frectuency locked oscillation is obtained even below threshold when a weak single line of a CO₂ laser is externally injected into a Q switched CO₂ laser system. For such a regenerative optical amplifier, the input power is amplified by a factor of 10⁶. Without a dispersive element, a single line oscillation is obtained in the range of P(10) to P(32) and R(28) to R(14) of the 10.4 μm band transition for various external signals. The amplification mechanism of the input signal is explained by the assumption that the quantum noise and the external signal are amplified in the same manner, and by the exchange of the noise for the input power. Experimental results agree well with the theoretical results which are derived from the quantum mechanical Langevin equations.