The observation of transients in a CO2 or N2O ir laser by modulation of an intracavity absorber

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Abstract
A damped oscillation following a stepwise modulation of an intracavity saturable absorber has been observed in the output power of an infrared CO2 and N2O laser. A high frequency of oscillation (∼100 kHz) and a large damping rate were observed for a high laser power and, when the laser power was lowered, both were reduced with the damping rate becoming zero as the laser started passive Q switching. The smooth variation of the characteristics into the passive Q‐switching region indicates that the damped oscillation is caused by the same mechanism which causes the passive Q switching, that is, the exchange of radiative energy between the laser gain medium and the saturable absorber. For a laser operating in the low‐power regime, a narrow resonance has been observed in the laser modulation depth when the frequency of the stepwise modulation was varied continuously from 10 to 100 kHz. This resonance can be used effectively for increasing the sensitivity of intracavity laser spectroscopic experiments.