DYNAMICS OF A MODE-LOCKED LOW-PRESSURE PHOTOLYTIC I-ASTERISK LASER

A longitudinally pumped photolytic iodine laser has been reliably mode -locked over a broad range of iodide pressures (1-30 Torr). Average mo de-locked pulse widths ranging from 1,4-2,5 ns were observed as a func tion of CF3I Iodide pressure and added buffer gas (Ar). Low-pressure d ata indicate an increased gain bandwidth as a result of an initial non thermal I atom distribution following rapid (<20 us) photolysis of th e parent molecule, CF3I, Nearly 1.75 eV of excess pump energy is avail able and is deposited into the internal vibrational and rotational deg rees of freedom of the large radical and into the translation of the n ascent iodine atom, allowing for high iodine atom velocities in the fr ame of observation, A diode laser system tuned to the 3-4 transition o f spin-orbit excited iodine atoms was used to observe the time-depende nt behavior of line center gain along the optical axis, Preliminary da ta indicate an Ir atom velocity relaxation on the order of 1 mu s for an iodide pressure of 1 Torr, and approximately 300 ns for a pressure of 10 Torr, At 5 Torr of CF3I, the laser mode build np time is 200 ns, allowing access to the increased gain bandwidth and resulting in mode -locked pulse widths less than the predicted transform-limited pulse w idth for an inhomogeneous gas laser.