The Rydberg matter laser: excitation, delays and mode effects in the laser cavity medium

Temporal and temperature effects are studied in Rydberg matter (RM) formed from K atoms and N₂ molecules as the active medium in a cavity. The function of this setup as a laser was recently described. Temperature-variation studies show that the photons re-exciting the RM clusters usually have a longer wavelength than the photons emitted in the stimulated emission process in the cavity. The deficit is probably covered by background photons. Very long time constants observed after emitter temperature changes indicate that long-wavelength photon energy is accumulated in the RM clusters. Long-wavelength modes are located farther from the RM emitter. The modal structure can be TEM₀₁ or TEM₀₀, as observed clearly by the spatial structure in rapid pulsing experiments. The in-cavity chopped beam signal is delayed by approximately 50 μs. The initial growth rate of the signal during chopping is temperature dependent. Tailing is also observed by chopping, but rapid pulsing of the beam with a spinning mirror does not show any delay of the start of the lasing. The conclusion is that delays exist in the stimulated emission process. The broad intense band appearing at 11 000 nm is shown to be formed partly by light in the range 3500–5000 nm, probably by standing wave interaction at the grating surface (grating bands).