On the temporal behavior of Nd^3+ random lasers

Abstract

The temporal dynamics of random laser emission from Nd-doped crystal powders has been investigated by using an improved detection device. The precise conditions to detect high contrast, fast oscillations are described. The measured period is about one order of magnitude shorter than the one given in the literature for relaxation oscillations in these materials. The origin of these differences is discussed.

Random laser model for Nd3+-doped powders and its application to stimulated emission cross-section calculations

“…7(a). In this case, the output intensity essentially follows in time the pumping intensity (after build-up of the laser pulse), as observed in experiments [30], and in Fig. 7(b) [39].…”

“…Although separate paths cannot be measured, we can measure the emission from small areas, of a size of the order of the distance of minimum transversal coherence, the transport length, which is about 10 microns. This can be achieved by using a lens that projects the image of the emitting surface on a plane where a pin-hole of the appropriate size [30] is placed. Under these conditions, no periodical fluctuations with a time range of tens of ps are detected.…”

“…This average length is provided by the diffusion theory and it turns out to be proportional to the inelastic length (inverse of the absorption coefficient) [19,20,24]. These models are not able to provide results about absolute output energy, and their prediction of temporal behavior does not fit the experimental evidence [30].…”

Random Laser Action in Nd:YAG Crystal Powder

“…We have observed that, in Nd stoichiometric crystal powders with a similar grain size, this delay time is much shorter [34,35]. In regular laser systems, this delay time between pump intensity and emission fluctuations is determined by the residence time of the photon inside the resonator [36].…”

Random-laser dynamics with temporally modulated pump

“…A technical challenge is the high speed required for temporal modulation. Prior experimental studies with pulsed excitations have revealed fast dynamic response of random lasers [8][9][10][11][12][13][14][15][16][17][18][19][20], and the pump modulation needs to be on a comparable time scale.…”