Influence of the Excitation Light Disorder on the Spatial Coherence in the Stimulated Raman Scattering and Random Lasing Coupled Regime

We present a new experimental procedure, based on the use of disordered light patterns, to improve the efficiency of random lasing and stimulated Raman scattering (SRS), which appear to be simultaneous and coupled at high intensities. A dual-regime random laser (RL) was achieved by using silver nanowires as scattering elements to induce an optical feedback in cavity-free lasers that use a Raman dye as the gain medium. It is shown that in the SRS-RL coupling regime, the random modulation of the pump intensity profile promotes efficient amplification of coherent Stokes photons in small randomly distributed regions, which simulate the formation of transverse laser modes. As a consequence, the spatial coherence of radiation emitted by the SRS-RL source can be tuned by managing the speckle contrast and the random wavevector distribution, corresponding to the parameters that define the degree of disorder introduced in the light pulses that pump the random lasing medium. Measurements of the 2D spatial intensity-correlation function of the emitted fields were performed to evaluate the efficiency of disordered light to control the spatial coherence of SRS-RL.

Automated summary

A new experimental procedure using disordered light patterns was presented to enhance the efficiency of random lasing and stimulated Raman scattering (SRS), achieving a dual-regime random laser. It was found that in the SRS-RL coupling regime, random modulation of the pump intensity profile promoted efficient amplification of coherent Stokes photons, simulating the formation of transverse laser modes.