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(a) A sketch of the setup for tuning a random laser. Light, generated by a Nd:YAG pulsed laser (9 ns, 532 nm, 20 mJ max pulse energy) is modulated by the SLM and then directed onto the sample from underneath. Average dimension of the rhodamine drop and of the wedge are indicated in the figure. The RL emission is collected from a microscope objective (0.55 numerical aperture) shown in the upper part of the figure. (b) A generic mask sent to the SLM with the parameters θ and ϕ indicated.
Images of cluster C1 for 4 different pumping configurations (in the insets) and relative spectra. Scale bar is 9 μm.
Spectra obtained for two different target frequencies at the end of the preliminary optimization (a) and (b) and at the end of the optimization process (c) and (d). The experimental parameters are indicated in each panel (FLU stands for Fluence).
(a) Average spectrum obtained by averaging the spectra measured at the first optimization step (configurations with different values of ϕ (θ fixed to 6°)). In panel (b) the enhancement as a function of the wavelength. In panel (c) the SNR is reported instead.
Parameters varied in each stage of optimization, range, and step of variation and magnitude optimized. Scan. var. stands for “scanned variable,” while Max. magn. stands for “maximized magnitude.”
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