(a) Absorption (dashed line), fluorescence (λexc = 500 nm, dotted line), and laser spectra (solid line) of derivative 24 (23 mm) doped in PMMA. (b) DFB output intensity as a function of pump intensity from thin films of commercial PM597 (17, Scheme 2) 19 mm (filled circles) and derivative 24 (23 mm; hollow circles) doped in PMMA. Inset: sketch of DFB laser. The arrows represent in-plane feedback owing to second-order diffraction (solid arrows) and outcoupled laser emission owing to first-order diffraction (dashed arrow). Reproduced from Ref. [101] with permission from 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany.