Amplified Spontaneous Emission and Waveguiding Properties of the Colored Merocyanine Form of (1‘,3‘-Dihydro-1‘,3‘,3‘-trimethyl-6- nitrospiro[2H-1-benzopyran-2,2‘-(2H)-indole] Molecules

We report a complete study of the properties of amplified spontaneous emission (ASE) of the merocyanine form of the photochromic system, 1‘,3‘-dihydro-1‘,3‘,3‘-trimethyl-6-nitrospiro[2 H -1-benzopyran-2,2‘-(2 H )-indole], under nanosecond excitation conditions. ASE line narrowing is clearly observed for excitation densities larger than 400 μJ cm - 2 with a threshold pumping length in the range 0.5−1.2 mm. Remarkable waveguiding properties were observed, with losses throughout the organic slab of about 5.7 cm - 1 . The observation of ASE is discussed in terms of a possible S 1 -dominated photoconversion and excitation/de-excitation dynamics of the photochromic system. These results are important in view of the application of merocyanine-based films as active layers for potentially gateable laser devices.