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[2H-1-benzopyran- 2,2'-(2H)- indole], under nanosecond excitation conditions. ASE line narrowing is clearly observed for excitation densities larger than 400 mu J 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.