Light amplification at 501 nm and large nanosecond optical gain in organic dye-doped polymeric waveguides

We report on the results of a gain measurement on a substituted stilbene-dye-doped polymer waveguide operating in the blue-green spectral region. By monitoring amplified spontaneous emission from the waveguides under nanosecond photopumping, we deduced net modal gain as large as 84 +/- 6 cm(-1) at 501 nm, the peak of the gain spectrum, when pumped with a fluence of 1.1 mJ/cm(2). Moreover, the effective stimulated emission cross section of 2.7x10(-16) cm(2) and the loss coefficient of 0.3 cm(-1) at 501 nm are extracted. The transparency pump fluence and the corresponding excited state population density are found to be 17 mu J/cm(2) and 8.8x10(15) cm(-3) which is approximately 0.1% of total population, respectively. Comparison is made with other organic and inorganic gain media operating in the short wavelength (violet-green) region of the spectrum. We demonstrate that small-molecule-doped polymers show large gain, comparable with those in conjugated polymers and dendrimers.