Enlargement of the organic solid-state DFB laser wavelength tuning range by the use of two complementary luminescent dyes doped into the host matrix.

The spectral tuning range of dye lasers is closely associated with the gain profile provided by the utilized luminescent compound. Here, we present the results of studies aimed at broadening the wavelength tuning range in distributed feedback (DFB) lasers, made up of polymeric layers doped with a mixture of two complementary dyes. We have used the 3-(2,2-dicyanoethenyl)-1-phenyl-4,5-dihydro-1H-pyrazole (DCNP) luminescent dye, showing stimulated emission in its crystalline form, and the Rhodamine 700 (Rh700) laser dye, which is red-shifted in luminescence relative to DCNP, both doped into a poly(methyl methacrylate) (PMMA) host matrix. We have investigated the relationships between the additives' relative weight to weight ratios and their ability to exhibit a nonradiative energy transfer process that is inherent with a luminescence quenching of the shorter wavelength emitter, the so-called donor. This in turn directly reflects the efficiency of simultaneous utilization of both dyes' emission bands for lasing. By the proper engineering of the gain material composition, it was possible to broaden the DFB lasing tuning spectral range up to 125 nm, which is twice as much compared to the DCNP/PMMA material, i.e. without addition of Rh700. Finally, the presented results have shown that additional random feedback, which is detrimental to the DFB lasing, originating from the presence of DCNP crystals within the polymeric bulk, can be effectively suppressed by the superposition of a temporary DFB resonator.