Abstract
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.
Highlights
IntroductionThe chosen dyes, which could be effectively excited by the same wavelength of pumping light
One of the most valuable features of organic materials designed for lasing purposes is their ability to exhibit a relatively broad wavelength tuning range.[1]
The acceptor dye content threshold for the occurrence of the energy transfer process designates the limit of undisturbed DCNP crystal utilization in light amplification, while the obtained gain profile range reflects the capability of these materials to improve the lasing tuning performance
Summary
The chosen dyes, which could be effectively excited by the same wavelength of pumping light Such an approach was implemented in a tunable optofluidic laser by Li et al.,[10] as well as in a solid-state laser by Diao et al.[11] or Zhai et al.[12] In both of the above-described approaches aimed at broadening of the gain profile, the spectrally broad stimulated emission (STE) of each dye is highly desirable, which often may be achieved by forcing the formation of dye crystals or aggregates.[13,14]. The occurrence of the FRET process is inseparable from resonant quenching of the donor dye luminescence, and it detrimentally affects the spectral broadening of lasing wavelength tunability.[8] the serious optimization of the donor/ acceptor relative concentration is required to achieve the desired spectral parameters of the materials. The thicknesses of the obtained layers (serving as planar waveguides) were determined using a Veeco Dektak 3 stylus profilometer and ranged from 10 mm to 25 mm
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