Frequency-upconverted Lasing Research Articles

Push–Pull Organic Chromophores for Frequency-Upconverted Lasing

Push–Pull Organic Chromophores for Frequency-Upconverted Lasing

Two-photon pumped partially cross-linked polymer laser

Two-photon pumped (TPP) frequency-upconverted lasing properties of a partially cross-linked fluorescent polymer are reported. This lasing medium is a cross-linked homogeneous copolymer with two major compounds: the chromophore, 4-[bis(2-hydroxyethyl)amino]-N-methylstilbazolium iodide, and the monomer, 2-hydroxyethyl methacrylate. The spectral, temporal, and spatial structures as well as the output/input characteristics of the TPP cavity lasing were measured using a 13 mm long polymer rod. The net conversion efficiency from the absorbed 1064 nm pump pulse energy to the ∼606 nm upconverted cavity lasing energy was found to be ∼4%.

Studies of two-photon pumped frequency-upconverted lasing properties of a new dye material

The two-photon absorption (TPA), TPA-induced frequency upconversion emission, and two-photon-pumped (TPP) lasing properties of a new dye, trans-4[p-(N-hydroxyethylN-methylamino)stryryl]-N-methylpyridinium iodide (abbreviated as ASPI) were experimentally investigated. This new dye has a moderate TPA cross section (σ2≈3.9×20−20 cm4/GW in benzyl alcohol), but exhibits a low lasing threshold and high lasing efficiency when pumped with a 1064 nm pulsed laser beam. Furthermore, the TPA-induced fluorescence yield is strongly dependent on the polarity of the solvent, making it a promising dye for sensing applications. The spectral, temporal, and spatial structures as well as the output/input characteristics of the TPP cavity lasing and the superradiant (cavityless) lasing are systematically measured using a 1 cm path quartz cuvette filled with the ASPI solution or a doped polymer rod. The net conversion efficiency from the absorbed 1064 nm pump pulse energy to the ∼615 nm upconverted cavity lasing energy was found to be as high as ∼17%.

Two-photon pumped cavity lasing in novel dye doped bulk matrix rods

Trans-4-[p-(N-ethyl-N-hydroxyethylamino)styryl]-N-methylpyridi that possesses a much greater two-photon absorption cross section and much stronger upconversion fluorescence emission than common organic dyes (such as rhodamine), when excited with near infrared laser radiation. Utilizing ASPT doped bulk polymer rods, two-photon pumped frequency upconverted cavity lasing has been accomplished using a Q-switched Nd:YAG laser as the pump source. The wavelength and pulse duration were ∼600 nm and 3–6 ns, respectively, for the cavity lasing; whereas the corresponding values for pump pulses were 1.06 μm and ∼10 ns, respectively. For a 7 mm long sample rod with a dopant concentration d0=8×10−3 M/L, the conversion efficiency from the absorbed pump energy to the cavity lasing output was ∼3.5% at a pump energy level of 1.3 mJ. The lasing lifetime, in terms of pulse numbers, was more than 4×104 pulses at 2 Hz repetition rate and room temperature.