A waveguide-plasmonic scheme is constructed by coating the matrix of randomly distributed gold nanoisland structures with a layer of dye-doped polymer, which provides strong feedback or gain channels for the emission from the dye molecules and enables successful running of a random laser. Excellent overlap of the plasmonic resonance of the gold nanoislands with the photoluminescence spectrum of the dye molecules and the strong confinement mechanism provided by the active waveguide layer are the key essentials for the narrow-band and low-threshold operation of this random laser. This kind of feedback configuration potentially enables directional output from such random lasers. The flexible solution-processable fabrication of the plasmonic gold nanostructures not only enables easy realization of such a random laser but also provides mechanisms for the tuning and multicolor operation of the laser emission.

Optically pumped polymer lasers [1][2][3][4][5][6][7][8] achieved in a simple and effi cient way not only introduce new laser designs and laser sources, but also lay excellent physical and technical bases for the realization of electrically pumped organic lasers. As the most promising solution for polymer lasers, the distributed feedback (DFB) geometry has been investigated extensively. [9][10][11][12] A variety of fabrication schemes have been demonstrated to construct the DFB cavities, such as UV embossing, [ 12 ] nanoimprint lithography, [13][14][15] photolithography, [ 16 ] soft lithography, [ 17 ] liquid imprinting, [ 18 ] micromolding, [ 19 ] electron beam lithography, [20][21][22] reactive ion etching, [ 22 , 23 ] and reactive electronbeam deposition. [ 24 ] However, a simple and low-cost technique that enables highly reproducible mass fabrication is required for the easy realization and more profound investigation of the polymer lasers based on the DFB confi guration.In this work a direct-writing technique is reported that achieves large-area 1D and 2D DFB polymer lasers. The polymer thin fi lm is exposed to a single-shot illumination of the interference pattern of one UV laser pulse at 266 nm. Thus, the DFB structures consisting of periodically distributed polymer nanowires (1D case) or square lattices of polymer nanoislands (2D case) with a period of about 350 nm are easily produced, which support low-threshold lasing in the green region of the visible spectrum. Different 1D and 2D photonic structures can be written with periodic, quasi-periodic, and even aperiodic patterns, generating various designs of the photonic structures and laser devices. Herein, the direct writing and the lasing behaviors of the 1D grating and 2D square lattices of polymeric semiconductors are demonstrated.A typical light-emitting conjugated polymer, poly[(9,9-dioctylfl uorenyl-2,7-diyl)-alt-co -(1,4-benzo-{2,1 ′ ,3}-thiadiazole)] (ADS133YE, from American Dye Source, Inc.), is employed as the active material, which produces green light under excitation by a blue or UV laser. During fabrication, a solution of 15 mg mL − 1 ADS133YE in chloroform is spin-coated onto a fused silica glass substrate (15 mm × 15 mm × 1 mm), producing a thin, solid fi lm with a thickness of 100-200 nm, depending on the speed of spin-coating. Then, the thin-fi lm sample is exposed to the interference pattern of a UV laser pulse for about 6 ns, which corresponds to the pulse length of the UV laser. This induces ablation of the polymer at the bright interference fringes, resulting in the structure used for the 1D polymer lasers. For the fabrication of the 2D structures, we simply rotate the sample and perform a second exposure process, with further exposures performed as required. In this work, the square lattice structures are realized by double exposure with the sample rotated once by 90 degrees. Figure 1 a,b show the molecular structure and the spectroscopic properties of ADS133YE, respectively. The blue curve in Figure 1 b shows that the absorption o...

The active waveguide grating structures (AWGS) are demonstrated as distributed feedback (DFB) configuration for polymer lasers. The thin film of a typical light-emitting polymer poly [(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(1,4-benzo-{2,1',3}-thiadiazole)] acts both as the gain medium and as the waveguide. The grating structures are fabricated separately on top of the polymer film through interference lithography. The continuous and high-quality waveguide layer of the gain medium enables laser emission with narrow linewidth. Theoretical analysis and experimental verification imply potentially excellent performance of the organic DFB lasers based on the AWGS configuration. This kind of AWGS configuration is of particular importance for the design of electrically pumped polymer lasers.

Topological insulators (TIs), are novel two-dimension materials, which can act as effective saturable absorbers (SAs) in a fiber laser. Moreover, based on the evanescent wave interaction, deposition of the TI on microfiber would create an effective SA, which has combined advantages from the strong nonlinear optical response in TI material together with the sufficiently-long-range interaction length in fiber taper. By using this type of TI SA, various scalar solitons have been obtained in fiber lasers. However, a single mode fiber always exhibits birefringence, and hence can support two orthogonal degenerate modes. Here we investigate experimentally the vector characters of a TI SA fiber laser. Using the saturated absorption and the high nonlinearity of the TI SA, a rich variety of dynamic states, including polarization-locked dark pulses and their harmonic mode locked counterparts, polarization-locked noise-like pulses and their harmonic mode locked counterparts, incoherently coupled polarization domain wall pulses, including bright square pulses, bright-dark pulse pairs, dark pulses and bright square pulse-dark pulse pairs are all observed with different pump powers and polarization states.

We report direct writing of metallic photonic crystals (MPCs) through a single-shot exposure of a thin film of colloidal gold nanoparticles to the interference pattern of a single UV laser pulse before a subsequent annealing process. This is defined as interference ablation, where the colloidal gold nanoparticles illuminated by the bright interference fringes are removed instantly within a timescale of about 6 ns, which is actually the pulse length of the UV laser, whereas the gold nanoparticles located within the dark interference fringes remain on the substrate and form grating structures. This kind of ablation has been proven to have a high spatial resolution and thus enables successful fabrication of waveguided MPC structures with the optical response in the visible spectral range. The subsequent annealing process transforms the grating structures consisting of ligand-covered gold nanoparticles into plasmonic MPCs. The annealing temperature is optimized to a range from 250 to 300 °C to produce MPCs of gold nanowires with a period of 300 nm and an effective area of 5 mm in diameter. If the sample of the spin-coated gold nanoparticles is rotated by 90° after the first exposure, true two-dimensional plasmonic MPCs are produced through a second exposure to the interference pattern. Strong plasmonic resonance and its coupling with the photonic modes of the waveguided MPCs verifies the success of this new fabrication technique. This is the simplest and most efficient technique so far for the construction of large-area MPC devices, which enables true mass fabrication of plasmonic devices with high reproducibility and high success rate.