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Distributed feedback (DFB) lasing is observed in a metallic cavity, which consists of a gold grating and a polymer membrane. The gold grating is prepared by evaporating a 25 nm thin film of gold on the photoresist grating fabricated by interference lithography. A 150 nm thick polymer membrane is directly attached on the gold grating, forming a suspended membrane supported by the grating ridge. The assembly method decreases the metallic contact area, which makes the mode more photonic and thereby reduces the ohmic loss of the metal. Low threshold DFB lasing can be achieved when the sample is optically pumped. The fabrication technique provides a facile way to realize plasmonic DFB polymer lasers. [ABSTRACT FROM AUTHOR]

Multi-wavelength polymer lasers are produced with one-dimensional beat structures fabricated with multiple gratings at the same substrate location using interference lithography. As a distributed feedback cavity, the beat structure is equivalent to a linear superposition of multiple grating cavities. Each emission wavelength is determined by the corresponding grating cavity, which implies that interaction between different cavities is very weak. For a beat structure consisting of three gratings, emission peaks at 558 nm, 565 nm, and 569 nm originate from 350-nm, 362-nm, and 374-nm cavities, with thresholds of 14.5μJ/cm2, 15.0μJ/cm2, and 13.5μJ/cm2, respectively. This technique provides an alternative way to design compact polymer lasers. [ABSTRACT FROM AUTHOR]

One- and two-dimensional distributed feedback cavities were constructed on free-standing polymer membranes using spin-coating and lift-off techniques. Low threshold lasing was generated through feedback amplification when the 290-nm membrane device was optically pumped, which was attributed to the strong confinement mechanism provided by the active waveguide layer without a substrate. The free-standing membrane polymer laser is flexible and can be transplanted. Singleand dual-wavelength fiber lasers were achieved by directly attaching the membrane polymer laser on the optical fiber end face. This technique provides potential to fabricate polymer lasers on surfaces with arbitrary shapes. [ABSTRACT FROM AUTHOR]

Nanogratings with different duty cycles are directly written on gold films using interference ablation. After exposing the gold film to the interference pattern of ultraviolet laser beams, gold film in the bright fringes will be melted and ablated, whereas much weaker ablation occurs in the dark fringes. The duty cycle of gold nanogratings can be controlled by adjusting the pulse energy and the exposure times, which can be explained by the temperature rise and cumulative effect of the laser-metal interactions. These results introduce additional parameters for the fine fabrication of metal nanogratings based on interference ablation at a large scale and low cost. [ABSTRACT FROM AUTHOR]

Two types of bimetallic nanoparticle are constructed on soft substrates via a laser-induced transfer technique. One particle is a physical mixture with distinct gold and silver nanoparticles, while the other is a gold-silver alloy nanoparticle. Different hybrid plasmon responses can be achieved by these nanoparticles, which can be attributed to electromagnetic interactions between gold and silver. Both nanostructures can be fabricated using one or two ultraviolet laser pulses. Also, the stability of the spectra of these nanoparticles remains robust when the substrate is stretched and bended. These particles may provide an alternative way to investigate plasmonic sensors and random laser devices. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Dual-wavelength laser emission is achieved by using an active/inactive/active sandwich-like structure, which can be conveniently fabricated using spin coating technique. Poly [(9, 9-dioctylfluorenyl- 2, 7-diyl)-alt-co-(1, 4-benzo-(2, 1', 3) -thiadiazole)] and polyvinyl alcohol are employed as the active and the inactive materials, respectively. Two laser wavelengths are simultaneously observed, which are attributed to the difference of the surrounding refractive index of two active waveguides in the sandwich-like structure. Each wavelength is controlled by the respective waveguide structure, meaning that multi-wavelength laser can be designed by stacking the active/inactive layer pair. These results provide more flexibility to design compact laser sources. [ABSTRACT FROM AUTHOR]

Analytical solution of band gaps in two-dimensional (2-D) photonic crystals made by multi-beam interference was put forward. This solution gives concise analytical expression of every band gap. The quantitative relationship between the characters of band gaps and parameters of the materials of 2-D PC is different from that of one-dimensional (1-D) PC. For structures satisfying some conditions, the properties of band gaps obtained by the analytical solution are in good consistency with that obtained by the numerical simulations using plane wave expansion method. It showed why both TE and TM waves should have the same band structure in certain direction of 2-D PC with low refractive index. Also, it should be noted that the presented approach is accurate only for low index structures. [ABSTRACT FROM AUTHOR]

A structure with Dnv point group was fabricated by compounding a gradual heterostructure and a self-simulating sphere. The gradual heterostructure has two-dimensional omnidirectional band gap and the self-simulating sphere makes it possess a complete band gap. The experimental results were explained by theoretical analysis. This kind of structure can be implemented using low refractive index materials. [ABSTRACT FROM AUTHOR]

Gold-silver bimetallic nanoparticles with broad plasmon response were fabricated on soft substrates using a laser-induced transfer technique. The bimetallic nanostructures were fabricated with centimeter scale. By careful design, an approximately 200-nm broad plasmon response can be obtained by gold-silver alloy nanoparticles, which can be attributed to the electromagnetic interaction between gold and silver nanoparticles. This nanofabrication technique provides an annealing-free approach for the fabrication of flexible bimetallic nanostructures with a broad plasmon response with low cost. [ABSTRACT FROM AUTHOR]

Blue photoluminescence (PL) of 6H-SiC irradiated by an ultraviolet laser can be observed at room temperature in dark condition. PL spectra with Gaussian fitting curve of the irradiated SiC show that blue luminescence band (∼440 nm) is more pronounced than other bands. The blue PL enhancement is the combined result of the improved shallow N-donor energy level and the unique surface state with Si nanocrystals and graphene/Si composite due to the effect of photon energy input by the short-wavelength laser irradiation. The study can provide a promising route towards the preparation of well-controlled blue photoluminescence material for light-emitting devices. [ABSTRACT FROM AUTHOR]

Metallic photonic crystals (MPCs) with different periods have been fabricated by solution-processed method. Scanning electron microscopy images show that the structures with their period larger than 400 nm can easily maintain their morphologies during the high temperature lift-off process. The optical properties of the waveguided MPCs with different periods have been investigated. With an increase in the period, high-order coupling between particle plasmon resonance and the waveguide resonance modes can be observed in the spectra. We found that the 2 orders coupling of the structure with its period of 880 nm has similar tuning properties to the 1st orders coupling of the 430 nm period structures, which infers us that we can use the structures with larger period that can be controllably fabricated to replace the ones with smaller period. The results we obtained in this work provide reference for further applications of the MPCs. [ABSTRACT FROM AUTHOR]

An optical sensor based on the coupling between the plasmonic and photonic resonance modes in metallic photonic crystals is investigated. Large-area metallic photonic crystals consisting of periodically arranged gold nanostructures with dimensions down to sub-100 nm are fabricated using solution-processible gold nanoparticles in combination with interference lithography or interference ablation, which introduces a variety of fabrication techniques for the construction of this kind of sensor device. Sensitivity of the plasmonic response of the gold nanostructures to the changes in the environmental refractive index is enhanced through the coupling between the narrow-band photonic resonance mode and the relatively broad-band plasmon resonance, which is recognized as a Fano-like effect and is utilized to explore sensors. Theoretical modeling shows the characterization and the optimization of the sensitivity of this kind of sensor device.Theoretical and experimental results are demonstrated for the approaches to improve the sensitivity of the sensor device. [ABSTRACT FROM AUTHOR]