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We report polymer distributed feedback lasers with dramatically extended operational lifetimes by using a simple encapsulation process. The lasers are configured as surface emitting, two-dimensional distributed feedback lasers based on the polymer poly͓2-methoxy-5-͑2Ј-ethylhexyloxy͒-1,4-phenylene vinylene͔. The microstructure is transferred to the polymer surface through solvent assisted micromolding. Once encapsulated, a 2500-fold improvement in lifetime is demonstrated under ambient conditions, compared to the unencapsulated device. A blueshift of the emission wavelength observed during operation is characterized by absorption and ellipsometry measurements and attributed to a change in effective index due to a loss of conjugation in the polymer.Since the demonstration of lasing from a semiconducting conjugated polymer, 1 the development of lasers based on these fascinating materials has been a vigorous research topic. Their large gain cross sections coupled with broad emission spectra and ease of processing from solution, make conjugated polymers particularly suited to the fabrication of photonic devices. [2][3][4] The most common resonators now used are diffractive structures that incorporate wavelength scale microstructure to form distributed feedback ͑DFB͒ lasers. The corrugation can be etched into a silica substrate 5 or patterned directly into the polymer film using a soft lithographic method such as solvent assisted micromoulding 6,7 ͑SAMiM͒. In both cases, the high refractive index contrast of the microstructured interface can allow for very strong feedback in a compact device. 8 A significant challenge for the application of these devices is to develop configurations which achieve adequate stability. One limitation of these materials is their susceptibility to degradation in the presence of oxygen and water. To date, there is little quantitative data on the operating lifetimes of organic semiconductor lasers. 9-11 While a few polymer lasers have included a thin passive polymer cover layer, 12,13 the quantitative effect on lifetime was not discussed. Using encapsulation to extend operational lifetime is commonplace in the field of organic light emitting diodes ͑OLEDs͒, protecting the emissive polymer layer and metal contacts from oxidation. In the case of OLEDs, encapsulation is typically applied on top of the metal cathode so properties of the device are largely unaffected with little impact on the external quantum efficiency or the photoluminescence spectrum. 14 For DFB lasers, more care must be exercised when selecting encapsulating materials. Changes to the refractive index contrast between layers can have a dramatic effect on the waveguide modes of the device. The encapsulating layers should also be optically transparent and not react adversely with the polymer while still acting as an effective atmospheric barrier.In this letter, we show that a polymer laser can be encapsulated without degrading its performance when compared to an unencapsulated laser. Absorption and ellipsometry data are used to q...

Materials with hyperbolic dispersion are the key to a variety of photonic applications involving nanoimaging, hyper-lensing, and spontaneous emission engineering, due to the availability of high k modes. Here we demonstrate that spin-coated polycrystalline organic semiconducting films with a layered molecular packing structure can exhibit a hyperbolic dispersion over a wide spectral range and support the presence of surface excitonic polaritons. This was evidenced from 670 to 920 nm and is related to the negative real part of the dielectric permittivity of the selected quinoidal organic semiconductor. In addition, the accessible high k modes lead to changes in the spontaneous emission decay rate and photoluminescence quantum yield of emitters placed nearby the organic monolithic (composed of only one molecule and not necessitating an alternating multilayer structure) natural hyperbolic material. This study opens a new route toward single-step solution manufacturing of large-area, low-cost, and flexible organic photonic metadevices with hyperbolic dispersion.

The thickness dependence of the absorption spectrum of spin-coated films of poly[2-(2′-ethylhexyloxy)-5-methoxy-1,4-phenylenevinylene] has been studied using reflectivity and variable angle spectroscopic ellipsometry measurements. It is found that, for films with thicknesses in the range of 18–178 nm, a single set of optical constants is sufficient to simulate accurately all the experimental data used, including the absorption spectra, independently of the film thickness or the processing conditions. Thus, the observed changes in the absorption spectrum with thickness can be fully accounted for by reflectivity and interference effects alone without the need to invoke morphology differences between films.

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