͑ Color online ͒ ͑ a ͒ Scheme of the St-L apparatus. ͑ b ͒ Photograph of the packaged device system including resin element, plastic o-ring, and quartz window. ͑ c ͒ and ͑ d ͒ are schemes of the cross-sectional views AA and BB marked in ͑ b ͒ , respectively. Bottom-right dashed areas: St-L resin. Bottom-left dashed areas: polymer laser. Light areas: quartz for optical coupling. Arrow in ͑ d ͒ : vacuum connection. 

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... the discovery of their bright photoluminescence ͑ PL ͒ and electroluminescence, wide range of tunability, and large gain cross sections, conjugated polymers have attracted a lot of interest as active media for photonic devices, such as 1 2 3 light-emitting diodes, lasers, and solar cells. However, an important challenge for the massive diffusion of molecular optoelectronic devices stands in the capability of developing appropriate methods ensuring long operational stability. In- deed, exposing organic layers to air, under either optical or electrical excitation, results in rapid degradation of the emission properties because of the oxygen-induced formation of 4 exciton traps acting as luminescence quenching centers, such as carbonyl groups ͑ C = O ͒ in poly ͑ phenylene-vinylene ͒ 4,5 and its derivates. To date reported device encapsulation approaches in- 6 7,8 clude resin coating, polyacrylates, or hydrophobic perflu- 9 orinated materials, deposition of single or multilayer thin 7,8,10–12 13–15 films of metal oxides or silicon nitrides, by mag- 13 10–12 neton sputtering, atomic layer, or chemical vapor 14,15 deposition, and addition of desiccant calcium oxide 16 particles. All of these methods involve the deposition or gluing of additional layers acting as barrier to oxygen diffusion, thus affecting the device processing complexity. Packaging layers are deposited each time for the single device, and many employed materials do not assure adequate optical transparency. Finally, the deposition procedures of metal oxides and silicon nitrides can deteriorate active organics, and they are significantly more expensive than conjugated polymer device fabrication technologies. Importantly, an increase in device lifetime from the order of 10 3 to about 10 7 excitation pulses has been very recently reported for poly ͓ 2-methoxy-5- ͑ 2-ethylhexyl-oxy ͒ -1,4- phenylene-vinylene ͔ ͑ MEH-PPV ͒ distributed feedback ͑ DFB ͒ lasers upon encapsulation by an optical adhesive. 17 Encapsulating the devices is demonstrated to have little effect on the DFB spectral properties, the resulting reduction in refractive index contrast being compensated by an enhanced 17 electric field at the corrugated interface. Nevertheless, the encapsulation requirements of polymer vertical-cavity surface-emitting laser ͑ VCSEL ͒ can differ from those of organic DFB lasers. In fact, while DFB devices can be straight- 18 forwardly realized by high-throughput printing and step- 17 and-repeat or solvent-assisted soft lithography approaches, the fabrication of monolithic VCSELs is generally more complex and requires several steps of deposition and evapo- ration. For this reason, multiuse encapsulating elements, namely, sequentially employable for many VCSEL devices once fabricated, are highly desirable. In this letter, we propose a highly scalable method to encapsulate light-emitting devices based on conjugated compounds, which do not require additional layers to be incor- porated in the single-device geometry. We realize multiuse polymeric packaging elements by rapid prototyping stereolithography ͑ St-L ͒ using quartz windows for external optical coupling. We encapsulate a polymer VCSEL, improving the device operational lifetime by a factor of three upon pumping at an excitation fluence three times larger than lasing threshold. 19–21 The laser fabrication is described elsewhere. Briefly, a bottom distributed Bragg reflector ͑ DBR ͒ is deposited onto a quartz substrate ͑ 10 ϫ 10 mm 2 ͒ by an electron-beam system. A toluene solution of MEH-PPV is then spin-cast ͑ thickness of ϳ 190 nm ͒ . The top SiO x / TiO x DBR layer is deposited at temperature below 80 ° C. Packaging is accomplished employing a 3D System Viper Si2 St-L apparatus ͓ scheme in Fig. 1 ͑ a ͔͒ . The St-L 22 is based on the layer-by-layer polymerization of the compound RPC600ND ͑ Rapid Prototyping Chemicals Ltd. ͒ by focusing a UV laser beam ͑ ␭ = 355 nm ͒ onto the top of a vat containing the resin. A computer- controlled optical scanning system directs the beam to draw each layer of the intended object, with a vertical resolution of 50 ␮ m and a beam spot ͑ diameter at 1 / e 2 ͒ of 0.075 Ϯ 0.015 mm. The St-L packaging element and the polymer laser are assembled allocating the device in a lodger defined in the resin and covered by a quartz window. The resin-quartz sealing is assured connecting the system to a rotary pump. The emitted light from the devices, excited by a neodymium-doped yttrium aluminum garnet microlaser ͑ ␭ = 355 nm, repetition rate variable in the range of 10–100 Hz ͒ through the top mirror, is collected by an optical fiber and a monochromator. The packaged system is composed of the polymer laser and the resin device, shaped for lodging the sample, a sealing plastic o-ring and the external vacuum or nitrogen connection, and a quartz window ͓ photograph and cross sections in Figs. 1 ͑ b ͒ –1 ͑ d ͔͒ . The PL emission spectra of the encapsu- lated laser, as function of the excitation density, are displayed in Fig. 2. For excitation fluence E below 100 ␮ J / cm 2 ͑ dashed line spectrum in Fig. 2 ͒ , the emission from the cen- tral region of the device is peaked at about 619 nm with a full width at half maximum ͑ FWHM ͒ of about 3 nm. For excitation fluences above 100 J cm continuous lines spectra in Fig. 2 ͒ , the emission peak becomes more and more evident, with a fivefold increase in the emission intensity and a line narrowing down to a FWHM of 2 nm. The input- output characteristic is in accordance with the occurrence of lasing action in the microcavity, with a threshold of 80 ␮ J / cm 2 , followed by a linear increase in the emission intensity ͑ inset of Fig. 2 ͒ . We also evaluate the uniformity of emission over the MEH-PPV film after DBR deposition and device encapsulation. Both these processes may determine in principle thickness variations or local compressions in the active layer, which would result in differently emitting microscale lasing domains and hence in spectral disuniformities. Figure 3 dis- plays the collected laser spectra versus the device position over a section of 1 mm along the sample edge, where the intrinsic polymer thickness fluctuations due to spin-coating are more pronounced. The laser peak intensity from these regions is centered at about 612 nm, shifting by about 1.6 nm upon moving over 1 mm along the sample edge, corresponding to a thickness variation of about 0.5 nm. This result is indicative of a quite uniform MEH-PPV thickness retained throughout the device. In order to assess the encapsulation performances, we study the temporal behavior of the emission intensity under pulsed excitation, pumping at excitation fluence of 250 ␮ J / cm 2 , i.e., three times the threshold value, before and after the laser packaging ͑ Fig. 4 ͒ . The unpackaged microcavity lasers operate in air over 5 ϫ 10 4 excitation pulses, corresponding to more 1.4 h at 10 Hz, before decaying to 50% of their initial emission intensity. Upon packaging, the laser emission intensity decays to 50% after about 1.5 ϫ 10 5 excitation pulses, corresponding to an operation time of more than 4 h. This demonstrates the effectiveness of the encapsulation provided by the rapid-prototyped St-L elements, lim- iting oxygen diffusion to the emissive layer and thus enhanc- ing the intrinsic encapsulation effect provided by the DBRs 21 surrounding the active medium. Taking into account the area of the fabricated VCSEL and the size of the employed excitation spot, we estimate an overall device operational lifetime of more than 3.3 ϫ 10 3 h. We point out that the mo- lecular oxygen permeation through the polymerized resin used in this study is of about 0.5 cc / m 2 per day, better encapsulation performances being achievable by employing St-L polymers or composites exhibiting lower gas diffusion. With respect to spin-coating methods, St-L can offer ad- vantages given by the fact that the resin polymerization is performed ex situ , i.e., before the final device assembly, thus not affecting the in-cavity conjugated material. This rules out any eventual UV-induced degradation of the active compound and the corresponding reduction in its absolute luminescence quantum efficiency. Furthermore, the optical emission of conjugated polymers embedded in vertical microcavities is demonstrated to exhibit thermal tunability mainly because the thermo-optic behavior of the organic or 23 mirror materials. However, for some polymers a role can be played by non-fully-reversible volumetric reorganization of disordered molecular compounds undergoing thermal 24 cycles. Therefore, also encapsulation methods involving in situ thermal curing of resins are preferably avoided with such polymers. Experiments by low-viscosity, photopolymerizable resins can certainly be useful for quantitatively comparing the encapsulation performances resulting by ex situ ͑ St-L ͒ and in situ ͑ spin-casting ͒ curing techniques. In conclusion, we demonstrate St-L on photopolymerizable resins as approach for realizing encapsulating elements for polymer lasers. The method is highly scalable, allowing one to fabricate multiuse packaging elements, embedding functional features such as high-transparency windows and vacuum connections, without adding additional layers to light-emitting devices. The operational lifetime of a polymer VCSEL is increased by a factor of three upon continuous pumping at an excitation fluence ͑ 250 ␮ J / cm 2 ͒ three times larger than lasing threshold. These results suggest St-L as promising We gratefully technology acknowledge for large-scale the financial prototyping support of pack- from aged the Apulia organic Regional light-emitting Explorative devices. Project “Technologies of fabrication and packaging of monolithic organic lasers.” We gratefully acknowledge the financial support from the Apulia Regional Explorative Project “Technologies of fabrication and packaging of monolithic organic ...