Papers by Keyword: Micro-Cavity

Abstract: The authors have investigated the edge emission of microcavities which are formed by low-molecular organic light emitting diodes sandwiched between dielectric mirrors and the metal cathode. The edge emission relative to the surface emission is found to significantly depend on the layer number of alternating high and low refractive index films in dielectric mirrors. The enhancement of cavity devices can reach a factor of ~3.0 compared with noncavity devices. Spectra of organic film pumped by edge emission of microcavity devices have been observed, a mechanism of achievement of an amplified spontaneous emission has been discussed theoretically.

Abstract: A DBR-Ag mixed organic micro-cavity structure solid-state laser was proposed in this paper. The influences of center wavelength, growth sequence and the cycle number of DBR, and the thickness of Ag mirror and organic light-emitting layer on performance of Ag-DBR mixed organic micro-cavity were investigated by simulation. According to PL characteristics of Alq3:DCM (0.5wt%), an optimal metal Ag-DBR micro-cavity structure was designed, and based on theoretical calculation results, a corresponding micro-cavity devices (glass/DBR/organic layer/Ag mirror) was fabricated. The theoretical simulation and experimental results are in good agreement.

Abstract: The present work reports the electrochemical anodization for porous silicon microcavity (PSM) fabrication, including the number of layers and electrochemical process effect in the optical response quality of PSM. These PSMs have been obtained by using PS technology. It is found that the electrochemical process limits the maximum number of layers because there is a chemical dissolution effect during electrochemical anodization. The reflectance spectra of the PSMs indicates that stop-band and the resonant peak of the PSM shift down with the increases of the number of layers due to the decrease of layer's thickness. The value of the full width at half maximum (FWHM) dependents on the number of layers, and the number of layer increases when the FWHM decreases, which is due to the light scattering at roughness interface layer.

Abstract: In this paper, we studied lasing action in dual-doped organic microcavity with cascade Forster energy transfer between polymer and two fluorescent dyes in surface emitting microcavities, which formed by sandwiching a poly(N-vinylcarzole) (PVK) film doped with 8-trishydroxyquinoline (Alq3) and 4-(dicyanomethylene)-2-tert-butyl-6 (1, 1, 7, 7-tet ramethyljulolidyl-9-enyl)-4H–pyran (DCJTB) between a distributed Bragg reflector (DBR) and a silver film mirror. The sample was optically pumped by a frequency-tripled Nd:YAG laser delivering 5.55ns pulses at 355nm with a 10Hz repetition rate. By optimizing the concentrations of Alq3 and DCJTB in PVK, a low lasing threshold of about 9.5µJ per pulse attributed to efficient cascade Forster energy transfer form PVK and Alq3 to DCJTB was obtained. The full width at half maximum (FWHM) of the emission was about 2nm with the peak wavelength at 628nm. Our results demonstrate that the PVK:Alq3:DCJTB could be a promising candidate as gain medium for red organic diode lasers.

Abstract: The use of conventional machining processes has been subject to important decline probably due to the increment in the use of emerging technologies. Therefore, the main applications of these traditional processes, such as automotive industry, are in crisis. In order to have a chance to compete successfully in the new trends, the machining industry must meet the needs of alternative sectors such as biomedical field. The aim of this study is to prove the capacity of micro-milling, by machining complex micro-cavities on aluminum workpiece using a conventional milling machine. Results are obtained by evaluating accuracy and geometric features. This study finds that the feed per tooth is a significant factor in order to obtain better results. The use of coolant increases the tool wear and therefore dimensional errors. This scope is a potential opportunity to reutilize the conventional machines from a new approach.

Abstract: The spontaneous emission rate of a two-level system quantum dots is not intrinsic properties of the emitter itself but is molded by the electromagnetic environment that surrounds it. Photonic crystal micro cavity can conveniently shape the states of electromagnetic modes by providing modes with the required small volumes and high quality factors. This paper studies spontaneous emission from quantum dots embedded in photonic crystal micro cavity, and introduces the coupling characters of photonic crystal and quantum dot, and analyses the effectiveness of spontaneous emission enhancement from quantum dots embedded in photonic crystal micro cavity in detail. The research of this paper provides a basic reference for dynamic control of optics quantum systems.

Abstract: We have studied the anodization behavior of an Al film electrodeposited on the 316L stainless steel (316L SS) substrate and demonstrated an effective approach to fabricate the micro-cavities on the conducting substrate through anodic aluminum oxide (AAO) template. The morphologies and composition of the electroplating aluminum layers and the micro-cavities were evaluated by SEM and energy dispersive X-ray analysis (EDXA) respectively. The results indicated that different shapes of cavities with size ranging from 0.6 to 2 mm were come into being directly on 316L SS substrates. The size of cavities could be controlled by adjusting the anodizing voltage and time. And the morphologies of the initial aluminum films were found to be critical factors for successfully anodizing the Al film on 316L SS surface.

Abstract: This paper analyzes the modality of two-dimensional photonic crystal micro-resonators by adopting equivalent refractive index mode. In this paper, it controls the optical field distribution only through altering the thickness of light guide layer, while the parameter like resonator structure and crystal lattice arrangement remain stable. It discusses that it would arrive at a satisfactory photon locality while the refractive index of light guide layer material is gallium nitride , the thickness of light guide layer is and its equivalent refractive index is 2.1.This reveals the influence of micro-resonator light guide layer’s thickness towards the modality, providing a preferable pre-estimate method for the actual research of micro-resonators with higher quality.

Abstract: Microfluidic channel and micro-cavities were fabricated from polyhydroxyalkanoate biodegradable polymer using a direct 20ns, 248 nm excimer laser writing method. First we give a design of the micro-analytical device; second we discussed the laser ablation of biodegradable ppolymer material. The morphology, dimensional accuracy, and surface conditions of the fabricated micro-devices were studied using atomic force microscopy, scanning electron microscopy, optical microscopy, and X-ray photoelectron spectroscopy. Melting of the biodegradable polymer was observed at a fluency of 50mJ/cm2 while ablation was observed at a fluency of 100mJ/cm2.The different width between bottom and top surface are studied in our research. The particle deposited on the polymer surface is seen from the SEM of 248nm laser ablation of PHA. However, the direct burning of PHA can be seen from the optical photo by 355nm laser. Compare to results of PHA with two different lasers, we can see that the 248nm laser is a suitable choice.

Abstract: Using TracePro® Monte-Carlo ray-tracing simulations, this paper investigates the improved light extraction efficiency (LEE) obtained by patterning the surface and/or substrate of GaN LEDs with unique three-dimensional micro-cavity patterns. The simulations commence by considering the case of a sapphire-based GaN LED. The effects on the LEE of the micro-cavity dimensions, the absorption coefficient of the active layer, the point source location, and the chip dimensions are systematically examined. Subsequently, the LEE performance of the sapphire-based GaN LED is compared with that of a thin-GaN LED for various surface texturing strategies. In general, the results show that patterning either the surface or the substrate of the LED structure provides an effective improvement in the LEE of both the sapphire-based GaN LED and the thin- GaN LED. For both LED structures, the maximum LEE enhancement is obtained by patterning both the upper surface of the LED and the substrate surface. However, the simulation results indicate that the improvement obtained in the LEE is the result primarily of pattering the upper surface of the LED.