Based on the model of microcavity theory and transfer matrix theory, we measured the influence of complex cathode by introducing dielectric layer. Dielectric layer greatly influence the property of microcavity. Complex cathode may have obvious improvement to the trait of microcavity. Both in the instances considering microcavity effect and not considering, we compared the reflectivity, phase of reflection and light outcoupling efficiency of complex cathode with that of single layer metal cathode. To make the model simple, we do not consider complicated effect induced by interface absorbance and combination, we got the greatest improvement to outcoupling efficiency at certain instance. The efficiency of optimum structure is twelve times higher than that of single metal layer cathode. This confirms that dielectric layer can be used to improve the performance of organic metal cavity devices. Based on this kind of structure, unsymmetrical metal may reach great application.
Microcavity structures are widely utilized as resonators in many optoelectronic devices to improve their optical performance. We present an analytic approach to study the angle-dependent properties in active microcavities with dielectric Bragg reflectors. Based on the hard mirror (HM) model and paraxial propagation approximation, the angle dependent resonance properties can be expressed analytically in virtue of the cavity parameters and incident angle. Making use of these expressions, we found both the position of the active layer and the configuration of dielectric Bragg mirrors contribute to the angular characteristics of resonance in the active microcavity. The varying trend of the standing wave effect, intracavity electrical field and the degradation of quantum efficiency due to different incident angle are discussed in detail. It's found that there exists an optimal cavity configuration where the enhanced intracavity resonance can keep high value within a broader incidence range. Then further performance optimization of the whole devices can be performed.
Soluble poly(phenylene vinylene)(PPV)-type polymers have been applied widely as active layers in many optoelectronic devices, such as light-emitting diodes and organic lasers. In such devices their physical thickness are commonly about 100~200 nanometers for the desirable charge transport characteristics and optical interference effects. In this work, poly[(2-methoxy,5-octoxy) 1,4-phenylenevinylene] (MO-PPV) thin films have been prepared from their chloroform solutions of different concentrations. Then their UV-VIS absorption (Abs), photoluminescence (PL) and selective-excitation photoluminescence (SEPL) spectra have been measured at room temperature. A long wavelength emission component near 630 nm has been identified as S2→S0 vibronic band through gaussian decomposition method and confirmed by experiments. The effect of annealing on the optical properties of MO-PPV thin films is also studied. The results show that there exists an optimal treatment temperature under which the maximal excitation intensity can arrive. It can be attributed to the different morphologies in films. In addition, an experimental research about the active polymer photonic well structures of MO-PPV/PMMA pairs has been carried out.
In this paper a complete model and theoretical analysis based on model-solid theory and the envelop-function approach are presented to investigate the strain effects in the interband quantum cascade lasers. The electronic properties and the optical gain of two different type-II quantum well configurations are calculated under different strain conditions and two kinds of active region configuration. Through the comparison and analysis between these example structures, the detailed quantitative results of the strain effects are given.
Semiconducting ferroelectric antimony sulphoiodide (SbSI) microcrystallite doped organically modified TiO2 thin films were successfully fabricated with the sol-gel process. Ferroelectric SbSI crystallites have some attractive properties, including high dielectric permittivity, high electro-optical coefficient and high photoconductivity. SbSI is also an intrinsic semiconductor with a relatively narrow eneryg gap. The Bohr radius of the SbSI crystal was calculated larger than other semiconductors due to its large dielectric constant. If the crystal size is smaller than its Bohr radius and the microcrystallite are dispersed in a suitable matrix, a dramatic improvement of the nonlinear three-order nonlinearity will be achieved due to the quantum confinement effect. The SbSI quantum dot composites were proved to be good candidates for nonlinear and electro-optical devices. Glycidopropyltrimetroxysilane modified TiO2 was chosen as the matrix and SbSI was synthesized in situ by using SbI3, SC(NH2)2. The materials in thin film were heat-treated in different conditions and the size of the microcrystallite was characterized by the XRD. A value of 3.5pm/V of effective transverse electro-optical coefficient reff for the nano-composite containing 8 wt percent of antimony sulfide iodide was measured. The third-order nonlinear optical susceptibility of the SbSI quantum dot thin film was measured by degenerate four-wave mixing at 532nm using a frequency double Nd:YAG laser beams with a pulse width of around 10ns, the x(3) value of 3 μm sample was measured to be 6 × 10-11 esu.
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