Detection and characterization of an optical vortex by the branch point potential method: analytical and simulation results.

Singularities are discontinuities in optical wavefronts that can be produced by turbulence effects. Since the presence of singularities in a wavefront severely degrades the adaptive optics correction performance, their detection is very important. The gradient of the wavefront phase, as measured by the Shack-Hartmann wavefront sensor in the presence of singularities, can be considered as the sum of the rotational and irrotational parts. The rotational part of the phase gradient originating from the phase singularities can be considered as a potential based on Helmholtz-Hodge decomposition. The potential at the singularities positions appears as peaks and valleys of the potential depending on the positive or negative charges of singularities. In this article, the detection of phase singularities based on the branch point potential (BPP) method is investigated. The irrotational part of the gradient produces a background potential where singularities positions appear as local extremum of the potential. With our method, the irrotational part of the gradient is eliminated and the value of peaks and valleys is increased. In addition, in this method, the potential value characterizes the optical singularities. Here, analytical and simulation results for the detection of general forms of the singularity are presented. Our simulations show the performance of singularities detection in noisy conditions.

Very low resistance ZnS/Ag/ZnS/Ag/ZnS nano-multilayer anode for organic light emitting diodes applications.

In this paper, design and simulation of conductive nanometric multilayer systems are discussed and optimum thickness of Ag and ZnS layers are calculated to reach simultaneously to high transmittance and low sheet resistance. The conductive transparent ZnS/Ag/ZnS/Ag/ZnS (ZAZAZ) nanometric multilayer systems are deposited on glass substrates at room temperature by a thermal evaporation method. The electrical, optical, and structural properties of these multilayers, such as sheet resistance, optical transmittance, and the root-mean-square surface roughness are obtained. High quality nanometric multilayer systems with sheet resistance of 2.7 Ω/sq and the optical transmittance of ~75.5% are obtained for the ZAZAZ system. Organic light emitting diodes (OLEDs) were fabricated and tested on the ZAZAZ anode. The ZAZAZ multilayer anode based OLED shows the performance comparable to that of the indium-tin oxide anode based OLED.

Theoretical and experimental investigation of generating pulsed Bessel-Gauss beams by using an axicon-based resonator.

Nondiffracting Bessel-Gauss beams are assumed as the superposition of infinite numbers of Gaussian beams whose wave vectors lie on a cone. Based on such a description, different methods are suggested to generate these fields. In this paper, we followed an active scheme to generate these beams. By introducing an axicon-based resonator, we designed the appropriate resonator, studied its resonance modes, and analyzed the beam propagation outside the resonator. Experimentally, we succeeded to obtain Bessel-Gauss beams of the first kind and zero order. We also investigated the changes in effective parameters on the output beam, both theoretically and experimentally.

Generation of pulsed Bessel-Gauss beams using passive axicon-theoretical and experimental studies.

We studied the conditions for generating passive Bessel-Gauss beams by using an axicon. We designed an appropriate Gaussian resonator and extracted a quasi-fundamental Gaussian mode from a pulsed Nd:YAG laser pumped by a Xenon flash lamp and measured its parameters, such as propagation factor, divergence angle, and Rayleigh range. Then we generated passive Bessel-Gauss beams using an axicon and investigated their propagation properties, theoretically and experimentally. For example, for the axicon of 1°, the output energy and the Rayleigh range of the generated Bessel-Gauss beams were measured to be 58 mJ and 229.3 mm, respectively. We compared these properties with our results of the Gaussian mode. Finally, by using axicons with different apex angles, and also by changing the beam spot size on the axicon, we generated Bessel-Gauss beams and studied their properties theoretically and experimentally.

MTF of compound eye.

Compound eye is a new field of research about miniaturizing imaging systems. We for the first time introduce a dual compound eye that contains three micro lens arrays with aspheric surfaces. The designed dual compound eye in one state is a superposition system in which each channel images all of field of view of the system. With adding a field stop we have decreased the stray light. MTF of ideal superposition compound eye calculated. Also with changing field stop the system is converted to an apposition compound eye in which each channel images only a part of total field of view and so the field of view is larger than that of superposition type.