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Wavefront shaping technology has mainly been applied to microscopic fluorescence imaging through turbid media, with the advantages of high resolution and imaging depth beyond the ballistic regime. However, fluorescence needs to be introduced extrinsically and the field of view is limited by memory effects. Here we propose a new method for microscopic imaging light transmission through turbid media, which has the advantages of label-free and discretional field of view size, based on transmission-matrix-based wavefront shaping and the random matrix theory. We also verify that a target of absorber behind the strong scattering media can be imaged with high resolution in the experiment. Our method opens a new avenue for the research and application of wavefront shaping. [ABSTRACT FROM AUTHOR]

We demonstrate a modified particle swarm optimization (PSO) algorithm to effectively shape the incident light with strong robustness and short optimization time. The performance of the modified PSO algorithm and genetic algorithm (GA) is numerically simulated. Then, using a high speed digital micromirror device, we carry out light focusing experiments with the modified PSO algorithm and GA. The experimental results show that the modified PSO algorithm has greater robustness and faster convergence speed than GA. This modified PSO algorithm has great application prospects in optical focusing and imaging inside in vivo biological tissue, which possesses a complicated background. [ABSTRACT FROM AUTHOR]

We present a digital micromirror device (DMD) based superpixel method for focusing light through scattering media by modulating the complex field of incident light. Firstly, we numerically and experimentally investigate focusing light through a scattering sample using the superpixel methods with different target complex fields. Then, single-point and multiple-point focusing experiments are performed using this superpixel-based complex modulation method. In our experiment, up to 71.5% relative enhancement is realized. The use of the DMDbased superpixel method for the control of the complex field of incident light opens an avenue to improve the enhancement of focusing light through scattering media. [ABSTRACT FROM AUTHOR]

A surface plasmon resonance (SPR) sensor with a high-order absentee layer on the top of metallic film is proposed. The performance of the SPR sensor with NaCl, MgO, TiO2 or AlAs high-order absentee layer is analyzed theoretically. The results indicate that the sensitivity and the full width at half maximum of those SPR sensors decrease with the increasing of the order of absentee layer, but the variation of the figure of merit (FOM) depends on the refractive index of absentee layer. By improving the order of absentee layer with high-refractive-index, the FOM of the SPR sensor can be enhanced. The maximum value of FOM for the SPR sensor with high-order TiO2 (or AlAs) absentee layer is 1.059% (or 2.587%) higher than the one with one-order absentee layer. It is believed the proposed SPR sensor with high-order absentee layer will be helpful for developing the high-performance SPR sensors. [ABSTRACT FROM AUTHOR]

Using temporal and spectral methods, the effects of dispersion and filtering induced by Mo/Si multilayer mirrors reflection on incident attosecond pulses were studied. First, two temporal parameters, the pulse broadening factor, and the energy loss factor, were defined to evaluate the effects of dispersion and filtering. Then, by analyzing these temporal parameters, we investigated and compared the dispersion and filtering effects on attosecond pulses. In addition, we explored the origins of pulse broadening and energy loss by analyzing the spectral and temporal characteristics of periodic Mo/Si multilayer mirrors. The results indicate that the filtering effect induced by Mo/Si multilayer mirrors reflection is the dominant reason for pulse broadening and energy loss. [ABSTRACT FROM AUTHOR]

The restabilizing mechanisms after the onset of thermal instability in bipolar transistors are studied by theoretical analyses, computer simulations and experimental measurements. Restability conditions are described by novel analytical formulae. Furthermore, the expression of collect current in the second fly-back point is given for the first time. The effects of emitter ballast resistance, collector-emitter voltage and thermal resistance on restabilization mechanisms are expressed and investigated. [ABSTRACT FROM AUTHOR]

A method of non-uniform finger spacing is proposed to enhance thermal stability of a multiple finger power SiGe heterojunction bipolar transistor under different power dissipations. Temperature distribution on the emitter fingers of a multi-finger SiGe heterojunction bipolar transistor is studied using a numerical electro-thermal model. The results show that the SiGe heterojunction bipolar transistor with non-uniform finger spacing has a small temperature difference between fingers compared with a traditional uniform finger spacing heterojunction bipolar transistor at the same power dissipation. What is most important is that the ability to improve temperature non-uniformity is not weakened as power dissipation increases. So the method of non-uniform finger spacing is very effective in enhancing the thermal stability and the power handing capability of power device. Experimental results verify our conclusions. [ABSTRACT FROM AUTHOR]