A novel scheme for generating optical chaos is proposed and experimentally demonstrated, which supports to simultaneously produce two low-correlation chaotic signals with wideband spectrum and suppressed time-delay-signature (TDS). In the proposed scheme, we use the output of an external-cavity semiconductor laser (ECSL) as the driving signal of a phase modulator to modulate the output of a CW laser. Then the phase-modulated continuous-wave (CW) light is split into two parts, one is injected back into the ECSL that outputs one chaotic signal, while the other part is passed through a dispersion module for generating another chaotic signal simultaneously. The experimental results prove that the proposed scheme has three merits. Firstly, it can improve the bandwidth of ECSL-based chaos by several times, and simultaneously generate another wideband flat-spectrum chaotic signal. Secondly, the undesired TDS characteristics of the simultaneously-generated chaotic signals can be efficiently suppressed to an indistinguishable level within a wide parameter range, as such the complexities of the chaotic signals are considerably high. Thirdly, the correlation coefficient between these two simultaneously-generated chaotic signals is smaller than 0.1. The proposed scheme provides an attractive solution for parallel multiple chaos generation, and shows great potential for multiple channel chaos communications and multiple random bit generations.
Single-shot high-speed 3D imaging is important for reconstructions of dynamic objects. For fringe projection profilometry (FPP), however, it is still challenging to recover accurate 3D shapes of isolated objects by a single fringe image. In this paper, we demonstrate that the deep neural networks can be trained to directly recover the absolute phase from a unique fringe image that involves spatially multiplexed fringe patterns of different frequencies. The extracted phase is free from spectrum-aliasing problem which is hard to avoid for traditional spatial-multiplexing methods. Experiments on both static and dynamic scenes show that the proposed approach is robust to object motion and can obtain high-quality 3D reconstructions of isolated objects within a single fringe image.
The current study is directed to the rapidly developing field of inorganic material 3D object production at nano-/micro scale. The fabrication method includes laser lithography of hybrid organic-inorganic materials with subsequent heat treatment leading to a variety of crystalline phases in 3D structures. In this work, it was examined a series of organometallic polymer precursors with different silicon (Si) and zirconium (Zr) molar ratios, ranging from 9:1 to 5:5, prepared via sol-gel method. All mixtures were examined for perspective to be used in 3D laser manufacturing by fabricating nano- and micro-feature sized structures. Their spatial downscaling and surface morphology were evaluated depending on chemical composition and crystallographic phase. The appearance of a crystalline phase was proven using single-crystal X-ray diffraction analysis, which revealed a lower crystallization temperature for microstructures compared to bulk materials. Fabricated 3D objects retained a complex geometry without any distortion after heat treatment up to 1400 °C. Under the proper conditions, a wide variety of crystalline phases as well as zircon (ZrSiO4 - a highly stable material) can be observed. In addition, the highest new record of achieved resolution below 60 nm has been reached. The proposed preparation protocol can be used to manufacture micro/nano-devices with high precision and resistance to high temperature and aggressive environment.
Single-molecule devices not only promise to provide an alternative strategy to break through the miniaturization and functionalization bottlenecks faced by traditional semiconductor devices, but also provide a reliable platform for exploration of the intrinsic properties of matters at the single-molecule level. Because the regulation of the electrical properties of single-molecule devices will be a key factor in enabling further advances in the development of molecular electronics, it is necessary to clarify the interactions between the charge transport occurring in the device and the external fields, particularly the optical field. This review mainly introduces the optoelectronic effects that are involved in single-molecule devices, including photoisomerization switching, photoconductance, plasmon-induced excitation, photovoltaic effect, and electroluminescence. We also summarize the optoelectronic mechanisms of single-molecule devices, with particular emphasis on the photoisomerization, photoexcitation, and photo-assisted tunneling processes. Finally, we focus the discussion on the opportunities and challenges arising in the single-molecule optoelectronics field and propose further possible breakthroughs.