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Laser light can trap and manipulate small particles. Scientists now show that femtosecond near-infrared laser pulses can split a single trap into two. The effect is a result of third-order optical nonlinearities that arise once the laser power crosses a certain threshold, and the direction of the split is determined by the light’s polarization.

When femtosecond laser pulses pass through a trapped polystyrene bead, water breakdown is induced even though the energy of laser pulse is much lower compared to the threshold value of breakdown when the femtosecond laser directly irradiates in water. This mechanism is assigned to the secondary convergence of the laser by the trapped bead.

Although the digital micromirror device (DMD) has been considered to be a spatial light modulator (SLM) for a long time, it is seldom utilized for holographic tweezers practically because of its energy loss. In this work, a multi-trapping system built with a DMD is demonstrated. But a problem of dispersion is found when the DMD is applied to femtosecond laser, and its mechanism is studied.

Luminescence thermometry usually suffer from cellular complexity of the biochemical environment (such as pH and ionic strength) and thus the accuracy and reliability of the determined intracellular temperature are directly affected. Herein, a photoluminescent nanothermometer composed of polymer encapsulated quantum dots (P-QD) has been developed. And the prepared nanothermometer exhibits some advantages: such as non-sensitivity to pH and ionic strength, as well as high detection sensitivity and ultrahigh reversibility. The intracellular temperature was accurately determined under physiological conditions with different pH and ionic strength and direct measurement of thermogenesis in individual cells has been achieved.

Materials possessing high two photon absorption (TPA) are highly desirable for a range of fields, such as three-dimensional data storage, TP microscopy (TPM) and photodynamic therapy (PDT). Specifically, for TPM, high TP excitation (TPE) brightness (σ × ϕ, where σ is TPA cross-sections and ϕ is fluorescence quantum yield), excellent photostability and minimal cytotoxicity are highly desirable. However, when TPA materials are transferred to aqueous media through molecule engineering or nanoparticle formulation, they usually suffer from the severely decrease of quantum yield (QY). Here, we report a convenient and efficient method for preparing polymer-encapsulated quantum dots (P-QD). Interestingly, the QY was considerably enhanced from original 0.33 (QDs in THF) to 0.84 (P-QD in water). This dramatic enhancement in QY is mainly from the efficiently blocking nonradiative decay pathway from the surface trap states, according to the fluorescence decay lifetimes analysis. The P-QD exhibits extremely high brightness (σ × ϕ up to 6.2 × 106 GM), high photostability, excellent colloidal stability and minimal cytotoxicity. High quality cellular TP imaging with high signal-to-background ratio (> 100) and tissue imaging with a penetration depth of 2200 μm have been achieved with P-QD as probe.

A phenomenon called “trap split” had been found when gold nanoparticles were trapped by femtosecond laser pulses, and the trap split was strongly dependent on the polarization, energy and wavelength of the laser pulses. The 3-Dimension distribution of trap split was investigated in this work.

In an optical tweezers system, the output signal of a photodiode quadrant detector and the temperature in a sample cell are two key factors for the quantitative measurements of mechanical properties of living biological objects such as cells, organelles and macro-molecules. In order to enhance the output of a quadrant detector and effectively control the temperature in a sample cell, the dependence of the temperature in the sample cell and the output of the quadrant detector for different illumination conditions are studied. The results show that appropriate illumination conditions can ensure both nearly constant temperatures in the cell and the desired output signal, which provides for the possibility of high precision and damage-free analysis of living biological objects.

In an optical tweezers system, the output signal of a photodiode quadrant detector and the temperature in a sample cell are two key factors for the quantitative measurements of mechanical properties of living biological objects such as cells, organelles and macro-molecules. In order to enhance the output of a quadrant detector and effectively control the temperature in a sample cell, the dependence of the temperature in the sample cell and the output of the quadrant detector for different illumination conditions are studied. The results show that appropriate illumination conditions can ensure both nearly constant temperatures in the cell and the desired output signal, which provides for the possibility of highprecision and damage-free analysis of living biological objects.

The direct measurement of the Mandel parameter of weak laser pulses, with 10 ns pulse duration time and the mean number of photon per pulse $$\bar n$$ being approximately 0.1, is investigated by recording every photocount event. With the Hanbury Brown and Twiss detection scheme, and not more than one photon per pulse being detected during the sample time by single-photon counters, we have found that the single mode diode laser with driving current lower than the threshold yields a sub-Poissonian statistics. In addition, when the diode laser driving current is much higher than the threshold, it is validated that the Mandel parameterQ C of the Poissonian coherent state is nearly $$ - \bar n/2$$ . The experimental results are in good agreement with theoretical prediction considering the measurement error.

Recently big data have become a research hotspot and been successfully exploited in a few applications such as data mining and business modeling. Although big data contain a plenty of treasures for all the fields of computer science, it is very difficult for the current computing paradigms and computer hardware to efficiently process and utilize big data to attain what are looked forward to. In this work, we explore the possibility of employing big data in recommendation systems. We have proposed a simple recommendation system framework BDRSF (Big Data Recommendation System Framework), which is based on big data with social context theories and has abilities in obtaining the Recommender based on the idea of supervised learning through big data training. Its main idea can be divided into three parts: (1) reduce the scale of the current recommendation problems according to the essence of recommending; (2) design a rational Recommender and propose a novel supervised learning algorithm to get it; (3) utilize the Recommender to deal with the later recommendation problems. Experimental results show that BDRSF outperforms conventional recommendation systems, which clearly indicates the effectiveness and efficiency of big data with social context in personalized recommendation.

This study was designed to test the feasibility of en face mapping of the transient intrinsic optical signal (IOS) response at photoreceptor outer segments and to assess the effect of spatial resolution on functional IOS imaging of retinal photoreceptors. A line-scan optical coherence tomography (LS-OCT) was constructed to achieve depth-resolved functional IOS imaging of living frog eyecups. Rapid en face OCT revealed transient IOS almost immediately (

We propose an equilateral triangle resonator filter with an output waveguide and analyzed by the finite-difference time-domain technique. The filter can realize directional output with a high Q mode by means of the mode-field coupled into the output waveguide, which results a reduction in the scattering loss at the vertices. In addition, to the deformed equilateral triangle resonator filter, an optimum parameter with a cut corner of 0.23 μm, which is equal to that of the input waveguide and can be an optimal cut, is found to help increase in finesse, Q factors, extinction ratio and the output intensity on resonance of the drop port normalized with the through port .

Fluorescence microscopy has become an essential tool for biological research because it can be minimally invasive, acquire data rapidly, and target molecules of interest with specific labeling strategies. However, the diffraction-limited spatial resolution, which is classically limited to about 200 nm in the lateral direction and about 500 nm in the axial direction, hampers its application to identify delicate details of subcellular structure. Extensive efforts have been made to break diffraction limit for obtaining high-resolution imaging of a biological specimen. Various methods capable of obtaining super-resolution images with a resolution of tens of nanometers are currently available. These super-resolution techniques can be generally divided into three primary classes: (1) patterned illumination-based super-resolution imaging, which employs spatially and temporally modulated illumination light to reconstruct sub-diffraction structures; (2) single-molecule localization-based super-resolution imaging, which localizes the profile center of each individual fluorophore at subdiffraction precision; (3) bleaching/blinking-based super-resolution imaging. These super-resolution techniques have been utilized in different biological fields and provide novel insights into several new aspects of life science. Given unique technical merits and commercial availability of super-resolution fluorescence microscope, increasing applications of this powerful technique in life science can be expected.

A phenomenon called “trap split” was found when gold nanoparticles were trapped by linear polarized femtosecond laser pulses. The trap split was strongly dependent on the polarization of trapping laser, besides the energy and wavelength of the laser pulses. The behaviors of trapped particles under various vector femtosecond laser pulses were investigated.

For the purpose of improvement of hoist safety, it's useful to monitor and analyze hoist load. However, existence of noise pollutes the load signals and causes trouble to study them. A certain denoising method should be adopted, which is just what this paper focuses on. As an effective way, wavelet analysis was discussed, about not only its basic principle but also the selection of different wavelet denoising methods which are compared in this paper. Among them, threshold denoising is proper according to the actual nature of the hoist load. This paper illustrated its effect through an application on a real signal segment. Furthermore, comparison between different wavelets was made, which showed their different effect. For instance, "db02" benefits the reservation of singular point information, while "db08" makes the denoised signal smoother. Further study also showed if scales are not set properly, ideal effect is difficult to achieve. Finally, diversification trend of computing time with scales growth was described.

In-class demonstration experiments give the real time validation or illumination about conceptual theory, especially in the science and engineering teaching progress of undergraduate education. This paper discusses the development and application of an new apparatus based on virtual instrument for in-class experiments demonstrations when the lecture topics need electronic test process. The apparatus is composed of modular circuits, data acquisition card, pc-camera and interface to multimedia computer, combined with the virtual instrument technology and specialty experiment content. It allows the instructor to carry out electronic solutions in real time using real physical devices during lecture rather than completely theoretical illation, which help most students to visualize concepts in the study pattern typically found for engineering students. In general the response was positive with students' recognition of the high value of in-class demonstrations and the apparatus.

When the conveyance travels over certain part of steel guide with faults, it will experience strong shocks and vibrations. The conventional signal processing methods to investigate the relation between the vibration signal and fault mode are concentrated in time domain. This paper deals with the analysis of different modal parameters of test signals with characteristic similar to the Laplace wavelet, a desirable wavelet basis to identify signals similar to impulse responses. The frequency and damping parameters estimates provided by Laplace wavelet correlation filtering method are studied and applied to the signal processing and fault diagnosis of steel guide.

Several kinds of manipulation of biological cells were performed utilizing regeneratively amplified femtosecond laser system. When single-shot pulse of an amplified Ti: Sapphire femtosecond laser pulse is focused on a culture medium, shockwave and cavitation bubble are generated with little heating. An impulsive force resulting in these phenomena was applied to pttern specific cells form a culture substrate. Furthermore, laser trapping of cells was realized using high-repetition rate pulses from the laser oscillator. Although the cell was trapped stably when the laser power was less than 100 mW, the cell was burst above the threshold laser power. The bursting would be due to heating inside cell, on which the laser was focused and multiphoton absorption was induced. On the bases of these results, we propose a new methodology to pattern biological cells, which is speedy and flexible when compared with previous micropatterning methods.

In force calibration, when triangular-wave input is exerted on the piezoelectric-driven substage, there is a damped oscillation superposed on the square-wave movement of the trapped bead in our experiments. This will bring about instability for well trapping bead and become the noise source of the bead signal. Consequently, the superposed vibration will influence the precision and the range of force that can be calibrated. In order to analyze derivation of the oscillation and solve it, a model of equivalent oscillator is put forward. Based on this model, we calculate the initial amplitude of oscillation and frequency spectra of the movement of trapped bead, which is well in agreement with the experimental one. We apply sinusoidal-wave input substituted for triangular one to the substage, as a result, oscillation disturbance is avoided effectively, so the trapping stability of optical trap increases and the range of calibrated force has been extended greatly.

Intravascular low level laser irradiation (ILLLI) therapy has been applied in clinic widely since Mester et a!. reported the beneficial effects of low-level laser treatment on wound healing in the early 1980s. Clinical reports show that is an effective measure. But the mechanism of ILLLI is not very clear yet. In this article, it will be discussed why the oxygen content in the blood increases after irradiated by He-Ne laser and how does it influence the functions of body. It will be proved that the ability of blood carrying oxygen acts as a key role in the ILLLI.

It has been discussed that the increasing of oxygen content in the blood acts as a key role during the intravascular low level laser irradiation (ILLLI) therapy. In this article, it was investigated why the content of oxygen in the blood would increase after He-Ne laser radiation via measuring the fluorescent spectra of blood and its components. The fluorescent spectra of human blood and its components (plasma, red blood cell) were measured before and after the samples were irradiated by He-Ne laser for 10 minutes, and the changes of spectra were investigated. The fluorescent spectra of human whole blood and components are different. The spectra of whole blood have peaks at 490nm and 614nm; plasma sends strong fluorescence between 410nm and 600nm; the spectra of red blood cell (RBC) have a strong peak at oI4nm. After irradiated by He-Ne laser for 10 minutes, it was found that there are changes in the spectra of RBC and whole blood. Such a conclusion can be drawn that He-Ne laser inadiation can affect the hemoglobin's energy levels structure and improve the ability of blood carrying oxygen. It is significant to the application of ILLLI.

When the PDL-2 dye laser was pumped longitudinally by the frequency-doubled DCR-3 YAG:Nd laser, it is found that two coherent radiations are generated by one dye medium ( LDS75 I or LDS750 ). Aside from the expected dye laser output, there appears another coherent radiation generated by a four-wave mixing process. This is caused by the YAG: Nd laser's two longitudinal mode. As far as we know, the four-wave mixing generated in above commercial laser systems hasn't been reported. This discovery is helpful for researches of using above laser systems.

Poly(thienylene vinylene) (PTV) is a low-bandgap polymer but shows poor performance in both light-emitting and photovoltaic applications. Recently a derivative of PTV with carboxylate substitution, poly(3-carboxylated thienylenevinylene) (P3CTV), has been synthesized and was shown to be fluorescent. The photovoltaic power conversion efficiency based on P3CTV has been found to be much larger than PTV, indicating an intrinsically concomitant relationship between light-emitting and photovoltaic properties. Employing quantum chemistry calculations coupled with our correlation function formalism for excited state decay and optical spectra, we have investigated a series of side-chain substituted PTVs targeting optimal optoelectronic performance. We predict that the carbonyl substituted PTV is a strongly fluorescent polymer with low bandgap, long exciton lifetime, and large spectral overlap between emission and absorption. It is expected that carbonyl PTV is a promising light-emitting and photovoltaic polymer. Methodology wise, we find that (i) our correlation function approach to calculate the optical spectrum has much lower computational scaling with respect to the system size than the conventional method; (ii) the harmonic oscillator approximation for the nonadiabatic decay works better for a large system than for a small system.

A nondestructive and noncontact method to trap and manipulate a microparticle in solution is proposed by utilizing femtosecond laser-induced nonlinear phenomena. A 90μm diameter polystyrene bead in solution was trapped and manipulated by scanning femtosecond laser pulses around it, which was ascribed to shockwave, cavitation bubble, and jet flow. The maximum mechanical force exerted by laser irradiation was estimated to be over 1μN. In comparison with conventional optical tweezers, this method provides not only a much larger trapping force but also a noninvasive advantage.