In order to explore the law and mechanism of the action of near-infrared pulsed laser on silicon materials, 1064nm nanosecond pulsed laser and millisecond pulsed laser were used to act on silicon materials, and the damage effects of single nanosecond laser and millisecond-nanosecond combined laser were studied. Analyze the real-time evolution of plasma in laser irradiation process, reveal the mechanism of damage morphology, and discuss the influence and law of laser energy density and other parameters on the damage effect. Studies have shown that the plasma generated by a single nanosecond laser acting on silicon instantly forms a shock wave surface, which expands against the laser transmission direction. As the laser energy density increases, the plasma generation speed increases, and denser plasma clusters are formed. The ablation of the morphology is aggravated. When the millisecond-nanosecond combined pulse laser is applied, the delay time between two pulses is an important parameter that affects the effect. During the millisecond pulse time, as the delay time increases, the peak temperature rises. The same energy density combined laser acts on silicon under different delay time conditions, the damage morphology is quite different. The material properties of the silicon target change under the action of the millisecond pulse laser. The delay time determines the nanosecond injection in the shape of the specific silicon target. The nanosecond laser will give impact to the damaged silicon target. The cleavage damage morphology was observed under the action of the combined pulsed laser. This article can provide a reference for the research of laser processing and anti-laser damage silicon materials.
The laser pulse broadening and delay caused by cloud and aerosol can degrade the data transmission rate. The pulse broadening and the time delay induced by atmosphere channel are analyzed. Then the corresponding performance of communication rate for DSOC system which based on PPM scheme are investigated.In this paper, both the pulse broadening caused by cloud, aerosol and atmospheric turbulence and the time delay induced by turbulence are analyzed. Then the corresponding performance of communication rate for DSOC system which based on PPM scheme are investigated. Numerical results indicate that the cloud physical thickness and aerosol particle optical thickness can affect the communication rate severely. But, the rate can be improved by choosing lower modulation order and initial pulse width under clear atmosphere condition. The results enable us to determine suitable parameters in practical applications for better communication rate.
KEYWORDS: Photodynamic therapy, Tumors, In vivo imaging, Cancer, Quantum dots, Organisms, Femtosecond phenomena, Biomedical optics, Absorption, Resonance energy transfer
Recently, near-infrared (NIR) excitation has been suggested for PDT improvement and therapy of cancer.In this study, 5-aminolevulinic acid (ALA), a kind of photosensitizer, were coordinated to CuInS2/ZnS QDs to form the CuInS2/ZnS-ALA conjugates. An efficient transfer of energy from the donor (QDs) to the acceptor (ALA) was demonstrated through forster resonance energy transfer (FRET). The treatment effects of the conjugates in vivo was confirmed under 1300nm femtosecond laser. The results demonstrate that the CuInS2/ZnS-ALA conjugates are promising for PDT and can be used in imaging and biomedical field.
The level of glutathione in human are closely related to various diseases. In this paper, a sensitive “Turn-On” sensor for glutathione is reported. The sensor was designed based on fluorescence resonance energy transfer (FRET) between fluorescein isothiocyanate (FITC) and gold nanoparticles (AuNPs). Energy transfer form donor (FITC) to acceptors (AuNPs) because of the electrostatic absorption, resulting in the quenching of FITC fluorescence. With the addition of glutathione, FITC detach from the surface of AuNPs, because of the strong force of Au-S bond. The distance between the FITC and AuNPs increased, the fluorescence of FITC will restore because of the destruction of FRET process. Based on this principle, we construct the “Turn-On” sensor to detect GSH and give fluorescence tests in different buffers and pH values.The results revealed that the neutral PBS buffer environment is the most suitable environment for sensor. The fluorescence intensity of system decrease gradually with the decreasing concentration of GSH. The linear range of glutathione concentrations in the detection system is 1~650mg/L. We obtain a satisfying result and it can be used to detect the high concentrations of glutathione content in human body environment.
We report the observation of a supercontinuum (SC) in aqueous CdTe/ZnSe quantum dots (QDs) pumped by 800-nm femtosecond laser pulses based on simulations and experiments. For an average nanocrystal of 5.5 nm in size and a weight concentration of 5 mg/mL, the SC generated with a low-input energy range exhibits high optical to optical conversion efficiency. The measured SC spectrum exhibits spectral broadening that is significantly influenced by the nonlinear coefficient of the QDs. This nanoparticles-based SC effect may have special applications for optical coherence imaging and ultrashort pulse compression.
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