Raman spectrometry was employed to study the characteristics of Raman spectra of polyethylene terephthalate (PET), which were treated with sodium hydroxide, sulfuric acid and copper sulfate, respectively. Raman spectra under different conditions were obtained and the characteristics of the Raman spectra were analyzed. The morphology structures were observed under different conditions using Atomic Force Microscope. The results show that the spectral intensity of PET treated with sodium hydroxide is higher than that untreated between 200-1750 cm-1, while the intensity of PET treated with sodium hydroxide is lower than that untreated beyond 1750 cm-1 and the fluorescence background of Raman spectra is decreased. The spectral intensity of PET treated with sulfuric acid is remarkably reduced than that untreated, and the intensity of PET treated with copper sulphate is much higher than that untreated.
In this work it is shown the benefit of using waveform integration of the avalanche pulses of MPPC for enhancing the photon number resolving capability of Multi-Pixel Photon Counter (MPPC). Up to 47 photon equivalent peaks can be distinguished in the Photon-Number-Resolving (PNR) spectrum with a repetition frequency of 80 MHz, which is the largest reported number obtained at room temperature as far as we know.
Raman spectrometry was employed to study the characteristics of Raman spectra of aliphatic polyamide fiber and polyethylene terephthalate (PET), which were treated with sodium hydroxide, sulfuric acid and copper sulfate, respectively. Raman spectra under different conditions were obtained and the characteristics of the Raman spectra were analyzed. The results show that Raman peaks beyond 1200 cm-1 appear for aliphatic polyamide fiber processed by sodium hydroxide, while the Raman peaks beyond 1000 cm-1 disappear for aliphatic polyamide fiber processed by sulfuric acid. Raman peaks beyond 1750 cm-1 decrease for polyethylene terephthalate processed by sodium hydroxide, while Raman peaks beyond 1000 cm-1 disappear, except weak peaks around 3000 cm-1 , for polyethylene terephthalate processed by sulfuric acid. The variations of the Raman spectra are primarily related to the changes of chemical bonds and molecular structures.
Two wavelength optical signals in the infrared regime were generated in atomic rubidium (Rb) vapor using a Ti:sapphire laser amplifier and competition between the two signals was observed. The effects of Rb number density, pump laser intensity and the chirp of laser pulses on the characteristics of the two signals were investigated. The results show that the two signals were mainly generated by two coupled difference frequency six wave mixings and, in the meantime, two coupled six wave mixing channels were identified. The competition between the two signals is dominantly governed by phase matching conditions in the two six wave mixing processes. The phase matching conditions in the two channels are primarily determined by the Rb number density and, whereas, the phase matching conditions are scarcely related to pump laser intensity and the chirp of pump laser pulses.
A chalcogenide glass was used for an optical Kerr gate to sampling pulse contrast of femtosecond lasers with low repetition rate ( 40 Hz). The dynamic range of this method reached 103, with a scanning range of 150ps and temporal sampling rate of 6.3 fs. The advantage of this method lies in its broad spectrum range including visible and NIR spectral region and easy operation.
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