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Digital coherent detection research on Brillouin optical time domain reflectometry with simplex pulse codes 下载免费PDF全文
The X-ray spectrometer used in high-energy-density plasma experiments generally requires both broad X-ray energy coverage and high temporal, spatial, and spectral resolutions for overcoming the difficulties imposed by the X-ray back- ground, debris, and mechanical shocks. By using an elliptical crystal together with a streak camera, we resolve this issue at the SG-II laser facility. The carefully designed elliptical crystal has a broad spectral coverage with high resolution, strong rejection of the diffuse and/or fluorescent background radiation, and negligible source broadening for extended sources. The spectra that are Bragg reflected (23° 〈 θ 〈 38°) from the crystal are focused onto a streak camera slit 18 mm long and about 80 μm wide, to obtain a time-resolved spectrum. With experimental measurements, we demonstrate that the quartz(1011) elliptical analyzer at the SG-II laser facility has a single-shot spectral range of (4.64-6.45) keV, a typical spectral resolution of E/△E = 560, and an enhanced focusing power in the spectral dimension. For titanium (Ti) data, the lines of interest show a distribution as a function of time and the temporal variations of the He-α and Li-like Ti satellite lines and their spatial profiles show intensity peak red shifts. The spectrometer sensitivity is illustrated with a temporal resolution of better than 25 ps, which satisfies the near-term requirements of high-energy-density physics experiments. 相似文献
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在有损耗、色散和自相位调制的影响下,通过分段分析法计算了自发拉曼散射光子的二阶相关函数,研究了长光纤中脉冲光泵浦下自发拉曼散射的时间模式特性。研究结果表明:在无色散和自相位调制的情况下,自发拉曼散射光子的二阶相关函数不受泵浦光损耗的影响,仅由泵浦光脉宽和拉曼光子相干时间之间的比值决定,与自发参量下转换光子的二阶相关函数具有相同的表达式;在有色散和自相位调制的情况下,由色散和自相位调制共同引起的泵浦光脉宽变化,以及泵浦光和拉曼光子间色散致走离,使拉曼光子的时间模式发生改变。自发拉曼散射光子的二阶相关函数取决于光纤损耗系数、色散参数和初始泵浦光脉宽等因素,不再与自发参量下的转换光子相同。 相似文献
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Influence of laser linewidth on performance of Brillouin optical time domain reflectometry 下载免费PDF全文
The effects of optical sources with different laser linewidths on Brillouin optical time domain reflectometry (BOTDR) are investigated numerically and experimentally. Simulation results show that the spectral linewidth of spontaneous Brillouin scattering remains almost constant when the laser linewidth is less than 1 MHz at the same pulse width; otherwise, it increases sharply. A comparison between a fiber laser (FL) with 4-kHz linewidth at 3 dB and a distributed feedback (DFB) laser with 3-MHz linewidth is made experimentally. When a constant laser power is launched into the sensing fiber, the fitting linewidths of the beat signals (backscattered Brillouin light and local oscillator (LO)) is about 5 MHz wider for the DFB laser than for the FL and the intensity of the beat signal is about a half. Furthermore, the frequency fluctuation in the long sensing fiber is lower for the FL source, yielding about 2 MHz less than that of the DFB laser, indicating higher temperature/strain resolution. The experimental results are in good agreement with the numerical simulations. 相似文献
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采用高温固相法合成出正交相和三斜相结构的BiNbO4∶Eu3+样品,利用X 射线衍射(XRD)、拉曼光谱、吸收光谱和荧光光谱对样品的结构和光学性能进行了研究。结果表明:900 ℃合成样品为正交相结构α-BiNbO4,而1 200 ℃得到三斜相结构β-BiNbO4。吸收光谱得到α相和β相BiNbO4的光学带隙分别为2.69 eV和2.96 eV,与第一性原理的理论结果2.640 eV和3.032 eV相吻合。Eu3+掺杂诱导二者的光学带隙蓝移至2.89 eV和3.05 eV,有效改变了其光响应范围。荧光光谱表明:Eu3+在两种结构的最强荧光峰均来自5D0→7F2电偶极跃迁,最强荧光峰分别位于615 nm和611 nm。Eu3+在β-BiNbO4中的荧光强度更高,而且其5D0→7F2和5D0→7F1的荧光强度比值更大。与Eu3+相似,Er3+在β-BiNbO4中具有更高的上转换荧光强度,其强度约是在α-BiNbO4中荧光的近40倍,说明三斜结构BiNbO4更适合做稀土离子的基质材料。 相似文献
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Wen-Yan Zhang 《中国物理 B》2021,30(11):114212-114212
We report experimental observations performed using a net anomalous dispersion Er-doped fiber ring laser without polarization-selective elements, highlighting the domain-wall solitary pulses generated under the incoherent polarization coupling. By adjusting the pump power and the polarization state appropriately, bright and dark solitons can stably co-exist in the cavity, both centered at 1562.16 nm with a 3-dB spectral width of ~ 0.15 nm and a repetition rate of 3.83 MHz. Moreover, the 0.8 mm long thulium-doped fiber (TDF) facilitated the mode-locking and self-starting of the laser. This is the first demonstration of a laser being used to generate bright and dark solitons synchronously while using TDF as the saturable absorber (SA). Except possessing the all-fiber structure, the laser exhibits good stability, which may have a significant influence on improvement of the pulse-laser design, and may broaden practical applications in optical sensing, optical communication, and soliton multiplexed systems. 相似文献
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