对检测烧结矿的实验参数进行优化，使其光谱信号的相对标准偏差（RSD）维持在4%左右。再结合内标法，分别选择合适的Fe元素谱线作为Ca、Si元素的内标谱线，利用内标后的比值与碱度值进行拟合分析。相比于无内标方法，其校准模型的决定系数（R²）从0.468提升至0.951，且预测值的相对误差最高为1.14%。结果表明，在实验条件优化下，内标法对烧结矿碱度的预测精确度高。

为了明确外源激素诱导水稻抗旱性的效果及其生理机制。以中嘉早17为材料,分析外源激素在淹水灌溉、干湿交替灌溉和干旱灌溉方式下叶绿素荧光参数的差异及其对产量与产量构成的影响。结果表明,干旱灌溉显著降低了叶片光系统Ⅱ(PSⅡ)最大光化学量子产量、实际光量子效率、非光化学猝灭值、有效穗数、每穗粒数、结实率,孕穗期比分蘖期更为敏感,表现为相同胁迫时间下最大光化学量子产量、每穗粒数、单株穗数等下降更显著。赤霉素(gibberellin, GA3)处理后降低了PSⅡ最大光化学量子产量、非光化学猝灭和光化学猝灭系数,导致有效穗数减少、千粒重和结实率降低。脱落酸(abscisic acid, ABA)处理能缓解孕穗期干旱胁迫,减轻水稻叶片的光抑制程度,提高叶绿素荧光参数,增强抗旱能力。综合来看,以分蘖期淹水条件下结合IBA处理产量最高,比对照增产7.4%,这可能与淹水条件下吲哚丁酸(indolebutyric acid, IBA)处理能提高光合效率有关。

叶绿素含量是评价水稻光合效率的重要指标, 实时无损监测叶绿素含量对水稻生长诊断具有重要意义。以水稻P88S(绿叶)和黄1S(黄叶)为试验材料, 分析高光谱指数与水稻叶绿素含量的关系, 并构建冠层反射光谱与水稻叶绿素含量监测模型。研究结果表明: 水稻不同叶色的冠层光谱反射率随着植株生长而不断变化, 在绿叶材料P88S的502-711 nm和黄叶材料黄1S的487-716 nm可见光波长范围内, 叶绿素含量与一阶微分光谱的相关系数呈极显著正相关。以P88S RVI(363, 675)和黄1S DVI′(639, 680)作为光谱参数, 与叶绿素含量建立估算模型拟合效果最佳, 说明利用高光谱技术结合一阶微分光谱的方法可以监测水稻叶绿素含量。

With the use of pulsed pumping, an optical fiber amplifier with all-fiber structure is developed based on the fused tapered fiber combiner and Yb+{3+}-doped double cladding fiber (YDCF). From the experimental results, 47-dBm peak power and 100-ns pulse duration are obtained when the repetition rate of pumping pulses is 100 Hz. The gain of the amplifier is up to 30 dB. It is shown that due to the use of pulsed pumping, pump light emits only when the signal light reaches the amplifier and thus the amplified spontaneous emission (ASE) is significantly suppressed.

Sn/Yb codoped silica optical fiber preform is prepared by the modified chemical vapor deposition (MCVD) followed by the solution-doping method. Ultraviolet (UV) optical absorption, photoluminescence (PL) spectra under 978-nm laser diode (LD) pumping, and refractive index change after exposure to 266-nm laser pulses are obtained. There is only a little change in the PL spectra while a positive refractive index change up to 2\times10^{-4} is observed after 30-min exposure to 266-nm laser pulses. The results show that both of the peculiar photosensitivity of Sn-doped silica and the gain property of Yb-doped silica fiber are preserved in the Sn/Yb codoped silica optical fiber preform. The experimental data suggest that the photosensitivity of the fiber preform under high energy density laser irradiation should be mainly due to the bond-breaking of oxygen deficient defects, while under relatively low energy density laser irradiation, the refractive index change probably originates from the photoconversion of optically active defects.

从波动理论出发,对锥形光纤的纵向传播常数进行泰勒(Taylor)级数展开,经近似得到了锥形光纤功率分布的解。基于此理论,对锥形光纤的功率分布特性进行了讨论,并分析了锥形光纤的长度、锥度和光纤折射率等参数对锥形光纤不同模式功率分布的影响。为了减小功率泄漏,当光从锥形光纤大端入射时,应当减小锥长,减小锥度,增大纤芯包层折射率差; 当光从锥形光纤小端入射时,应当增加锥长,增加锥度,增大纤芯包层折射率差。在长锥长、大锥度情况下,光纤折射率分布的影响相对较小。

We propose a kind of photonic crystal fiber with flat-top fundamental mode by introducing a depressed central dip into the core of the conventional index-guiding photonic crystal fiber. The design guidelines and characteristics of the large flattened mode photonic crystal fiber (LFM-PCF) are discussed in detail. By appropriate design, the effective area of the LFM-PCF can be increased by a factor of greater than 2 as compared with conventional index-guiding photonic crystal fiber with the same hole and pitch parameters. The improved effective area, single mode operation and flat-top fundamental mode output make LFM-PCF an ideal candidate to realize high power, high beam quality fiber amplifiers and lasers.