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51.
激光器是现代光学中一种常用的光源,分析其谱宽特性对于激光的研究具有重要意义.由于高性能窄线宽激光的半高全宽通常在几十M Hz以内,难以直接满足宽光谱领域的应用需求,因而无法发挥其在成本和性能方面的优势,这在一定程度上限制了激光的发展.如果在激光内部直接进行调制实现线宽展宽,又会导致频率的严重漂移,破坏稳频特性.为了在激... 相似文献
52.
Two-sample (Allan) variance with a modified algorithm was applied to the determination of the experimental linewidth of a thermoelectrically-cooled continuous-wave distributed feedback quantum cascade laser at a wavelength of 4.333 μm. From successive laser transmittance scans over the CO2 ν3, (0111 − 0110) P(33) absorption line at 2307.653 cm− 1, two-sample variances were calculated for the laser frequency difference between different points on the sides of the absorption peak. From the minimum two-sample variance of the laser frequency difference between two adjacent points (5 μs between the points) on the same side of the absorption line the experimental laser linewidth was estimated to be less than 36(7) kHz at a laser power of ~ 25 mW, a laser current of 976 mA and a laser temperature of + 19.5 °C. 相似文献
53.
Differential-phase-shift (DPS) quantum key distribution (QKD) is one of the QKD protocols, featuring simplicity for practical implementation. It uses a coherent pulse train whose phase should be stable at least within the pulse interval. This paper quantitatively investigates the phase stability required for DPS-QKD systems. The phase stability is characterized by the spectral linewidth of the light source. A theoretical model and experiments are presented, the results of which indicate that the linewidth should be, for example, less than 0.35% of the free-spectral-range of an asymmetric Mach-Zehnder interferometer in a receiver to achieve quantum bit error rate of less than 0.5% due to linewidth broadening of the light source. 相似文献
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55.
通过单次穿过PPMgO:LN晶体产生了2.06 W的780 nm可调谐的连续倍频光. 采用1560 nm的分布反馈式(DFB)半导体激光器、光栅外腔半导体激光器(ECDL)和分布反馈式掺铒光纤激光器(DFB-EDFL)分别作为掺铒光纤放大器(EDFA)的注入光源, 所用的EDFA具有保持窄线宽的功能, 因此可以忽略它对基波线宽的展宽. 研究了激光线宽对单次通过PPMgO:LN 晶体的倍频效率的影响. 控制三台激光器各自注入EDFA的功率一致, 同时也保持EDFA 的输出功率. 在基波功率为12.42 W 时, 使用DFB半导体激光器注入EDFA时得到了1.36 W的780 nm倍频光输出, 转换效率为11.0%; 使用ECDL作为种子源时得到了1.78 W 的780 nm倍频光输出, 转换效率为14.3%; 使用DFB-EDFL作为种子源时得到了2.06 W的780 nm倍频光输出, 转换效率为16.6%. 测得三台种子激光器的线宽分别为1.2 MHz (DFB), 200 kHz (ECDL)和600 Hz (DFB-EDFL). 线宽越窄, 倍频效率越高, 实验结果与理论分析一致. 相似文献
56.
Abstract With increasing X on Ca1-xSrxF2 mixed crystals doped with Eu2+ (4f65d) ions, the absorption peak shifted linearly to that of SrF2:Eu, while the luminescence one moved parabolically with a minimum at around x=0.5. The linewidth broadened nearly twice as large as that of CaF2 in the vicinity of x=0.5 and subsequently renarrowed for x > 0.5. The temperature dependences of the luminescence intensity and life time revealed that the nonradiative activation energy has a minimum of 0.40 eV around x=0.5. From the calculated result of the lineshape, these non-linear behaviors against x were explained by adjusting the electron-phonon coupling strength. 相似文献
57.
Enhancement of magnetic and dielectric properties of low temperature sintered NiCuZn ferrite by Bi2O3-CuO additives
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With a series of 1.0 wt%Bi$_{2}$O$_{3}$-$x$ wt% CuO ($x =0.0$, 0.2, 0.4, 0.6, and 0.8) serving as sintering additives, Ni$_{0.23}$Cu$_{0.32}$Zn$_{0.45}$Fe$_{2}$O$_{4}$ ferrites are successfully synthesized at a low temperature (900 $^\circ$C) by using the solid state reaction method. The effects of the additives on the phase formation, magnetic and dielectric properties as well as the structural and gyromagnetic properties are investigated. The x-ray diffraction (XRD) results indicate that the added Bi$_{2}$O$_{3}$-CuO can lower the synthesis temperature significantly without the appearing of the second phase. The scanning electron microscope (SEM) images confirm that Bi$_{2}$O$_{3}$ is an important factor that determines the sintering behaviors, while CuO affects the grain size and densification. With CuO content $x=0.4$ or 0.6, the sample shows high saturation magnetization, low coercivity, high real part of magnetic permeability, dielectric permittivity, and small ferromagnetic resonance linewidth ($\Delta H$). The NiCuZn ferrites are a promising new generation of high-performance microwave devices, such as phase shifters and isolators. 相似文献
58.
基于Kogelnik理论模型,以平面波为入射光,分析了双体布拉格光栅(VBG)的反馈特性。理论分析表明,采用双VBG结构,通过控制两个VBG的中心波长差,可以使光栅反馈的效率提高,带宽加宽。对于由两块带宽100 pm、衍射效率20%的VBG组成的双VBG反馈系统,中心波长相同时,衍射效率最大(33.3%);中心波长相差84 pm时,其带宽为单VBG带宽的1.8倍(180 pm)。由于VBG的中心波长存在温度漂移特性,因此通过改变双VBG结构中VBG的温度可以实现衍射效率和带宽的改变,为泵浦源的优化提供有效可行的方法。 相似文献
59.
We investigate the steady optical response of a coherently driven five-level M-type atomic system in three different situations.When all three coupling fields have the same zero detuning,we just find one deep transparency window accompanied by a steep normal dispersion in the probe absorption and dispersion spectra.When two coupling fields are detuned from the relevant transitions to the same extent,however,a second deep transparency window may be observed in the presence of a narrow absorption line of linewidth ~50 kHz.In this case,two single-photon far-detuned transitions can be replaced by a two-photon resonant transition,so the five-level M system in fact reduces into a four-level quasi-Λ system.Finally,we note that no deep transparency windows and no narrow absorption lines can be found when all three coupling fields have unequal detunings. 相似文献
60.