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在生长Fe∶LiNbO3熔体中掺进摩尔分数x(Ru2O3) =0.1%和x(MgO)=1%、3%、7%,用提拉法生长镁钌铁铌酸锂(Mg ∶ Ru∶Fe∶LiNbO3)晶体.通过二波耦合光路,分别以红光(632.8 nm)、绿光(532 nm)和蓝光(476 nm)为光源测量晶体的全息存储性能.实验结果表明,在476 nm下,Mg∶Ru∶Fe∶LiNbO3晶体全息存储性能随着Mg离子掺杂浓度的增加而呈现逐渐增强的趋势,与其在红光和绿光下不同.研究了Mg离子掺杂浓度的增加使Mg∶Ru∶Fe∶LiNbO3晶体的蓝光全息存储性能增强的机理. 相似文献
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利用傅里叶变换法在自散焦LiNbO3:Fe晶体中写入光子晶格的过程中发现,阵列光束与写入晶格相互作用产生的空间二次谐波对写入晶格的结构具有一定的影响。表现为光子晶格中空间频率的倍频现象,干涉条纹的分裂现象和布拉格带隙的展宽现象。通过对一维光子晶格中空间二次谐波的数值模拟和理论计算,证明了空间二次谐波的产生是晶格结构发生改变的主要原因。实验表明,通过控制空间二次谐波的产生情况可以有效地改变写入光子晶格的内部结构。 相似文献
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以双中心模型为基础,研究了同成份和近化学比掺铁铌酸锂晶体在稳态情况下的非挥发双色二步全息存储性能.通过比较在相同记录条件下同成份(锂的摩尔浓度为48.5%)与近化学比(锂的摩尔浓度为49.5%)掺铁铌酸锂的总空间电荷场的大小可以看到,在连续光所能达到的光强范围内,近化学比LiNbO3:Fe的总空间电荷场明显大于同成份LiNbO3:Fe的总空间电荷场.但是在高光强下,同成份与近化学比LiNbO3:Fe都可以达到106V/m量级的光致空间电荷场. 相似文献
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在LiNbO3中掺杂光折变敏感杂质离子Fe^2 /Fe^3 和抗光致散射杂质离子Mg^2 ,以提拉法生长Mg∶Fe∶LiNbO3晶体。测试晶体吸收光谱、红外光谱,Mg∶Fe∶LiNbO3晶体的吸收边相对Fe∶LiNbO3晶体发生紫移。当Mg^2 浓度达到阈值浓度,Mg(6%):Fe∶LiNbO3晶体OH^-吸收峰由3482cm^-1移到3529cm^-1,测试晶体的位相共轭反射率和响应时间,计算光电导。Mg(6%):Fe∶LiNbO3晶体的响应速度和光电导比Fe∶LiNbO3晶体有较大提高。 相似文献
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红外弱光诱导掺铟铁铌酸锂晶体的光折变效应 总被引:3,自引:0,他引:3
掺铟铁铌酸锂(In:Fe:LiNbO3)晶体在红外弱光辐照下正常折射率变化量△n可以达到10-4数量级.探讨了光生载流子在漂移、扩散和光生伏打效应三种机制下输运迁移以及空间电荷场的形成过程.研究结果表明,光致折射率变化的机制主要是由光生伏打效应引起,并观察到在正常偏振光辐照下,红外弱光与可见光引起晶体的正常折射率变化分布明显不同. 相似文献
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构建了基底介质为SiO2、表面覆层介质为TiO2 的二维光子晶体,采用严格耦合波法分析了二维光子晶体的窄带光学传输特性。分析了二维光子晶体的晶格周期、波导层的折射率及厚度对其反射光谱的影响。分析结果表明:当光子晶体的晶格周期和波导层介质厚度为常数时,随着波导层介质折射率的增大,光子晶体的反射峰值波长红移,且波导层折射率与反射峰值波长呈线性关系。当光子晶体波导层介质折射率为常数时,波导层厚度增大或光子晶体晶格周期的增大都会引起光子晶体反射峰值波长增大,但这两个参数与反射峰值波长只是在一定的变化范围内为线性关系。此种结构的二维光子晶体覆层表面吸附分布不均匀的介质时,通过分析光子晶体的呈现光谱可获得其表面吸附介质的不均匀特性。 相似文献
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以双中心模型为基础,研究了同成份和近化学比掺铁铌酸锂晶体在稳态情况下的非挥发双色二步全息存储性能.通过比较在相同记录条件下同成份(锂的摩尔浓度为48.5%)与近化学比(锂的摩尔浓度为49.5%)掺铁铌酸锂的总空间电荷场的大小可以看到,在连续光所能达到的光强范围内,近化学比LiNbO3:Fe的总空间电荷场明显大干同成份LiNbO3:Fe的总空间电荷场.但是在高光强下,同成份与近化学比LiNbO3:Fe都可以达到10^6V/m量级的光致空间电荷场. 相似文献
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Yu. F. Vaksman Yu. A. Nitsuk V. V. Yatsun A. S. Nasibov P. V. Shapkin 《Semiconductors》2010,44(4):444-447
ZnSe:Fe single crystals obtained by the diffusion doping are studied. The spectra of optical density in the range of energies
of 0.4–3 eV are studied. The iron concentration in the studied crystals is determined using the magnitude of the shift of
the absorption edge. The nature of the optical transitions determining the optical properties of ZnSe:Fe single crystals in
the visible and IR regions of the spectrum is identified. The diffusion profile of Fe impurity is determined by measuring
the relative optical density of crystals in the visible spectral region. The diffusivities of Fe in the ZnSe crystals are
calculated for temperatures of 1120–1320 K. At 1270 K, the diffusivity of Fe is 3 × 10−10 cm2/s. 相似文献
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We present a detailed numerical study of Archimedean-like tilings and quasi-crystals. Archimedean-like tilings are periodic structures like conventional 2D photonic crystals. However, the use of two kinds of polygons for the tiling and thus, the use of crystal unit cells of several atoms, can lead to a 12-fold local symmetry. We show that Archimedean-like tilings offer a much higher degree of isotropy than a conventional 2D Bravais lattice because the gap widths are almost independent of the light propagation direction. Besides, the conditions for gap opening and the mean gap widths remain similar to those met for conventional triangular and honeycomb lattices. The comparison between Archimedean-like tilings and quasi-crystals is carried out in two steps according to the level of the refractive index modulation. In the case of strong modulation, we show that Archimedean-like tilings with a few atoms per unit cell are simple and well-working alternatives to complex quasi-crystals. They can present the same degree of isotropy for the same positions and widths of the photonic gaps. A good fit is also found between quasi-crystals and periodic structures constructed from the simplest approximants, thereby showing the importance of short-range wave-lattice interactions in that case. In a second step, we consider weakly (or moderately) modulated structures, where long-range interactions are possible. A quasi-periodic (fractal) structure recently reported in the literature is compared to an Archimedean tiling of very large unit cell (181 atoms). Surprisingly, the unusual quasi-crystal gap at long wavelength cannot be reproduced for the Archimedean tiling in spite of its very large unit cell size 相似文献
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M. Y?lmaz N. Balkan B. Ulug M. Sopanen M. Mattila A. Arnoult 《Microelectronics Journal》2009,40(3):406-409
Experimental results concerning the steady-state photoluminescence (PL) studies in n and p modulation doped and undoped GaInNAs/GaAs quantum wells are presented. The effects of modulation, type of doping and nitrogen concentration on the PL and the temperature dependence of the band gap, carrier localization and non-radiative recombination are investigated. Increasing the nitrogen composition decreases energy band gap as expected. The n-type modulation doping eliminates most of the defect-related effects and blue shifts the energy band gap. However, the p-type doping gives rise to additional features in the PL spectra and red shifts energy band gap further compared to the n-type-doped material. 相似文献
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A novel measurement system provides determination of pump induced phase shifts in erbium doped fibers with an accuracy of ~π/20. Using this system, a systematical analysis of the pump induced modulation of the refractive index and dispersions for a signal at 1550 nm and a pump at 980 nm is reported. The analysis contains measurements of pump induced refractive index changes as function of wavelength, pump power, and doping concentration. A model taking account of the contribution to the refractive index changes from optical transitions between 4 I15/2 states and 4I13/2 states in Er3+ yields good agreement to experimental results apart from a wavelength independent offset. The offset is interpreted to originate from high energetic optical transitions. The results show that for a large refractive index modulation, a short and highly doped fiber should be used with limited amplified spontaneous emission effect. In optical communication systems comprising erbium doped fiber amplifiers, a tradeoff between dispersion and amplification must be made 相似文献
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CdTe crystals of two types have been grown by the vertical Bridgman method: (i) crystals doped with Bi to ~1018 cm?3 and (ii) double-doped (Bi + Cl) crystals with a Bi concentration of ~1018 cm?3 and a Cl concentration of ~1017 cm?3. The temperature dependences of the resistivity, photoconductivity, and low-temperature photoluminescence are investigated for the crystals grown. Analysis has shown that doping with Bi (crystals of the first type) leads to compensation of the material. The resistivity of the CdTe:Bi samples at room temperature, depending on the doping level, is varied in the range of 105–109 Ω cm. The hole concentration is determined by the acceptor level at E v + 0.4 eV in lightly doped CdTe:Bi samples and by the deep center at E v + 0.72 eV in heavily doped CdTe:Bi samples. Double doping leads to inversion of the conductivity type and reduces the resistivity to ~1 Ω cm. Heavily doped CdTe:Bi crystals and double-doped crystals exhibit the presence of acceptors with an ionization energy of 36 meV, which is atypical of CdTe. 相似文献
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利用由传输矩阵法得到的一维光子晶体的反射率计算公式,针对具体的一维全息光子晶体周期结构,计算了折射率调制周期的改变以及光学厚度的改变对光子禁带结构的影响.结果表明:随着折射率调制周期参数的增大,禁带宽度减小,禁带中心的位置移向短波;随着光学厚度的增大,禁带宽度增大,禁带中心的位置移向长波.在设计光子晶体时,可以根据需要,通过改变光子晶体基本周期结构的参数来实现对光子带隙的控制. 相似文献
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Experimental results of studying the process of transmutation doping of InP single crystals by irradiating with nuclear-reactor neutrons are reported; the possibility of doping with tin in a wide range of concentrations and obtaining the concentration of free electrons as high as 2×1019 cm?3 is demonstrated. Electrical properties of InP and their behavior under irradiation and in the course of subsequent heat treatments were studied. The prospects for utilization of the nuclear-transmutation method for doping are assessed. 相似文献