亚微米光栅零级衍射特性的数值研究

用耦合波理论分析了亚微米光栅对光波场的衍射作用,给出了在TE和TM偏振入射条件下矩阵形式的耦合波方程,研究了光栅在TE偏振入射条件下可见光波段内的反射和透射零级衍射特性。亚微米光栅零级衍射效率是波长、偏振和入射角的函数,在不同照明、观察和光栅参数条件下,光栅零级衍射具有非常复杂的光谱结构,经过适当的优化光栅参数,零级衍射具有许多独特的衍射特性,在许多应用领域具有广泛的应用前景。     

亚波长光栅的偏振闪耀特性

 使用琼斯矩阵的方法推导了连续结构亚波长光栅的衍射方程,给出了光栅衍射效率表达式,对偏振特性与衍射特性进行了研究。发现连续结构亚波长光栅仅存在３个衍射级,总衍射效率为100%,且衍射效率可在衍射级间任意分配,0级的偏振态与入射光的偏振态相同,±1级衍射光偏振态与入射光无关,－1级为左旋圆偏振光,＋1级为右旋圆偏振光。通过设置入射光偏振态与光栅相位延迟等参数,可使光栅具有闪耀特性,据此可用于设计高效偏振光分束器和偏振光开关。     

亚微米光栅的制作和零级衍射效率滤波特性的验证

从亚微米光栅的特点出发,分析了应用于防伪技术领域的亚微米光栅的各项关键制作技术和特点,制作了具有零级衍射效率滤波特性和用于光变色防伪的亚微米光栅,光栅零级衍射效率滤波特性的测量结果与使用耦合波理论计算得到的结果是完全一致的。由此可以根据防伪技术所需要的滤波特性设计亚微米光栅的参数。     

基于SOI的亚波长偏振分束器的研究

运用严格耦合波理论对亚波长光栅的模场分布进行讨论,通过位相匹配方程建立衍射级、光栅矢量和波导传输常数的关系,得到波导光栅实现偏振分束功能时对应的设计参数;针对布拉格反射层良好的反射特性,设计了一种亚波长偏振分束器。为了提高光栅的耦合效率,在基底增加Bragg反射层,将传统偏振分束器的透射光反射,与输入光相干叠加,满足相位匹配条件后耦合输出,使耦合效率大大增加。     

用于谐波分离的三角形槽亚波长光栅设计

根据亚波长光栅的导模共振异常特性,提出三角形槽亚波长光栅实现惯性约束聚变驱动器谐波分离的技术方案.定义了用于描述谐波分离性能优劣的谐波分离品质函数,对影响三角形槽亚波长光栅的谐波分离品质函数的光栅参量进行了详细的分析,基于矢量衍射理论设计了能够实现谐波分离的三角形槽亚波长光栅,确定了用于谐波分离的三角形槽亚波长光栅的设计思路和方法.     

用于谐波分离的三角形槽亚波长光栅设计

根据亚波长光栅的导模共振异常特性,提出三角形槽亚波长光栅实现惯性约束聚变驱动器谐波分离的技术方案.定义了用于描述谐波分离性能优劣的谐波分离品质函数,对影响三角形槽亚波长光栅的谐波分离品质函数的光栅参量进行了详细的分析,基于矢量衍射理论设计了能够实现谐波分离的三角形槽亚波长光栅,确定了用于谐波分离的三角形槽亚波长光栅的设计思路和方法.     

用于ICF驱动器谐波分离的亚波长光栅优化设计

针对惯性约束聚变(ICF)驱动器对谐波分离的苛刻要求,利用基于矢量衍射理论开发的商用软件Gsolver,在布拉格(Bragg)入射角下,设计满足分光要求的光栅参数,并根据对影响谐波分离性能的亚波长光栅的各个参数进行了分析,研究了实现谐波分离的亚波长光栅的优化设计方法,并设计得到了满足谐波分离要求的亚波长光栅。研究结果为亚波长光栅用于谐波分离提供了理论支持。     

线偏振高斯光束通过复合型衍射光栅的传输特性

提出一种集合浮雕和折射率周期分布调制的复合型衍射光栅,并利用角谱表示和严格的模式理论研究了线偏振高斯光束通过这种复合型衍射光栅的传输特性.数值计算结果表明,在光栅的同一透射深度处复合型衍射光栅光强的起伏频率要比浮雕型光栅光强的起伏频率小.最后使用复合型衍射光栅模型,研究了亚波长体积相位全息光栅的表面起伏和入射光束的束腰宽度对衍射效率的影响. 关键词： 复合型衍射光栅 亚波长体积相位全息光栅 高斯光束 严格模式理论     

基于共振异常的消偏振型窄带滤波器分析

亚波长光栅因光栅参量的不同而具有不同的衍射特性,通过对亚波长光栅参量的合理设计来实现消偏振窄带滤波是一种新的方法与途径。首先分析了基于共振异常的窄带滤波的物理机制及存在条件,讨论了二维亚波长光栅实现消偏振窄带滤波的可能性。然后,利用严格模式理论进行了计算模拟,其计算结果与导波理论所得结果基本吻合,其衍射特性表现出周期性共振异常、敏感的角度依赖性和波长依赖性。最后,讨论了由工艺误差对滤波特性所带来的影响。为具体工艺制作提供了一定的指导。     

基于光谱合束技术的透射光栅模拟设计

半导体激光器光谱合束技术能够实现近衍射极限的高功率激光输出,已成为当前研究热点。衍射光栅的性能直接决定光谱合束的激光输出效果。模拟设计了一种针对940 nm波长、熔融石英材料的亚波长透射光栅。基于严格耦合波理论对光栅结构进行初步设计,运用Rsoft软件依次对光栅占空比、脊高和周期等参数进行优化确定,同时分析了各个参数对光栅衍射效率的影响。所设计的透射式光栅实现第-1级衍射级次的波分复用功能,衍射效率达到91.2%(TE模式),同时压缩其他衍射级次,使其衍射效率降到1.2%以下。同时在光栅入射角度59°±3°范围内保持90%以上的衍射效率,实现高功率激光输出的同时具有较高的误差容错率,易于调节,满足光谱合束技术的要求。     

凹面光栅衍射效率的研究进展

凹面光栅因同时具有聚焦和色散功能而广泛应用于各类紫外、可见和红外波段的光谱分析仪器中,尤其是平场凹面光栅可以结合线阵或面阵探测器来实现即时分析。凹面光栅衍射效率的高低直接影响光谱仪器的信噪比和信号采集,其相关研究也逐渐为人们所关注。介绍了凹面光栅衍射效率的研究进展,比较了由机械刻划法和全息法制作的凹面光栅在掠入射下衍射效率的差别,分析了现有计算衍射效率方法的优缺点,并且对凹面光栅衍射效率的研究趋势做了简要预测,提出了需要同时在凹面光栅的主截面和非主截面内考虑光束对其衍射效率的影响。     

Optimization of near-field optical field of multi-layer dielectric gratings for pulse compressor

Multi-layer dielectric (MLD) gratings for pulse compressors in high-energy laser systems should provide high diffraction efficiency as well as high laser induced damage thresholds (LIDT). Nonuniform optical near-field distribution is one of the important factors to limit their damage resistant capabilities. Electric field distributions in the gratings and multi-layer film region are analyzed by using Fourier modal method. Optimization of peak electric field in the gratings ridge is performed with a merit function, including both diffraction efficiency and electric field enhancement when the top layer material is HfO₂ and SiO₂, respectively. A set of optimized gratings parameters is obtained for each structure, which reduce the peak electric field within the gratings ridge to being respective 1.39 and 1.84 times the value of incident light respectively. Finally, we also discuss the effects of gratings refractive index, gratings sidewall angle and incident angle on peak electric field in the gratings ridge.     

多层介质膜脉宽压缩光栅的严格矢量分析

用于展宽和压缩激光脉冲的多层膜脉宽压缩光栅是由多层介质高反膜和位于其顶层的浮雕光栅构成。以设计的高反射多层膜为基础,利用傅里叶模式理论分析了其衍射场分布,给出了TE波自准直角入射的使用条件下,多层介质膜脉宽压缩光栅衍射效率的表达式。以-1级衍射效率为评价函数,分别讨论了HfO2和SiO2为顶层材料时,多层膜脉宽压缩光栅-1级衍射效率高于0.95的光栅结构参量范围。结果表明,在该条件下,选择HfO2为顶层材料时,光栅结构参量有较大的取值范围。给出了优化的光栅结构参量,并分析了光栅制作误差及其使用条件的宽容度,对光栅制作工艺和使用具有一定的指导意义。     

大角带宽高衍射效率体全息光栅的设计和制备

高性能体全息光栅是全息波导的重要耦合元件,角带宽小、平均衍射效率不高是制约体全息光栅性能的重要因素.以不对称倾斜记录为出发点,设计并制备了大角带宽高衍射效率的体全息光栅.首先讨论在横电模式光和横磁模式光下体全息光栅的记录参数与其衍射效率的关系,找到平均衍射效率较高的记录参数范围,随后进一步分析在此范围内的记录参数与体全...     

On the Fresnel diffraction pattern of phase holographic gratings

The Fresnel diffraction pattern of phase diffraction gratings is studied on the example of idealized sinusoidal relief-phase plane holographic thermoplastic gratings. It is shown that, in the region of low spatial frequencies, which are more than two times lower than the inverse wavelength of the reading coherent radiation, the intensities of the main diffraction maxima, the diffraction efficiency, and the light-scattering power are independent of the spatial frequency of the phase gratings under investigation, which are characterized by a sinusoidal law of modulation of the reading-radiation phase. It is established that the range of spatial frequencies at which a plateau is observed in these dependences increases with decreasing amplitude of the phase modulation of the reading light. These dependences are also observed to have similar character for the thermoplastic holographic gratings under study. Calculations were performed to analyze the influence of real profiles of thermoplastic strain on the diffraction efficiency and light-scattering power of such gratings. On the basis of analysis of the results obtained, recommendations on using holographic and raster techniques of recording data on phase carriers are given that make it possible to improve the quality of the restored optical image.     

Diffraction properties of ultrashort pulsed beams with arbitrary temporal profiles by a reflection volume holographic grating

The diffraction properties of reflection volume holographic gratings are studied when the gratings are illuminated by an ultrashort beam with arbitrary temporal profiles. The modified Kogelnik's theory of coupled waves is used. Simple analytical expressions for spectral and temporal distribution of the transmitted and diffracted are obtained. The dependences of the diffraction bandwidth, the Bragg selectivity bandwidth and the total diffraction efficiency of the reflection volume grating on the temporal profiles of the input ultrashort pulse are investigated. Study shows that the bandwidth of the reflection volume holographic gratings varies with the grating parameters more slowly than the transmitting volume holographic gratings. For three different temporal profiles, numerical results about diffraction properties of the reflection volume holographic gratings are given and compared with the transmitting volume holographic gratings.     

可见光波段双层浮雕型导模共振滤波器设计与分析

基于傅里叶模式理论分析了双层浮雕型导模共振光栅的共振效应,分别讨论了光栅的槽深、剩余厚度、周期以及填充系数对峰值反射率、带宽、旁带反射率的影响. 数据计算表明,欠刻蚀情形的误差宽容度远远优于过刻蚀情形,两者在光栅槽深相对误差小于15％的范围内,都能保证共振峰的衍射效率高于99.5%,在相同的误差范围内,共振峰线宽的相对误差将分别达到7％和60％,因此厚度误差集中反映在对共振线宽的改变上. 另外,光栅周期和填充系数的变化将明显改变共振峰中心波长和线宽. 关键词： 导模共振 平面波导 窄带滤波     

辅助紫光提高菌紫质全息衍射效率的实验和理论研究

由于菌紫质样品的饱和吸收特性，在全息记录中，当记录光强大于样品的饱和光强时，全息光栅透过率随记录光相位差的分布远离余弦型，因此衍射效率的稳定值很低.菌紫质样品在红光和紫光共同作用下存在着双光束互补抑制效应，紫光可以抑制红光的透过率，提高红光的饱和光强，使记录区域由非线性区移至线性区，从而使全息光栅透过率随记录光相位差的分布变为余弦型，可以有效地提高全息衍射效率.实验证明，辅助紫光大大提高了菌紫质样品全息衍射效率的稳定值.根据此原理，建立了三光束全息光存储系统，在红光记录全息图的同时加入辅助紫光，可以使全息图衍射效率及衍射像的像质得到提高. 关键词： 菌紫质 全息存储 衍射效率 饱和吸收     

Effect of recording conditions on the anisotropic diffraction of volume holographic gratings

The anisotropic Bragg diffraction of the volume holographic gratings in photorefractive crystals are investigated based on the model of anisotropic coupled-wave theory. The effect of the initial intensity ratio and the recording angles of the two recording waves on the anisotropic Bragg diffraction properties is discussed. It is shown that both the ratio of the initial intensity and the incident angles of the recording waves are selective action for the anisotropic Bragg diffraction efficiency of the volume holographic gratings, while these two recording conditions are not selective action for the isotropic Bragg diffraction. Furthermore, the Bragg phase matching condition of anisotropic diffraction is analyzed when the recording angles change.     

高衍射效率亚波长结构Dammann光栅的设计

传统的Dammann光栅是基于标量衍射理论设计的二值相位等光强分束器件，其衍射效率的典型值为80%左右.基于严格耦合波分析理论和遗传算法，提出了一种设计亚波长结构Dammann光栅的新方法，且该新型二值相位光栅具有较高的衍射效率.同时利用自编的仿真程序包设计了多个光栅，并分析了制作误差对其衍射效率和光强均匀性的影响.仿真结果表明，用该方法所设计的Dammann光栅的衍射效率超过92%.