高斯光束照射下与矩孔相关的孔径衍射

依据基尔霍夫衍射理论,利用幂级数展开的方法,推导出傍轴条件下高斯光束的矩孔及单缝衍射的近似计算公式,并通过数值计算、数值模拟等方法对衍射场的基本特性进行了讨论。     

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.     

Diffraction characteristics of chirped femtosecond laser pulse by rectangle reflection grating

The spectral and temporal intensity distribution expression for the chirped femtosecond laser pulse diffracted by a rectangle reflection grating is derived. The effects of the chirped coefficient on the spatiotemporal and spectral characteristics are theoretically investigated in detail, and a criterion for judging whether or not the diffraction pulse is just split into two independent pulses in the temporal domain is obtained. The results show that the envelope curve of spectral intensity on the diffraction axis is more blue-shift, and its full width at e^? 1 maximum is wider for bigger chirped coefficient. The principal maximum on the temporal axis can split into two independent principal maximums for enough height from the upper and the nether reflection surface of the grating. Each principal maximum splits into two smooth pulses, namely one principal pulse and one secondary pulse, and the secondary pulse gradually increases with the increasing of the chirped coefficient; the duration of two principal pulses increases with the increasing of the height of the upper and the nether reflection surface of the grating.     

Changes in polarization of Gaussian Schell-model beams and partially polarized Gaussian Schell-model beams through a polarization grating

The polarization properties of Gaussian Schell-model (GSM) beams and partially polarized Gaussian Schell-model (PGSM) beams passing through a polarization grating (PG) are studied based on the beam coherence-polarization (BCP) matrix formulism, where the finite size of the PG is considered. Detailed numerical calculation results are given and compared with the previous work.     

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

In this paper, the diffraction properties of an ultrashort optical pulse with arbitrary profiles in time diffracted by a volume holographic grating are investigated using the modified Kogelnik coupled-wave theory. Simple analytical expressions for the spectrum and spatial profiles of the transmitted and diffracted beams are obtained. The dependences of the diffraction bandwidth, the Bragg selectivity bandwidth and the total diffraction efficiency of the volume grating on the temporal profiles of the input ultrashort pulse are investigated. For three different temporal profiles, numerical results of diffraction properties are given. It is shown that the temporal shapes of the input pulsed beams have been found to be an important factor in the analyses of the propagation characteristics.     

Diffraction properties of partially coherent electromagnetic four-petal Gaussian beams

The concept of existing scalar coherent four-petal Gaussian (FPG) beam is extended to the more general partially coherent electromagnetic four-petal Gaussian (PCFPG) beam, and the cross-spectral density matrix of the latter is derived in analytical expressions. Intensity distributions and degree of polarization in free space are investigated by numerical examples. Results show that propagation properties of the PCFPG beam are different from their scalar coherent and scalar partially coherent counterparts. Both intensity distributions and polarization strongly depend on transversal coherence lengths. When the propagation distance increases to a large value, intensity distributions of PCFPG beams convert into the Gauss profile. Polarization of PCFPG beams shows an oscillating characteristic upon propagation, and the oscillation would enhance with the increase of coherence lengths. These results may find potential applications in beam shaping and free space optical communications.     

线偏振高斯光束通过条形浮雕光栅的传输

使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特征尺寸与波长可比拟的条形浮雕光栅的传输，系统参数误差对浮雕层中光强最大值的影响.研究表明，光束在条形浮雕光栅各层中有不同的光强分布，浮雕层的介质填充部分中的光强明显高于展空部分的光强.光栅周期误差对浮雕层中最大光强的影响起主要作用.并利用模拟退火优化算法优化系统参数以控制出射光束的光强分布.     

Diffraction grating with rectangular grooves exceeding 80% diffraction efficiency

A novel design for a surface relief grating with rectangular grooves is presented. The first reflected diffraction order shows experimentally 84% diffraction efficiency for a metallic grating. The required binary surface relief can be manufactured by using one single microlithographic fabrication step similar to standard processes in microelectronics. Each period of the grating consists of a subwavelength “minilattice” with a variable duty cycle. A theoretical model of the structure is presented and compared to measurements at 10.6 μm wavelength. Applications ranging from deflectors, polarizing beam splitters, variable attenuators to general diffractive components such as kinoforms for laser beam shaping are proposed.     

Diffraction properties of four-petal Gaussian beams in uniaxially anisotropic crystal

Propagation properties of polarized four-petal Gaussian beams along the optical axis of uniaxially anisotropic crystals were investigated. Based on the paraxially vectorial theory of beam propagation, analytic expressions of the diffraction light field were obtained. The effects of the anisotropy on the polarization properties of the diffracted four-petal Gaussian beams have also been explained by numerical method. The results elucidate that the linear polarization state and the symmetry of the incident beams cannot be kept during propagation in anisotropic crystals.     

矩形分布高斯-谢尔模型列阵光束的等效曲率半径

推导出矩形分布高斯-谢尔模型（GSM）列阵光束通过湍流大气传输的等效曲率半径的解析表达式。研究表明,等效曲率半径由湍流强度、GSM列阵光束参数及光束的叠加方式等因素共同确定。湍流使得等效曲率半径减小,但湍流对交叉谱密度函数叠加时等效曲率半径的影响要比光强叠加时大。在自由空间中,交叉谱密度函数叠加时GSM列阵光束的等效曲率半径要比光强叠加时的大。但是,随着湍流的增强,交叉谱密度函数叠加时GSM列阵光束的等效曲率半径可以大于、等于或小于光强叠加时的等效曲率半径。此外,若光束相干参数和子光束数目越大,则等效曲率半径受湍流的影响越大。GSM列阵光束的等效曲率半径受湍流的影响比高斯列阵光束要小。     

矩形分布高斯-谢尔模型列阵光束的等效曲率半径

 推导出矩形分布高斯-谢尔模型（GSM）列阵光束通过湍流大气传输的等效曲率半径的解析表达式。研究表明,等效曲率半径由湍流强度、GSM列阵光束参数及光束的叠加方式等因素共同确定。湍流使得等效曲率半径减小,但湍流对交叉谱密度函数叠加时等效曲率半径的影响要比光强叠加时大。在自由空间中,交叉谱密度函数叠加时GSM列阵光束的等效曲率半径要比光强叠加时的大。但是,随着湍流的增强,交叉谱密度函数叠加时GSM列阵光束的等效曲率半径可以大于、等于或小于光强叠加时的等效曲率半径。此外,若光束相干参数和子光束数目越大,则等效曲率半径受湍流的影响越大。GSM列阵光束的等效曲率半径受湍流的影响比高斯列阵光束要小。     

Design of two-dimensional apodized grating couplers with Gaussian diffractive mode

Two-dimensional apodized grating couplers are proposed with grating grooves realized by a series of nanorectangles, with the feasibility of digital tailoring the equivalent refractive index of each groove in order to obtain the Gaussian output diffractive mode in order to enhance the coupling efficiency to the optical fiber. According to the requirement of leakage factor distribution for a Gaussian output profile, the corresponding effective refractive index of the grating groove, duty cycle, and period are designed according to the equivalent medium theory. The peak coupling efficiency of 93.1% at 1550 nm and 3 d B bandwidth of 82 nm are achieved.     

Diffraction from a moving grating

A first-principles tutorial account is given for the diffraction of either light or free, non-relativistic, massive particles from a moving grating. Discussion on the properties of the moving grating including non-reciprocity is followed by considering both Raman-Nath (thin grating) diffraction and Bragg (thick grating) diffraction in either transmission or reflection geometry. Use of four-momentum conservation with dispersion relations yield the angles of diffraction. The increase in the angle of diffraction for grazing incident by using a moving grating relative to using a static grating is calculated. It is shown that this increase is possible only for Raman-Nath geometry.     

Diffraction of a Gaussian Beam by a Periodic Screen

Based on the plane wave analysis and the superposition of the plane waves, the diffraction of a Gaussian beam by a periodic screen with a dielectric plate is analyzed. The reflection power coefficient for different parameters of the beam and the screen is given. When the beam waist size is increased the results reaches that of the plane wave. It has been found that the power reflection coefficient is not sensitive to the beam waist size, however, it is sensitive to the period of the grating and polarization angle.     

Diffraction of metastable helium atoms by a transmission grating

We report on the diffraction of metastable helium atoms (de Broglie wavelength _dB 1Å) passing a free-standing gold grating with a periodicity of 0.5 m. The observed positions and intensities of the different diffraction peaks are in good agreement with a theoretical model for the grating shape. The overall transmission of the grating for the excited state atoms is about 30%, mainly determined by the grating geometry. Our result indicates that microfabricated transmission gratings can be used as efficient and coherent beam splitters for rare gas atoms in long-lived excited states. This fact offers interesting possibilities in view of atom interferometry with metastable noble gas atoms.     

Autocollimation reflection by a ribbon grating with a screen

Institute of Radiophysics and Electronics, Academy of Sciences of the Ukrainian SSR. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 33, No. 3, pp. 348–356, March, 1990.     

光阑对高斯谢尔模型光束偏振特性的影响

根据光束的相干-偏振矩阵理论,应用柯林公式对部分相干光经光阑衍射后的轴向、横向偏振特性从近场区到远场区的演化规律进行了详细的数值计算。经研究表明,由于光阑的衍射效应,使得高斯谢尔模型光束的偏振出现非均匀分布,光束偏振度沿轴向、横向分布出现多峰振荡现象,并且随着光阑截断参数的减小、光束空间相干长度的增大和传输距离的增大,多峰振荡逐渐增强。光束在自由空间沿轴向传输时,在近场区偏振度分布均匀,与源平面相同,随着传输距离的增大和空间相干长度的减小,偏振度沿轴向分布逐渐增大,无振荡现象。