Study On A Novel Single - Order Diffraction Grating And Its Diffraction Efficiency

Laser Drive Inertial Confinement Fusion is one of the most promising means to solve the Energy Crisis of Human. In the process of Laser Drive Inertial Confinement Fusion, plasma of high temperature and high density will be generated when short pulse laser interaction with matter. And x-rays radiation related with energy level would be produced by the plasma of high temperature and high density. We can get the density, temperature and other information of plasma by the spectrum of x-rays.Transmission grating spectrometer is widely used in the measurement of x-rays spectrum because of its ease of alignment. Transmission grating is the core element of the transmission grating spectrometer. Classical black-white transmission gratings consist of a series of parallel slits on an opaque screen and have a square wave transmission function, which lead to the inevitable generation of higher-order diffraction. Due to the overlapping of higher-order diffraction, x-rays spectra measured with classical black-white transmission grating will be contaminated. The accuracy of spectral data is decreased since a complex unfolding process is needed to get the real spectra from the data of x-rays spectra obtained with classical black-white transmission grating. In the optical region, ideal sinusoidal transmission grating can be used to suppress the higher order diffraction. But due to related phase problems of x-ray in materials, sinusoidal transmission grating cannot be used in x-ray region.Recently, a novel concept of binary sinusoidal transmission grating had been proposed by Cao et al to solve the problem of the high-order diffraction of diffraction grating. This article reports a new single-order diffraction grating based on this proposal, which can suppress high-order diffraction efficiently and may be used in the measurement of x-rays spectra.In this paper, the development of diffraction theory is reviewed. The principle of Huygens-Fresnel, the theory of Kirchhoff, the formula of Fresnel, the formula of Fraunhofer, the theory of Rayleigh-Sommerfeld and other common theory are introduced in detail.Some kinds of novel single-order diffraction gratings are reviewed, including quantum-dot-array diffraction grating (QDADG), qua si-sinusoidal single-order diffraction transmission grating (QSTG), zigzag transmission grating, spectroscopic photon sieve, Quasi-random Radius Pinhole Array Spectroscopic Photon Sieves (QRSPS). These gratings can effectively restrain the high-order diffractions. It demands an extremely critical nanofabrication technique to make those gratings with high line density since to modulate the transmittance function of the diffraction gratings a large number of very small or complicated shaped structures were introduced.The new single-order diffraction grating proposed in this paper attempt to adjust the transmittance function of the diffraction gratings by modulating the position of the straight slits. The new grating consists of simple slits which is similar to classical black-white transmission grating, thus is easier to be fabricated. It also can stand free. Its structure is reported in detail. Theoretical analysis proves that this new grating can suppress high order diffraction efficiently, which is also stood by the simulation on computer. A sample had been fabricated and an experimental demonstration in visible light region had been done. It shows good agreement with the theoretical prediction.