Wide spectrum metal dielectric film grating and optimization method thereof

Abstract

The invention relates to a wide spectrum metal dielectric film grating and an optimization method thereof; the grating comprises a substrate, a metal Ag film, a multi-layer dielectric film, a residual film layer and a surface grating structure; and every layer of dielectric reflective film comprises a SiO2, a HfO2 and a TiO2 dielectric films. The method first defines a grating diffraction efficiency spectral property value evaluation function, selects the refractive index of metal media and a plurality of layers of dielectric film materials as well as the grating parameters which are optimized, and builds a wide spectrum metal dielectric film grating TE wave diffraction efficiency value analyzing model according to a strict coupled-wave theory. Through the optimization of a plurality of parameters, the obtained grating cycle is 1480lines / mm, the groove depth is 290nm, the thickness of the residual film layer is 10nm, the duty cycle is 0.28, and an incident angle is 60 degrees. According to the invention, when TE polarized light with the wavelength being 1053nm enters, the diffraction efficiency of the wide spectrum metal dielectric film grating in a wide spectrum bandwidth being more than 190nm in the -1 grade direction of reflection diffraction is over 97 percent.

Description

technical field [0001] The invention relates to a wide-spectrum dielectric film grating for a femtosecond chirped pulse amplification system, in particular to a wide-grating high-diffraction-efficiency metal dielectric film grating for a femtosecond laser pulse amplification system with a central wavelength of 1053 nanometers and The optimization method belongs to the technical field of diffraction gratings. Background technique [0002] The performance of the chirped pulse amplification technology (Chirped-pulse amplification, CPA) to obtain ultra-short and ultra-intense laser pulses mainly depends on the pulse width compression grating. The diffraction grating as the core component of the CPA system must have the highest possible diffraction efficiency and The anti-laser damage threshold, which uses a wavelength of 1053 nm and TE mode. [0003] Designing and fabricating pulse width compression gratings with high diffraction efficiency, high damage threshold and wide spect...

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Problems solved by technology

[0004] Although gold-plated grating (Metal grating) has a relatively wide operating bandwidth, it has strong absorption characteristics, and it is difficult to obtain high diffraction efficiency and anti-laser damage threshold

[0005] Multi-layer dielectric grating (Multi-layer dielectric grating, MDG) has the advantages of high diffraction efficiency and high anti-laser damage threshold, but due to the interference of multi-layer dielectric films, its working bandwidth is only limited to tens of nanometers. , and its bandwidth is far from meeting the requirements of femtosecond lasers for the wide spectrum of pulse width compression gratings

[0006] At present, some of the existing technologies adopt the method of all-dielectric multilayer film. By optimizing the film layer structure of the multilayer dielectric reflective film and the parameters such as the period, duty cycle, and groove depth of the grating layer, it can be achieved at a wavelength of 1053 nanometers. The bandwidth to obtain more than 97% of the diffraction efficiency is 100nm, which is far from meeting the requirements of femtosecond lasers for wide spectrum and high diffraction efficiency

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