Research On Fabrication And Applications Of Special Holographic Gratings

Holographic grating is a widely used chromatic dispersion device in optical spectrum instrument, which determinates the resolution and accuracy of spectrum instrument. Currently, in domestic market of optical spectrum instruments, most of high-class products are imported from oversea or fabricated in China but developed by foreign corporations. Therefore, developing and fabricating high-performance key device of optical spectrum instruments with ourselves intellectual properties has great economic value. Relied on the National Science Instrument Important Project(2011YQ15004), depended on the basis of Fourier syntheses expourse, this thesis researched the fabrication process of two kinds of special holographic gratings—holographic echelle grating and nanowire-grid grating, and also numerically simulated the polarization character of dual-layer nanowire-grid gratings and its potential applications.Echelle grating—a special blazed grating, which is a key dispersion device in high resolution optical spectrum instruments, only could be fabricated by several foreign corporations with the mechanical ruling on the surface of metal film so far. In this dissertation, a fabrication method for blazed holographic grating—decompose the unsinusoidal exposure intensity into a serial of sinusoidal exposure intensity and realize by superpose a serial of two-beam interference patterns—is proposed and verified by the illustrational experiment of echelle grating, which is a novel thinking about the fabrication of holographic blazed grating with any shape of grooves. Comparing with traditional fabrication method--mechanical ruling process, this holographic method is faster, lower cost, no ghost line, less scattered light and looser requirement in fabrication environment, especially easy to adjust the parameters for different type of holographic blazed grating with arbitrary groove shape theoretically.Metal nanowire-grid grating is a novel kind of optical polarizer based on the nano-structure with advantages such as compact size and high performance comparing with the traditional birefringence crystal polarizer. Therefore, it has been widely applied in many fields, such as optical fiber communication, LCD display and polarized imaging system. In this thesis, the influences to the polarization characters of all structure parameters of single and double-layer nanowire-grid grating were calculated and analyzed with FDTD algorithm, which is the theoretical basis of designing nanowire-grid polarizer. Considering the holography and ion etch condition in our laboratory, we designed and fabricated a nanowire-grid polarizer in infrared region, which could be used in optical fiber communication region based on the performance test by spectrophotometer Lambda 1050.Currently, there is no nanowire-grid polarizer for ultraviolet region in the market because of the tremendous absorption of metal in ultraviolet waveband. In this dissertation, an ultraviolet nanowire-grid polarizer was designed with double-layer nanowire-grid structure, which could enhance the transmission of TM polarization by constructive interference and reduce the transmission of TE polarization by destructive interference and then get an extreme high extinction ratio for particular wavelength. It could be applied in ultraviolet region by adjusting the distance between these the layers of nanowire-grid.Furthermore, the double-layer nanowire-grid has many additional physical characters beside the polarization property, such as similar Fabry-Perot cavity resonance effect when the distance is great big than the wavelength and coupling effect of surface plasmon resonance with evanescent wave in the grating structure when the distance is close to wavelength.Anti- reflective coating has been a hot research topic and has many applications such as optical fiber communication system, solar cell, photoelectric detector and so on. For laser optical system, optical feedback is fatal to laser power stability, which could make the laser unstable and even chaotic. Therefore, extreme low reflective structure is great important to laser and laser system. In this thesis, double layers grating structure is proposed and simulated for its extreme low reflection about 10-4 for reflective intensity.Using these characters of double-layer nanowire-grid structure, we proposed a modified type of F-P cavity refractive index sensor, which has two signals from TM polarization and TE polarization respectively used to judge the variation trend of refractive index, increase or decrease. This function will be useful to monitor the concentration change of matter in reciprocal chemical reaction.