Icf Drive Subwavelength Grating Harmonic Separation Techniques

Physics experiments need 3ωbeam entering the target cavity only to generate uniform irradiation field to increase the energy utilization ratio at the process of the coupling of the beam and the target in Inertial Confinement Fusion(ICF). At present, coupled harmonic waves transfer technique can transfer laser at 1ωto 3ω, so it demands that 1ωand 2ωlaser had been removed before the laser entering the target cavity. It is one of the difficult that how to realize the separation of three kinds harmonic waves absolutely, avoid the influences of the remainder laser at 1ωand 2ωon physics experiments in high power solid laser.The sub-wavelength grating unusually presents a kind of unique diffraction phenomenon under the specific grating parameter condition and incidence condition because of guided-mode resonances occurring, shown as narrowband, high diffraction efficiency, extreme spectrum sensitiveness and angle sensitiveness. Therefore, a new harmonic waves separation technological schemes is proposed which based on sub-wavelength grating technology. This dissertation mainly studies the grating diffractive character on harmonic waves separation, analyzes the grating tolerance, and guides the improvement of the grating processing technique.The main research topics of the dissertation included:1. Sub-wavelength grating design methods were studied on the basis of vector diffraction theory firstly. Then, the merit function was defined which is used to estimate the performance of harmonic waves separation. And, grating parameters which affecting the merit function were analyzed in details. At last, the grating design methods for harmonic waves separation are proposed.2. The influences of grating period, duty ratio, grating trough form and grating trough depth vary on 3ωenergy utilization ratio, color separation metric and color separation angle are Analyzed. The tolerance of sub-wavelength grating parameters, which can meet the demands of harmonic waves separation, is provided.3. The sample gratings are designed. The experiments results proved that the best angle of incidence and each of grating diffraction are same as the numerical designed results. The diffraction efficiencies of T-1 diffraction order are measured under the best incidence angle, and the paper analyzed why diffraction efficiencies is lower, and point out it must improve the grating processing technique.