Research On Large-diameter Multi-band High-energy Laser Emission Window

As an important component of a laser emission system window can be used to protect the components within the system and to improve the adaptive capacity to environment. Art-of-the-state laser emission systems use two kinds of windows are respectively crystal windows and pneumatic windows. However, the modern laser emission system apertures become larger and larger such that crystal windows have a limitation in crystal dimensions while pneumatic windows consume lots of energy. Both of these two sorts of windows cannot satisfy the working requirements in large-diameter high-energy laser emission systems. It is rarely reported in domestic in large-diameter multi-band high-energy laser emission systems while in engineering areas the laser emission systems with diameters of more than 500 mm are still owning no windows resulting in less use of laser emission systems in extreme environments. In this context this thesis proposes a combined seal method of pneumatic window with mechanical shutter window and puts forward the design of the associated shutter window. To meet the working requirements we also design the stitching crystal window for the large-diameter multi-band high-energy laser emission system.Structural design of stitching window: we first time propose a mirror stitching method to design the large-diameter laser emission window. In terms of engineering we analyze the efforts of design requirements, machining accuracy, and assembly accuracy on the emitted laser. According to the Geometrical Optics and Laser Optics we establish the relevant assessment model based on which the structure of stitching window is optimized.Strength calculation of stitching window: we analyze the efforts of laser emitting and different settings on the stitching window. By combining the Fracture Mechanics with Mechanics of Materials, an assessment model is built up. The window is also optimized directly on the basis of strength, stiffness and dynamical properties. We also design the flexible hinges for the window’s radial supporting mechanism and derive out the mechanical model of flexible hinge bending stiffness.Beam quality analysis: We apply the finite element method to solve the temperature field and strain field for the window. Using the thermal-mechanical coupling method calculates the surface distortion of the window and using homogeneous transformation separates the stiff displacements. Subsequently, by adopting Zernike polynomials we fit the surface of the window and calculate the effort of stitching window on emitted laser by analyzing the variations of laser far-field intensity. Via the observations the efforts of stitching window on diffraction limit rate, encircling ratio and Strell ratio are less than 5% while on laser divergence angle are less than 0.1’’. The crystal mass is reduced by 60% compared with that of the single-mirror window.The design of shutter window: We first time propose a combined seal method of pneumatic window with mechanical shutter window in terms of laser emission system characteristics. The structure is typically designed by the requirements. The dimensions of window can be optimized naturally by load conditions of transmission links and the wind-resisting model of relevance.Theoretical work of shutter window: We establish the wind load model for bending stiffness-free dust cover by using the rope mechanics and similarly establish the wind load model for bending stiffness dust cover by using the shell large deformation theory and film mechanics. These two mathematical models have been respectively shown that they can satisfy different laser emission window. With the use of the mechanical dynamics and finite element method we calculate the dynamical properties.Experiments: Experiments: Through testing the wind-resisting abilities, dynamical properties and adaptation in different environment temperatures of shutter window, we validate the theoretical analysis. The engineering practice also indicates that the calculation error of wind load model is less 15% and the mechanical window is capable of resisting the invasion of wind and dust that can be up to 8 magnitude. The window can be used normally in environmental temperature ranging from-40C-60 C. Moreover, the combined seal method of pneumatic window with mechanical window can significantly and effectively improve the adaptive ability of facilities.