Research On High-Power Laser-Induced Damage And Protective Technology Of Opoelectronics Systems

Along with laser technology being widely applied in martial field, modern warfare is threatened by laser. Except for plentifully equipped laser telemeter, laser radar, and laser irradiator, multifarious tactical laser weapons used to attack optoelectronic sensor is plentifully applied in many martial great powers of the world. People pay more and more attention on laser damage to eyes, optical system and optoelectronic system. Laser damage and defending technology of optoelectronic system is the focus of optoelectronic counterwork, which has become a part of the field.With the help of item funds including the experimentation technology of the total accouterments department and the martial research and Ordnance Engineering College's fund, a series of research work have been finished, which is about the high power laser damage to optical material, optical elements, optoelectronic sensors and optoelectronic system. On the other hand, the high intensity laser defending technology is also researched in the paper. The thesis is mainly about high intensity laser damage with optoelectronic instruments and defending technology. The main contents and key creation points of the thesis are as following:ⅠCoupled thermal-mechanical model is systemically establishedOn the base of heat conduction equation, coupled thermal-mechanical model is systemically established for the first time. One-dimensional dynamic temperature field, two-dimensional dynamic temperature field and three-dimensional dynamic temperature field are studied and analyzed. The materials'temperature rise equations and the thermal stress equation under different conditions are deducted. Furthermore, the meilting time, maximal melting depth, gasification, ablation, the spread of shock wave and lamination crack theory are analyzed and discussed.ⅡDamage effect on optical material irradiated by laser is researchedThe mathematics model about damage effect on optical material with out-band spectra CW laser is established. Taking CO2 laser irradiating K9 glass for example, under the condition of basic mode gaussian laser irradiating optical material, the materials'temperature rise distribution and thermal stress transient distribution is calculated and simulated for the first time. The weakest position is found out by curve-fitting, and damage threshold of material is calculated. It indicates that the damnification morphology of K9 glass is cleavage damage, the reason of which is that the hoop tensile stress overtops materials'tensile strength. And the materials'damage threshold is inversely proportional to irradiation time.The mathematical model of in-band CW laser irradiating optical material is established. The analytic solution of three-dimensional heat conduction equation is accurately solved for the firsttime, and three-dimensional temperature field and thermal stress distribution is deducted. Taking CO L irradiating molten quartz for example, optical material damage by in-band spectra laser is researched. It indicates that when the irradiation time reaches 8 seconds, the temperature of incidence surface directly irradiated by laser and exit surface are both higher than material fusion temperature, which makes the material melt and punching is induced. Meanwhile the maximal numerical values of radial stress, hoop stress and the stress in laser transmission direction are not overrun materials'tensile strength or compressive strength, so splitting crack or cleavage is impossible to occur. The damage of molten quartz by CO L is mainly molten ablation and punching.Damage mechanism of the semiconductor irradiated by CW laser is researched. Two-dimensional physical model of the semiconductor disk irradiated by laser is established for the first time. Heat conduction equation and thermal stress equation are solved, and material temperature distribution and transient distribution of thermal stress are deducted. It indicates that the damage threshold of InSb is inversely proportional to irradiation time, facula radius and nonlinear parameter. Melt damage threshold is lower than thermal stress threshold under the same conditions, so damnification morphology of InSb is melt damage. When nonlinear effect leaves out of account, comparative error is bigger resulting from the analysis of nonlinear parameter. Therefore, when damage threshold and irradiation effect are calculated, nonlinear effect of semiconductor should be considered.ⅢDamage effect of optical elements by laser is researchedThermal shock effect of diamond-like carbon thin film by 1.06μm pulse laser is researched for the first time. The theoretic model is established, and the heat conduction equation and the thermal stress equation are solved. And the thin film's temperature distribution and transient distribution of thermal stress are deducted. Theoretic analysis indicates that the thermal stress damage plays a dominant part in thermal shock effect of diamond-like carbon thin film by high power laser pulse. Under the condition that irradiation energy density reaches 100mJ·cm-2, compressive stress of the hoop area evidently overruns its fracture intensity, the radius of which is 40μm from facula centre. It will result in film desquamation and exfoliation. Experiment results conform well with theoretical calculation, so it indicates that the established thermal shock effect model is correct.The theoretic analysis and experiment research of laser damage to quadrantal detector is done for the first time. It indicates that there are two key reasons for laser damage and interference of optoelectronic detector. Firstly, semiconductor melting and crystallization is reduced by laser irradiation, so electric leakage channels is formed, which is equivalent with ashunt-wound resistance. Secondly, when semiconductor is damaged by laser, the area of its photoconductive surface will diminish. The experiment results indicate that if one or two quadrants are irradiated by laser, the meterage error of faula centroid is reduced.The dynamic mathematic model of HgCdTe PC detector irradiated by laser is established for the first time, and the numerical solution of dynamic temperature field is obtained. The variation of dynamic temperature field with time is analyzed, and the effect on parameter of detector irradiated by laser is discussed. Theoretic analysis shows that the damage to CdTe PC detector irradiated by laser is mainly thermal stress damage, and the bandgap width, spectrum characteristic, electronic characteristic of the material are changed. Furthermore, detector will lose its capability, and its detection quality will decline, and the elements ablation elements is even possible to occur.ⅣOptimization design of optical limiting equipmentBased on Z-scan technique, some factors'effect on optical limiting equipment is systemically researched, including thickness and position of nonlinear medium, position and size of the aperture, nonlinear refraction and nonlinear absorbability.ⅤOptical limiting research about solubilized carbon nanotubeOptical limiting effect of carbon nanotube to 1.06μm and 0.53μm laser is systemically researched. Experiment results show that solubilized carbon nanotube has good optical limiting effect to both 1.06μm and 0.53μm laser.