The Study Of The Characteristics Of Thermal Deformation Of K9Glass Mirror Irradiated By High Power Laser

In this paper, the characteristic of thermal deformation of K9glass mirror whichis widely applied in laser system is researched by theoretical analysis and numericalcalculation with considering the temperature rise of the air around the mirror andthermal radiation of the mirror. The relation of the temperature distribution of the K9glass mirror and the surrounding air and thermal deformation of the mirror changingwith time is obtained.A detail identities analysis of the mirror’s temperature and thermal deformationcaused by laser is done. And the simulation analysis of temperature field shows that:at the initial stage of laser irradiation, the temperature of the mirror rises fast, withthe increase of time, the temperature rises gradually slow down; at the same time,due to convection, the temperature of the surrounding air will increase with timeconstantly. At a distance from the mirror of10mm, the temperature is close to theambient temperature. In the whole process of temperature rise of the mirror, thetemperature of the area irradiated by the laser is higher than other area. From theanalysis of the deformation of the mirror, we can see that the deformation is relatedto the power absorbed, spot size and the time irradiated. Similarly, in the initial stageof laser irradiation, the deformation increases rapidly, the deformation rises gradually slow down with the increase of time. But the time of mirror reaching to thestability state of thermal deformation is shorter than that of thermal balance.Finally, the variation of temperature distribution and deformation of the mirrorwith the time is measured by experiment, and the factor which affect thermaldeformation of the mirror is quantitatively analysised. The error in incident angle ofthe beam and the size of the spot is the main factors which affect the accuracy of themeasurement results. The result shows that, the deformation of the mirror irradiatedby laser can be well predicted by this model. A theoretical basis for the theoreticalsimulation and experimental verification of thermal deformation is provided by theanalysis of this model.