Thermal effects of the narrow band filter irradiated by laser at oblique incidence

Abstract

Based on the Maxwell equations and the heat conduction theory, the thermal effects of the 10.6μm narrow band filter are analysed under the irradiation of the pulsed laser at oblique incidence. The temperature field and the drift effect of the narrow band filter are compared and discussed at different incident angles and polarizations. Results show that,with the increase of incident angle,the amplitude and position coordinates of the peak temperature rise have changed greatly.The peak value of the temperature rise decreased gradually with the increasing incident angles. The position coordinates of the peak temperature rise gradually approaches to the interface of the filter and air with the increasing incident angle.The difference of thermal effects between the P and S polarized laser irradiation becomes more and more obvious. The passband drift characteristics under different laser incident angles are compared. When the incident angle is small, the central wavelength deviation of the filter reached over 200nm, and the transmittance decreased to less than 6%.With the increase of the incident angle, the melting damage threshold of the filter is getting bigger and bigger. When the incident angle is greater than 30°, the difference of the melting damage threshold between P and S polarized light becomes larger and larger.The incident angle and polarization state of the laser should be considered in order to realize the laser damage to the narrow band filter with a small power.