Research Of The Influence Of Short Pulse Laser On Refractive Index Of Optical Glass

Due to the short pulse laser machining has relatively narrow pulse width, high average power, high processing efficiency, short wavelength, it can be focused into a smaller spot to achieve precision machining. The short pulse laser machining has a very good prospect in optical microstructure manufacturing, such as optical storage, grating production, optical waveguide production, optical coupler production and many other optical microstructure production. Almost all of these optical microstructure manufacturing developed based on transparent material modified induced by short pulse laser machining. Transparent material modification mainly includes light damage, glass crystallization, color center formation, photoinduced refractive index changes.In this paper.we study on darkening and permanent refractive index changes in quartz glass and K9 glass induced by short pulse laser under different radiation conditions.The main work carried out as follows:1)The basic characteristics of the optical glass, including refractive index and dispersion are discussed in detail. It introduces the main optical property about quartz glass and K9 glass.2)It studies on the dominant mechanism of the transparent material index change under the short pulse laser irradiation, It establishes a theory model relation between refractive index (n)and laser light intensity(I), and respectively carries out numerical simulation for (I)and refractive index (n). Finally, we draw the conclusion that when the short pulse laser irradiation spreads in the optical materials, the refractive index (n) affected by light intensity decays through exponential damping as the increase of the depth of penetration. On the same incident plane, refractive index (n) is conform to gaussian distribution.3)It analysis the relationship between refractive index and the wavelength. Based on the dispersion theory, it obtains the main factor that affect dispersion coefficient by logical derivation. It draws the conclusion that the dispersion coefficient will change under the laser irradiation, which will lead the result that the relationship between refractive index and the wavelength is not strictly conform to the normal dispersion curve again.4)It designs and carries out the nanosecond pulse laser irradiate quartz glass experiment work. It researches on darkening areas of the quartz glass irradiated by laser according to microscopic examination and gray value analysis. Based on the relevance between darkening effects and refractive index, we obtain the result:the refractive index in the irradiated darkening areas conforms to gaussian distribution. The spectrum transmittance is detected by using a U-3501 spectrophotometer, according to the formula relationship between spectrum transmittance and refractive index, finally it gets refractive index change as the wavelength change.5)It designs the femtosecond pulse laser irradiate K9 glass experiment. K9 glass is irradiated by femtosecond pulse laser. It analyses color center production which was induced by femtosecond pulse laser irradiation. According to analysis the gray value of darkening areas, unite the theory relationship between color center concentration and the refractive index, it obtains a result that the refractive index in the irradiated area center of K9 glass distributes as gaussian distribution.In this paper,according to theoretical modeling、numerical simulation and experiments,we research on the refractive index distribution in irradiated area of the quartz glass and K9 glass,study on the changes in dispersion coefficient irradiated area of the quartz glass and the refractive index as the wavelength change Finally it proves that the experiment results conforms to the theory...