Fabrication of Internal Diffraction Gratings in Transparent Materials Using Femtosecond Laser
用飞秒激光在透明介质体内形成衍射光栅

The fabrication of an internal transmission diffraction grating with laser induced refractive index modification was demonstrated in ZK6 and K9 glasses respectively, using femtosecond (200 fs) Ti: sapphire laser with a energy that is near the energy threshold focused by 40× microscope objective with 0.65-NA. The diffraction efficiency of the grating was measured with a CW He-Ne laser at 633 nm. The diffraction efficiency of the phase gratings was calculated with curve fitting. The width of the groove calculated with curve fitting accord with that was measured, it is confirmed the premise of the phase shift of each groove approximated by a supergaussian indirectly. It is observed that a groove is widened by multiple-shot cumulative effect. A way increasing the diffraction efficiency is presented.