Optical tuning of a silicon Fabry-Perot interferometer by a pulsed 1.06 µm laser

Refractive index changes have been produced in a silicon crystal by excitation of electron-hole pairs with an Nd-YAG laser. The index changes were detected by observing the temporal shape of an initially smooth pulse after transmission through a silicon Fabry-Perot etalon. The index varies during the pulse with the absorbed energy and tunes the Si cavity over several resonances. The transmitted pulse shapes are modulated with a corresponding number of peaks. The frequency dependence of the index change was investigated with an Nd-YAG laser at 1.06 μm and with an F-center laser at 1.32 μm, and found to be consistent with the Drude model.