The Theoretic Model And Measurement Of The Dielectric Function For Germanium Under Multi-physical Fields

Semiconductor germanium?Ge?is a commonly infrared optical material and excellent sensitive material.In the semiconductor material,the thermal characteristics are very prominent.The optical communication window of 1550 nm is right near the germanium absorption edge.However,the research of absorption region of the optical properties of semiconductor materials is still lacking.An abnormal dispersion has been observed in the refractive index spectra of the polycrystalline Ge near the absorption edge.The refractive index spectrum of the amorphous Ge is normal dispersion.A negative value of pressure-dependence refractive index is observed near the absorption edge,it's different from previous report that shows a positive value of pressure-dependent refractive index.To better understand this phenomenon,we use the critical points model including the pressure effect to successfully fit the experimental data.We obtain the abnormal dispersion range of 1505¹580 nm and the range of negative value of pressure-dependent refractive index of 1500¹580 nm from the critical points model.Our work uses coated germanium film structure of optical fiber sensing probe measures the reflectivity of multi-physical fields of germanium film near the absorption edge?1530¹530 nm?,and then calculate the refractive index.Measurement experiment device is simple,temperature field and stress field environment equipment for special custom,10^-3,the precision of the measurement system satisfies the requirement of experiment.In the research work,the germanium film was coated on the end face of the optical fiber by electron beam evaporation coating machine.The polycrystalline germanium film with high crystallinity could be prepared by heating the substrate at the time of coating and annealing after coating.The anomalous dispersion of germanium near the absorption edge is observed.The results obtain the refractive index of the Ge film and its pressure dependence near the C-band of the optical fiber communication,and allow for optimized design of the Ge-based optical systems near the C-band of the optical fiber communication.