Infrared Spectrum Study Of Silicon Dioxide And Other Materials

Silica glass is the most important material for glass fibers, whereas the crystallineα-quartz is a widely used piezoelectric and optical material. The structure and properties of silicon dioxide (both amorphous and crystalline states) play an important role in device applications. Amorphous and crystalline SiO2 is transparent in visible frequency range. Applications of the glass fiber are mainly in the infrared region. On the other hand,α-quartz possesses piezoelectricity, which has been widely applied at low frequencies. To extend the application of piezoelectricity to the infrared frequencies, it is necessary to study the propagation of the infrared waves throughα-quartz. In this work we use the Fourier Transform Infrared Spectroscopy to measure the reflection spectra of the silica glass and the transmission spectra ofα-quartz. The main results are summarized as follows:1. Splitting of the transverse (TO) and longitudinal (LO) modes was observed on reflection at the interface of silica glass. TO-LO splitting was found to depend on the angle of incidence and the polarization state of the incident light. In terms of the Kramers-Kronig transformation, the reflection peak near 1120 cm-1 is assigned to be the TO mode, whereas the peak in the vicinity of 1270 cm-1 is the LO mode. The TO mode and the LO mode are concerned with the incident angle and the polarization state of incident light. The conclusion is follows:(a) The frequency,ωTO of the main TO mode remains constant at different angles of incidence and under different polarization states of the incident light.(b) In the case of randomly polarized incident light,ωLO increases with increasing angle of incidence. The reflection of the LO mode, RLO, and its ratio, RLO/RTO, with the reflection RTO of the LO mode increase with increasing angle of incidence.(c) In the case of the polarized incident light,ωLO is a function of angle of incidence and polarization state of the incident. At a critical angle of incidence near 45°,ωLO is almost independent of the polarization direction of the plane-polarized incident light. Beyond this critical angle the dependence ofωLO on the azimuth angle...