In this article, we describe our high-pressure infrared (IR) spectroscopy techniques for studying the electronic structures of materials at high pressures. High pressure of up to 20 GPa is applied to a sample using a diamond anvil cell (DAC). To accurately perform IR spectroscopy in the limited sample space of a DAC, synchrotron radiation is used as a bright IR source. Our techniques allow reflectance studies of a single crystal sample and determination of the optical functions of the sample such as dielectric function and optical conductivity. To illustrate the capability and usefulness of our techniques, some actual results of high-pressure IR studies on rare-earth compounds are described
