This is an external transmission and reflectance sample chamber that can be mated to the output port of both the SPS-200 and SPS-300 FTIRs. This sample chamber allows small samples such as liquid in a cuvette or thin films to be studied under both transmission and reflection modes. The sample chamber shares the vacuum environment with the FTIR (an optional window or vacuum gate is available to totally isolated from the SPS-200/SPS-300 from the output port of the SPS FTIR) this upgrade enabling the user to change samples without upsetting the SPS-200/SPS-300 vacuum housing. The sample chamber utilizes reflective aspheric optics with gold coating for far infrared and terahertz operation. A manual flipping mirror inside the sample chamber allows the user to select between transmission and reflective modes. In transmission mode, an internal mirror focuses the sample onto the detector, whereas in reflection mode, a secondary internal mirror focuses onto the sample. All optics are pre-aligned and focused for a specific detector positions at the sample chamber output port. An optional peltier cooler is also available to maintain the temperature of the sample holder. For this option, a water cooling loop inside the sample chamber is required. This water cooling loop can be connected to the same water re-circulating system as the main SPS-200/SPS-300 body or though a separate independent cooler such as the Sciencetech Model 160-REC water recirculator.