Ultraprecision diamond machining enables physical realization of freeform surfaces of nearly arbitrary complexity through turning and milling processes. Achievable form accuracies make diamond machining a viable alternative to conventional techniques particularly for infrared and longer wavelength applications. This dissertation aims to further the knowledge base for manufacturing of infrared optics. Many infrared materials including germanium and chalcogenide glass (As40Se60, trade name IRG 26) are brittle, but under appropriate conditions, they can be machined in a ductile-dominated manner, resulting in a fracture-free and often optical quality surface. The cutting mechanics, surface condition, and subsurface integrity of these materials were studied to independently isolate effects due to cutting velocity, rake angle, and tool-workpiece interaction time. Experiments were performed under steady-state conditions using orthogonal, oblique, and round-nosed turning geometries, as well as under interrupted cutting conditions using flycutting and milling configurations. To overcome the limitations of conventional computer aided manufacturing packages, an analytical strategy for toolpath generation for slow tool servo machining operations was developed and verified in conjunction with an artifact-based approach for pre-process mapping and compensation of tool- and machine-based process error sources. The research findings were then used to select appropriate machining parameters and generate toolpaths for the manufacturing of several freeform optics including a chalcogenide glass Alvarez lens pair and the primary and tertiary mirrors of a compact imaging spectrometer.