Fiber optics for low-temperature spectroscopy: Applications to photoluminescence from (Cd, Mn)Te

A simple fiber-optic system for optical spectroscopy is demonstrated. It allows experiments to be performed at low temperatures without an optical Dewar. This low-cost apparatus is useful for a variety of optical experiments such as photoluminescence, reflectivity, and absorption, in addition to polarization measurements such as Faraday rotation. The main feature is an all-glass system made from commercially available fiber-optic cables and glass rods, and contains no focusing optics. Small diameter (<1 cm) sample holders are constructed that fit conveniently into storage Dewars or small diameter Dewars for high-field magnets. Large diameter (few mm) flexible fiber bundles permit efficient coupling to inexpensive light emitting diode (LED) sources and to fiber-optic illuminators. Fiber-optic measurements of photoluminescence in Cd1-xMnxTe, x=0.1, at high magnetic fields is illustrated.