2011-034 – Semiconductor-Based Optical Refrigerator

Background Optical refrigerators are solid-state devices that produce cooling by the interaction of substantially monochoromatic light with selected materials. Earlier examples of this technology employed ytterbium-doped and thulium-doped glass, crystals and laser-dye. Nevertheless, their application was limited by the efficiency and operating temperature of these devices. Semiconductor-based optical refrigerators rely on the excitation of sub-thermal electron hole pairs. To accomplish this, a laser is tuned to a wavelength just below the edge of the bandgap of the semiconductor, exciting these electron hole pairs. The excited free carrier becomes thermally equilibrated by absorbing phonons, consequently cools the semiconductor. The excited free carriers recombine, and emit photons of higher energy than the photons received from the laser, therefore removing the thermal energy absorbed. However, total internal reflection occurs inside the semiconductor materials due to their high indices of refraction and therefore prevents the re-emitted light from escaping quickly. This difficulty is a significant setback for this technology. Technology Description This novel invention is a semiconductor based optical refrigerator cooled by optical radiation from a diode laser. It allows efficient optical refrigerators to be made using semiconductor materials with a novel arrangement of materials that facilitates emission of the fluorescence from the semiconductor material in an efficient manner. It also efficiently utilizes the input laser energy. Andrew Roerick aroerick@innovations.unm.edu 505-277-0608