Optical Cryocooling for Precision Metrology

Optical cryocoolers, which are compact and produce no vibrations, are ideal for many electronics and sensor applications. In particular, some advanced metrology systems require cooling to around 124 K, the temperature at which the coefficient of thermal expansion for crystalline silicon goes through a null point. Currently, the dominant solid-state cooling technology is thermoelectric cooling, which uses the electrical Peltier effect. Despite decades of effort, the lowest achievable temperature for multi-stage thermoelectric coolers (TECs) is around 170 K. ThermoDynamic Films, LLC, together with it collaborators at the University of New Mexico (UNM) have been pursuing an alternative, approach to solid-state cooling technology, optical refrigeration. To date, the TDF/UNM collaboration has cooled an optical-refrigerator from room temperature to 91 K with about 1% efficiency. This is the world record cooling for optical refrigeration (or any solid-state cooling technology). Under the STTR Phase II contract the TDF/UNM team will build an optical cryocooler to be used to cool a crystalline silicon laser reference cavity. The TDF/UNM team will build the cryocooler and adapt it to cool silicon mono-crystalline optical reference cavities.