(Left) Koji Usami in Quantop laboratories at the Niels Bohr Institute. (via Ola J. Joensen) (Right) Vibration velocity at certain temperatures


The world of quantum mechanics is full of paradoxes and anomalies that really put to question our concept of reality. In an experiment done at the Niels Bohr Institute, quantum mechanics is again rearing its paradoxical head in a new process that cools semiconductor material by shining a laser on it, inadvertently cooling it by heating it.


At the Niels Bohr Institute, researchers were aware of the cooling capabilities of lasers as they have use them to cool gasses down to fractions of a degree above absolute zero. But broadening the linking between the quantum mechanical world with the macroscopic world proved to be a material science problem; researcher and assistant professor Koji Usami coincidentally found the perfect material that links the two. Usami believed that the electronic and optical properties of Gallium Arsenide would be perfect to further the science of optomechanics, the interaction between optical radiation and mechanical motion.


Dr. Usami was able to cool a minute semiconducting membrane of just 160 nanometers thickness and 1 squared millimeter surface area to a blistering cold temperature of negative 269 degrees Celsius (4 degrees above absolute zero).  A GaAs membrane is positioned across from a mirror. A laser is beamed at the membrane, some of the laser is absorbed and some is reflected to the mirror. The incoming and reflected radiation creates vibrations in the membrane, which can vary with the distance between the membrane and mirror. At certain distances, resonant modes can result. The mode lowers the thermal energy of the gallium arsenide. Thus, the cooling effect results from the movement of the semiconductor membrane, the properties of the semiconductor and the optical resonance.


This efficient cooling process could prove indispensable for systems like quantum computers and the development for ultra sensitive electronic and mechanical sensors, replacing expensive cryogenic cooling.