- Choose a dual-frequency laser that produces different colored light—in this case, it's infrared light and a green light. The colors chosen by the team depended on the availability of specific lasers in the lab. According to Weng, however, optimal color choices can improve the thermometer sensitivity even more.
- Beam the laser at your resonator, which is a crystalline disk. The crystalline materials (calcium fluoride and magnesium fluoride) were chosen for their transparent nature, which means light suffers the least loss when traveling inside these materials. The less light loss, the more accurate the measurements.
- The green and red light travels around the disk thousands of times—similar to the phenomenon known as a "whispering gallery," where sound waves cling to circular walls and allow whispered communication to be heard anywhere along the internal circumference. In this case, light waves are circulating the edge of the disk in the same way.
- Measure the difference in the frequencies (equivalent to the travel speed) of the two colors and use the known relationship between temperature fluctuation and light frequency to calculate the temperature. Luiten notes that the experiment reveals "the minute fluctuations that occur in even a perfectly temperature-stabilized environment."