Optical cavity for Rubidium molecule experiments

We have constructed a medium finesse optical cavity for laser stabilization at 680 nm, which will be used for experiments involving rubidium molecules. The cavity is based on an ultra-low expansion glass spacer (ULE) placed inside a vacuum chamber, which is maintained at 10^-7 Torr by a 2 l/s ionic pump. The spacer temperature is stabilized with a precision of 0.01 K by in vacuum TEC elements. Variable sidebands are created by using a computer-controlled radiofrequency synthesizer and an electro-optical modulator (EOM), which allow us to lock the laser to molecular transitions of interest by using the PDH technique. By performing iodine laser spectroscopy, we can determine the temperature for the minimum of the coefficient of temperature expansion. With this design, we expect to achieve a frequency drive of only 1 MHz per day, which will guarantee an improvement in the quality of our measurement at a relatively low cost.