Mode Number Determination of Optical Cavities for Next Generations of Gravity Missions

Abstract

Next generations of gravity missions require new technologies for an absolute frequency determination of cavity stabilized lasers. One proposed technology uses a readout of the free spectral range of the cavity to process it along with the mode number to the absolute frequency. This technology would require only a small amount of hardware but presupposes a stable mode number. In a laboratory experiment, this technology is analyzed for an existing high finesse cavity setup and the mode number is determined with an accuracy up to three digits. These measurements carry out a non-negligible fractional offset of alpha = 0.786 +/- 0.003, where a part of gamma = 0.69 is probably caused by the mirror coatings. For further investigation of how external influences can affect this offset, the plans for a new compact cavity setup which is designed precisely for these studies are presented here.