Contribution of Different Noise Sources to the Relative Instability of Laser Systems Stabilized by External Silicon Cavities

Here we consider creation of laser systems stabilized by external macroscopic monolithic Fabry – Perot cavities made of single-crystalline silicon operating at cryogenic temperatures. Fundamental thermal noise floor for fractional frequency instability was evaluated with its dependency on cavity’s spacer, mirror’s substrate and coatings material. Silicon cavities with dielectric SiO2 /Ta2 O5 and crystalline GaAs/InGaAs mirror coatings were created, its finesse at room temperatures was investigated. Two ultra-high vacuum optical cryostats were developed. Two ultra-stable laser systems based on cavities with dielectric mirrors were assembled. Comparison scheme via beat signal frequency counting was implemented for the characterization purpose. Different noise sources presenting at assembled systems are considered. Its impact to relative frequency instability of our laser systems is being explored.