Stable Frequency References in the Optical Domain for Aerospace Applications - Part I - Preliminary Considerations on Cavity Design and Thermal Stabilization

Long term frequency stability of lasers is a key parameter in many research areas ranging from dimensional metrology to fundamental physics. Many solutions have been proposed by the scientific community and lasers whose frequency is referenced to molecular transitions are commonly used when long term stability and wavelength accuracy are needed. This report describes the design of an high-finesse optical cavity to be used as a reference for laser frequency stabilization. High finesse cavities have been widely studied (and used) in many application: the novelty of our work is the use of the cavity on board of a spacecraft. Given the particular application, the cavity must be compliant with the huge acceleration experienced during the launch phase (up to 30g at 1 kHz). A pecularity of our realization is that, contrary to the normal practice, the cavity is used as a long-term reference (over a one-day time scale typically). Since the resonant frequency depends on the cavity length, it is necessary to control the environment in order to avoid mechanical and thermal disturbances which can possibly lead to a variation of the cavity length. Our goal is the development of a frequency stabilization system with a relative frequency stability (Allan variance) of 10−12 over 1 second integration time which will be suitable for aerospace applications.