An Inexpensive Field-Widened Monolithic Michelson Interferometer for Precision Radial Velocity Measurements

摘要

We have constructed a thermally compensated field-widened monolithicMichelson interferometer that can be used with a medium-resolution spectrographto measure precise Doppler radial velocities of stars. Our prototype monolithicfixed-delay interferometer is constructed with off-the-shelf components andassembled using a hydrolysis bonding technique. We installed and tested thisinterferometer in the Exoplanet Tracker (ET) instrument at the Kitt Peak 2.1mtelescope, an instrument built to demonstrate the principles of dispersed fixeddelay interferometry. An iodine cell allows the interferometer drift to beaccurately calibrated, relaxing the stability requirements on theinterferometer itself. When using our monolithic interferometer, the ETinstrument has no moving parts (except the iodine cell), greatly simplifyingits operation. We demonstrate differential radial velocity precision of a few ms$^{-1}$ on well known radial velocity standards and planet bearing stars whenusing this interferometer. Such monolithic interferometers will make itpossible to build relatively inexpensive instruments that are easy to operateand capable of precision radial velocity measurements. A larger multi-objectversion of the Exoplanet Tracker will be used to conduct a large scale surveyfor planetary systems as part of the Sloan Digital Sky Survey III (SDSS III).Variants of the techniques and principles discussed in this paper can bedirectly applied to build large monolithic interferometers for suchapplications, enabling the construction of instruments capable of efficientlyobserving many stars simultaneously at high velocity-precision.