This project aims to enable the use of diamonds with a high density of nitrogen vacancy (NV) centres as a laser medium, to allow for innovative and precise magnetic field measurements (magnetometry). The material characteristics of NV-doped diamonds are studied and improved, the diamond is utilized and characterized in a laser cavity, and the laser system is combined with a radio frequency antenna for magnetic resonance. An innovative and highly precise sensor at room temperature could revolutionize medical applications, such as MEG and MCG.