The research that will be presented may be divided into two major parts. The first one concerns longitudinally pumped, bulk Er-Yb lasers. The main limitation in these lasers is the thermal shortcomings of the phosphate glass host material. Using laser experiments and spectroscopic measurements on crystalline host materials, some novel results contributing to the search for a crystalline replacement will be presented. The second part concerns novel laser concepts applied to Yb-doped double tungstate lasers. Different crystal orientations are investigated, such as an athermal orientation for reduced thermal lensing and a conical refraction orientation for complete polarization tuning. The introduction of volume Bragg gratings in the cavity, a concept that can be easily applied to several other laser materials, enables wide spectral tuning ranges and extremely low quantum defects.
