Octahedral Molybdenum Cluster-Based Single Crystals as Fabry–Pérot Microresonators

Single crystals built up from octahedral Mo6 cluster units, with appropriate geometry and size, constitute Fabry–Pérot-type optical microcavities with well-defined resonances. Such resonances appear in the VIS-NIR range when performing optical transmittance (OT) or photoluminescence (PL) measurements. They strongly depend on the crystal thickness and on the optical constants of the material, specifically the real and imaginary parts of the refractive index. In this work, the accurate measurement of the crystal thickness is used for the determination of the optical constants by means of a fitting process, and the preferred orientation of the crystals was determined by X-ray diffraction.