Highly Efficient Oval Hollow Mode Operation in a Laser-Diode-Pumped Microchip Solid-State Laser

Abstract

One possible basis of a new definition of the kilogram is the Avogadro constant determined by measuring the lattice parameter and molar volume of a silicon single crystal. Data of molar volumes derived from different silicon crystals in the international framework differ significantly. It was suggested that the differences are produced by holes or voids in the crystal lattice exceeding today's experience in silicon perfection. To illuminate this problem, test crystals were grown in different ambient conditions in order to generate areas in the material with vacancies or light elements. Macroscopic defects were generated by hydrogen in the growth atmosphere and detected by preferential etching, laser scattering tomography and x-ray topography. Using the pressure-of-flotation method for the evaluation of density differences in silicon, relative loss in the macroscopic density of float-zone silicon up to 1 × 10 −7 was observed when the growth ambient contained 2% hydrogen. However, the reason for the reported molar volume differences of the order of 10 −6 is still not found and will be the subject of further investigations.(Some figures in this article are in colour only in the electronic version)