Innretning for gammastrålepåvisning og - måling

摘要

A laser, e.g. a microchip laser, comprises a laser cavity (13) having reflectors (17), (18) at each end of an optical path, a first layer of gain material (15) such as Nd : YVO 4 and a second layer of a second material (14, 16) disposed along the optical path, wherein the first and second layers are directly optically contacted to one another at associated faces and are held together by Van der Waals forces. The layer (14) may serve as a mount. The cavity may include crystals (14, 16) having anisotropic refractive indices, the laser being oscillatory in a preferred mode having a particular orientation of polarisation, the crystal (16) being a frequency doubler such as KTP oriented with respect to the path to cause no appreciable net depolarisation of the preferred mode, and the crystal (14) being arranged such that the preferred mode is transmittable therethrough with minimal refraction. The length of the frequency doubler crystal (16) may be controlled by temperature tuning.