分类： 光学 >> 量子光学 提交时间： 2023-02-23
摘要： In this article, we explore how cryogenic cooling of the Ti:sapphire laser crystal greatly reduces thermal lensing by over an order of magnitude because of two factors: (i) the increase in the thermal conductivity of the crystal, and (ii) the decrease in the temperature dependence of the refractive index. We obtained analytical expression of the focal length of thermal lens for the pump inside the laser crystal being a Gaussian beam. Through analysis of the laser cavity stability, we found that in order for the relative difference between the optimal laser cavity path lengths in the horizontal and vertical directions to be less than 0.1%, the focal length of thermal lens should be longer than 0.5 m. Such a requirement can be met if the laser crystal is cooled to temperatures below 100 K while being pumped at a power that is enough to produce 100 W output. Therefore, it is very likely that an output power of 100 W can be achieved on a single Ti:sapphire laser by cryogenic cooling of the laser crystal.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： The spontaneous emission of atoms can be controlled by placing them between two mirrors that form an optical cavity. Rapid advances in material processing techniques in the last 10 years have made it possible to fabricate microscopic optical cavities that can be finely tuned into resonance with the emitter. This has enabled progress in single-photon sources, nano-lasers and spectroscopy of new nano-emitters such as semiconductor quantum dots and Nitrogen-vacancy centres in diamond. Here we introduce a step-by-step method for computing the Purcell factor of the latest generation of open tunable Fabry-Perot microcavities used in micro-photoluminescence studies. We discuss how the Purcell factor can be optimised as a function of the cavity's geometry and find the conditions for resonance with the emitter. Subtleties such as the optical properties of the emitter and penetration depth of the electric field into the cavity mirrors are also considered.
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