RIMI: Effects of Crystal Field in Quasi Four-Level Lasers

HRD-9628321邦纳生产的更小、更节能的激光器为许多应用提供了方便的光源。效率的关键是了解激光介质中的能量损失过程。许多有用的激光器工作在准四能级模式下，在这种模式下，它们的损耗很大，效率很低。当激光介质为晶体时，晶场与掺杂剂的能量流形相互作用。晶场相互作用可以使晶体中掺杂物的能量流形调整达500 cm-1，并引起相对于自由离子的较大分裂。这些歧管的位置和分裂对于有效的激光性能至关重要。这项研究将研究晶场对影响稀土离子激光器性能的关键指标--准四能级固态截面性能的关键因素的影响，以及晶场对能量传递、上转换和非辐射弛豫等过程的影响，将使人们对晶场对激光器性能的影响有更全面的了解。低能级和高能级流形中晶场分裂的程度决定了每个能级上的热布居数，最终决定了激光器的性能。晶场分裂越大，下能级布居越小，上能级布居越高。较低激光能级的降低和较高激光能级布居的增加以及较大的吸收和发射截面将显著提高激光阈值和斜率效率。这些分裂对能量传递、上转换、流形间和流形内弛豫等关键过程的有利影响有助于提高激光器的性能。在所提议的三年中，研究的具体目标是确定晶场对准四能级系统阈值和斜率效率的影响，并了解场效应对影响激光性能的参数和过程的影响。研究了晶场对吸收截面和发射截面等参数的影响，以及能量转移、上转换和非辐射弛豫等过程。氟磷灰石系列，特别是Ca5(PO4)3F，SR5(PO4)3F和Ba5(PO4)3F，由于其大的晶场分裂和晶场参数随碱土金属的取代而变化，因此被选为高效准四能级激光器的优秀候选者。利用从Ca到Ba的晶场参数的变化趋势，研究其对上述影响激光器性能的参数和工艺的影响。由于Tm3+具有丰富的过程，影响了许多准四能级系统的激光性能，因此Tm3+将被用作探针。Tm3+本身也是一种重要的准四能级激光离子。在拟议的研究中，我们将在评估潜在有用的激光系统(如掺Tm3+的氟磷灰石)时，充分了解晶场参数对准四模激光器性能的影响。研究团队结合了高质量介电晶体晶体生长、固态材料光谱分析、超快动力学和稀土离子激光开发的专业知识。该团队将在校园内的实验室中生长、制造和全面评估材料。温度相关的吸收和发射将被用来确定晶场分裂、吸收和发射截面以及能量分支比。时间分辨发射和吸收将被用来检查材料中的辐射、非辐射和上转换速率。将建立激光试验台，以评估材料的激光性能。

HRD-9628321 Bonner The production of smaller, more energy efficient lasers offer the promise of a convenient light source for many applications. The key to the efficiency is an understanding of the energy loss processes in the lasing media. Many useful lasers operate in quasi-four level mode where they experience large losses and low efficiencies. When the laser media is a crystal, the crystal field interacts with the energy manifolds of the dopant. The crystal field interaction can adjust the energy manifolds of the dopant in the crystal by as much as 500 cm-1 and cause large splittings relative to the free ion. The position and splittings of these manifolds are critical for efficient laser performance. The proposed research will investigate the effect of the crystal field on the critical factors affecting the performance of quasi-four level solid state cross sections which are key metrics in rare earth ion laser performance and the effects on processes such as energy transfer, upconversion, and non-radiative relaxation will provide full understanding of effect of the crystal field on laser performance. The degree crystal field splitting in the lower laser level and the upper level manifold dictates the thermal population on each level and ultimately laser performance. The larger crystal field splitting, the smaller the lower laser level population and higher upper laser level population. The decreased lower laser level and increased upper laser level populations and larger absorption and emission cross sections will significantly improve laser thresholds and slope efficiencies. A favorable effect of these splittings on key processes such as energy transfer, upconversion, inter-manifold, and intra- manifold relaxation contributes to improved laser performance. For the proposed three years, the specific objectives of the investigation are to determine the effect of crystal field on the threshold and slope efficiency of quasi-four level systems and understanding the field effects on the parameters and processes influencing laser performance. The effect of the crystal field on parameters such as absorption and emission cross sections, and processes such as energy transfer, upconversion and non-radiative relaxation will be studied. The fluorapatite family, specifically Ca5(PO4)3F, Sr5(PO4)3F, and Ba5(PO4)3F have been chosen since they are excellent candidates for efficient quasi-four level lasers due to their large crystal field splittings and crystal field parameters are varied by substitution of the alkaline earth metal. This trend on the crystal field parameters from Ca to Ba will be utilized to study its affect on the parameters and processes influencing the laser performance above mentioned. Tm3+ will be utilized as the probe since it exhibits a wealth of processes which affects the laser performance in many quasi-four level systems. Tm3+ itself is also an important quasi-four level laser ion. In the proposed investigation, a full understanding of the effect of crystal field parameters on quasi-four laser performance will be achieved while evaluating a potentially useful laser system such as Tm3+ doped fluoroapatites. The investigative team combines the expertise of crystal growth of high quality di-electric crystals, spectroscopy in solid state materials, ultrafast kinetics, and rare earth ion laser development. This team will grow, fabricate, and fully evaluate the materials in laboratories housed on campus. Temperature dependent absorption and emission will be used to determine the crystal field splitting, absorption and emission cross sections and energy branching ratios. Time resolved emission and absorption will be used to examine the radiative, non- radiative, and upconversion rates in the materials. A laser test bed will be constructed to evaluate the laser performance of the materials.