International Cooperative Study of Multiphonon Relaxation of Mid IR Transitions in Laser Crystals with Short Phonon Spectra

0140484 MirovIt建议扩大亚拉巴马大学伯明翰分校（UAB）和普通物理研究所激光材料和技术研究中心（LMT RC GPI）之间的合作研究工作。目前在激光光谱学方面的合作，对激光晶体中电子激发能量的基本光学性质和光学弛豫过程的研究将继续下去，并扩大到包括对影响有前途的稀有金属的光学激发态的弛豫过程的全面研究，这项研究将联合收割机结合俄罗斯研究人员在激光和基本物理过程方面的专业知识，利用亚拉巴马大学伯明翰分校在激光和激光光谱学方面的专业知识以及先进的设备，研究了掺杂三价稀土离子Pr3+，Nd3+，Dy3+，Ho3+，Er3+、Tm3+和二价过渡金属离子如Ti2+、V2+、Cr2+、Mn2+、Fe2+、Co2+、Ni2+。寻找在中红外光谱区具有高效率辐射跃迁的掺杂晶体基质，在此过程中，将从理论上考虑晶体基质振动光谱的简正模和不同稀土掺杂物可能的光学中心类型的电子跃迁选择规则。将分析它们对辐射和非辐射跃迁速率的影响。经过理论研究，我们将生长出具有中红外波段电子跃迁、辐射强度大、多声子弛豫率低的晶体基质。将在潜在的中红外激光跃迁处提供使用高灵敏度相关光子计数技术和中红外光谱区高灵敏度快速光电探测器的选址光谱研究和温度依赖荧光动力学测量。将测量和分析中红外激光的几乎所有光学RE跃迁的多声子弛豫率的温度依赖性。 自发（无温度模拟）多声子弛豫率将在氦温度下测量和理论计算。计算将考虑多声子弛豫的非线性机制，同时考虑晶体基质的真实的声子谱和部分能级间多重态自发多声子弛豫速率。这些结果将与晶格振动的简单单频近似进行比较。将提供理论和实验的比较。荧光的量子产率和相应的光跃迁的吸收和发射截面将被确定并与预测的结果进行比较。将确定辐射和多声子弛豫速率对阴离子和阳离子质量和晶格单位尺寸以及稀土离子和光学跃迁类型的一般关系，预期的结果是更好地理解影响有前途的RE和TM掺杂中红外激光材料的光学激发态的弛豫过程。在不同类型的上述晶体中获得中红外激光的前景，包括广泛的可调谐的二价过渡金属离子将进行分析。

0140484MirovIt is proposed to extend a collaborative research effort between the University of Alabama at Birmingham (UAB) and Laser Materials and Technology Research Center of General Physics Institute RAS (LMT RC GPI). The current cooperation in laser spectroscopy, investigations of the fundamental optical properties and optical relaxation processes of the energy of electronic excitation in laser crystals would be continued and broadened to include a comprehensive study of the relaxation processes which affect the optically excited state of promising rare-earth and transitional metal doped laser materials.The proposed research would combine the expertise of the Russian investigators in lasers and fundamental physical processes with the expertise in lasers and laser spectroscopy and state-of-the-art facilities at the University of Alabama at Birmingham.Investigation of the multiphonon relaxation (MR) at the potential mid- IR laser transitions (4- 7 um) in the fluoride, chalcogenide, chloride and bromide crystals with short phonon spectra doped with trivalent rare- earth ions like Pr 3+ , Nd 3+ , Dy 3+ , Ho 3+ , Er 3+ and Tm 3+ and divalent transient metals ions like Ti 2+ , V 2+ , Cr 2+ , Mn 2+ , Fe 2+ , Co 2+ and Ni 2+ will be done. A search of doped crystal matrixes with highly efficient radiative transitions in the mid IR spectral region minimally by-passed by multiphonon relaxation will be provided.In doing so the normal modes of vibrational spectra of crystal matrixes and electronic transitions selections rules for possible types of optical centers of different rare- earth dopants will be considered theoretically. Their influence on both radiative and nonradiative transition rates will be analyzed. After theoretical study the crystal matrixes having the electronic transitions in the mid- IR spectral region with large radiative and low multiphonon relaxation rates will be grown. Site- selective spectroscopic studies and temperature dependent fluorescence kinetics measurements using highly sensitive correlated photon counting technique and highly sensitive in the mid- IR spectral region fast photodetectors will be provided at the potential mid IR laser transitions. The temperature dependencies of multiphonon relaxation rates of practically all optical RE transitions perspective for mid IR lasing will be measured and analyzed. Spontaneous (without temperature simulation) multiphonon relaxation rates will be measured at helium temperatures and calculated theoretically. The calculations will be provided considering nonlinear mechanisms of multiphonon relaxation taking into account the real phonon spectra of crystal matrix and partial level- to level inter- multiplet spontaneous multiphonon relaxation rates. These results will be compared with the simple single frequency approximation of lattice vibrations. Comparison of the theory and experiment will be provided. The quantum yield of fluorescence and absorption and emission cross- sections of corresponding optical transitions will be determined and compared with the predicted ones. The general regularities of the radiative and the multiphonon relaxation rates on the anion and cation masses and unit dimensions of crystal lattice and on the rare- earth ion and optical transition types will be determined.The anticipated result of this research effort is a better understanding of relaxation processes which effect the optically excited states of promising RE and TM doped mid-IR laser materials. The perspectives of obtaining mid-IR lasing including broadly tunable for divalent transient metal ions will be analyzed in different types of above-mentioned crystals.