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

[04:44 . 84]提议扩大阿拉巴马大学伯明翰分校（UAB）和英国RAS普通物理研究所激光材料与技术研究中心（LMT RC GPI）之间的合作研究。目前在激光光谱学、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方面的合作将继续进行，并扩大到包括影响有前途的稀土和过渡金属掺杂激光材料光学激发态的弛豫过程的全面研究。拟议的研究将把俄罗斯研究人员在激光和基本物理过程方面的专门知识与伯明翰阿拉巴马大学激光和激光光谱学方面的专门知识和最先进的设施结合起来。调查multiphonon放松(MR)的潜在的红外激光转换中期(4 - 7嗯)氟、硫族化物,氯和溴化和短的声子晶体光谱掺杂三价罕见——地球离子像公关3 +,Nd 3 +, Dy, 3 + 3 +, Er 3 + Tm 3 +和二阶暂态金属离子如Ti 2 + V 2 +, Cr 2 +, Mn 2 +,菲2 + Co 2 +和倪2 +将完成。将提供在中红外光谱区域中具有高效辐射跃迁的掺杂晶体基质的搜索，该辐射跃迁最小程度地通过了多声子弛豫。在此过程中，将从理论上考虑晶体基质振动谱的正态模式和不同稀土掺杂剂可能的光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，在中红外光谱区生长出具有大辐射和低多声子弛豫率的电子跃迁晶体基质。利用高灵敏的相关光子计数技术和高灵敏的中红外光谱区域快速光电探测器，将在潜在的中红外激光跃迁中提供位点选择光谱研究和温度依赖荧光动力学测量。测量和分析了中红外激光中几乎所有光学RE跃迁角度下多声子弛豫率的温度依赖性。自发（没有温度模拟）多声子弛豫率将测量在氦温度和理论计算。考虑到晶体矩阵的实际声子谱和部分能级间多声子自发弛豫率，将提供考虑非线性多声子弛豫机制的计算。这些结果将与晶格振动的简单单频近似进行比较。将理论与实验进行比较。测定荧光的量子产率和相应的光学跃迁的吸收和发射截面，并与预测结果进行比较。确定了辐射弛豫率和多声子弛豫率对阴离子和阳离子质量、晶格单位尺寸、稀土离子和光跃迁类型的一般规律。本研究工作的预期结果是更好地理解影响有前途的稀土和TM掺杂中红外激光材料光学激发态的弛豫过程。本文将分析在上述不同类型晶体中获得二价瞬态金属离子宽可调谐中红外激光的前景。

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.