MULTIPHONON RELAXATION OF RARE-EARTH IONS IN OXIDE GLASSES
MULTIPHONON RELAXATION OF RARE-EARTH IONS IN OXIDE GLASSES
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DOI：
10.1103/physrevb.16.10
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发表时间：
1977-01-01
影响因子：
3.7
通讯作者：
WEBER, MJ
中科院分区：
文献类型：
--
作者：
LAYNE, CB;LOWDERMILK, WH;WEBER, MJ
本文研究了稀土离子在一系列氧化物玻璃中受激态的多声子发射的无辐射衰减。选择性地激发各种稀土电子水平的短时间激光脉冲和多声子弛豫率测定从荧光的上升和衰减时间的测量。荧光测量的时间分辨率为3纳秒，因此探测了衰变主要是非辐射的激发态。研究了Nd 3+、Er 3+和Tm 3+的激发态，其能隙为1300至4700 cm-1。每种玻璃的多声子弛豫速率与能隙近似呈指数关系。在小能隙的区域中观察到这种依赖性破裂的证据。所测量的衰减速率的温度依赖性建立的松弛发生主要通过激发与玻璃网络形成剂的拉伸模式相关的最高频率的振动。硼酸盐，硅酸盐，磷酸盐，锗酸盐，碲酸盐玻璃进行了研究。根据拉曼光谱，这些玻璃的最高频率振动范围为700 - 1400 cm-1。对于一个给定的能隙，相应的多声子弛豫速率相差三个数量级。离子-声子耦合的强度被认为是近似相等的所有玻璃。
Nonradiative decay of excited rare-earth ions by multiphonon emission has been investigated in a series of oxide glasses. Various rare-earth electronic levels were selectively excited by short-duration laser pulses and multiphonon relaxation rates were determined from measurements of fluorescence rise and decay times. Time resolution for fluorescence measurements was 3 nsec, so excited states were probed for which the decay was predominantly nonradiative. Excited states of Nd 3+, Er 3+, and Tm 3+ with energy gaps to the next-lower J state ranging from 1300 to 4700 cm− 1 were studied. The multiphonon relaxation rates for each glass investigated exhibited an approximately exponential dependence on energy gap. Evidence of breakdown of this dependence was observed in the region of small energy gaps. The measured temperature dependences of the decay rates establish that the relaxation occurs predominantly by excitation of the highest-frequency vibrations associated with stretching modes of the glass network former. Borate, silicate, phosphate, germanate, and tellurite glasses were studied. From Raman spectra, the highest-frequency vibrations for these glasses ranged from 700 to 1400 cm− 1. The corresponding multiphonon relaxation rates for a given energy gap differed by three orders of magnitude. The strength of the ion-phonon coupling was found to be approximately equal for all glasses.