Investigation of Population Dynamics in 1.54-μm Telecom Transitions of Epitaxial (ErxSc1-x)2O3 Thin Layers for Coherent Population Manipulation: Weak Excitation Regime

• Published in: Applied sciences 2018-06, Vol.8 (6), p.874
• Main Authors: Adachi, Satoru, Kawakami, Yoshihiro, Kaji, Reina, Tawara, Takehiko, Omi, Hiroo
• Format: Article
• Language: English
• Subjects: Crystal growth; Crystals; Energy; epitaxial film; erbium; Excitation; Investigations; Optics; Phonons; Population; Population dynamics; Population studies; Quantum dots; Relaxation time; Scandium; Silicon substrates; Single crystals; Symmetry; Temperature; Thin films
• ISSN: 2076-3417; 2076-3417
• DOI: 10.3390/app8060874

In this study, we investigate the population dynamics in a whole system which consists of not only the inter- and intra-site ETs but the non-radiative relaxation in Er 2 O 3 and (Er, Sc) 2 O 3 single crystals grown on Si(111). Since the UC process occurring in the C2 site makes the population dynamics complicated, the low power resonant excitation of one of Stark levels (Y 3′ ) in the C3i site is employed in order to minimize the effect of UC process. [...]we focus on the τslow , which is assumed to include the two different decay components, the radiative and the non-radiative relaxations. Since the radiative relaxation rate is determined quantum-mechanically and is independent of temperature in principle, we consider that the temperature-sensitive property of τslow component is caused by the thermally-activation type non-radiative relaxation process. The MP relaxation time τMP ordinarily depends on the sample temperature, and it is proportional to the following factor, 1-exp(-Ep/kBT)-m in the single frequency model, where Ep is the phonon energy and m is the number of phonons, respectively [38]. Since the Ep in Sc 2 O 3 is about 74 meV [18] and the corresponding one in (Er, Sc) 2 O 3 crystal seems to be close with that, the MP relaxation rate for m = 1−15 is insensitive to the change in temperature below 100 K, and it agrees qualitatively with the behavior of the experimentally obtained τfast . 3.3. [...]detail experimental investigation to specify the physical origins of those non-radiative relaxations and the analysis by the microscopic theory such as Inokuti-Hirayama model [39,40] are required. 4.