Er 3+ イオンの励起吸収を用いた光の負性非線形吸収効果

佳伸 前田, 正俊 右高

Mark Hughes, Huan Liu, Adam Brookfield +3 more

Erbium-implanted silicon (Er) holds promise for quantum networking, but the formation of multiple Er centres poses a challenge. We show that the cubic centre (Er-C) has C2v or lower symmetry, with Er centres ranging from fully Si- to fully O-coordinated. By co-implanting Si with Er and O (each at 1019 cm-3) and increasing the thermal anneal quenching rate from ~100 °C/s to ~1000 °C/s, we shifted the dominant optically active centre from Er2O3 clusters to the less stable Er-C centre with mixed Si and O coordination. Temperature-dependent photoluminescence reveals Er2O3 clusters and Er-C centres have O-related defect states at ~200 and 90 meV above the 4I13/2 Er manifold, respectively.

佳伸 前田, 正俊 右高

Mark Hughes, Huan Liu, Adam Brookfield +3 more

Erbium implanted silicon (Er:Si) is a promising platform for quantum networking applications, but a major obstacle is the formation of multiple Er centres. We show that the previously identified cubic centre (Er-C) has C2v or lower symmetry. Using crystal field analysis of Er-C and other Er centres, and by comparison with extended X-ray absorption fine structure (EXAFS) measurements, we show that Er centres can be arranged in a sequence, ranging from entirely Si coordinated, through mixed Si and oxygen (O) coordination, to entirely O coordinated. G-factors calculated from our crystal field fitting closely match those determined by Zeeman splitting and electron paramagnetic resonance (EPR) measurements. We co-implanted Si with Er and O (each to a concentration of 1019 cm-3). By increasing the quenching rate of the subsequent thermal anneal from ~100 °C/s to ~1000 °C/s, we change the dominant optically active centre, formed from Er2O3 clusters to the less energetically favourable Er-C centre with mixed Si and O coordination. Temperature dependent photoluminescence (PL) shows that Er2O3 clusters and Er-C centres have an O-related defect state at ~200 and 90 meV above the 4I13/2 Er manifold, respectively. PL lifetime measurements show that the Er2O3 clusters and Er-C centres fall into two or three classes, characterised by different non-radiative PL decay rates. Our high quench rate annealing process could facilitate the formation of a single, optically active Er centre, which is preferable for quantum networking applications of Er:Si.

Tomohiro Inaba, Takehiko Tawara, Hiroo Omi +2 more

Epitaxial growth of erbium-doped cerium oxide (Er:CeO2) is achieved on Si (111) substrates by the cooperative integration of Si and oxide molecular beam epitaxy (MBE) technologies. Lattice matching between CeO2 and Si provides an attractive opportunity to build dilutely doped Er-based optical devices on a Si chip. The CeO2 host crystal is optically transparent for the telecom C-band wavelength and has quite a small magnetic moment, which serves as a disturbance-free environment for the two-level system formed in the doped Er. After the systematic optimization of the growth conditions for stoichiometric Er:CeO2; i.e., (Er + Ce)/O = 1/2, we varied the Er concentration in a range of 1 ~4%. The doped Er showed well-defined optical transitions at the wavelength of 1.533 μm irrespective of the Er concentration. With decreasing Er concentration, enhancement of the luminescence intensity, narrowing of the spectral width, and an increase in the radiative lifetime were observed. The results suggest that CeO2 on Si is promising as a platform for the doped-Er-based optical devices and their quantum optics applications.

大佑 橋本, 薫 清水