Theodore Alekel

Formation of a Photoluminescent Surface on n‐Si by Irradiation Without an Externally Applied Potential

A porous, luminescent surface is produced on n-Si by irradiation in anhydrous or aqueous hydrogen fluoride without an externally applied potential. The photoluminescence spectra of the resulting surfaces are similar to those obtained by the anodization method. A porous surface is only produced when electrical contact is made between the n-Si disk and a metal surface such as Au or Hg, and, in the aqueous system, when dissolved O 2 is present

Spectroscopic and laser properties of Nd3+ in LaSc3(BO3)4 host

Spectroscopic and laser properties have been characterized for Nd3+ in LaSc3(BO3)4. The Judd–Ofelt analysis has been applied to the measured room temperature absorption spectrum to determine the radiative decay rates and branching ratios of Nd3+ transitions from the 4F3/2 metastable state to the 4IJ lower-lying manifolds. The parameters Ω2, Ω4, and Ω6 are larger than those reported for Nd3+ in other laser host crystals. The value of Ω4/Ω6 is approximately 3.0 times larger than that of Nd3+ in yttrium–aluminum–garnet (YAG) and about 1.4 times larger than that of Nd3+ in the β phase of LaSc3(BO3) reported recently. The measured room temperature fluorescence lifetime of the 4F3/2→4I11/2 transition is 150 μs, while the Judd–Ofelt analysis predicts a radiative lifetime for the 4F3/2 state to be 249 μs, resulting in the fluorescence quantum efficiency of 60%. The emission cross sections of the 4F3/2→4I11/2 and 4F3/2→4I13/2 intermanifold transitions have been also determined at room temperature. Finally, these r...

Spectra and energy levels of Nd3+ in LaSc3(BO3)4

We report a detailed spectroscopic analysis of Nd3+(4f3) as a dopant in single crystals of LaSc3(BO3)4 (LSB). Absorption spectra were obtained between 570 and 1750 nm at temperatures as low as 8 K. Fluorescence spectra and lifetimes were obtained at similar temperatures from 4F3/2 to 4I9/2, 4I11/2, and 4I13/2 multiplet manifolds. The observed spectra are similar to spectra reported earlier for Nd3+ as a dopant in the alpha phase of LSB. The observed crystal-field splitting of the 2S+1LJ multiplet manifolds of Nd3+ was modeled using a Hamiltonian, which includes atomic and crystal field terms. A least-squares fitting between 57 calculated-to-observed energy (Stark) levels gave a root mean square deviation of 8 cm−1 for the 13 lowest-energy multiplet manifolds. With wave functions obtained from the modeling studies, multiplet-to-multiplet and line-to-line branching ratios were calculated as well as the radiative lifetime for emission from 4F3/2. The results are compared with experimental values obtained in ...