Charge transfer processes and ultraviolet induced absorption in Yb:YAG single crystal laser materials

Abstract

Charge transfer (CT) transitions and UV induced color centers in Yb:YAG single crystals have been investigated. A simultaneous pair formation of a stable Yb 2þ ion and a hole related ðO À Þ color center (hole polaron) are observed through a CT-process. Slightly different types of hole related color centers are formed in Yb:YAG crystals containing small levels of iron impurities. Furthermore, excitation spectroscopy on the UV irradiated Yb:YAG samples could confirm an energy transfer process between Yb 3þ and Yb 2þ ions. The findings are important for an increased knowledge of the physical loss mechanisms observed in Yb-doped laser materials, such as the nonlinear decay process in Yb:YAG crystals as well as the photodarkening phenomenon in Yb-doped fiber lasers. V C 2013 AIP Publishing LLC. [http://dx

Experimental evidence for the formation of divalent ytterbium in the photodarkening process of Yb-doped fiber lasers

“…Hence, the nature of the electron trap that charge compensate the Al-OHCs in photodarkened fibers is still unclear. We have recently performed UV-irradiation experiments on Yb:YAG single crystals and could experimentally verify relation (1) above [15]. Characteristic Yb 2+ absorption bands are observed in UV-irradiated Yb:YAG single crystals in addition to a superimposed absorption band centered near 300 nm attributed to bound hole polarons.…”

A study of radiation effects on LuAG:Ce(Pr) co-activated with Ca

“…Fig. 4(b) shows γ-irradiation induced absorption spectrum in an un-doped LuAG; besides the well-established bands at 375 and 600 nm related to Yb 2 þ , there are absorptions in the 300-350 nm range the origin of which is often ascribed to Yb 2 þ (280-300 nm [34,35]), Fe 2 þ ( $ 307 nm [36]) or O À [37,38]. In Ca 2 þ codoped crystal the overall induced absorption in the range of emission is higher, although the intensities of induced bands related to Yb 2 þ , as expected, are lower (inset shows the difference spectrum).…”

Influence of air annealing temperature and time on the optical properties of Yb:YAG single crystal grown by HDS method

“…Thus the optimum crystals must be annealed in an oxidized atmosphere. annealing processes to eliminate color centers at a single high temperature or long time such as 1650°C for 36 h or 1100°C for 100 h [14][15][16][17], but the influence of a series of annealing temperatures or hours on the optical properties has not been discussed in detail.…”