Intense optical absorption of defects created in Er 3+ -diffused layer in MgO (5 mol%)-doped LiNbO 3 crystal by local Er
- PDF / 159,984 Bytes
- 6 Pages / 584.957 x 782.986 pts Page_size
- 110 Downloads / 228 Views
win Yue-Bun Pun Department of Electronic Engineering, City University of Hong Kong, Kowloon, Hong Kong, People’s Republic of China (Received 20 October 2011; accepted 14 March 2012)
Intense broad absorption bands centered around 1.7, 2.5, 3.1, and 3.7 eV take place in Er31-diffused layer formed near MgO (5 mol%)-doped LiNbO3 crystal surface by in-diffusion of Er metal under Li-poor atmosphere. These bands are tentatively attributed to the defect absorption of small polarons, bipolarons, F-centers, and Q-polarons created due to Er31 in-diffusion and Li2O loss from the crystal. It is interesting that the number, type, area, and peaking position of the bands can be controlled by the diffusion temperature and further oxidation treatment. Such material is a promising medium for data storage based upon two-color holography. I. INTRODUCTION
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2012.97
from Del Mar Photonics Inc. (San Diego, CA), were used as the starting materials. At first, pure Er metal (99.99%) film with a thickness of 44 6 2, 50 6 2, and 60 6 2 nm was locally coated onto a part of one surface of each plate. Subsequently, these plates locally coated with Er films, named Sample 1, 2, and 3 in order, were annealed at different temperatures of 1060, 1100, and 1130 °C, respectively, in a Li-poor atmosphere created by a closed Nb-rich two-phase [LiNbO3 (32 mol%) 1 Li3NbO4 (68 mol%)] crucible, i.e., the Li-poor vapor transport equilibration (VTE). The two-phase crucible was prepared by sintering homogeneous Nb-rich mixture of Li2CO3 and Nb2O5 powder, which has the same purity of 99.99%. The molar ratio was 32 mol% (Li2CO3):68 mol% (Nb2O5). The mixture was pressurized and molded into a crucible model of 6 cm in inner diameter and 4 cm in height. A precalcination at 1000 °C for 10 h and an additional calcination at 1100 °C for 1 h produced a Nb-rich two-phase crucible. The solid phase reaction involved is 32 mol% Li2CO3 1 68 mol% Nb2O5 5 32 mol% CO2[ 1 28 mol% LiNbO3 1 36 mol% LiNb3O8. The detailed Li-poor VTE procedure is described as follows. At first, the plate to be treated was wrapped with Pt wires and placed on a Pt foil, which was placed in the crucible before the crystal to be treated. Then, the crucible was sealed by a lid, made of the same Nb-rich two-phase powder, and heated up to a target temperature and dwelled for a scheduled duration. Due to the Li concentration gradient inside and outside the crystal, the Li ions inside the crystal diffused away from the crystal surface at the elevated temperature and the crystal evaporated the Li2O gas,
1482
Ó Materials Research Society 2012
31
Locally Er -doped LiNbO3 (Er:LN) is a promising substrate material for integrated optics as it combines Er31 laser property with excellent electrooptic, acoustooptic, and nonlinear optical properties of LiNbO3 (LN). Over the past years, a family of Ti:Er:LN waveguide lasers (amplifiers) and integrated devices have been reported.1 5 Another potential application of LN crystal is utilizing
Data Loading...
