Implantation Doping and Stimulated Emission of Er 3+ in LinbO 3 :Ti Optical Waveguides
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Implantation Doping and Stimulated Emission of Er3+ in LiNbO3 :Ti Optical Waveguides Ch.
Buchall,
R.
2 Brinkmann ,
W. Sohler
2
and H.
Suche
1) ISI-KFA, D-5170 Jilich, Germany 2) Angew. Physik, Universitdt, D-4790 Paderborn,
2
Germany
ABSTRACT We have implanted Nd and Er ions into x- and z-cut LiNbO3 single crystals and investigated the recrystallization of the host and the rare earth solubility and diffusion. The diffusion is substitutional, fastest parallel to c-axis and characterized by an activation energy of 3.6 eV. Optical fluorescence experiments of Er 3 + in a waveguide configuration show stimulated emission and amplification at 1.53, 1.55 and 1.56 Am wavelength. INTRODUCTION LiNbO3 is the best dielectric substrate for Integrated Optical (10) applications, especially if one wants to make use of the electro-optical effect [1]. The formation of optical waveguides in LiNbO3 by Ti indiffusion, proton exchange or ion implantation is well established.. 10 devices on LiNbO3 perform numerous linear and nonlinear functions, but do not amplify the intensity of light. Reliable optical amplifiers or lasers in LiNbO 3 have not yet been realized, although several prototypes have been evaluated (2-4]. On the other hand, the stimulated emission from optically pumped rare earth [R.E.] ions such as Er 3 +, doped into the glass core of optical fibers, has frequently been used to fabricate high gain optical fiber amplifiers [5, 6]. This letter communicates results of ion implantion doping of Nd and Er into LiNbO3 and optical investigations of implanted Er 3 + in a waveguide of LiNbO3 :Ti. A process of locally doping LiNbO3 , using Erimplantation and subsequent annealing, will be an elegant way to achieve active regions for monolithic integration of guided optical amplifiers and lasers together with passive components on a common chip. ION IMPLANTATION AND DIFFUSION Samples from optical grade wafers of xand z-cut orientation were implanted at substrate temperatures ranging from 80 K to 620 K. Because the final results did not depend significantly on implantation temperature, we will discuss the 300 K data only. The results communicated here were obtained at 200 key implant energy. Scanned beam currents were 5 - 10 pA/cm2 ; the dose was typically 10 1 6 /cm 2 . After implantation, Mat. Res. Soc. Symp. Proc. Vol. 201. c 1991 Materials Research Society
308
Energy [MeV]
Fig.
la:
1016 Er/cm2 at 200 keV as implanted
-o
0
Fig. ib: Annealed for 1 h at 1300 K Note lattice recovery of LiNbO3 and channeling of indiffused Er.
4000 2000 Er-depth [A]
0
C 0
Fig. 2: Schematic of Er diffusion profiles for 3 times t3 > t 2 > tI
C: 0 Lj
C/2
x3
x1
x2 -
depth
x0
surface
309
the samples were immediately annealed in
an oxygen atmosphere.
For the RBS/Channeling evaluation of the LiNbO3 lattice regrowth and the R.E. depth profiling, a collimated He beam of 4.5 MeV energy was used. It was incident normal to the sample. At a detector angle of 1700 this results in a maximum accessible depth of 4500 A for Nd and 5500 A f
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