Ion beam processing of LiNbO 3
- PDF / 950,151 Bytes
- 10 Pages / 595.44 x 841.68 pts Page_size
- 97 Downloads / 218 Views
P. R. Ashley U. S. Army Missile Laboratory, Redstone, Arsenal, Alabama 35898 (Received 14 October 1985; accepted 13 December 1985) Ion implantation and ion beam mixing have been investigated as alternative techniques to hightemperature diffusion for introducing dopants into LiNbO 3 . Heavy ion bombardment at both 77 and 300 K initiated a near-surface decomposition causing Li to diffuse to the surface where it formed a nonuniform agglomerate. The damage and annealing characteristics of this effect were studied by ion scattering/channeling, secondary ion mass spectrometry, and optical microscopy. The origins of the surface decomposition are discussed along with possible solutions, and selected samples were evaluated for waveguide properties.
I. INTRODUCTION LiNbO 3 single crystals are widely utilized for fabricating integrated optical elements and devices because of the high optical quality of the crystals and because they possess both electro-optic and piezoelectric effects. The most successful devices, including waveguides, couplers, modulators, switches, mode splitters, and more complex devices, have been made by in-diffusion of metals like Ti, V, Ni, etc.,1"7 or by out-diffusion of Li.7"10 More recently the possible use of proton exchange as a method of making waveguides in LiNbO 3 has been proposed.7'11"14 Ion bombardment of LiNbO 3 has also been studied extensively,15"39 and has been utilized to fabricate optical waveguides,17'18'21'29 modulators,18 strip waveguides,20 buried waveguides,30 grating couplers,32 and surface acoustic waveguides.34 Although diffusion techniques appear more successful at present for low-loss waveguide fabrication, ultimately microintegrated optical systems will be necessary and ion implantation can provide some promising advantages. The lateral spread of patterns formed using masks will be less with implantation than with diffusion as will the depth or range straggling. The variety of ion species and accurate control of energy make implantation a potentially more versatile processing method. Many doping procedures can be performed near room temperature rather than at high temperatures which, for materials such as LiNbO 3 , can result in detrimental optical damage.40 There is already a need for precision gratings with submicron patterning and diffusion techniques are incapable of fabricating such structures because of diffusive smearing. If
*' Also at Department of Physics, Millsaps College, Jackson, Mississippi 39202. b) Also at Department of Physics, Wright State University, Dayton, Ohio 45435.
104
J. Mater. Res. 1 (1), Jan/Feb 1986
http://journals.cambridge.org
low-temperature ion implantation doping could be successfully developed, strong, compact gratings could be made using masking techniques already developed. However, in order to utilize ion beam processing techniques successfully, detrimental effects such as ion-induced optical defects, phase changes, structural alterations, and chemical instabilities must be understood and controlled. This paper reports investigations
Data Loading...
