Ti:LiNbO3-based guided wave optics has produced the largest and most sophisticated integrated optic structures to date. At present these devices lack the ability to produce or amplify light. As a result design must be kept conservative to reduce optical loss, thus placing severe limitations on the allowable number of integrated optic elements and their packing density. Certain important functions, like signal regeneration and fan-out (i.e., the distribution of one data stream to many outputs), must also be done electronically- re-imposing both the bandwidth limitations and the added complexity of electronics. A solution to these limitations is an integrable guided wave optical element gain. One of the goals of the proposed research is to fabricate a LiNbO3-based guided wave optical amplifier, incorporating Er3+ as the amplifying medium. (Er has a strong emission line at ~ 1500 nm, a wavelength of importance for telecommunications systems and well beyond the optical region where optical damage to LiNbO3 can take place.) Toward this end, the PI has recently developed a method for locally incorporating much higher concentrations of Er into LiNbO3 than previously reported. This research has several promising waveguide circuits which take advantage of the unique characteristics of intersecting waveguides. We have previously developed a rigorous theory which correctly explains both the coupling and radiative loss characteristics of intersecting optical waveguides and we are applying this theory to the design and analysis of Er:Ti:LiNbO3 guided wave optically pumped amplifiers and light sources. Preliminary measurements and calculations indicate that reasonable gain coefficients (g ~ 400m-1@ 1mW pump power) can be obtained. We propose to continue our study of the enhanced incorporation of Er by way of co-diffusion of Ti and to investigate several other promising co- diffusants. In this study will also examine the incorporation of pairs of rare earth elements. Such paired systems may provide additional useful pump transitions (e.g., diode laser) as well as more efficient energy transfer mechanisms for optical gain. Site-selective fluorescence spectroscopy will be used to characterize the optical properties of rare earth ions in the LiNbO3 matrix, as well as to identify the substitution site and transport mechanisms for this co-diffusion process.
