Development of tapered glass coupling waveguides for source radiation input into multichannel LiNbO3 modulator arrays

The investigation shows that a tapered glass optical waveguide provides an effective coupling device for introducing and directing radiation from a semiconductor laser source (e.g., GaAs) into a multichannel Ti:LiNbO₃ optical array modulator. A tapered planar waveguide was produced by RF sputter depositing Corning 7059 glass on Corning 2947 microscope slides which were used as substrates. The waveguide thickness tapers from 2 to 1 μm over a waveguide propagation distance of 1 cm. In addition, graded index silver indiffused waveguides suitable for couplers were also produced in this investigation by indiffusing silver ions into Corning 2947 microscope slides. An inverse WKB analysis of these graded index waveguides was used to explore the refractive index profile. Microprobe X-ray wavelength-dispersive analysis measurements of the silver concentration profile show that the deep multimode silver guides have an index profile that is more parabolic in shape than Gaussian. Shallow, single-mode, or two-mode silver waveguides appear to have a complementary error function index profile