Fabrication parameters optimization of Ti-diffused Nd:LiNbO 3 channel waveguide lasers

Abstract

The variations of lower-order TM mode size and corresponding effective refractive index, effective pump area and coupling efficiency between pump and laser modes with the controllable fabrication parameters, i.e. initial Ti-strip width W, diffusion temperature T and initial Ti-strip thickness H in c-cut Ti-diffused Nd:LiNbO3 waveguide lasers have been calculated by using a variational method, taking into account both laser wavelength, 1085 nm, and pump wavelength, 815 nm. The main features of these curves were summarized and discussed in detail; consequently, the single-mode, fundamental mode cutoff and multimode conditions were presented and compared with the published experimental data. The effective pump area, directly proportional to threshold pump power, reveals a weak dependence on W in the considered range 4–16 μm and strong dependences on T and H in, respectively, the ranges studied 950–1100°C and 40–160 nm, while the coupling efficiency, directly proportional to slope efficiency, is hardly changed (with the values 0.82–0.85) with these parameters. Finally, appropriate diffusion parameters were proposed for the fabrication of a more efficient laser.