DESIGN OF A SPOTSIZE-CONVERTER-INTEGRATED LASER-DIODE (SS-LD) WITH A LATERAL TAPER, THIN-FILM CORE AND RIDGE IN THE 1.3-MU-M-WAVELENGTH REGION-BASED ON THE 3-D BPM

In order to develop spotsize-converter-integrated laser diodes (SS-LD' s) with high efficiency and large-misalignment tolerances in the 1.3-m u m-wavelength region, spotsize converters (SSC's), which consist of a lateral taper, thin-film core and ridge, are investigated employing t he three-dimensional (3-D) semivectorial finite-difference beam propag ation method (FD-BPM) with nonequidistant discretization, The sum of t he spot-conversion loss and coupling loss between the laser diode (LD) eigenmode and the single-mode fiber (SMF) eigenmode are calculated fo r various structural parameters, Small loss of around 1.5 dB can be ac hieved by introducing a nonlinear taper, The fabrication tolerances fo r the SSC's are also clarified. The calculated results agree well with the results for actually fabricated SS-LD's, It is also shown that th e radiation loss and coupling characteristics of the SS-LD's with a bu ried thin-film core structure can be improved using a nonlinear taper.