Bernd Klepser

Low-cost edge-emitting DFB laser arrays for DWDM communication systems implemented by bent and tilted waveguides

This paper emphasizes methodology concerning variations of the emission wavelengths of edge-emitting semiconductor lasers. We present a method based on tilted distributed feedback (DFB) gratings to be used in combination with specially bent or tilted straight waveguides for the low-cost and ultraprecise definition of different wavelength channels in lasers for Dense wavelength division multiplexing (DWDM) fiberoptic communication systems. The homogeneous DFB grating field is defined using low-cost processes and is tilted with respect to a preferential direction defined by the device borders or the crystal geometry. Our method allows ultraprecise definitions of the DWDM wavelengths and is applicable index- and complex-coupled DFB gratings in both isolated lasers and arrays. Design, technological implementation, and experimental characterization of the devices is presented in this paper. Thin-film heaters are used for correcting small wavelength deviations occurring due to technologically induced tolerances.

Semiconductor lasers for high-bit-rate optical data transmission: investigations to increase the yield of laser arrays

Our studies on the thermal cross talk of laser arrays with integrated thin film heaters involve theoretical as well as experimental investigations. Comparing the effects of intentional geometrical variations of the device design, we found that the relative thermal crosstalk depends critically on the distance between the active area and the film heater. The most striking result is that a minimization of the thermal resistivity of the device does not always lead to a reduced thermal crosstalk. We demonstrate that an additional heat barrier close to the active region and/or an improved heat transfer between the submount and the heat sink may reduce the relative thermal crosstalk, a result completely unexpected from intuitive considerations. Model calculations showed that the device yield can be increased by 20 percent improving the heat transfer between the submount and the heat sink.