1.55 µm BH-DFB laser with integrated spot-size converter for flip-chip applications

We report on a 1.55 µm BH l/4 phase-shifted DFB laser with integrated spot-size converter for flip-chip mounting based on the InGaAsP/InP material system. Self-aligning passive flip-chip technique for multi-wavelength transmitter device set-up is a cost efficient technology. As an example we will give the design and the results of a flip-chip DFB laser diode to be butt coupled to a silicon waveguide within a silicon on insulator (SOI) optical board or in an optical single mode fiber both with a near field spot size extension of about 5 µm and a small far field angle. Essential requirements for such flip-chip adapted laser diodes are: single mode power output in the range of mW, low sensitivity to back reflections from the board interface, large alignment tolerances concerning optical interfacing, reliable passive self-alignment via multiple solder bumps and integrated alignment stops. The solution presented in this paper is a laser diode consisting of a 300 µm l/4 phase shifted DFB section and a separate 200 µm spot size converter region. In a CWDM (= Coarse Wavelength Division Multiplexing) operation regime the devices need no cooling and can be directly modulated at data rates up to 10 Gbit/s.