Demonstration of Monolithically-Integrated InP Widely-Tunable Laser and SOA-MZI Wavelength Converter Milan L. Mašanović, Erik J. Skogen, Jonathon S. Barton, Vikrant Lal, Daniel J. Blumenthal, Larry A. Coldren Electrical and Computer Engineering Department University of California Santa Barbara, Santa Barbara, CA 93106 Abstract The first monolithically integrated widely tunable wavelength converter, consisting of a Sampled-Grating Distributed-Bragg-Reflector laser and a semiconductor optical amplifier-based Mach-Zehnder interferometer, is reported. Static extinction ratios better than 19dB and 13 dB using electrical and optical control, respectively, were measured over a 22nm laser wavelength range. I. Introduction The monolithic integration of tunable lasers and all-optical wavelength converters is a critical step towards solving one of the last obstacles for all-optical switching to have the functionality and flexibility needed to be a serious candidate to replace electronic switches. These structures allow data to be imprinted from an input wavelength to a tunable output wavelength without passing the signal through electronics. The semiconductor optical amplifier Mach- Zehnder interferometer (SOA-MZI) wavelength converter is an important class of integrated wavelength converters that also implements the significant feature of digital signal regeneration. InP integration of SOA-MZIs has been reported (1,2,3), however, to the best of our knowledge, a tunable laser integrated with a wavelength converter has never been reported. Previously, an SOA-MZI was integrated with a non- tunable DFB laser, but there were severe tradeoffs due to reflections from the MZI back to the laser (4). Nonetheless, despite the fact that minimization of reflections has to be considered carefully, this level of integration also reduces the coupling loss between laser and converter as well as improves the converter noise figure, conversion efficiency and size/complexity/cost of the entire component. For wide wavelength tunability, the sampled grating distributed Bragg reflector (SGDBR) laser is well suited for integration with other components due to its lithographically defined mirrors that enable lasing without a facet reflection. Integration of tunable lasers with other elements has been reported, for example the SGDBR laser with an SOA (6) and Mach- Zehnder modulator (7). II. SGDBR/SOA-MZI Design and Fabrication The device consists of an InP SGDBR laser integrated with a SOA-MZI (Fig. 1). The laser is 1.5mm long and has five sections: front mirror, gain section, phase section, back mirror and back facet detector. The front and back mirrors of the laser consist of periodically sampled DBR gratings to form a comb-like reflectivity spectrum (5). Since the sampling periods of the mirrors differ, they have different peak reflectivity spacing, so that only one set of mirror reflectivity peaks is aligned within the desired tuning range. By differentially tuning the front and back mirrors a small amount, adjacent reflectivity peaks can be aligned, and the laser will operate at this new wavelength (5). The interferometer branches are defined by two S- bends and 1mm long SOAs (Fig. 1). The total waveguide separation in the interferometer is 70 µm. The laser and the interferometer are connected via a multimode interference (MMI) splitter. Fig. 1. SEM image and a schematic of the device