InP/InGaAsP broadly tunable filters/receivers with grating-assisted codirectional couplers

One of the key elements in a wavelength division multiplexing (WDM) direct detection system is a wavelength-tunable receiver capable of detecting a desired channel from incoming data streams. In this study, we monolithically integrate a semiconductor optical amplifier (SOA), a two-stage grating-assisted codirectional coupler (GACC) optical filter, and a waveguide photodetector on InP/InGaAsP based materials. This photonic integrated circuit (PIC) approach gives us the advantage of reduced coupling loss and capacitance between individual components. The use of the SOA boosts the signal on-chip so as to compensate for the propagation loss. The choice of GACC filter enables us to have wide and fast tunability.;The first chapter of this dissertation is devoted to explain the basic operation principle of the GACC integrated receiver. In chapter 2 and 3, the design, fabrication, and characterization of the integrated GACC receivers with uniform coupling coefficient distributions will be discussed. A GACC receiver with 45 nm of tuning range will be presented there. In chapter 4 and 5 of the dissertation, the design, fabrication, and characterization of the integrated GACC receivers with tapered coupling coefficient distributions will be discussed. It will be shown that the side-lobe suppression ratio (SSR) can be drastically improved by tapering the coupling strength. Filters with SSRs better than that achieved by conventional GACCs will be demonstrated. An integrated receiver with a 16 dB SSR and a 40 nm tuning range will also be shown there. Finally, in chapter 6, summary of the dissertation as well as suggestions for future work will be given.