| Integration of three generic types of optical functions (light generation or amplification, light guiding or coupling, and light detection) has been demonstrated using asymmetric twin-waveguide (ATG) technology. In this integration scheme, different optical functions are performed in different, separately optimized, and vertically displaced waveguides, while light is then transferred between the waveguides via lateral adiabatic taper couplers defined by photolithography.; The primary virtue of the ATG scheme is that it eliminates the need for material regrowth or any post-growth modification to the epitaxial structure to achieve the separate device functionalities, thereby leading to high yield and low cost. Furthermore, this "platform" integration scheme shares several similarities with the electronic CMOS platform in that both schemes are based on a standard library of devices, computer aided design (CAD), and a common and tolerant package design for all devices. Like CMOS, ATG technology allows for the realization of a wide variety of photonic integrated circuit (PIC) functionalities using universal epitaxial structures and standard fabrication techniques.; In this work, light transfer process between different waveguides was analyzed using perturbation and coupled local mode theories. A design algorithm of the adiabatic taper couplers was obtained based on the analysis of the light coupling process. Moreover, general design rules of the ATG-based devices were proposed.; Using the ATG scheme, a variety of long wavelength optical receivers were demonstrated in InGaAsP/InP material system, including the ATG-based p-i-n photodiode, avalanche photodiode, semiconductor optical amplifier (SOA) coupled to a p-i-n photodiode, and coherent heterodyne receiver. The coherent heterodyne receiver is the most complex PIC demonstrated to date using the ATG technology. In this receiver chip, light guiding and coupling components (the input fiber waveguide and multi-mode interference coupler), light generation and amplification components (the distributed Bragg reflector laser and SOA), and light detection components (a pair of balanced waveguide photodiodes) were monolithically integrated using separately optimized materials without regrowth. A 3GHz frequency modulated coherent optical link was also constructed using this chip along with a wideband rectifier narrowband amplifier (WIRNA) receiver. |
