We demonstrate 10Gbit/s operation of two different types of monolithic photocurrent driven wavelength converters (PD-WC). These photonic integrated circuits use a Semiconductor Optical Amplifier (SOA)-PIN photodetector receiver to drive an Electro-absorption (EA), or Mach-Zehnder (MZ) modulator that is integrated with a SGDBR tunable laser. We demonstrate improvements in optical bandwidth, insertion losses, device gain, and modulation efficiency.
The evolution of optical communication systems has facilitated the required bandwidth to meet the increasing data rate demands. However, as the peripheral technologies have progressed to meet the requirements of advanced systems, an abundance of viable solutions and products have emerged. The finite market for these products will inevitably force a paradigm shift upon the communications industry. Monolithic integration is a key technology that will facilitate this
shift as it will provide solutions at low cost with reduced power dissipation and foot-print in the form of highly functional optical components based on photonic integrated circuits (PICs). In this manuscript, we discuss the advantages, potential applications, and challenges of photonic integration. After a brief overview of various integration techniques, we present our novel approaches to increase the performance of the individual components comprising highly functional PICs.
Wavelength converters are seen as important to the scalability, flexibility, and cost of future optical networks. These devices have opportunities for deployment in optical switches, routers and add/drop multiplexers. This talk will outline the latest results of monolithic and hybrid photocurrent-driven wavelength converters (PD-WC) based on either the direct modulation of a bipolar cascade SGDBR laser or by external modulation using an Electro-absorption (EA), or Mach-Zehnder (MZ) modulator using integration building blocks such as a semiconductor optical amplifiers (SOA), SGDBR lasers, PIN detectors and EA and MZ modulators. As the input and output waveguides are separate in this configuration of wavelength converter, an optical filter is not required to reject the input signal at the output which is desirable particularly with wavelength tunable applications where the response time of a filter could limit system performance.
In this work, we describe tunable wavelength converters based on a photodiode receiver integrated with a tunable laser transmitter. Devices are fabricated on a robust InP ridge/InGaAsP waveguide platform. The photodiode receiver consists of an integrated SOA pre-amplifier and a PIN diode to improve sensitivity. The laser transmitter consists of a 1550 nm widely tunable SGDBR laser modulated either directly or via an integrated modulator outside the laser cavity. An SOA post-amplifier provides high output power. The integrated device allows signal monitoring, transmits at 2.5 GB/s, and removes the requirements for filtering the input wavelength at the output. Integrating the SGDBR yields a compact wavelength agile source that requires only two fiber connections, and no off-chip high speed electrical connections. Analog and digital performance of directly and externally modulated wavelength converters is also described.
The Sampled-Grating Distributed-Bragg-Reflector laser(SGDBR) provides wide tunability (>40nm), and high output power (>10mW). Driven by the demand for network reconfigurability and ease of implementation, the SGDBR has moved from the research lab to be commercially viable in the marketplace. The SGDBR is most often implemented using an offset-quantum well epitaxial structure in which the quantum wells are etched off in the passive sections. Alternatively, quantum well intermixing has been used recently to achieve the same goal - resulting in improved optical gain and the potential for multiple bandgaps along the device structure. These epitaxial "platforms" provide the basis for more exotic opto-electronic device functionality exhibiting low chirp for digital applications and enhanced linearity for analog applications. This talk will cover state-of-the-art opto-electronic devices based on the SGDBR platform including: integrated Mach-Zehnder modulators, and integrated electro-absorption modulators.
The fabrication and performance of selectively oxidized 850 nm vertical cavity surface emitting laser (VCSEL) diodes which emit through transparent GaP substrates is reported. Emission through the substrate is advantageous for many VCSEL configurations, such as for the incorporation of optical elements in the substrate or flip-chip integration to microelectronic circuitry. The short wavelength bottom- emitting VCSELs are fabricated by wafer fusion using an inert gas low temperature annealing process. The electrical characteristics of n- and p-type GaAs/GaAs and GaAs/GaP wafer bonded interfaces have been examined to optimize the annealing temperature. A significant reduction of the current-voltage characteristics of the VCSELs bonded to GaP substrates has been achieved whereby the bottom-emitting VCSELs show similar threshold voltage as compared to top- emitting lasers.