In this paper we report on the progress in the development of modelocked ring lasers that are integrated on a single chip in the InP/InGaAsP material system. With the current optical integration technology it is possible to integrate quantum well optical amplifiers, phase modulators and passive optical components such as waveguides, splitters and spectral filters as standardized building blocks on a single chip. Using such standardized components a number of passively modelocked ring laser devices have been realized in a standardized fabrication process. Results from a few of these devices are presented here. We have observed a record width of the frequency comb from a modelocked quantum well ring laser operating at a 20 GHz repetition rate. The optical coherent comb is centered around 1542 nm and has a 3 dB bandwidth of 11.5 nm. A minimum pulse width of 900 fs was observed. A second device that is highlighted is a modelocked ring laser with a 2.5 GHz repetition rate. Its 33 mm long cavity is fitted onto a chip of 2.2x1.9 mm2. One of the goals of this work is to make such designs available in device libraries for use in more complex integrated optical systems using standardized technology platforms.
Application Specific Photonic Integrated Circuits (ASPICs) are considered key elements to make photonic systems or subsystems cheap and ubiquitous. ASPICs still are several orders of magnitude more expensive than their microelectronic counterpart: ASICS, which has restricted their application to a few niche markets. A novel approach in photonic integration is emerging that will reduce the R&D costs of ASPICs by more than an order of magnitude. It will bring the application of ASPICs that integrate complex and advanced photonic functionality on a single chip within reach for a large number of small and larger companies and initiate a breakthrough in the application of Photonic ICs. In this paper the process is explained. A significant number of designs has been realized the last 4 years, for a variety of applications in telecoms, datacoms, medical and sensing, from parties all over the world.
We have investigated the potential of asymmetric current injection for polarization switching in GaAs-based intra-cavity contacted vertical cavity surface emitting lasers using two sets of p- and n-contacts per device. We simulated the current paths in both symmetric and asymmetric contacted devices. A large lateral current component is present in the asymmetric case; this induces a certain anisotropy in comparison to the symmetric case, possibly able to stabilize the polarization in one direction. Intra-cavity devices are processed on a standard air-post VCSEL wafer. When using the contacts set along the [1-10] direction, the polarization was set along  while using the contacts along  the polarization switches from the direction along  to a direction making an angle of 25° to 90° towards . This peculiar result can be explained by the fact that the used VCSEL structure is not designed for intra-cavity contacting.