The objective of this project is to develop monolithic integrated optical components and to assess the potential for this technology to yield high performance, manufacturable components, to be used in future subscriber and customer access systems of the IBC network.
The aim is to group, on each of these components, at least two basic optical functions. Specifications for these components will be taken from the requirements of RACE projects R1010 and R1012, both of which deal with optical systems.
The objective of the research was to develop monolithic integrated optical components and to assess the potential of this technology to yield high performance manufacturable components, to be used in future subscriber and customer access systems of the integrated broadband communications (IBC) network. The aim was to group at least 2 basic optical functions on eachcomponent.
Key issues in the research included:
the identification of system requirements;
the compatibility of manufacturing technologies;
the design, fabrication and testing of components;
system testing of components;
The research started with an initial definition of a set of requirements, followed by experimental work on first basic and integral structures. Ridge type 15 micron distributed feedback (DFB) and Fabry-Perot (FP) laser diodes and basic amplifier structures have been fabricated. A process for efficiently butt coupling these structures to low loss waveguides has been devised.
Three basic switch structures have been selected and modelled;
the passive Y type;
total internal reflection type;
directional coupler type.
Wavelength division multiplexing (WDM) chip waveguide material structures have been designed and evaluated. Holographic gratings for use in WDM couplers have been fabricated.
Integration with passive waveguides has been demonstrated for monitor photodiodes, optical switches, optical amplifiers, laser diodes and WDM couplers. These structures have been optimized for mutual onchip integration.
The chosen approach is structured as four hierarchical phases. During the first phase, the basic optical functions to be developed were studied in terms of the requirements expressed by the system projects. These included such functions as an optical amplifier, an optical switch, a laser diode, a photo-diode with a waveguide or a wavelength division multiplex unit. The project considered whether the technologies necessary to manufacture these individual components are compatible within a common process. This comparative evaluation of technologies continued in later phases of the project.
During the second phase, all the basic optical components have been designed, fabricated and tested. In the third phase, the results of the two previous phases are used to develop a set of four integrated components. These are to be:
. an optical amplifier with an optical switch
. a laser diode with an optical switch
. a laser diode with photo-diode and a waveguide
. a wavelength division multiplex unit with a laser diode.
The fourth and final phase will be dedicated to testing the developed components and assessing their conformance with the techno-economic requirements of system manufacturers.
. Identification of system requirements.
. Compatibility of manufacturing technologies.
. Design, fabrication and test of components.
. System test of components.
. Techno-economic considerations.
The project started with an initial definition of a set of requirements, followed by experimental work on first basic and integral structures. Ridge type 1.5 micron DFB and FP laser diodes and first basic amplifier structures have been fabricated. A process for efficiently butt coupling these structures to low-loss waveguides has been devised, and the coupling has been achieved by both the LPE and the MOVPE technique. First monitor photo-diodes have been made using the ridge waveguide structure operating under reverse bias, and a sensitivity of 0.34 A/W has been achieved.
Three basic switch structures have been selected and modelled, the passive Y type, total internal reflection type, and directional coupler type. Directional coupler switches making use of the free carrier plasma effect were fabricated and operated at an extremely low switching current of 4 mA, the lowest value reported today.
WDM chip waveguide material structures have been designed and evaluated. Holographic gratings for use in WDM couplers have been fabricated.
Integration with passive waveguides has been demonstrated for monitor photo-diodes, optical switches, optical amplifiers, laser-diodes and WDM couplers. These structures have been optimised for mutual on-chip integration.
The project contributes significantly to establishing the InP-based integrated optics technology, which is considered a key technology for the cost-effective implementation of customer access systems in optical communication networks.