School of Information and Communication Technology (ICT) at Kungliga Tekniska Högskolan (KTH) is vertically integrated to cover a range of activities from quantum optics and materials science over photonic devices to design of complex electronic systems. By concentrating available microelectronics, optics and photonics research resources, KTH has been positioning itself amongst the internationally leading universities in industrially relevant as well as academic speculative research in microelectronics and photonics. As a joint effort with Acreo, ICT also participates in the Kista Photonic Research Center (KPRC). The school has a number of well-equipped diagnostics laboratories with resources for both physical and electrical analyses of materials and devices, and access to the Electrum Laboratory, with more than 1000 square meter clean room area and extensive resources for processing of electronic and photonic devices and circuits based on silicon, gallium arsenide, and indium phosphide.
The participation in the HECTO project is conducted by the Laboratory of Photonics and Microwave Engineering (FMI), which is a unit within ICT. FMI has been active in several EU projects and cooperates with leading universities all over the world, as well as with electronics and telecommunications companies. The research of FMI spans over a wide spectrum from basic physics, such as electron waveguide physics and devices, to electronic and photonic devices, and fiber-optical transmission systems and networks. Current research projects treated by FMI are, among others, intersubband modulators, modelling, design and characterization of semiconductor lasers, photonic crystal devices, photonic integrated circuits, photonic systems, and design, modelling and characterization of travelling-wave electroabsorption modulators (TWEAM). The TWEAM project started around 1997/1998 benefiting from FMI's know-how in research and development on semiconductor lasers and InP-HBT based monolithically integrated optoelectronic receivers (OEIC) for fiber-optical communications. On the basis of such an expertise in InP process technology and high-frequency optoelectronic device design and characterization, FMI's first TWEAM with almost record high bandwidth was presented in 2001 (see PTL, July 2002, pp. 923-925). Two years later, after a very fruitful collaboration with Optillion AB, what is believed to be the world's fastest light intensity modulator was presented (see OFC'03, PD38), with a 3dB-bandwidth that was estimated to be ca 90GHz. Later investigations of other individual chips have resulted in bandwidths of ca 100GHz. This TWEAM relies on an innovative design approach providing ultra-high bandwidth at device impedance levels on the order of 30-50Ohm. The latter property becomes very important when connecting the modulator to a signal source, i.e., the electrical driver. Based on these results, one of FMI's concrete goals is to improve the TWEAM performance even further by optimizing the microwave design and improving the design of the optical waveguide. Simulations indicate that the drive voltage for 100GHz 3dB electrical bandwidth designs can be reduced from ca 3V for 10dB optical extinction ratio to less than 2V, and that designs with >150GHz bandwidth should require less than 3V drive voltage. These designs are expected to be suitable for use in transmitters in the range of 100-160Gbit/s.
FMI manages the Photonic Systems Measurement Laboratory at KTH/IMIT with access to a 50Gbit/s NRZ bit-error rate test set, vector network analyzers up to 60GHz, electrical sampling oscilloscopes with bandwidths up to 50GHz, electrical spectrum analyzers up to 50GHz, electrical signal source and power detection up to 110GHz, HF probe stations, optics tables, a 800GHz bandwidth optical sampling oscilloscope (Terascope) and several optical spectrum analyzers.
This collection of equipment is essential for FMI to reach the results defined by the HECTO proposal. Currently, the personnel at FMI, with long-term experience in high-speed electronics and photonics and especially in research on high-speed modulators, is ready to continue with future modulator development and to make use of the highly sophisticated characterization equipment.