Photo Hybrid Architecture based on two- and three-dimensional silicon photonic crystals

Project Information

PHAT

Grant agreement ID: 510162

Start date 4 June 2004

End date

Funded under

• Information Society Technologies: thematic priority under the specific programme "Integrating and strengthening the European research area" (2002-2006).

Total cost € 1 986 748,00

EU contribution € 1 498 250,00

Coordinated by

UNIVERSITY COLLEGE CORK - NATIONAL UNIVERSITY OF IRELAND, CORK
Ireland

Exploitable results

One step closer to photonic transistors for faster and faster computers

The project 'Photonic hybrid architectures based on two- and three-dimensional silicon photonic crystals' (PHAT) started on January 1st, 2004 with the following key objective: - To combine two complementary approaches, namely 2D Si-based PhCs and 3D Si-based PhCs templated on self-assembled matrices, to design, fabricate, characterise, study and model hybrid 2D-3D PhC platforms (architectures), offering routing and light emission functions on the same 'chip'. Thus to meet the key objective our approach has been to carry out a focused study of (a) materials and nanofabrication methods, with inherent high versatility, manufacturability and efficiency and (b) two key functionalities to test the integration of 2D and 3D PhCs. Work towards electrical connections for electroluminescence was not carried out as this aim was foreseen too ambitious after the first year. One of the components to be coupled, the 2D photonic crystal waveguide, was changed to a ridge waveguide also at the end of the first year of the project after a comprehensive study of the modelling and fabrication options. The consortium carried out work on material synthesis, crystallisation on patterned substrates, emission properties, waveguides, modelling and investigated several integration strategies. For the photonic crystal functionality the 3D photonic crystal had to be inverted in order to provide a suitable environment, i.e., a full photonic bandgap, for enhanced emission, furthermore the emitting centres had to be incorporated in the presence of a well-designed defect. Finally the 3D photonic crystal emitter and waveguide had to be integrated in a configuration which guaranteed efficient coupling while at the same time remained manufacturable. At the end of the project the main achievements were: 1. The preparation of silica and polymer beads of characteristics suitable for crystallisation of high quality 3D colloidal photonic crystals for work both in the visible and in the near infrared. This work included preparing silica beads of approximate 900 nm diameters as well as tailored polymer beads containing UV sensitive polymers for optical defect inscription. 2. The conditions for crystallisation of these size range beads on flat and patterned substrates were determined and opal 3D photonic crystals, suitable for inversion, were obtained and some of them inverted. In particular, with the aid of simulations it was found out that larger basins resulted in structures with a stronger confined electromagnetic radiation, thus minimising leakage to the substrate. In the crystallisation research, a successful correlation between stochastic resonance theory and experiment concerning the acoustic vibration-assisted vertical (AVAV) drawing deposition for silica opals was established. Furthermore, the work on sedimentation in basins based on capillary filling yielded know-how that has been patented. 3. Spectroscopic methods have been developed which allow the understanding of optical processes as well as characterisation of the optical quality of the inversion process. The latter has been interpreted as a 3D graded PhC. These structures in device-relevant configurations with light coupled through ridge and strip waveguides have been characterised, probably for the first time. 4. The theory and simulation work showed that it is possible to couple efficiently the light emitted from a source within an inverse opal structure to both PhC and bulk output waveguides. This research also pointed out the challenges in using transmission measurements to characterise the coupling. 5. Light coupling from ridge waveguides to direct and inverted direct opals by both transmission and internal light source experiments was demonstrated. The transmission spectrum for a polycrystalline direct opal showed several partial gaps. The signature of the photonic bandgap in an inverted opal is 8dB deep and 20 nm wide in the transmission spectrum. 6. Concerning the realisation of a defect in a 3D photonic crystal to use it as an efficient light source, the patterning of 2D defect layers in PMMA opals is now a well controlled and highly reproducible depending only on the crystalline quality of the opal, which was significantly enhanced by the acoustic vibration assisted growth. Deterministic buried defects have been realised. 7. Other integration strategies were explored and among the main results of these are: - We succeeded in sedimenting a 3D PhC around 2D PhC waveguides and around silicon line defects. Transmission measurements indicated that the suspended waveguides are intact. Moreover, a quality factor of 1700 was measured for a L3 cavity surrounded with a direct opal. The Al2O3 cladding makes opal inversion possible without clogging the PhC holes. - We designed and fabricated simple SOI based photonic structures integrating strip waveguides and 3D PhC opal. These structures where modelled and both experimental and calculated results are in agreement. The intentions for use and impact of the PHAT results are mainly in the area of optoelectronic integration of miniature components using existing Si fabrication methods combined with cost-efficient self-organisation techniques. The know-how gained has shown that the methods developed are suitable for a whole range of micro and nanosystems which combine silicon platforms and microfluidics. It is expected that the impact will therefore be also in the field of nano-biotechnology. Moreover, it is expected that the results of PHAT will impact not only academic research but contribute to the basis of future photonic platforms in the context of heterogeneous integration. The compliance with the scientific and technical deliverables was normally on target with minor delays due to a fire in the VTT room, but rapidly sorted out by outsourcing some of the fabrication steps. Other delays in the last reporting period were due to the building work taking place at NMRC, which reduced the useful working time for spectroscopy and electron beam lithography by nearly 40 % due to vibrations in the last year. However, these delays were dealt with appropriately and there was no impact on the deliverable schedule. In addition to the results reported above the output of the project can be summarised as follows: - 20 published papers, 17 in press, 3 papers submitted and 5 in preparation, - 39 presentations at meetings and or conferences, of which 9 were international invited talks (1 plenary talk) - 1 patent was filed.