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Opening up more laser potential

Finland’s cradle of photonics, the Optoelectronics Research Centre, concentrates on two key areas: semiconductor physics and technology, and ultra-fast laser optics. It has been particularly active in commercialising the results of its research, with a number of spin-offs launched over the years.
Optoelectronics Research Centre

Based at the Tampere University of Technology (TUT), the Optoelectronics Research Centre (ORC ) has operated there since 1999. Employing around 65 researchers and associates, it is one of the best-equipped academic research units in Finland and the largest university-based research centre in Europe in the field of molecular beam epitaxy (MBE) crystal growth technology, with six commercial MBE reactors and comprehensive optoelectronic device processing and characterisation facilities.

ORC is currently involved in running more than 25 national and international research projects with around 50 universities and companies worldwide. The Centre has been very successful in achieving innovative scientific results, developing new technologies, and transferring know-how to industry – and has played a seminal role in creating a laser manufacturing industry in Finland.

ORC established a service centre and industry network in 2004. Now known as Laser Competence Centre Finland, this initiative is designed to strengthen the position of its members in R&D related to photonics applications by building a critical mass of equipment and expertise.

Core expertise

Much of ORC’s recent work has been concerned with high-power vertical external cavity surface emitting lasers (VECSELs) for high-power applications.

ORC ’s core activity is to study and develop novel epitaxial compound semiconductor heterostructures using MBE for crystal growth, light emitting and light modulation devices, and ultra-short-pulse high-power fibre lasers. It also develops ‘cold’ ablation and thin-film deposition methods based on the use of ultra-fast fibre lasers.

Much of its recent work has been concerned with high-power vertical external cavity surface emitting lasers (VECSELs) for high-power applications, and the development of UV nanoimprint lithography (NIL) for fabricating sub-100 nm surface structures cost-effectively for nanophotonic components.

Major international projects

One of ORC ’s recent research successes was the three-year NATAL project funded by the European Commission under the EU’s Sixth Framework Programme, and which focused on developing photonic nanomaterials and technologies for visible light generation.

The project was coordinated by ORC and was carried out as a joint effort between some of Europe’s leading academic institutions and industrial partners in the field of photonics, and driven by novel semiconductor gain material grown by ORC and the Technical University of Berlin.

The key technology used was Optically-Pumped Semiconductor Vertical External Cavity Surface-Emitting Semiconductor Lasers (OPS-VECSEL). These exciting new lasers combine many of the advantages of conventional diode-pumped solid-state lasers with the flexibility of semiconductor gain material.

Blue laser diodes were used for the first time ever for the direct optical pumping of red SDL material, highlighting new potential for the development of compact and powerful lasers with emission in both the visible and UV spectrum. Many of the highlights of the project related to the development of new quantum well- and quantum dot-based thin-disk laser gain materials.

NATAL achieved breakthrough results in the fabrication of novel compound semiconductor materials application, new laser architectures, and new operation wavelengths. QD VECSELs were demonstrated for the first time, and this technology is now being pursued within the FAST-DOT project.

The most important impact on the commercialisation of VECSEL technologies is expected to be made by OSRAM, which is working on VECSEL-based technology for low-power RGB projection. Finnishbased EpiCrystals, an ORC spin-off, has also entered the commercial field with its proprietary DeCIBEL technology, a complementary platform.

Other recent FP6 projects include URANUS, again coordinated by ORC , which concentrated on ultra-fast technology for multicolour compact highpower fibre systems; and DELILA, which focused on developing lithography technology for the nanoscale structuring of materials using laser beam interference.

High-performance lasers for telecommunications

Nanoimprint lithography (NIL) is a particularly exciting area of technology, as it can already be used to fabricate any type of nanophtonic surface relief and looks set to become a cost-effective mass-production method.

It is this potential that is now being addressed by the ORC -coordinated DeLight project, aimed at developing advanced structures and low-cost technologies for the fabrication of high-performance telecommunication lasers operating at 1.3 and 1.55 μm, with a particular emphasis on NIL.

ORC is working with the University of Kassel, the University of W├╝rzburg, Politecnico di Torino, the Israel Institute of Technology, Wroclaw University of Technology, the Alcatel-Thales III-V Lab, and two companies, Finnish-based ORC spin-off Modulight Inc., and German-based MergeOptics. The project is being funded under the EU’s Seventh Framework Programme and will run for three years from September 2008.

The aim is to create a common technological fabrication platform for both high-performance, surface grating-based DFB/DBR telecommunications lasers and ultra-high-speed directly modulated lasers. The surface-oriented technology used in the project is largely independent of the underlying semiconductor structure and will be used for fabricating InP- and GaAs-based edge-emitting lasers (EELs).

> Pekka Savolainen
(Published in HighTech Finland 2009)