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Selected list of current projects

Optics integration by flip-chip bonding on a silicon waveguide platform
Acronym: FLIPSOI

Partners:    VTT Micronova (Coordinator), ORC

FLIPSOI (Optics integration by flip-chip bonding on a silicon waveguide platform) is a TEKES-funded project which will develop dilute nitride semiconductor optical amplifiers, mode-locked semiconductor lasers, and modulators for hybrid integration on SOI (silicon on insulator) platforms.

The main objective of this project is to develop commercially viable technologies for hybrid integration of discrete optical chips into highly functional, state-of-the-art optical modules. The target applications are mainly in optical telecommunication and short-range optical interconnections where the total data rate per optical module can reach terabits per second. The modules can be used for example in optical fiber networks, high end routers, super computers, data centres and satellites. ORC’s role in this project is related to the fabrication of active chips, i.e. lasers, amplifiers and modulators based on GaAs technology.

InGaAsN/GaAs quantum-well (QW) heterostructures will be used to build SOAs, mode-locked lasers, and EAMs operating at 1.25–1.3 μm. The III-V chips will be bonded by VTT on the SOI platform. Finally, silicon-based packaging concepts will be developed as an alternative to presently used packaging methods that dominate the total cost of most optical modules.

Project duration: 2009 - 2012

For more information, please contact Prof. Mircea Guina, mircea.guinatut.fi

Advanced III-V semiconductors for multi-junction high efficiency solar cells
Acronym: SOLAR III-V

Partners:    ORC (Coordinator), Helsinki University of Technology, University of Turku

SOLAR III-V is a consortium research project funded by the Finnish Funding Agency for Technology and Innovation (TEKES) within the framework of the Functional Materials program. The general goal of the project is the development of functional semiconductors and nano-scale epi-structures for high efficiency solar cells.
Multi-junction (MJ) III-V compound semiconductor solar cells are the prime choice for efficient harvesting of solar energy. The key to pitching the conversion efficiency at the highest attainable level rests upon the ability to fabricate monolithic semiconductor heterostructures in MJ configuration, with each of the junctions being optimized to harvest a different part of the solar spectrum.  When combined with concentrator photovoltaic (CPV) techniques, high efficiency III-V solar cells offer attractive opportunities for achieving the price target required to make solar energy competitive with traditional energy sources. The efficiency of current multi-junction cells can be increased by a more efficient conversion of the radiation band from about 0.8 eV to 1.25 eV. This is possible with the use of dilute nitride heterostructures (InGaAsN or InGaAsNSb); solar cells incorporating dilute nitrides are expected to reach efficiencies beyond 50 %. The main research topic to be addressed in SOLAR III-V is concerned with the rapid degradation of electrical and optical properties of InGaAsN as the mole fraction of [N] is increased. In parallel with improving the quality of semiconductor heterostructures, we will work on demonstrating novel solar cell concepts incorporating dilute nitrides.

Project duration: 2009 - 2012

Contact person: Prof. Mircea Guina, mircea.guinatut.fi

Academy of Finland: REDMETA - Resonance-domain metamaterials for sub-wavelength optics

Metamaterials often consist of nanoparticle arrays with periods of a few hundred nanometers. Such structures support propagating electromagnetic modes, which can be resonantly excited even when the period is smaller than wavelength in air. Under resonant conditions, these modes provide long-range coupling between the particles and can give rise to very interesting properties, such as high polarization rotation, sharp spectral features, strong local fields, and enhanced nonlinearity. Such resonance-domain metamaterials have been greatly underexploited, because today's research is focused on approaches that describe the medium by effective parameters, which are actually not valid in the presence of resonant excitation. The overall goal of the REDMETA Consortium is to develop resonance-domain metamaterials that will give rise to unprecedented and advantageous optical properties due to the interplay between the Mie-like resonances of individual particles and propagating modes of the structure.

It is expected that such metamaterials will outperform conventional ones in (i) the tunability of spectral features; (ii) the ability to form a desired local-field distribution and to use it for radiation control; and (iii) the magnitude of the optical nonlinearity. The work will be based on a close collaboration between Prof. Yuri Svirko at the Department of Physics of the University of Joensuu (coordinator), Dr. Goëry Genty at the Nonlinear Optics Group at the Department of Physics of the Tampere University of Technology, and Dr. Janne Simonen at the Optoelectronics Research Centre (ORC) of TUT.

Project duration: 2010 - 2013

Contact person: janne.simonentut.fi

ERA-NET NanoSci-E+: ACEPLAN - Active plasmonics and lossless metamaterials

Metal surfaces can support so called surface plasmons, density waves of free electrons. These plasmon waves can interact with light, opening the way to a novel area of optics, namely plasmonics. When the metal surface is nanostructured, a possibility for true nanoscale optics emerges. This work aims to alleviate or even remove the unavoidable absorption losses caused by the metal by amplifying the plasmon waves with semiconductor quantum wells and dots, thus demonstrating low-loss plasmonic components. They will be designed by novel electromagnetic simulation methods developed during the project, running on a supercomputer cluster. This approach will also be used to design and fabricate novel wide-band low-loss or even lossless metamaterials, highly promising structures with a negative refractive index that can for example slow or even stop incoming light pulses. The final aim of the project is to demonstrate applications for telecom wavelengths.

The partners of the project are Dr. Janne Simonen from ORC (coordinator), Prof. Ortwin Hess from the University of Surrey, UK, and Dr. Antonella Bogoni from CNIT, Italy.

Project duration: 2009 - 2012

Contact person: janne.simonentut.fi

Academy of Finland: A-PLAN - Active plasmonics

The post-doctoral project A-PLAN (2008-2010) concerns plasmonics, the optics of metal nanostructures. Specifically, A-PLAN aims to combine plasmon nanostructures in metallic films with quantum-regime semiconductors to achieve low-loss or lossless propagation of plasmonic waves and to enhance light emission from semiconductor devices. The semiconductor quantum well and dot substrates are grown by molecular beam epitaxy, whereas the metal nanostructures are prepared by UV-nanoimprint lithography. The project also involves detailed simulations of the plasmonic nanostructures.

Project duration: 2008- 2010

Contact person: janne.simonentut.fi

EU FP7: DeLight -- Development of low-cost technologies for the fabrication of high-performance telecommunication lasers

The DeLight project develops advanced structures and low-cost technologies, in particular nanoimprint lithography (NIL), for the fabrication of high-performance telecommunication lasers. Surface gratings a thousand times smaller than the diameter of human hair are used to generate ultra-pure light and multiple laser sections are employed to provide direct-modulation speeds of 43 Gb/s and beyond. The surface-gratings - applied in the fabrication of distributed feedback (DFB) and distributed Bragg reflector (DBR) lasers at 1.3 and 1.55 µm - are compatible with a single-sweep epitaxial growth and processing. This avoids all the fabrication complication, yield reduction, performance impairment and, ultimately, device cost increase associated with the overgrowth required in the conventional DFB/DBR semiconductor laser fabrication process. High-order photon-photon resonances, taking place in multiple longitudinal section lasers, are exploited to extend the direct modulation bandwidth far beyond the limits imposed currently by the electron-photon resonance.

The DeLight project web page: http://www.delightproject.eu/

Project duration: 2008 - 2011 (3 years)

Academy of Finland: DAUNTLESS – Development of vanguard semiconductor sources for single and entangled photon emission

The DAUNTLESS project is developing semiconductor sources targeting the cavity quantum electrodynamic (QED) strong coupling regime, which would enable the study of single and entangled photon emission. These sources are based on the strong coupling of an excitonic state with the mode of a 3D photonic cavity. Quantum dots (QDs) are the primary sources for the excitonic state, to be placed in 3D photonic cavities, which are created by etched pillars or 2D photonic crystal defects in the transverse plane and by semiconductor and hybrid distributed Bragg reflector (DBR) mirrors in the vertical direction. Selective epitaxial growth of QDs on patterned substrates and self-aligned processing are applied for placing the excitonic source close to the in-plane antinode of the 3D photonic cavity. Modulated DBRs are employed to produce 3D photonic cavities resonant both at the pump and emission wavelength.

Project duration: 2008 – 32011 (4 years)

Contact person: Mihail.Dumitrescutut.fi

European Space Agency: Development of extremely narrow-band semiconductor distributed feedback laser technology

The project target is the development of ultra-narrow-band distributed feedback (DFB) and distributed Bragg reflector (DBR) semiconductor lasers operating at 894 nm, as needed for Caesium beam atomic clocks. The DFB/DBR lasers are based on surface gratings fabricated in a single-sweep exitaxial growth and processing sequence, avoiding the problematic overgrowth used in the fabrication of the conventional buried gratings. Nanoimprint lithography is employed for defining the processing masks. The most important goals in terms of device performance improvement are higher side-mode suppression ratio, narrower linewidth and lower noise level than those of currently available conventional DFB/DBR laser devices. Lower fabrication costs, reduced performance drift in time and increased reliability are also targeted.

Project duration: 2008 – 2010 (2 years)

Contact person: Mihail.Dumitrescutut.fi