Mid-IR Technology: Project brings ‘CLARITY’ to mid-IR optoelectronic devices

Twenty years after the invention of quantum cascade lasers (QCLs) in 1994, the interest in mid-infrared applications has reached a new level. Among others, mid-IR wavelengths have been used in optical communication, tunable laser spectroscopy, and most recently also in microscopy exhibiting substantial benefits in transmittance and sensitivity with respect to the broadly used light in the visible or near-infrared. Despite the huge progress, mid-infrared technology has not yet reached the same level of maturity as its near infrared counterparts due to the lack of efficient broadband detectors and the difficulty in fabricating fully integrated optoelectronic components in this wavelength range.

The recently finished European Union-funded research project CLARITY (Compact uLtrA-efficient mid-infRared photonIc sysTems based on low noise quantum cascade laser sources, wide band frequencY converters and near infrared photodetectors) has managed to address many of the weaknesses of mid-IR technology working in parallel in fundamental and engineering issues.

SiGe photonic integrated platform for mid-IR applications.

The continuously increasing interest in silicon photonics inspired the CLARITY consortium to investigate CMOS compatible technologies for the mid-infrared aiming at the development of devices such as integrated multiplexers, couplers, splitters, and the investigation of non-linear behavior. The nonlinear activities focused on mid-IR to near-IR wavelength conversion which was one of the most prevailing goals of the project manifesting as a potential solution for filling the gap of inefficient mid-IR detectors.

CLARITY strategically invested on a SiGe-platform due to its inherent advantage in achieving efficient coupling with QCLs and the flexibility it offers for proper dispersion engineering. In the context of CLARITY, a wide range of devices were designed by National and Kapodistrian University of Athens and CEA-LETI, fabricated by CEA-LETI, and characterized by University of Southampton and Technical University Darmstadt demonstrating mid-IR to near-IR wavelength conversion, broadband supercontinuum generation, and the successful fabrication of multi-functional CMOS compatible chips which set the basis for the mid-term implementation of smart lab-on-a-chip systems. 

Low loss highly nonlinear telluride fibers in the mid-IR Tellurite glass is a highly nonlinear, highly transparent mid-infrared glass material, however its absorption peak of the OH fundamental vibration is located in the range between 3-4 µm. Reducing the OH impurity level is critical when considering the use of tellurite glass optical fibers for nonlinear applications in the 2-5 µm wavelength region. Within the CLARITY project, the Optoelectronics Research Centre at the University of Southampton demonstrated a reduction in the OH-induced loss at 3.4 µm down to 10 dB/m in an optical fiber. On the basis of this result, within the CLARITY project different small-core fiber samples were fabricated and proved their potential for non-linear applications above 2 μm.

Calming the noise of QCL sources

Low intensity noise performance of mid-infrared emitting quantum cascade lasers is indispensable for many sensing applications. The CLARITY members National and Kapodistrian University of Athens and Technical University Darmstadt (TUD) have pursued two strategies to achieve an improvement of this important key performance of lasers. Injection-locking has been realized below and near threshold of a free running slave laser, resulting in efficient low-noise operation. A direct absorption experiment of carbon monoxide at 2193 cm-1 exploiting the detectivity improvement potential of an intensity-noise reduced DFB laser was carried out at TUD. Under optimum intensity noise reduction conditions a 30% lower detection limit has been achieved in comparison to the free-running case.

Mid-infrared multi-λ laser-source

III-V Lab in collaboration with CEA-LETI managed to design and fabricate a monolithic integrated multi-λ source consisting of fifteen lasers emitting from 2220 cm-1 to 2320 cm-1 which was assembled to a SiGe wavelength multiplexer. The large tunability allows the detection of several molecules with narrow absorption features (like carbon monoxide and carbon dioxide) or one complex molecule with a broad absorption profile (e.g. heavier carbohydrates). Norsk Elektro Optikk has designed a new laser driver with excellent noise properties that is able to drive single-QCLs and arrays of QCLs. 

The CLARITY project started in September 2011 and ended in February 2015; for more information see www.clarity-project.eu or contact the project coordinator:

Professor Dimitris Syvridis
Optical Communications Laboratory 
National and Kapodistrian 
University of Athens 
Dept. of Informatics and Telecommunications 
Panepistimiopolis, 
Ilissia, Athens 15784, 
Greece 

Tel: +30 210 727 5322 
Fax: +30 210 727 5333 
Email: dsyvridi@di.uoa.gr 

Significant publications

• C. Juretza, H. Simos, A. Bogris, D. Syvridis, W. Elsaesser, M. Carras, “Intensity Noise Properties of Mid-Infrared Injection Locked Quantum Cascade Lasers: II. Experiments,â€? IEEE Journal of Quantum Electronics, Volume 51, Issue 1 (January 2015)

• M. A. Ettabib, L. Xu, A. Bogris, A. Kapsalis, M. Belal, E. Lorent, P. Labeye, S. Nicoletti, K. Hammani, D. Syvridis, J.H.V. Price, D. J. Richardson, and P. Petropoulos, “Telecom to Mid-infrared Supercontinuum Generation in a Silicon Germanium Waveguideâ€?, OFC 2015, Los Angeles, paper Tu2C.5.

• F. Michel, C. Juretzka, M. Carras and W. Elsäßer, “30% improvement in absorption spectroscopy detectivity achieved by the detuned loading of a quantum cascade laserâ€?, Optics Letters, Vol. 39, Issue 21, pp. 6351-6354 (2014)

• K. Hammani, M. A. Ettabib, A. Bogris, A. Kapsalis, D. Syvridis, M. Brun, P. Labeye, S. Nicoletti, and P. Petropoulos, “Towards nonlinear conversion from mid- to near-infrared wavelengths using Silicon Germanium waveguides,â€? Optics Express, Vol. 22, Issue 8, pp. 9667-9674 (2014).

• M. Brun, P. Labeye, G. Grand, J. M. Hartmann, F. Boulila, M. Carras, and S. Nicoletti, “Low loss SiGe graded index waveguides for mid-IR applications,â€? Optics Express, Vol. 22, Issue 1, pp. 508-518 (2014).

• X. Feng, J. Shi, M. Segura, N. M. White, P. Kannan, W. H. Loh, L. Calvez, X. Zhang, and L. Brilland, “Halo-tellurite glass fiber with low OH content for 2-5µm mid-infrared nonlinear applications,â€? Optics Express, Vol. 21, Issue 16, pp. 18949-18954 (2013)

• M. Carras, G. Maisons, B. Simozrag, V. Trinité, M. Brun, G. Grand, P. Labeye, S. Nicoletti, "Monolithic tunable single source in the mid-IR for spectroscopy", SPIE Photonics West, Anaheim, USA, Session 7:III-V on Si Integration, p.8631-34, invited paper