Quantum Cascade Lasers (QCLs) represent a fundamentally new class of semiconductor lasers that are capable of generating light in the mid- to longwave infrared portions of the spectrum, generally between 4 and 12 microns. Having no serious competition from other solid state light sources in this spectral window in wavelength agility, optical power, and size/weight, QCLs further existing applications and enable new ones in fields as diverse as spectroscopy, free space optical communications, and directed infrared countermeasures and other security areas.
QCLs are typically fabricated from the same materials and using the same technologies as the traditional diode lasers. However, while diode lasers rely on electron-hole recombination across the bandgap of their materials, which then determines their emission wavelength, QCLs are unipolar devices, generating light through radiative transitions of electrons between engineered quantum states entirely within the conduction band. This property opens an entirely new realm of laser design, the so-called band structure engineering, where laser designers can tailor the wavelength of a QCL to a particular application.
Since their first demonstration in 1994 [1], QCLs have undergone rapid progress. In output power, the progress was marked by first operation at room temperature in (1996) [2], first operation in continuous wave at room temperature (CW/RT) in 2001 [3], and by exceeding 1W CW/RT level in 2008 [4, 5]. From the spectral standpoint, notable milestones are the first distributed feedback (DFB) QCL in 1997 [6], first broadly and continuously tunable external cavity (EC) QCL in 2004 [7], and first high power CW/RT EC QCL in (2006) [8].
However, until recently, QCLs remained no more than a laboratory curiosity, being sold basically as kits that made them effectively inaccessible to the non-specialist market. This, coupled with generally low device performance, precluded widespread acceptance of QCLs in real-world applications. Recognizing the existence of this “accessibility gap”, Pranalytica’s first contribution to the QCL field was the development of an industrial mounting and thermal management technology [9]. Our approach provides a high performance and high reliability solution to the problem of efficient system integration of QCLs.
Today, Pranalytica is a vertically integrated QCL company, specializing in high power QCL devices and systems. For many applications, output power is the main figure of merit. To address this need, Pranalytica begins with its own proprietary QCL designs that specifically target high power, high temperature operation. Our QCLs are fabricated in state-of-the-art facilities using the best available technologies. Pranalytica then applies its proprietary packaging and thermal management solutions to fully extract the available device performance and to provide well-characterized and reliable products that can be easily integrated into real world systems. Our unique ability to handle the extreme demands of high power, continuous wave, room temperature QCL sets us apart from our competition. In fact, Pranalytica is the first and so far the only manufacturer to commercially offer fully packaged QCL devices and complete laser systems that exceed 2W CW/RT output power.
Another area of specialization for Pranalytica is broadly and continuously tunable QCL systems. This area grew out of the needs of Pranalytica’s gas sensing business. Using external grating cavity geometry, Pranalytica has demonstrated spectroscopic quality tunable QCL sources at multiple wavelengths between 4 and 12 microns [8, 10, 11, 12].
Finally, a very important aspect of bridging the “accessibility gap” is a well-designed set of support electronics. Pranalytica designs and manufactures fully integrated QCL controllers. By incorporating all the necessary functions of QCL temperature control, bias current supply and conditioning, and QCL protection, our controllers hide the significant complexity of properly operating high power QCLs from the end user. By removing the need for the users to learn the intricacies of QCL operation, our system enable them to concentrate on what they really want to do – to use these revolutionary new infrared light sources to open new frontiers in their respective fields of science and engineering.
REFERENCES
[1] J. Faist, F. Capasso, D. L. Sivco, C. Sirtori, A. L. Hutchinson, and A. Y. Cho "Quantum Cascade Laser", Science, 264, 553, (1994).
[2] Jérôme Faist, Federico Capasso, Carlo Sirtori, Deborah L. Sivco, James N. Baillargeon, Albert L. Hutchinson, Sung-Nee G. Chu, and Alfred Y. Cho, "High power mid-infrared (~ 5 µm) quantum cascade lasers operating above room temperature", Appl. Phys. Lett. 68, 3680 (1996).
[3] Mattias Beck, Daniel Hofstetter, Thierry Aellen, Jérôme Faist, Ursula Oesterle, Marc Ilegems, Emilio Gini, and Hans Melchior, "Continuous-wave operation of a mid-infrared semiconductor laser at room-temperature", Science 295, 301 (2002).
[4] Y. Bai, S. R. Darvish, S. Slivken, W. Zhang, A. Evans, J. Nguyen, and M. Razeghi, "Room temperature continuous wave operation of quantum cascade lasers with watt-level optical power", Appl. Phys. Lett. 92, 101105 (2008).
[5] A. Lyakh, C. Pflügl, L. Diehl, Q. J. Wang, Federico Capasso, X. J. Wang, J. Y. Fan, T. Tanbun-Ek, R. Maulini, A. Tsekoun, R. Go, and C. Kumar N. Patel, "1.6 W high wall plug efficiency, continuous-wave room temperature quantum cascade laser emitting at 4.6 µm", Appl. Phys. Lett. 92, 111110 (2008).
[6] Jérome Faist, Claire Gmachl, Federico Capasso, Carlo Sirtori, Deborah L. Sivco, James N. Baillargeon, and Alfred Y. Cho, "Distributed feedback quantum cascade lasers", Appl. Phys. Lett. 70, 2670 (1997).
[7] R. Maulini, M. Beck, J. Faist, and E. Gini, "Broadband tuning of external cavity bound-to-continuum quantum-cascade lasers", Appl. Phys. Lett. 84, 1659 (2004).
[8] Michael Pushkarsky, Alexei Tsekoun, Ilya G. Dunayevskiy, Rowel Go and C. Kumar N. Patel, "Sub-parts-per-billion level detection of NO2 using room temperature quantum-cascade lasers", Proc. Natl. Acad. Sci. USA 103, 10846 (2006).
[9] Alexei Tsekoun, Rowel Go, Michael Pushkarsky, Manijeh Razeghi and C. Kumar N. Patel, "Improved performance of quantum cascade lasers through a scalable, manufacturable epitaxial-side-down mounting process", Proc. Natl. Acad. Sci. USA 103, 4831 (2006).
[10] Michael B. Pushkarsky, Ilya G. Dunayevskiy, Manu Prasanna, Alexei G. Tsekoun, Rowel Go, and C. Kumar N. Patel, "High-sensitivity detection of TNT", Proc. Natl. Acad. Sci. USA 103, 19630 (2006).
[11] I. Dunayevskiy, A. Tsekoun, M. Prasanna, R. Go, and C. K. N. Patel, "High-sensitivity detection of triacetone triperoxide (TATP) and its precursor acetone", Appl. Opt. 46, 6397 (2007).
[12] A. Mukherjee, I. Dunayevskiy, M. Prasanna, R. Go, A. Tsekoun, X. Wang, J. Fan, and C. K. N. Patel, "Sub-parts-per-billion level detection of dimethyl methyl phosphonate (DMMP) by quantum cascade laser photoacoustic spectroscopy", Appl. Opt. 47, 1543 (2008).