- Ph.D., Technical University of Vienna, Austria, 1995
- M.Sc., Physics, University of Innsbruck, Austria, 1991
Eugene Higgins Professor of Electrical Engineering
Associated Faculty in the Princeton Materials Institute (PMI)
My research group is working on the development of new quantum devices, especially lasers, and their optimization for sensor systems and their applications in environment and health. Our special focus is currently on Quantum Cascade (QC) lasers, a novel type of semiconductor injection laser based on electronic intersubband transitions in the conduction band of a coupled quantum well heterostructure. Quantum wells are slivers of one type of semiconductor material, just a few atomic layers thick, interleaved with another type of semiconductor (the barriers).
Many performance features of the lasers, such as their power, modulation capabilities, or emission wavelength in the mid- to far-infrared, are designed into the device by choice of the thicknesses of the quantum wells and barriers. With some 500 to 1000 quantum wells and barriers in a single laser, there are endless opportunities for creativity!
Our current projects include the development of high-temperature, high-power, high-efficiency QC lasers. Widely tunable, monolithic, and external cavity QC lasers are being developed for optical sensors in environmental, medical, and security applications. While my group is focused mainly on the development of the lasers, we maintain strong collaborations with many expert spectroscopists who are building sensor systems in academia, government, and industrial labs.
My group's working style is collaborative and open. Group members expect to work hard and to have a lot of fun, too! Device modeling on the computer, device fabrication in the PMI cleanroom facilities, and optical device characterization in our labs each take up about 30 percent of the work week. The remaining 10 percent or so is reserved for tasks such as scientific writing or attending conferences.
I am also the director of the education program of MIRTHE, the NSF-sponsored Engineering Research Center for Mid-InfraRed Technologies for Health and the Environment. A group of 6 universities and approximately 40 faculty, 120 students, and 40 industry and practitioner organizations, MIRTHE members collaborate to develop the next-generation sensor platforms for chemical trace gas sensing using mid-infrared spectroscopy.
Y. Yao, X.J. Wang, J.Y. Fan, and C.F. Gmachl, “High performance "continuum-to-continuum" quantum cascade lasers with a broad gain bandwidth of over 400 cm 1”, Appl. Phys. Lett. 97(8) 081115 (2010)
W.O. Charles, Y. Yao, K.J. Franz, Q. Zhang, A. Shen, C. Gmachl, and M.C. Tamargo, “Growth of Znx,Cd(1-x ')Se/ZnxCdyMg(1-x-y)Se-InP quantum cascade structures for emission in the 3-5 mm range”, J. Vac. Sci. B 28(3) (2010)
Y. Yao, W.O. Charles, T. Tsai, J.X. Chen, G. Wysocki, and C.F. Gmachl, ”Broadband quantum cascade laser gain medium based on a "continuum-to-bound" active region design”, Appl. Phys. Lett. 96(21) 211106 (2010)
P.Q. Liu, A.J. Hoffman, M.D. Escarra, K.J. Franz, J.B. Khurgin, Y. Dikmelik, X.J. Wang, J.Y. Fan, and C.F. Gmachl, “Highly power-efficient quantum cascade lasers”, Nature Photonics 4(2) 95 – 96 (2010)
K.J. Franz, P.Q. Liu, J.J.J. Raftery, M.D. Escarra, A.J. Hoffman, S.S. Howard, Y. Yao, Y., Dikmelik, X.J. Wang, J.Y. Fan, J.B. Khurgin, and C. Gmachl, “Short Injector Quantum Cascade Lasers”, IEEE J. Quantum Electron. 46(5) 591 – 600 (2010)
Honors and Awards:
- Graduate Student Mentoring Award, Princeton University (2009)
- Austrian Academy of Sciences, Corresponding member abroad (2008)
- MacArthur Fellow (2005)
- Runner-up Salzburger of the year 2005, Austria
- Popular Science Magazine's list of Brilliant 10 (2004)
- The Snell Premium award of the IEE, UK, August (2003)
- MIT's Technology Review magazine TR100, (2002)
- IEEE/LEOS Distinguished Lecturer 02-03, (2002)