Thomas Südmeyer of Uni Neuch/FS/IP/LTF, expert in ultrafast laser physics
Bernd Witzigmann of University of Kassel, expert in VCSELs modelling for narrow line-width and broad tuning with current
Short pulse laser sources have enabled many applications in science and technology. Numerous laboratory experiments have confirmed that they can significantly increase telecommunication data rates, improve computer interconnects, and optically clock in the future multicore microprocessors. New applications in metrology, supercontinuum generation and life sciences with two-photon microscopy and optical coherence tomography only work with ultrashort pulses, but have relied on bulky and complex ultrafast solid-state lasers. However, users in health care and life sciences generally would rather get the short pulses without any further overhead and with a simple turn-on-off switch. It is therefore essential for them to have access to compact, easy-to-use and inexpensive ultrafast lasers. Recent developments in novel semiconductor lasers have the potential to reduce the complexity of ultrafast lasers.
Semiconductor lasers are ideally suited for mass production and widespread applications, because they are based on a wafer-scale technology with a high level of integration. Not surprisingly, the first lasers entering virtually every household were semiconductor lasers in compact disk players. A new ultrafast semiconductor laser concept has been introduced by Prof. Keller, which is power scalable, suitable for pulse repetition rate scaling in the 10 to 100 GHz regime, supports both optical and electrical pumping and allows for wafer-scale fabrication. This class of devices is referred to as the modelocked integrated external-cavity surface emitting laser (MIXSEL). The next step towards even lower-cost and more compact ultrafast lasers will be electrical pumping with both pico- and femtosecond pulses. This would result in devices ideally suited for many applications such as telecommunications, optical clocking, frequency metrology, high resolution nonlinear multiphoton microscopy, optical coherence tomography, laser display . anywhere where the current ultrafast laser technology is considered to be too bulky or expensive.
The project aims to demonstrate optically and electrically pumped MIXSELs in both the pico- and femtosecond regime. Picosecond MIXSELs are ideally suited for clocking applications whereas femtosecond MIXSELs are required for continuum generation and many biomedical applications. For both cases, average powers above 100 mW with electrical pumping and above 500 mW with optical pumping should be reached, which represent significant advances of ultrafast MIXSELs.
Figure shows vertical integration scheme, progressing from conventional VECSEL-SESAM modelocking with (a) large mode area ratios and thus large cavities (Phys. Rep. 429, 67, 2006), (b) to absorber-gain integration in a MIXSEL (Appl. Phys. B 88, 493, 2007). The MIXSEL semiconductor wafer structure contains two high reflectors (HR), quantum dot (QD) saturable absorber, quantum well (QW) gain and an anti-reflective (AR) coating. The QW gain can also be replaced with QD gain layers.
Electrically Pumped VECSELs and MIXSELs Wolfgang Pallmann, Martin Hoffmann, Christian Zaugg, Imad Dahhan, Bernd Witzigmann, Matthias Golling, Yohan Barbarin, Thomas Südmeyer, Ursula Keller
Compact ultrafast semiconductor disk laser: targeting GFP based nonlinear applications in living organisms R. Aviles-Espinosa, G. Filippidis, C. Hamilton, G. Malcolm, K. J. Weingarten, T. Südmeyer, Y. Barbarin, U. Keller, S. I. C. O Santos, D. Artigas and P. Loza-Alvarez, Biomedical Optics Express, (0, 2011)
Femtosecond high-power quantum dot vertical external cavity surface emitting laser M. Hoffmann, O. D. Sieber, V. J. Wittwer, I. L. Krestnikov, D. A. Livshits, T. Südmeyer, U. Keller, Optics Express, (0, 2011)
High-Power 1.48-?m Wafer-Fused Optically Pumped Semiconductor Disk Laser J. Lyytikäinen, J. Rautiainen, A. Sirbu, V. Iakovlev , A. Laakso, S. Ranta, M. Tavast, E. Kapon, and O. G. Okhotnikov IEEE Photonics Technology Letters, (0, 2011)
Timing jitter characterization of a free-running SESAM mode-locked VECSEL V. J. Wittwer, C. A. Zaugg, W. P. Pallmann, A. E. H. Oehler, B. Rudin, M. Hoffmann, M. Golling, Y. Barbarin, T. Südmeyer, U. Keller, IEEE Phot. Journal, (0, 2011)
1.38-µm mode-locked Raman fiber laser pumped by semiconductor disk laser Chamorovskiy, A. Rantamäki, A. Sirbu, A. Mereuta, E. Kapon, and O. Okhotnikov, Opt. Express (0, 2010)
1.3-?m Mode-Locked Disk Laser With Wafer Fused Gain and SESAM Structures J. Rautiainen, J. Lyytikäinen, L. Toikkanen, J. Nikkinen and A. Sirbu, A.Mereuta, A. Caliman, E.Kapon and O. Okhotnikov, IEEE Photonics Technology Letters, (0, 2010)
A simple approach to the relation between laser frequency noise and laser lineshape G. Di Domenico, S. Schilt, P. Thomann, Applied Optics, (0, 2010)
Experimental verification of soliton-like pulse-shaping mechanisms in passively mode-locked VECSELs M. Hoffmann, O.D. Sieber, D. J. H. C. Maas, V. J. Wittwer, M. Golling, T. Südmeyer, and U. Keller, Opt. Express (0, 2010)
Novel ultrafast semiconductor laser with 6.4 W average output power B. Rudin, V. J. Wittwer, D. J. H. C. Maas, M. Hoffmann, O. D. Sieber, Y. Barbarin, M. Golling, T. Südmeyer, U. Keller, Optics Express, (0, 2010)
Picosecond diode-pumped 1.5-µm Er,Yb:glass lasers operating at 10-100 GHz repetition rate A. E. H. Oehler, M. C. Stumpf, S. Pekarek, T. Südmeyer, K. J. Weingarten, U. Keller, Appl. Phys. B, (0, 2010)
Raman fiber laser pumped by a semiconductor disk laser and mode locked by a semiconductor saturable absorber mirror A. Chamorovskiy, J. Rautiainen, J. Lyytikäinen, S. Ranta, M. Tavast, A. Sirbu, E. Kapon, and O. Okhotnikov, Opt. Lett. (0, 2010)
Ultrafast solid-state laser oscillators: a success story for the last 20 years with no end in sight U. Keller, Invited Paper, Appl. Phys. B, vol. 100, pp. 15-28, (0, 2010)
1.3-µm optically-pumped semiconductor disk laser by wafer fusion J. Lyytikäinen, J. Rautiainen, L. Toikkanen, A. Sirbu, A. Mereuta, A. Caliman, E. Kapon, and O. Okhotnikov, Opt. Express (0, 2009)
Power-scalable 1.57 µm mode-locked semiconductor disk laser using wafer fusion E. Saarinen, J. Puustinen, A. Sirbu, A. Mereuta, A. Caliman, E. Kapon, and O. Okhotnikov, Opt. Lett. (0, 2009)
Self-referencable frequency comb from a 170-fs, 1.5-?m solid-state laser oscillator M. C. Stumpf, S. Pekarek, A. E. H. Oehler, T. Südmeyer, J. M. Dudley, and U. Keller, Applied Physics B: Lasers and Optics (0, 2009)
Short pulse laser sources have enabled many applications in science and technology. Numerous laboratory experiments have confirmed that they can significantly increase telecommunication data rates, improve computer interconnects, and optically clock in the future multicore microprocessors. New applications in metrology, supercontinuum generation and life sciences with two-photon microscopy and optical coherence tomography only work with ultrashort pulses, but have relied on bulky and complex ultrafast solid-state lasers. However, users in health care and life sciences generally would rather get the short pulses without any further overhead and with a simple turn-on-off switch. It is therefore essential for them to have access to compact, easy-to-use and inexpensive ultrafast lasers. Recent developments in novel semiconductor lasers have the potential to reduce the complexity of ultrafast lasers. 
