Series
in Quantum Electronics
edited by
Henry Baltes, Peter Günter, Ursula Keller,
Fritz K. Kneubühl †, Walter Lukosz,
Hans Melchior, Markus W. Sigrist
Vol. 51
Benjamin Rudin
High-Power Optically Pumped VECSELs and
MIXSELs.
1st edition 2010. XXVIII, 160 pages, € 64,00.
ISBN 978-3-86628-368-8
Ultrafast lasers drive applications in areas
as diverse as biology, telecommunication, metrology, or material structuring.
So far, multi-Watt power levels required ion-doped dielectric laser materials
in combination with additional intra-cavity components for the pulse formation,
resulting in high complexity and costs. Modelocked semiconductor lasers have
the potential for cost-efficient mass production, a necessary requirement for
applications such as biomedical imaging or optical clocking. For modelocked edge-emitters
the dispersion, nonlinearities and end facet damage are severe challenges for
achieving multi-Watt power levels. Vertical external cavity surface emitting
lasers (VECSELs) appear to be better suited, because the pulses propagate
mostly in the external cavity and experience only low dispersion and
nonlinearities from the vertical propagation through the epitaxial
semiconductor layers of only a few m thickness. Since the gain structure and the saturable absorber for the
pulse formation, typically a semiconductor saturable absorber mirror (SESAM),
are both made of semiconductor material, the integration of both elements into
a single structure become possible, leading to very simple ultrafast lasers.
In this thesis we present we the first
realization of such a laser, which we refer to as modelocked integrated
external-cavity surface emitting laser (MIXSEL). One of the key challenges has
been the development of quantum dot (QD) saturable absorbers that enable
modelocking with equal mode sizes on gain and absorber. The laser generates
185 mW average output power in 32 ps pulses at a repetition rate of
2.8 GHz. With the development of low saturation fluence quantum dot
absorbers, enabling a more sophisticated MIXSEL-structure design, and with
improved thermal management, we were able to boost the average output power to
6.4 W. Due to the shorter pulse length of 22 ps, the repetition rate
could be increased to up to 10 GHz. We believe that these devices will
fill a gap in the performance spectrum of today’s laser technology.
Benjamin
Rudin received his diploma degree in physics from
the ETH Zurich in 2004. He joined the Institute of Quantum Electronics at ETH
Zurich in 2005. His research focused on ultrafast high-power vertical external
cavity surface emitting lasers (VECSELs) and modelocked integrated
external-cavity surface emitting lasers (MIXSELs) and on measurement methods
for timing jitter and amplitude noise. He has written and co-authored more than
40 scientific journal articles and conference proceedings. In his spare time he
is designing and constructing electronics and mechanics for autonomous walking
robots.
Keywords: VECSEL, MIXSEL,
semiconductor disk laser, ultrafast, modelocking
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