Marc Dignam
Ph.D., P.Eng.
Professor,
Department of Physics, Engineering Physics and Astronomy
Queen’s University
Stirling Hall Room 371
Tel: (613) 533-6804
E-mail: dignam@physics.queensu.ca
GRADUATE STUDENT OPENING
I am currently looking to add a new Ph.D.
student to my group in September 2012 or January 2013. This student would work on the development of
theoretical and computation models of the nonlinear response of graphene and a variety of semiconductor nanostructures to
intense terahertz pulses. This work is
linked to experimental work being performed at McGill and INRS. If you are interested, and are a Canadian
citizen or landed immigrant, please contact me.
RESEARCH INTERESTS
All of my research lies in the area of
theoretical condensed-matter physics and nonlinear and quantum optics. This work ranges from pure to applied physics
and often involves collaboration with experimentalists. The following is a brief overview of some of
my current research interests.
Quantum Optics in
Photonic Crystals
It
is well known that the spontaneous emission of atoms, molecules, and quantum
dots can be drastically affected by the environment in which they are
placed. For example, the rate of spontaneous
emission of an atom in vacuum will be very different from that of an atom in a
small metallic cavity with dimensions on the order of the wavelength of the
emitted radiation. 
Similarly,
if an atom is located within the bandgap of a photonic crystal -- i.e. in the
frequency range where there are no propagating electromagnetic modes in the
structure – then the spontaneous emission can be completely suppressed. Conversely, the rate of spontaneous emission
can be greatly enhanced if the atom is placed at the location of a defect in
the photonic crystal, where the mode density is very high. This last effect is called the Purcell
effect.
We are currently researching the interesting dynamics of spontaneous emission in photonic crystals with multiple, coupled-cavity defect states [2,7,9,11,13,14,16,17]. We use a projected Green tensor approach to calculate the local density of states and spontaneous emission dynamics. We have found that the radiation dynamics can be very interesting in such structures. In particular, the spontaneous emission rate can be either enhanced or diminished due to quantum-path interference effects in the structure. This is demonstrated in the plot to the left, where we plot the local density of states for a double-cavity structure showing a large peak in the defect near x=-2 but a dip in the defect near x=+3. This approach makes it much easier to understand the basic physics of multiple-defect structures and has possible implications for quantum-computing applications of photonic crystals. More recently [11], we have developed a projected master equation approach to quantum optics for multiple photons in multi-cavity photonic crystal systems in the presence of quantum dots. Until recently, such calculations were prohibitive due to the complexity of the system. However our new projective technique [2] make a wide variety of complex structure amenable to investigation.
Optical and
Terahertz Response of Semiconductor Nanostructures
Another
area of research that I am currently pursuing involves the theoretical and
computational investigation of coherent electron dynamics in semiconductor
superlattices and other nanostructures.
This work is progressing in a number of directions. One of the main thrusts involves modeling the
nonlinear interaction of light with semiconductor nanostructures. Of particular interest are the dynamics of
electrons that have been set into motion by shining ultra-short ( < 100 fs) pulses of laser
light on the nanostructures. One
important system that we are investigating is a biased semiconductor superlattice (BSSL).
In a photo-excited BSSL, the excitons (electron-hole pairs) undergo an
oscillatory motion called Bloch oscillations (BO) [18-21,24-27,30,35-37,41,42]. Studying the dynamics of BO in superlattices
is proving very instructive in trying to understand electron and exciton
dynamics and relaxation in nanostructures on a very fast time scales (< 1ps)
-- a topic that is becoming more important as the size of semiconductor devices
go down and their speed goes up. It is
also an excellent system to test many-body theories of nonlinear optics of
semiconductors. A more immediately
practical goal of this work is to lay the groundwork for the development of the
first compact, tunable THz laser.
“T-ray” lasers, which emit radiation that lies between the microwave and
infrared portions of the spectrum, are becoming important tools in materials
research and in biological and mechanical imaging. We have recently shown [10] that THz gain in
suitably excited BSSLs should be comparable to current quantum cascade lasers.
We are currently developing theoretical formalisms and computational models to treat the response of optically-pumped semiconductor nanostructures and graphene to intense Terahertz fields. Some of the formalisms employ an excitonic basis, while others employ an electron-hole basis. All of the models treat the terahertz field non-pertubatively.
Dynamic
Localization in Waveguide Arrays
A
number of researchers have shown in recent years that when a sinusoidal ac
electric field of precisely the correct amplitude is applied to electrons in a
periodic potential, the electron wave packets become localized in space. This effect is called dynamic
localization. It was quickly realized
that the effect of dynamic localization does not occur for general bandstructures, but only for nearest-neighbour
tight-binding bands. We have recently
shown that there is a general class of discontinuous ac fields for which
dynamic localization will occur for any bandstructure
[15, 33,34]. We
have found that such fields must have discontinuities at all changes in sign
and have developed a scheme for constructing such fields. The tolerance to smoothing of these
discontinuities is rather large, but a sinusoidal field is far from being the
best continuous field to achieve dynamic localization.
Apart from its intrinsic importance to the better understanding of transport in ac fields, this work has important implication with respect to the ac conductivity and nonlinear optical response of superlattices, including excitonic effects [31]. Finally, this work has an important analog in the area of waveguide optics. It turns out that the mathematics involved in modeling electron dynamics in semiconductor superlattices is very similar to that required to model the propagation of optical beams down arrays of coupled optical waveguides. We have found that under the right conditions one can observe “Bloch oscillations” of the beam between the waveguides as it propagates down the waveguides. More importantly, by curving the waveguide arrays in carefully specified ways, one can observe the analog of the dynamic localization of electrons that can occur in superlattice in ac electric fields. The plots at the left show the measured and calculated beam intensity in a particular curved waveguide array as a function of propagation distance, v, and transverse direction, u [15]. The transmission properties of these waveguide arrays as a function of wavelength can be tailored over a wide range by choosing the curvature profile [1,23]. This, and related phenomena have potential in the design of optical filters, multiplexing devices and all-optical switches for fibre-optic communications systems.
RESEARCH GROUP
Current Group Members
¨
Mohsen Kamandar (Ph.D.) m.kamandar.dezfouli@queensu.ca
¨
Nicole Day (M.Sc.) nday@physics.queensu.ca
¨
Fredrik Sy (M.Sc.) fredriksy@gmail.com
¨
Sean Doutre (M.Sc.) sdoutre@physics.queensu.ca
Group
Alumni
¨
Andrew Parks (M.Sc., 2011)
¨
John Simpson-Porco (Undergraduate Summer Researcher 2010)
¨
Dawei Wang (Ph.D., 2008)
¨
Arvin Reza (M.Sc., 2008)
¨
Dr. David Fussell (Postdoctoral
Fellow, 2005-2007)
¨ Lijun Yang (M.Sc., 2001;
Ph.D., 2005)
¨
Julius Wan (Ph.D., 2005)
¨ Dr. Aizhen Zhang
(Postdoctoral Fellow, 2002-2004)
¨ Jean-Marc Lachaine (M.Sc., 2002)
¨ Martin Laforest
(Undergraduate Summer Researcher 2002)
¨ Michael Sawler
(M.Sc., 2001)
¨ Richard Wassenaar (Undergraduate Summer Researcher 1999)
¨ More than 30 undergraduate
thesis students…
COLLABORATIONS
I am currently part of an NSERC strategic grant
studying high-field THz characterization of transport phenomena in graphene and semiconductor nanostructure with
experimentalists D. Cooke (McGill), T. Osaki (INRS) and R. Morandotti
(INRS). My group at Queen’s will be
involved in developing theoretical models of the response of graphene and semiconductor quantum wires, wells, dots and
superlattices to intense terahertz fields and applying those models to the
experimental systems investigated at McGill and INRS.
I have collaborated and continue to collaborate with
a number of top experimental and theoretical groups from around the world. In addition, I have collaborated with and
done consulting for a number of companies in the field of optical
communications.
Much of my work involves a strong interaction with
experimentalists and I have collaborated with the following
internationally-renowned experimentalists:
¨ Prof. Karl Leo: Ultrafast optics of semiconductors, Technical University of Dresden,
Germany.
¨ Prof. Andrew Weiner: Ultrafast optics of semiconductors,
¨ Dr. Jagdeep Shah: Ultrafast optics of
semiconductors, Bell Labs,
¨ Prof. Emilio Mendez: Optical properties of superlattices, I.B.M.
¨ Prof. Horst Stormer (Nobel Laureate 1998):
Quantum transport, Bell Labs,
¨ Prof. Stewart Aitchison: Dynamic localization in coupled optical waveguide
arrays,
¨ Prof. Hartmut Roskos: Terahertz radiation gain
in semiconductor superlattices, Gothe Universitat,
CURRENT PROJECTS
Quantum optics and cavity
QED in photonic crystals
Linear and
nonlinear optical properties of photonic crystals
The coherent
dynamics and coherent control of excitons excited by ultra-short optical
pulses in semiconductor nanostructures
The
response of semiconductor nanostructures to intense THz fields
Treating Phase-Space
filling and exchange effects using an excitonic approach to ultrafast
carrier dynamics in semiconductor nanostructures
Linear and
nonlinear optics of coupled waveguide arrays
Modes and
energy transport in negative-index metamaterial waveguide structures
SELECTED PUBLICATIONS (past 10 years)
1.
Ibraheem Al-Naib,
Gargi Sharma1, Marc M. Dignam,
Hassan Hafez, Akram Ibrahim, David G. Cooke, Tsuneyuki Ozaki, and Roberto
Morandotti, Amplitude modulation in
nonlinear terahertz metamaterials enabled by
carrier dynamics in silicon, (Submitted to Phys. Rev. Lett.).
2.
A. Joushaghani, R. Iyer,
J. K. S. Poon, J. Stewart Aitchison, C. M. de Sterke, J.
Wan and M. M. Dignam, Generalized Exact Dynamic Localization in
Curved Coupled Optical Waveguide Arrays, Phys. Rev. Lett.
109, 103901 (2012).
3.
M. M. Dignam and M.
Kamandar Dezfouli, Photon–quantum-dot dynamics in coupled-cavity photonic crystal slabs,
Physical Review
A, 85, 013809 (2012).
4.
Peijun Yao, A. Reza, C. Van Vlack, M.M. Dignam and S. Hughes, Ultrahigh Purcell Factors in Slow-Light
Metamaterial Waveguides, Physical Review B 80, 195106 (2009).
5.
A. Joushaghani,
R. Iyer, J.K.S. Poon, J.S. Aitchison, C.M. de Sterke,
J. Wan and M.M. Dignam, Quasi-Bloch
Oscillations in Curved Coupled Optical Waveguides, Phys.
Rev. Lett. 103, 143903 (2009).
6.
Dawei Wang and Marc M.
Dignam, Excitonic Approach to the
Ultrafast Optical Response of Semiconductor Quantum Wells, Phys. Rev. B 79,
165320 (2009).
7.
A. Reza, M.M. Dignam and S. Hughes, Can
Light be Stopped in Realistic Metamaterials?, Nature
455, E-10 (2008).
8.
D. P. Fussell, S. Hughes and M. M. Dignam, The Influence of Fabrication Disorder on the Optical Properties of
Coupled-Cavity Photonic Crystal Waveguides, Phys. Rev. B 78, 144201 (2008).
9.
A. Lisauskas, M.M.
Dignam, N.V. Demarina, Ernst Mohler,
and H. Roskos, Examining
the Terahertz Signal from a Photoexcited Biased
Semiconductor Superlattice for Evidence of Gain, Appl. Phys. Lett.
93, 021122 (2008).
10. D. P. Fussell and M. M. Dignam, Quasimode-Projection Approach to Quantum--Dot--Photon Interactions in Photonic
Crystal Slab Coupled-Cavity Systems, Phys. Rev. A 77, 053805 (2008).
11. Dawei Wang, Aizhen Zhang, Lijun Yang, and M. M. Dignam, Tunable Terahertz Amplification Using Excitonic States in
Optically-Excited Biased Semiconductor Superlattices, Phys. Rev. B 77, 115307 (2008).
12. David P. Fussell
and Marc M. Dignam, Quantum-Dot-Photon Dynamics in a Coupled-Cavity Waveguide: Observing Bandedge Quantum Optics, Phys. Rev. A 76,
053801 (2007).
13.
Dawei Wang, Margaret Hawton
and Marc M. Dignam, Excitonic Approach to the Ultrafast Optical
Response of Semiconductors, Phys. Rev. B 76, 115311 (2007).
14. D. P. Fussell and M. M.
Dignam, Spontaneous Emission in
Coupled Microcavity-Waveguide Structures at the Band
Edge, Optics Letters 32, 1527 (2007).
15. David P. Fussell and Marc M.
Dignam, Engineering the Quality
Factors of Coupled-Cavity Modes in Photonic
16. R. Iyer, J. S. Aitchison,
J. Wan, M. M. Dignam and C. M.
de Sterke, Exact Dynamic Localization in
Curved AlGaAs Optical Waveguide Arrays, Optics Express
15, 3212 (2007).
17. D. P. Fussell, M. M. Dignam,
M. J. Steel, C. Martijn de Sterke, and R. C. McPhedran,
Spontaneous Emission and Photon Dynamics
in Dielectric Microcavities, Phys. Rev. A 74, 043806 (2006).
18.
M. M. Dignam, D. P. Fussell,
M. J. Steel, R. C. McPhedran, and C. M. de Sterke, Spontaneous Emission Suppression via
Quantum Path Interference in Coupled Microcavities,
Phys Rev Lett. 96,
103902 (2006).
19.
Lijun Yang and M. M.
Dignam, Nonlinear Ultrafast Optical
Absorption and Pump-Probe Spectroscopy in Biased Semiconductor Superlattices,
Phys. Rev. B 73,
035334 (2006).
20. Lijun Yang and M. M.
Dignam, Self-generated Bloch
Oscillations in Biased Semiconductor Superlattices, Phys. Rev. B 73,
075319 (2006).
21.
Lijun Yang, Ben Rosam, and M. M. Dignam, Density-Dependent THz Emission in Biased Semiconductor
Superlattices: from Bloch Oscillations
to Plasma Oscillations, Phys. Rev. B 72,
115313 (2005).
22. R. Fanciulli, A. M. Weiner, M. M. Dignam, D. Meinhold,
and K. Leo, Coherent Control of Bloch
Oscillations by Means of Optical Pulse Shaping, Phys. Rev. B 71, 153304 (2005).
23.
24.
J. Wan, M. Laforest, C. M. de Sterke, and M. M. Dignam, Optical Filters
Based on Dynamic Localization in Curved Coupled Optical Waveguides, Optics Communications 247, 353 (2005).
25.
M. M. Dignam, M. Hawton, L.
Yang, and B. Rosam, The Interplay of Intraband and Interband Polarization in Biased
Semiconductor Superlattices, Acta Physica Polinica A 107, 56 (2005).
26.
Ben
Rosam,
27. J. Wan, C. Martijn de
Sterke, and M. M. Dignam, Dynamic Localization and Quasi-Bloch
Oscillations in General Periodic ac-dc Electric Fields, Phys. Rev. B 70,
125311 (2004).
28. Lijun Yang,
Ben Rosam, Jean-Marc
Lachaine, Karl Leo, and M. M. Dignam, Intraband
Polarization and THz Emission in Biased Semiconductor Superlattices with Full
Excitonic Basis, Phys. Rev. B 69,
165310 (2004).
29.
30. J. Wan, P. Domachuk, M. M.
Dignam, and C. Martijn de Sterke,
Electron dynamics and dynamic localization in asymmetric periodic potentials,
Phys. Rev. B 69,
113304 (2004).
31. M. Hawton and M. M. Dignam, Infinite Order Excitonic Bloch Equations for Asymmetric Nanostructures,
Phys. Rev. Lett.
91, 267402 (2003).
32.
Aizhen Zhang, Lijun Yang,
and M. M. Dignam, Influence of Excitonic Effects on Dynamic
Localization in Semiconductor Superlattices in Combined dc and ac Electric
Fields, Phys. Rev. B 67, 205318 (2003).
33. M. M. Dignam and M. Hawton, Intraband Polarization as the Source of Degenerate Four-Wave Mixing
Signals in Asymmetric Semiconductor Quantum Well Structures, Phys.
Rev. B 67, 035329 (2003).
34.
P.
Domachuk, C. M. de Sterke, J. Wan, and M. M. Dignam,
Dynamic Localization in Continuous ac
Electric Fields, Phys. Rev. B 66,
165313 (2002).
35.
M. M. Dignam and C. Martijn de Sterke, Conditions for Dynamic
Localization in Generalized ac Electric Fields, Phys.
Rev. Lett. 88,
046806 (2002).
36.
F.
Löser, B. Rosam, D. Meinhold, V. G. Lyssenko, M. Sudzius, M. M.
Dignam, S. Glutsch, F. Bechstedt,
F. Rossi, K. Köhler and K. Leo, Nonlinear
transport in superlattices: Bloch oscillations and Zener
breakdown, Physica E 11,
268-276 (2001).
37.
M.
Sudzius, V. G. Lyssenko, F. Löser, G. Valusis, T. Hasche, K. Leo, M.
M. Dignam, K. Köhler, Bloch-Oscillations In Semiconductors: Principles And Applications,
Chapter 3 in Ultrafast Phenomena in Semiconductors, Ed. K.-T. Tsen, Springer-Verlag, (2000).
38.
F.
Löser, M. M.
Dignam, Yu. A. Kosevich, K. Köhler, and K. Leo, Self-Induced Shapiro Effect in
Semiconductor Superlattices, Phys.
Rev. Lett. 85,
4763 (2000).
39.
J. M. Lachaine,
40.
M. M. Dignam, Excitonic
Bloch Oscillations in a Terahertz Field, Phys. Rev. B 59,
5770 (1999).
41. D.D. Yang and M. M. Dignam, New Generation of
Amplifiers Arrives for Optical Networking, Lightwave
(Special Reports, August 1999).
42.
M.
Sudzius, V.G. Lyssenko, F. Loser,
K. Leo, M. M. Dignam, and K. Kohler,
Optical control of Bloch oscillation
amplitudes: from harmonic spatial motion to breathing modes, Phys. Rev. B 57,
R12693-R12696 (1998) (Rapid Communications).
43.
V.
G. Lyssenko, G. Valusis, F. Loser, T.
Hasche, K. Leo, M.
M. Dignam, and K. Kohler, Direct
measurement of the spatial amplitude of Bloch oscillations in semiconductor
superlattices, Phys.
Rev. Lett. 79 (2), 301-304 (1997).
Member’s of Dignam Research Group in Bold