209 research outputs found
Phonon-Assisted Gain in a Semiconductor Double Quantum Dot Maser
We develop a microscopic model for the recently demonstrated double quantum
dot (DQD) maser. In characterizing the gain of this device we find that, in
addition to the direct stimulated emission of photons, there is a large
contribution from the simultaneous emission of a photon and a phonon, i.e., the
phonon sideband. We show that this phonon-assisted gain typically dominates the
overall gain which leads to masing. Recent experimental data are well fit with
our model.Comment: v1: 6 pgs, 2 figures; v2: 6 pgs, 3 figures, added Fig 2b and Fig. 3b,
modified main text; v3: 6+ pgs, 3 figures, modified main tex
High-Order Multipole Radiation from Quantum Hall States in Dirac Materials
We investigate the optical response of strongly disordered quantum Hall
states in two-dimensional Dirac materials and find qualitatively different
effects in the radiation properties of the bulk versus the edge. We show that
the far-field radiation from the edge is characterized by large multipole
moments (> 50) due to the efficient transfer of angular momentum from the
electrons into the scattered light. The maximum multipole transition moment is
a direct measure of the coherence length of the edge states. Accessing these
multipole transitions would provide new tools for optical spectroscopy and
control of quantum Hall edge states. On the other hand, the far-field radiation
from the bulk appears as random dipole emission with spectral properties that
vary with the local disorder potential. We determine the conditions under which
this bulk radiation can be used to image the disorder landscape. Such optical
measurements can probe sub-micron length scales over large areas and provide
complementary information to scanning probe techniques. Spatially resolving
this bulk radiation would serve as a novel probe of the percolation transition
near half-filling.Comment: v2: 8 pages, 4 figure
Injection Locking of a Semiconductor Double Quantum Dot Micromaser
Emission linewidth is an important figure of merit for masers and lasers. We
recently demonstrated a semiconductor double quantum dot (DQD) micromaser where
photons are generated through single electron tunneling events. Charge noise
directly couples to the DQD energy levels, resulting in a maser linewidth that
is more than 100 times larger than the Schawlow-Townes prediction. Here we
demonstrate a linewidth narrowing of more than a factor 10 by locking the DQD
emission to a coherent tone that is injected to the input port of the cavity.
We measure the injection locking range as a function of cavity input power and
show that it is in agreement with the Adler equation. The position and
amplitude of distortion sidebands that appear outside of the injection locking
range are quantitatively examined. Our results show that this unconventional
maser, which is impacted by strong charge noise and electron-phonon coupling,
is well described by standard laser models
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