494 research outputs found
On the Z_p-ranks of tamely ramified Iwasawa modules
For a prime number p, we denote by K the cyclotomic Z_p-extension of a number
field k. For a finite set S of prime numbers, we consider the S-ramified
Iwasawa module which is the Galois group of the maximal abelian pro-p-extension
of K unramified outside S. This paper treats the case where S does not contain
p and k is the rational number field or an imaginary quadratic field. In this
case, we prove the explicit formulae for the free ranks of the S-ramified
Iwasawa modules as abelian pro-p groups, by using Brumer's p-adic version of
Baker's theorem on the linear independence of logarithms of algebraic numbers
Strong photo-absorption by a single quantum wire in waveguide-transmission spectroscopy
We measured the absorption spectrum of a single T-shaped, 14x6 nm
lateral-sized quantum wire embedded in an optical waveguide using
waveguide-transmission spectroscopy at 5 K. In spite of its small volume, the
one-dimensional-exciton ground state shows a large absorption coefficient of 80
/cm, or a 98 % absorption probability for a single pass of the 500-um-long
waveguide.Comment: 4 pages, 3 figure
Room-temperature excitonic absorption in quantum wires
We measured absorption spectra of T-shaped quantum wires at room temperature
using waveguide-transmission spectroscopy. Strong and narrow room-temperature
one-dimensional-exciton absorption peak was observed, which shows peak modal
absorption coefficient of 160 cm per 20 wires with -factor of
, width of 7.2 meV, and strong polarization anisotropy.Comment: 3pages, 3figure, 1tabl
Imaging of emission patterns in a T-shaped quantum wire laser
Spatially and spectrally resolved microscopic images of spontaneous and
stimulated emissions are imaged at the mirror facets of a GaAs T-shaped quantum
wire laser with high uniformity. Laser emission from the one-dimensional ground
state reveals a circular image located at the core of a T-shaped optical
waveguide but significantly smaller in area than the low power spontaneous
emission from the same waveguide. These images unambiguously allow assignment
of all spontaneous and laser emissions to the wire ground state and respective
intersecting wells in the structure.Comment: 4 pages, 3 figure
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