13 research outputs found
Characteristics of the New Modulated Grating Y laser (MG-Y) for future WDM networks
During the past years widely tunable laser structures that can be used in future telecom networks were designed and fabricated within the IST project NEWTON. This paper
introduces the device principle and the measurement results of the new widely tunable MG-Y laser concept. With measured characteristics such as a 40nm tuning range, a side mode suppression of more than 40dB and a high output power this design has the same qualities as non-tunable lasers. Its wide tunability makes it possible to add extra flexibility, functionality and performance to the network.status: publishe
Charging effects in a quantum wire with leads
We investigate the distribution of the electron density and the potential in
a quantum wire coupled to reservoirs, treating this structure as a unified
quantum system and taking into account the Coulomb interaction of electrons.
The chemical potential difference that exists between a decoupled, isolated
quantum wire and the reservoirs gives rise to charge transfer in the coupled
system. We show that the quantum wire can be charged positively or negatively
or remain neutral as a whole, depending on such factors as the wire radius and
the background charge density in the wire. The magnitude of the charge and its
sign are to a large extent determined by the exchange interaction of the
electrons in the wire. Using a Hartree-Fock approach, we develop a model of a
quantum wire which includes the reservoirs. This model allows us to find the
self-consistent distribution of the electron density and the potential in the
wire both at equilibrium and in the presence of transport. The linear
conductance is investigated as a function of the chemical potential. The
nonadiabatic transition from the reservoirs to the wire leads to conductance
oscillations caused by multiple scattering of electron waves. The period of the
oscillations depends on the charge acquired by the wire and the exchange
energy. We find that the exchange interaction strongly enhances the Friedel
oscillations near the contacts. However, they do not noticeably suppress the
conductance because the wire has a finite length and is charged. Under far from
equilibrium conditions, which appear when the applied voltage exceeds the Fermi
energy in the wire, the system becomes unstable with respect to fluctuations of
the electric potential and the electron density. The instability results in the
appearance of multistable electron states.Comment: 13 pages, Latex, 9 figure