22,762 research outputs found
Physics of quantum light emitters in disordered photonic nanostructures
Nanophotonics focuses on the control of light and the interaction with matter
by the aid of intricate nanostructures. Typically, a photonic nanostructure is
carefully designed for a specific application and any imperfections may reduce
its performance, i.e., a thorough investigation of the role of unavoidable
fabrication imperfections is essential for any application. However, another
approach to nanophotonic applications exists where fabrication disorder is used
to induce functionalities by enhancing light-matter interaction. Disorder leads
to multiple scattering of light, which is the realm of statistical optics where
light propagation requires a statistical description. We review here the recent
progress on disordered photonic nanostructures and the potential implications
for quantum photonics devices.Comment: Review accepted for publication in Annalen der Physi
Past observable dynamics of a continuously monitored qubit
Monitoring a quantum observable continuously in time produces a stochastic
measurement record that noisily tracks the observable. For a classical process
such noise may be reduced to recover an average signal by minimizing the mean
squared error between the noisy record and a smooth dynamical estimate. We show
that for a monitored qubit this usual procedure returns unusual results. While
the record seems centered on the expectation value of the observable during
causal generation, examining the collected past record reveals that it better
approximates a moving-mean Gaussian stochastic process centered at a distinct
(smoothed) observable estimate. We show that this shifted mean converges to the
real part of a generalized weak value in the time-continuous limit without
additional postselection. We verify that this smoothed estimate minimizes the
mean squared error even for individual measurement realizations. We go on to
show that if a second observable is weakly monitored concurrently, then that
second record is consistent with the smoothed estimate of the second observable
based solely on the information contained in the first observable record.
Moreover, we show that such a smoothed estimate made from incomplete
information can still outperform estimates made using full knowledge of the
causal quantum state.Comment: 11 pages, 4 figure
On curves with one place at infinity
Let be a plane curve. We give a procedure based on Abhyankar's
approximate roots to detect if it has a single place at infinity, and if so
construct its associated -sequence, and consequently its value
semigroup. Also for fixed genus (equivalently Frobenius number) we construct
all -sequences generating numerical semigroups with this given genus.
For a -sequence we present a procedure to construct all curves having
this associated sequence.
We also study the embeddings of such curves in the plane. In particular, we
prove that polynomial curves might not have a unique embedding.Comment: 14 pages, 2 figure
Ring Resonators with Sagnac Loops for Photonic Processing in DWDM Backbone Networks
In this paper, optical configurations based on ring resonators (RR) with an internal Sagnac (SG) loop in the feedback path, are analyzed in terms of their amplitude response and dispersive properties for filtering and chromatic dispersion managing in digital transmission systems over amplified single- mode fiber (SMF) spans in DWDM backbone networks. Design issues for the architecture as regards quadratic dispersion and magnitude distortion are provided. The RR+SG compound filter provides frequency tunability of the amplitude and dispersion peaks by adjusting a coupling coefficient of an optical coupler, with no need for using integrated thermo-optic nor current- injection based phase shifters. The configuration can be employed as an additional structure for a general RR-based design and synthesis architecture, allowing bandwidth increase of dispersion compensators and flexibility. The performance of a compound filter consisting of a two RR in series stage and a RR+SG filter are reported as a more compact and effective solution for existing multi-channel SMF backbone links operating at high bit rates. Design guidelines of an integrated ring resonator based on polymer technology for showing feasibility of the proposal is reported.This work was partially supported by Spanish CICYT (TEC2006-13273-C03-03-MIC), European project NoE
EPhoton/One+, CAM (FACTOTEM-CM:S-0505/ESP/000417), FENIS-CCG06-UC3MITIC-0619.Publicad
Radio-frequency ring resonators for self-referencing fiber-optic intensity sensors
A theoretical and experimental study of radiofrequency ring resonators (RR) for referencing and improving the sensitivity of fiber-optic intensity sensors (FOS) is
reported. The separation between lead and transducer losses in the FOS is solved by converting the light intensity fluctuations to be measured into RR losses that produce
high amplitude variations in the proximity of the RR resonance frequencies. Two different self-referencing techniques are developed. Via the definition of the measurement parameter RM , sensor linearity and sensitivity are analyzed. A calibration
using an optical attenuator is reported to validate the model.Publicad
Impact of Gamma Radiation on Dynamic RDSON Characteristics in AlGaN/GaN Power HEMTs
GaN high-electron-mobility transistors (HEMTs) are promising next-generation devices in the power electronics field which can coexist with silicon semiconductors, mainly in some radiation-intensive environments, such as power space converters, where high frequencies and voltages are also needed. Its wide band gap (WBG), large breakdown electric field, and thermal stability improve actual silicon performances. However, at the moment, GaN HEMT technology suffers from some reliability issues, one of the more relevant of which is the dynamic on-state resistance (RON_dyn) regarding power switching converter applications. In this study, we focused on the drain-to-source on-resistance (RDSON) characteristics under 60Co gamma radiation of two different commercial power GaN HEMT structures. Different bias conditions were applied to both structures during irradiation and some static measurements, such as threshold voltage and leakage currents, were performed. Additionally, dynamic resistance was measured to obtain practical information about device trapping under radiation during switching mode, and how trapping in the device is affected by gamma radiation. The experimental results showed a high dependence on the HEMT structure and the bias condition applied during irradiation. Specifically, a free current collapse structure showed great stability until 3.7 Mrad(Si), unlike the other structure tested, which showed high degradation of the parameters measured. The changes were demonstrated to be due to trapping effects generated or enhanced by gamma radiation. These new results obtained about RON_dyn will help elucidate trap behaviors in switching transistors
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