Search results for "Linear optics"
showing 10 items of 493 documents
π conjugation across the tetrathiafulvalene core: Synthesis of extended tetrathiafulvalene derivatives and theoretical analysis of their unusual elec…
2000
A series of extended tetrathiafulvalene (TTF) derivatives bearing one or two 1,4-dithiafulven-6-yl substitutents has been prepared. The new compounds present remarkable electrochemical singularities compared with other TTF derivatives, which are strongly affected by the nature of the substitution on the lateral heterocycle(s). This unusual electrochemical behaviour follows a square-scheme sequence and is attributed to structural changes upon oxidation of the pi-donating molecules. Digital simulations of the electrochemical data have been used to reach the values of the kinetic and thermodynamic constants involved in the square scheme. Theoretical calculations establish an important contribu…
Nonlinear polarization effects in optical fibers: polarization attraction and modulation instability [Invited]
2014
We review polarization stabilization techniques based on the polarization attraction effect in low-birefringence fibers. Polarization attraction or pulling may be based on cross-polarization modulation, on parametric amplification, and on Raman or Brillouin scattering. We also review methods for laser frequency conversion based on polarization modulation instabilities in low- and high-birefringence fibers, and photonic crystal fibers. Polarization instabilities in nonlinear fibers may also be exploited for sensing applications.
All-optical regeneration of polarization of a 40 Gbit/s return-to-zero telecommunication signal
2013
International audience; We report all-optical regeneration of the state of polarization of a 40 Gbit/s return-to-zero telecommunication signal. The device discussed here consists of a 6.2-km-long nonzero dispersion-shifted fiber, with low polarization mode dispersion, pumped from the output end by a backward propagating wave coming from either an external continuous source or a reflection of the signal. An initially scrambled signal acquires a degree of polarization close to 100% toward the polarization generator output. All-optical regeneration is confirmed by means of polarization and bit-error-rate measurements as well as real-time observation of the eye diagrams. We show that the physic…
Ferroelectric liquid crystalline polysiloxanes designed for high second-order nonlinear susceptibilities
1994
Ferroelectric liquid crystalline (FLC) copolysiloxanes containing suitable comonomers («NLO-chromophores») for second harmonic generation (SHG) have been prepared. Their important feature is a donor-acceptor x-system sited perpendicular to the long axis of the side-group moieties in order to adopt the polar ordering of the ferroelectric LC phase. The influcences of the mesogen structure and of the content of NLO-chromophores on the liquid crystalline and ferroelectric properties are studied. The desired chiral smectic C * phase is retained up to 30 mol-% of chromophore. Also, first measurements of second harmonic generation have been performed
Synthèse de nouveaux agents bimodaux hydrosolubles pour l'IRM, l'imagerie nucléaire, l'imagerie biphotonique et la génération de second harmonique
2015
The goal of my PhD studies was to synthesize new compounds for possible medical imaging applications. The first part of my thesis focused on the synthesis of heteroleptic ligands to achieve the chelation of two different metals aimed at addressing two types of medical imaging. We first synthesized porphyrins, which are well-known for the chelation of numerous transition metals. We focused on copper, whose copper-64 isotope is a β+ emitter usable in Positron Emission Tomography (PET). These porphyrins have been coupled with a DOTA derivative. This molecule, metallated with gadolinium, is well-known in Magnetic Resonance Imaging (MRI). Our compounds display encouraging relaxivities for MRI ap…
Sub-200-kHz single soliton generation in a long ring Er-fiber laser with strict polarization control by using twisted fiber
2020
Abstract In the present work we demonstrate a novel single-soliton ultra-low pulse repetition frequency passively mode-locked erbium-doped fiber laser. We mitigate the residual linear birefringence of fiber by fiber twist to achieve a strict control of polarization. For mode-locking the nonlinear polarization rotation (NPR) was used. Special technique was applied to reduce the overdriving of NPR that allows the generation of single soliton in ultra-long cavity. The strict control of polarization yields a stable relation between the polarization state of the pulses propagating in the cavity and the regimes of generation. A 192.12-kHz train of soliton pulses was obtained with pulse duration o…
Practical system for the generation of pulsed quantum frequency combs
2017
The on-chip generation of large and complex optical quantum states will enable low-cost and accessible advances for quantum technologies, such as secure communications and quantum computation. Integrated frequency combs are on-chip light sources with a broad spectrum of evenly-spaced frequency modes, commonly generated by four-wave mixing in optically-excited nonlinear micro-cavities, whose recent use for quantum state generation has provided a solution for scalable and multi-mode quantum light sources. Pulsed quantum frequency combs are of particular interest, since they allow the generation of single-frequency-mode photons, required for scaling state complexity towards, e.g., multi-photon…
Novel Narrow-Band Spectral Interference Filter with Very High Transmittance
2011
We report a novel scheme to improve the effective transmission of a standard interference filter, and demonstrate over 97% passband transmission. Such high efficiency is critical for quantum information applications, e.g. high-efficiency single-photon generation utilizing parametric down-conversion. The scheme can also be modified to function with a tilted filter, thereby allowing tuning of the passband frequency. In addition, the tilted configuration creates an infinite number of consecutive reflections from and transmissions through the filter, further improving the net filter transmission. Because spectral interference filters are a key element in optical quantum information experiments …
Influence of pump coherence on the dynamic behavior of a laser
1988
The dynamic behavior of a coherently pumped single-mode unidirectional ring laser with a homogeneously broadened three-level active medium is studied. Our formulation is based on a set often real equations of the plane-wave, mean-field Maxwell–Bloch type. The instability domain in the main control parameters space is determined. Our numerical study of these equations for a parameter range of the type explored in the recent experiments by Weiss Brock [ Phys. Rev. Lett.57, 2804 ( 1986)] reveals some similarities, but striking differences between our theoretical predictions and their experimental observations are also noted.
Generation and coherent manipulation of complex quantum states based on integrated frequency combs
2018
The investigation and use of integrated frequency comb sources (i.e. featured by equally-spaced discrete spectral modes) have recently provided a unique framework to address the challenges of generation and coherent manipulation of complex quantum states in on-chip devices. We exploit integrated frequency combs for generating entangled photon pairs, as well as multi-photon states, and high-dimensional (D-level, i.e. quDit) entangled photons. In particular, we manage to coherently manipulate such complex quantum systems by using telecommunications components (standard fiber telecom).