Search results for "Width"
showing 10 items of 690 documents
Laser Pulse Effects in Two-level Systems Driven by Coherent and Fluctuating Radiation Fields
1988
Abstract We reconsider the problem of a two-level system interacting with a radiation field in order to study some new features suggested by the actual experimental conditions. Pulse shape and duration effects are included in the formalism and the counter-rotating terms are retained. The criterion of validity of the rotating wave approximation (RWA) for pulsed fields is investigated; generalizing results well known in RWA, we establish some new formal results, including non-RWA contributions to all orders and for any pulse shape. The analysis is then carried out for fluctuating fields, by developing a method based on the theory of multiplicative stochastic differential equations. For short …
Source linewidth effects in temporal imaging of Gaussian Schell-model pulses
2006
A transform-limited Gaussian pulse generated from an externally modulated stationary source is launched within a temporal imaging system composed of a second-order dispersion followed by a time lens and a subsequent quadratic dispersion. We consider the effect of the statistical properties of the emitted light for temporal imaging. In particular, it is shown that the design parameters that ensure a received signal with the minimum root-mean-square (rms) width achievable, which is called the temporal image of the incident pulse, are strongly dependent on the coherence properties of the input waveform. Finally, limitations on the temporal resolution of the setup are highlighted and a realisti…
Spectral analog of the Gouy phase shift
2013
We demonstrate the existence of the spectral phase shift a pulse experiences when it is subjected to spectral focusing. This $\frac{\ensuremath{\pi}}{2}$ phase shift is the spectral analog of the Gouy phase shift a 2D beam experiences when it crosses its focal plane. This spectral Gouy phase shift is measured using spectral interference between a reference pulse and a negatively chirped parabolic pulse experiencing spectral focusing in a nonlinear photonic crystal fiber. To avoid inherent phase instability in the measurement, both reference and parabolic pulses are generated with a $4\mathrm{\text{\ensuremath{-}}}f$ pulse shaper and copropagate in the same fiber. We measure a spectral phase…
Moderate-to-Strong Turbulence Generation in a Laboratory Indoor Free Space Optics Link and Error Mitigation via RaptorQ Codes
2016
Free Space Optics (FSO) is rapidly gaining interest as a line-of sight communication technology that offers capabilities similar - in terms of bandwidth and transfer rates - to optical fibre, also possessing several advantages compared with traditional radio frequency links. However, FSO link quality can be strongly affected by unfavourable weather conditions and also by the phenomenon of optical turbulence, even in clear sky. In this work, we have implemented an indoor FSO link and generated moderate-to-strong turbulence conditions along the optical path by using heaters and a mechanical ventilation system. In this way, we have been able to investigate the effects of the generated turbulen…
A Novel Method Of Measuring Light Absorption On A Self-Assembled Single Quantum Dot
2005
Abstract. We present a novel method by wich excitonic interband optical transitions within single InAs self-assembled quantum dots can be directly observed in a transmission experiment. Due to the extremely high resolution of the tecnique, individual peaks associated to single exciton absorption resonances in single quantum dots can be spectrally resolved. Using this technique we investigate the oscillator strength, homogeneous linewidth and fine structure splitting in a collection of such individual resonances.
Multimodal reflectivity of CRIGF filters: First experimental observation and modelling
2015
International audience; Cavity Resonator Integrated Guided-mode Resonance Filter (CRIGF) are a new class of filtering reflectors whose selected wavelength and spectral width are independent of the angle of incidence unlike GMRF. These particular properties allow both compactness and a high angular acceptance. However, ours studies show that CRIGFs offer simultaneously spectral and modal filtering and we evidence high-spatial-order reflected modes. In this paper, we will present characterization of the spectral and spatial profile that demonstrates the existence of these high-order modes. In addition, we will present a model based on the physical understanding of implied phenomena to explain…
Soliton pairs in a fiber laser: From anomalous to normal average dispersion regime
2003
We report the observation of self phase-locked pulse pairs in a stretched-pulse fiber laser operating in the normal path-averaged dispersion regime. Numerical simulations agree with our experimental results. More insight is provided with a numerical comparison between intracavity profiles of pulse pairs in anomalous and in normal dispersion regimes. © 2003 Optical Society of America.
Design of an integrated low-noise, low-power charge sensitive preamplifier for γ and particle spectroscopy with solid state detectors
2014
The design of an integrated charge-sensitive preamplifier suitable for γ-ray spectroscopy is presented. It is fully integrated, except for the feedback resistor, and can drive directly a 50Ω cable with its low impedance output stage. It is designed in AMS 0.35µm technology and its small dimensions and low power consumption (10 mW) are optimized for multi-channel applications. It works both with germanium and silicon detectors for a large range of values of electrode and feedback capacitances. Its wide bandwidth ensures a risetime of 10 ns or less in most configurations. This characteristic makes the preamplifier suitable not only for high resolution spectroscopy but also for pulse-shape ana…
Ultra-broadband terahertz time domain spectroscopy by Solid State Biased Coherent Detection
2017
The spectral fingerprint of ibuprofen within the THz frequency window has been retrieved through an ultra-broadband THz Time Domain Spectrometry set-up. The latter implements the Solid State Biased Coherent Detection scheme, based on a compact CMOS-compatible integrated device. Such a technique shows unprecedented advantages in term of bandwidth (greater than 10 THz) over other solid state methods like electro-optic sampling.
Spatio-temporal control of ultra-short pulses by using diffractive optical elements
2012
Diffractive optical elements (DOEs) have shown their applicability to control the spatio-temporal characteristics of ultra-short laser pulses. DOEs can provide high efficiency, compactness, very low material dispersion and, when implemented with spatial light modulators, real-time pulse engineering. In this communication, we report management of temporal and spectral profiles of ultra-short pulses by means of a quasi-direct space-to-time (QDST) pulse shaper. Moreover, we present spatio-temporal control, including dispersion compensation, by DOEs, and applications for activating nonlinear processes. On the other hand, we have achieved complete spatial control of ultra-short pulses, overcomin…