排序方式: 共有11条查询结果,搜索用时 15 毫秒
1.
Barland S. Spinicelli P. Giacomelli G. Marin F. 《Quantum Electronics, IEEE Journal of》2005,41(10):1235-1243
We present a complete experimental evaluation of the effective parameters necessary to describe the dynamical behavior of an air-post vertical-cavity surface-emitting lasers, on the basis of theoretical equations which are also derived in this paper. The experimental investigation is composed of several steps, including power versus current measurement, noise spectrum analysis, linewidth evaluation. The complete set of parameters derived, in particular the linewidth-enhancement factor and the spontaneous emission factor, is particularly important for accurate comparisons of theoretical models on the laser dynamics with experiments. 相似文献
2.
S.?Barland X.?Hachair M.?GiudiciEmail author S.?Balle J. R.?Tredicce G.?Tissoni L.?Spinelli L.?Lugiato M.?Brambilla 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2005,32(1):75-82
We analyze experimentally the spatio-temporal dynamics of the
transverse structures appearing in broad area edge-emitting
semiconductor amplifiers under CW optical injection. We
demonstrate that, in certain conditions, the light reflected by
the system exhibits a multipeaked structure whose dependence on
the parameters suggests an interpretation in terms of
cavity solitons. These structures can exhibit self-pulsations with
periods of the order of few milliseconds, which we explain in
terms of regenerative thermal oscillations. In a particular device,
we generate two single-peak structures which are spatially
uncorrelated, as required for cavity solitons. A microscopic model
shows good agreement with the main body of the experimental
results. 相似文献
3.
We show that the transition between fixed points in a separable dynamical system is fully described by an invariant integral. We discuss in detail the case of a system with two temporal variables with bilinear coupling, where the new stable state is attained asymptotically through spiraling into the fixed point. Through the invariance, it is possible to establish conditions for the control parameter that permit a (targeted) transition in finite time and without relaxation oscillations. 相似文献
4.
Miryem Hrarti Abdelhakim Saadane Mohamed-Chaker Larabi Remi Barland 《Signal Processing: Image Communication》2013,28(8):843-855
Rate control algorithm adopted in H.264/AVC reference software shows several shortcomings that have been highlighted by different studies. For instance, in the baseline profile, the frame target bit-rate estimation assumes similar characteristics for all frames and the quantization parameter determination uses the Mean Absolute Difference for complexity estimation. Consequently, an inefficient bit allocation is performed leading to important quality variation of decoded sequences. A saliency-based rate-control is proposed in this paper to achieve bit-rate saving and improve perceived quality. The saliency map of each frame, simulating the human visual attention by a bottom-up approach, is used at the frame level to adjust the quantization parameter and at the macroblock level to guide the bit allocation process. Simulation results show that the proposed attentional model is well correlated to human behavior. When compared to JM15.0 reference software, at the frame level, the saliency map exploitation achieves bit-rate savings of up to 26%. At the MB level and under the same quality constraint, bit-rate improvement is up to 42% and buffer level variation is reduced by up to 71%. 相似文献
5.
We experimentally demonstrate low-repetition-rate mode-locked operation of a macroscopic semiconductor ring laser. Since antiphase periodic pulses are observed only when the two directions of operation are constrained to spatially overlap in the semiconductor medium, we interpret this regime as a result of coupling and competition between clockwise and counterclockwise emission directions. Because of its time constants and the possibility of unidirectional operation, the device could be highly suitable for the generation of temporal cavity solitons. 相似文献
6.
F. Marino S. Barland S. Balle 《Photonics Technology Letters, IEEE》2003,15(6):789-791
An experimental study of a vertical-cavity surface-emitting laser with frequency-selective feedback is reported. We show that we can force the laser to emit in its fundamental transverse mode or in a higher order transverse mode and that we can also control the polarization emitted in the fundamental one. We obtain single fundamental-mode operation within a large range of injection current values (almost /spl ap/2.5 I/sub th/) and a maximum optical power of 2.7 mW. In this current range, the output is found to be stable. 相似文献
7.
8.
Bonatto C Feyereisen M Barland S Giudici M Masoller C Leite JR Tredicce JR 《Physical review letters》2011,107(5):053901
Experimental observations of rare giant pulses or rogue waves were done in the output intensity of an optically injected semiconductor laser. The long-tailed probability distribution function of the pulse amplitude displays clear non-Gaussian features that confirm the rogue wave character of the intensity pulsations. Simulations of a simple rate equation model show good qualitative agreement with the experiments and provide a framework for understanding the observed extreme amplitude events as the result of a deterministic nonlinear process. 相似文献
9.
Ackemann T Barland S Tredicce JR Cara M Balle S Jäger R Grabherr M Miller M Ebeling KJ 《Optics letters》2000,25(11):814-816
We investigate the spatial structure of broad-area vertical-cavity regenerative amplifiers injected with a homogeneous beam. The emerging patterns have a predominantly sixfold rotational symmetry, verifying the recent prediction of formation of hexagons. The length scale is controllable by means of detuning and follows the prediction for tilted waves. 相似文献
10.
P. Genevet M. Turconi S. Barland M. Giudici J. R. Tredicce 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,59(1):109-114
We present recent developments of the Monte Carlo model
for heavy-ion therapy (MCHIT), which is currently based on the
Geant4 toolkit of version 9.2.
The major advancement of the model concerns the modelling of violent
fragmentation reactions by means of the Fermi break-up model, which is
used to simulate decays of hot fragments created
after the first stage of nucleus-nucleus collisions.
By means of MCHIT we study the dose distributions from therapeutic
beams of carbon nuclei in tissue-like materials, like water and
PMMA. The contributions to the total dose from
primary beam nuclei and from charged secondary fragments produced in
nuclear fragmentation reactions are calculated.
The build-up of secondary fragments along the beam axis is calculated and
compared with available experimental data. Finally, we demonstrate
the impact of violent multifragment decays on energy distributions of
secondary neutrons produced by carbon nuclei in water. 相似文献