Search results for "COMPRESSION"
showing 10 items of 774 documents
320GHz, 640GHz and 1THz femtosecond pulse sources based on multiple four wave mixing in highly non linear optical fibers
2006
Ultra-high repetition rate, transform-limited femtosecond pulse trains have been generated around 1555 nm at 320 GHz, 640 GHz and 1 THz through the compression of a dual frequency beat-signal in a highly nonlinear optical fiber.
Impact of initial pulse shape on the nonlinear spectral compression in optical fibre
2018
International audience; We theoretically study the effects of the temporal intensity profile of the initial pulse on the nonlinear spectral compression process arising from nonlinear propagation in an optical fibre. Various linearly chirped input pulse profiles are considered, and their dynamics is explained with the aid of time-frequency representations. While initially parabolic-shaped pulses show enhanced spectral compression compared to Gaussian pulses, no significant spectral narrowing occurs when initially super-Gaussian pulses are used. Triangular pulses lead to a spectral interference phenomenon similar to the Fresnel bi-prism experiment.
All-fiber spectral compression of picosecond pulses at telecommunication wavelength enhanced by amplitude shaping
2012
International audience; We demonstrate efficient spectral compression of picosecond pulses in an all-fiber configuration at telecommunication wavelengths. A spectral compression by a factor 12 is achieved. Performing temporal shaping with a parabolic pulse significantly improves the spectral compression with much lower substructures and an enhanced Strehl ratio.
Supercontinuum generation at 800 nm in all-normal dispersion photonic crystal fiber
2014
We have numerically investigated the supercontinuum generation and pulse compression in a specially designed all-normal dispersion photonic crystal fiber with a flat-top dispersion curve, pumped by typical pulses from state of the art Ti:Sapphire lasers at 800 nm. The optimal combination of pump pulse parameters for a given fiber was found, which provides a wide octave-spanning spectrum with superb spectral flatness (a drop in spectral intensity of ~1.7 dB). With regard to the pulse compression for these spectra, multiple-cycle pulses (~8 fs) can be obtained with the use of a simple quadratic compressor and nearly single-cycle pulses (3.3 fs) can be obtained with the application of full pha…
Pulse quality analysis on soliton pulse compression and soliton self-frequency shift in a hollow-core photonic bandgap fiber.
2013
A numerical investigation of low-order soliton evolution in a proposed seven-cell hollow-core photonic bandgap fiber is reported. In the numerical simulation, we analyze the pulse quality evolution in soliton pulse compression and soliton self-frequency shift in three fiber structures with different cross-section sizes. In the simulation, we consider unchirped soliton pulses (of 400 fs) at the wavelength of 1060 nm. Our numerical results show that the seven-cell hollow-core photonic crystal fiber, with a cross-section size reduction of 2%, promotes the pulse quality on the soliton pulse compression and soliton self-frequency shift. For an input soliton pulse of order 3 (which corresponds to…
Amplifier similariton fiber laser with nonlinear spectral compression
2012
International audience; We propose a new concept of a fiber laser architecture supporting self-similar pulse evolution in the amplifier and nonlinear spectral pulse compression in the passive fiber. The latter process allows for transform-limited picosecond pulse generation, and improves the laser's power efficiency by preventing strong spectral filtering from being highly dissipative. Aside from laser technology, the proposed scheme opens new possibilities for studying nonlinear dynamical processes. As an example, we demonstrate a clear period-doubling route to chaos in such nonlinear laser system.
Development and validation of a 5 stroke engine for range extenders application
2014
International audience; A 5-stroke turbo-charged port-injection spark-ignition engine has been developed in the present study for use as a range extender or series-hybrid main power source. The development and the design of the engine are based on 0D/1D model and experimental results have been compared with the engine model. The 5-stroke engine is a three-cylinder in which two cylinders perform a four-stroke cycle and alternatively a second expansion of the burnt gases is performed in the third cylinder. The boost pressure delivered by the turbocharger is controlled by a particular innovative system called “smart wastegate”, different from a conventional wastegate, consisting in a variable …
Tissue Sparing Posterior Cervical Indirect Decompression and Fusion in Foraminal Stenosis
2016
Treatment for patients with cervical foraminal stenosis that present with cervical radiculopathy has experienced rapid progress. Cervical spine surgical options have improved through advances in imaging, instrumentation, implant innovations and novel surgical techniques. While historical treatments are largely safe, comorbidities associated with procedures such as ACDF, TDR, and posterior foraminotomy beg the question if these procedures are too much surgery for select patients that could benefit from a tissue sparing approach. This chapter will introduce a novel, less disruptive surgical technique for achieving indirect decompression and fusion utilizing an intervertebral cervical implant.…
Study of interface formation during diffusion bonding : compact heat exchangers application
2014
Compact diffusion bonded heat exchangers are an attractive option in many fields (nuclear, (petro-)chemistry, solar…) due to their performance. This type of concept is especially intended for manufacturing the energy conversion system of the ASTRID reactor. During diffusion bonding by HIP, the problem is twofold: the channel deformation and microstructure evolution must be controlled, while at the same time, highly resistant interfaces are desired. This thesis is focused on the understanding and the control of the bonded components microstructure prepared by HIP in order to define « process » criteria to achieve welds in agreement with specifications of components containing fluidic channel…
Refined Sellmeier equations from phase-matching measurements over the complete transparency range of KTiOAsO4, RbTiOAsO4 and CsTiOAsO4
2000
Sum- and difference- frequency generation phasematching properties are measured in spheres of KTiOAsO4, RbTiOAsO4 and CsTiOAsO4 for Sellmeier equations refinement over their complete transparency range.