Search results for "PULSE SHAPING"
showing 10 items of 93 documents
Intensity Invariance of Strong-Field Two-Photon Absorption
2010
We demonstrate experimentally and theoretically the intensity-invariant scaling formula of coherent control of two-photon absorption as a function of pulse-shape parameters of ultrafast laser field in the strong-interaction regime.
Spectral broadening enhancement in silicon waveguides through pulse shaping
2012
Spectral broadening in silicon waveguides is usually inhibited at telecom wavelengths due to some adverse effects related to semiconductor dynamics, namely, two-photon and free-carrier absorption (FCA). In this Letter, our numerical simulations show that it is possible to achieve a significant enhancement in spectral broadening when we properly preshape the input pulse to reduce the impact of FCA on spectral broadening. Our analysis suggests that the use of input pulses with the correct skewness and power level is crucial for this achievemen This work was financially supported by the Plan Nacional Investigación, Desarrollo e Innovación (I+D +I) under the research project TEC2008-05490, by…
All-fiber incoherent frequency-to-time mapping method for microwave signal generation with baseband transmission and multicasting support
2008
We present a proof-of-principle experiment for achieving simultaneous distribution of baseband radio-frequency data and up-conversion with broadcasting support over a passive optical network. The technique is based on an incoherent frequency-to-time mapping method for pulse shaping. Specifically, we synthesize the spectral density function of sliced ASE noise from an EDFA with a periodic Mach-Zehnder fiber interferometer optical filter. By using external intensity modulation combined with propagation in an optical fiber, after photodetection, the resultant averaged temporal pulse profile resembles the shape of the incoherent source. The photodetected signal contains both the baseband data a…
In-fiber all-optical fractional differentiator
2009
We demonstrate that an asymmetrical pi phase-shifted fiber Bragg grating operated in reflection can provide the required spectral response for implementing an all-optical fractional differentiator. There are different (but equivalent) ways to design it, e.g., by using different gratings lengths and keeping the same index modulation depth at both sides of the pi phase shift, or vice versa. Analytical expressions were found relating the fractional differentiator order with the grating parameters. The device shows a good accuracy calculating the fractional time derivatives of the complex field of an arbitrary input optical waveform. The introduced concept is supported by numerical simulations.
Gouy wave modes: undistorted pulse focalization in a dispersive medium.
2007
Gouy wave modes are linear waves with finite energy that propagate without distortion at any phase and group velocity through a focal region in a dispersive medium. These features make them potentially useful for the onset and control of nonlinear interactions.
Spectral coherence in microresonator combs
2014
We provide a quantitative analysis of the coherence in microresonator frequency combs. We show how to achieve coherent transform-limited pulses on-chip without actively manipulating the pump setting conditions in the course of comb formation.
20 GHz arbitrary radio-frequency waveform generator based on incoherent pulse shaping
2008
We demonstrate a new approach of photonically assisted radiofrequency (RF) waveform generation using a spectrally incoherent light source. The system is based on the so-called generalized frequency-to-time mapping operation. In this work, external modulation of the source is done by concatenating two electro-optic Mach-Zehnder modulators properly biased to achieve short pulse gates which allow for broad bandwidth electrical signals. Also, the spectral shaping stage is performed prior to O/E conversion. A detailed theoretical analysis demonstrates that even in this case the frequency-to-time mapping is preserved. The key is that the noise level is greatly reduced because the amplitude filter…
Limits for the Generation of Ultra-Wideband Signals with the Incoherent-Pulse-Shaping Technique
2007
Recently, an nil-optical technique to generate arbitrary RF waveforms through Altering of the spectral density function of a broadband spectrally incoherent optical source has been introduced. The spectrum is tailored so that the output averaged intensity after large temporal modulation and subsequent distortion in a group-delay-dispersion circuit becomes the user-defined waveform. In general, there is a tradeoff between the spectral width and the signal-to-noise ratio of the output signal. Here, we provide an analytical treatment of the problem based on the optical coherence theory. In particular, we analyze the possibility to employ this technique for ultra-wideband (UWB) applications.
Experimental observation of the spectral Gouy phase shift
2013
We experimentally observe and measure the spectral phase shift of a pulse subjected to spectral focusing. We find a phase shift of π/2, reaffirming the Gouy phase shift as a general consequence of wave confinement whether in space/momentum or frequency/time coordinates.
Optimization of field-free molecular alignment by phase-shaped laser pulses
2007
We theoretically demonstrate the optimization of field-free molecular alignment by phase-shaped femtosecond laser pulses. The effect is assessed in ${\mathrm{O}}_{2}$ at $T=60\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ under realistic conditions of intensity and pulse shaping. The spectral laser phase is sampled through 128 control parameters and a self-learning evolutionary algorithm combined with a nonperturbative regime calculation is used in order to design the specific phase that maximizes the degree of alignment. The postpulse molecular alignment appears significantly enhanced compared to a Fourier-transform-limited pulse of same energy. The analysis of the target state reveals that the so…